網(wǎng)絡(luò)編程

• Java基礎(chǔ)：網(wǎng)絡(luò)編程
• Uri、URL、UriMatcher、ContentUris詳解
• Android應(yīng)用開發(fā)：網(wǎng)絡(luò)編程1
• Android應(yīng)用開發(fā)：網(wǎng)絡(luò)編程2

1. 請求網(wǎng)絡(luò)圖片

網(wǎng)絡(luò)交互就是基于HTTP協(xié)議請求和響應(yīng)的過程。XMPP協(xié)議用于即時通訊。

示例：res\layout\activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity" ><Button android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="請求圖片" android:onClick="click"/><ImageView android:id="@+id/iv"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerInParent="true"/></RelativeLayout>

src/cn.itcast.imageviewer/MainActivity.java

package cn.itcast.imageviewer;import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL; import android.app.Activity; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.Bundle; import android.view.View; import android.widget.ImageView; import android.widget.Toast;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){//向服務(wù)器發(fā)送Http請求去請求圖片String path = "http://192.168.1.100:8080/sh.jpg";try{//1. 把網(wǎng)址封裝成url對象URL url = new URL(path);//2. 打開一個連接對象HttpURLConnection conn = (HttpURLConnection) url.openConnection();//3. 給連接對象做設(shè)置conn.setRequestMethod("GET");conn.setConnectTimeout(8000);conn.setReadTimeout(8000);//4. 發(fā)送請求，建立連接conn.connect();//5. 獲取響應(yīng)碼，如果為200開頭，說明請求成功if(conn.getResponseCode() == 200){//獲取服務(wù)器的流，服務(wù)器返回的數(shù)據(jù)是通過流寫給客戶端的，也就是說，流里就是請求的圖片InputStream is = conn.getInputStream();//讀取流里的數(shù)據(jù)，把數(shù)據(jù)構(gòu)造成一個圖片對象Bitmap bm = BitmapFactory.decodeStream(is);//把圖片顯示至屏幕ImageView iv = (ImageView) findViewById(R.id.iv);iv.setImageBitmap(bm);}else{Toast.makeText(this, "請求失敗啦啦啦", 0).show();}}catch(Exception e){e.printStackTrace();}} }

添加權(quán)限：

在Tomcat服務(wù)器webapps\ROOT存放圖片：

運行結(jié)果：雙擊start.bat，啟動tomcat。

啟動2.3.3版本模擬器，圖片顯示成功：

Handler機制讓子線程刷新UI，如果上面的示例運行在4.3版本的模擬器上，就會報警告：

在Android中，主線程是絕對不能阻塞的。因為，網(wǎng)絡(luò)請求是耗時操作，主線程處于阻塞狀態(tài)，用戶任何操作都無效，處于類似于死機的狀態(tài)。此時，點擊HOME鍵有效，點擊返回鍵、菜單鍵都沒有反應(yīng)。因為，返回鍵和菜單鍵是由當(dāng)前應(yīng)用程序自行處理，HOME鍵是由系統(tǒng)處理。應(yīng)用程序可以阻塞自己的主線程，不可能阻塞Android系統(tǒng)。
為了保證用戶體驗良好，所有的耗時操作都不要寫在主線程里，包括：請求網(wǎng)絡(luò)、加載數(shù)據(jù)（數(shù)據(jù)庫）和資源。
ANR：Application Not Responding，應(yīng)用長時間不能響應(yīng)用戶操作。

查看出現(xiàn)ANR的原因，導(dǎo)出data/anr/traces.txt文件，打開。

ANR無法調(diào)試，解決方法就是在主線程中不要做耗時操作。
只有主線程可以刷新UI，主線程又稱UI線程。這樣做，是為了線程安全，只有一個線程可以刷新UI，如果有多個線程同時刷新UI，就可能出現(xiàn)線程安全導(dǎo)致UI刷新混亂的問題。

如果我們在MainActivity.java中啟動一個線程進行網(wǎng)絡(luò)請求，再次執(zhí)行該應(yīng)用程序就會報警告，如下：

通過異常可以看出來，刷新UI的代碼必須在主線程中執(zhí)行，但是請求圖片的代碼又由于不能引起阻塞，只能在子線程中執(zhí)行，而且只有請求完圖片之后才能刷新UI，這時候就形成了矛盾。Android里面提供了一種機制能夠解決這個問題，也就是Handler機制。

2. Handler機制

主線程創(chuàng)建的時候，主線程中有一個消息隊列MessageQueue，用來存放消息。還有一個Looper用來不斷檢測MessageQueue是否有消息。如果有消息就交給消息處理器Handler，Handler中有一個方法handleMessage，用來處理消息，這個方法是在主線程調(diào)用。那么，這個方法就可以刷新UI。如此，子線程想要刷新UI，只需調(diào)用Handler的sendMessag方法，將消息發(fā)送到MessageQueue即可。

示例：src/cn.itcast.imageviewer2/MainActivity.java

package cn.itcast.imageviewer2;import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL;import android.app.Activity; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.ImageView; import android.widget.Toast;public class MainActivity extends Activity {Handler handler = new Handler(){//程序員需要重寫handlerMessage方法，刷新UI@Overridepublic void handleMessage(Message msg) {switch(msg.what){case 1://判斷消息是成功消息還是失敗消息ImageView iv = (ImageView) findViewById(R.id.iv);iv.setImageBitmap((Bitmap)msg.obj);break;case 2:Toast.makeText(MainActivity.this, "請求失敗啦啦啦", 0).show();break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){Thread t = new Thread(){public void run(){String path = "http://192.168.1.100:8080/sh.jpg";try{URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(8000);conn.setReadTimeout(8000);conn.connect();if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();Bitmap bm = BitmapFactory.decodeStream(is);//創(chuàng)建消息對象Message msg = new Message();//消息對象可以攜帶數(shù)據(jù)msg.obj = bm;msg.what = 1;//發(fā)送消息至主線程的消息隊列handler.sendMessage(msg);}else{Message msg = new Message();msg.what = 2;handler.sendMessage(msg);//由于Message沒有攜帶任何數(shù)據(jù)，所以上面3句可以用下面1句替換。//handler.sendEmptyMessage(2);}}catch(Exception e){e.printStackTrace();}}};t.start();} }

運行結(jié)果：

添加緩存功能的圖片查看器，為了提升效率，查看圖片后，緩存起來，便于下次查看圖片不必在通過網(wǎng)絡(luò)請求。

代碼：src/cn.itcast.imageviewer3/MainActivity.java

package cn.itcast.imageviewer3;import java.io.File; import java.io.FileOutputStream; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL; import android.app.Activity; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.ImageView; import android.widget.Toast;public class MainActivity extends Activity {Handler handler = new Handler(){@Overridepublic void handleMessage(Message msg) {switch(msg.what){case 1:ImageView iv = (ImageView) findViewById(R.id.iv);iv.setImageBitmap((Bitmap)msg.obj);break;case 2:Toast.makeText(MainActivity.this, "請求失敗啦啦啦", 0).show();break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){final String path = "http://192.168.1.100:8080/sh.jpg";final File file = new File(getCacheDir(),getFileName(path));if(file.exists()){System.out.println("從緩存獲取");Bitmap bm = BitmapFactory.decodeFile(file.getAbsolutePath());ImageView iv = (ImageView) findViewById(R.id.iv);iv.setImageBitmap(bm);}else{Thread t = new Thread(){public void run(){try{System.out.println("從網(wǎng)絡(luò)獲取");URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(8000);conn.setReadTimeout(8000);conn.connect();if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();//需要自己開啟文件輸出流，讀取流里數(shù)據(jù)的同時，把數(shù)據(jù)寫到本地byte[] b = new byte[1024];int len;FileOutputStream fos = new FileOutputStream(file);while((len = is.read(b)) != -1){fos.write(b, 0, len);}fos.close();//流里數(shù)據(jù)已經(jīng)讀取完畢，這行代碼無法再構(gòu)造圖片了//Bitmap bm = BitmapFactory.decodeStream(is);Bitmap bm = BitmapFactory.decodeFile(file.getAbsolutePath());Message msg = new Message();msg.obj = bm;msg.what = 1;handler.sendMessage(msg);}else{Message msg = new Message();msg.what = 2;handler.sendMessage(msg);}}catch(Exception e){e.printStackTrace();}}};t.start();}}public String getFileName(String path){int index = path.lastIndexOf("/");return path.substring(index+1);} }

運行結(jié)果：

第一次，從網(wǎng)絡(luò)獲取。第二次再次點擊按鈕，從緩存獲取。

3. 獲取開源代碼

在程序開發(fā)中，會遇到很多問題。例如，請求圖片過程中遇到斷網(wǎng)，網(wǎng)速慢，圖片過大內(nèi)存不夠等等情況。由于這些情況大部分項目都會遇到，所以網(wǎng)上有很多寫好的現(xiàn)成的模塊。不要重新發(fā)明輪子，可以直接拿來用。
好的開源網(wǎng)站： http://code.google.com http://github.com
搜索，下載源碼，解壓，復(fù)制到我們自己的應(yīng)用程序項目中。

res\layout\activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity" ><Button android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="請求網(wǎng)絡(luò)圖片" android:onClick="click"/><com.loopj.android.image.SmartImageView android:id="@+id/iv"android:layout_width="wrap_content"android:layout_height="wrap_content"android:src="@drawable/ic_launcher"android:layout_centerInParent="true"/> </RelativeLayout>

SmartImageView是自定義控件，以后會有專門的課程講解。

src/cn.itcast.smartimageview/MainActivity.java

package cn.itcast.smartimageview;import android.app.Activity; import android.os.Bundle; import android.view.View;import com.loopj.android.image.SmartImageView;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){String path = "http://192.168.1.100:8080/sh.jpg";SmartImageView iv = (SmartImageView) findViewById(R.id.iv);iv.setImageUrl(path);} }

添加權(quán)限：

運行結(jié)果：

4. Html源文件查看器

代碼：res\layout\activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity" ><Button android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="請求網(wǎng)絡(luò)" android:onClick="click"/><ScrollView android:layout_width="match_parent"android:layout_height="match_parent"><TextView android:id="@+id/tv"android:layout_width="match_parent"android:layout_height="match_parent"/></ScrollView> </RelativeLayout>

src/cn.itcast.htmlviewer.tool/Tools.java

package cn.itcast.htmlviewer.tool;import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream;public class Tools {public static String getTextFromStream(InputStream is){try{byte[] b = new byte[1024];int len;ByteArrayOutputStream bos = new ByteArrayOutputStream();while((len = is.read(b)) != -1){bos.write(b,0,len);}//把輸出流里的內(nèi)容轉(zhuǎn)換成字節(jié)數(shù)組String text = new String(bos.toByteArray());return text;}catch(IOException e){e.printStackTrace();}return null;} }

src/cn.itcast.htmlviewer/MainActivity.java

package cn.itcast.htmlviewer;import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL;import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.TextView; import cn.itcast.htmlviewer.tool.Tools;public class MainActivity extends Activity {Handler handler = new Handler(){@Overridepublic void handleMessage(Message msg) {TextView tv = (TextView) findViewById(R.id.tv);tv.setText((String)msg.obj);}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){Thread t = new Thread(){public void run(){String path = "http://192.168.1.100:8080/baidu.html";try{URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(8000);conn.setReadTimeout(8000);//先發(fā)送請求，再獲取響應(yīng)碼，getResponseCode方法自身會發(fā)送請求消息if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();String text = Tools.getTextFromStream(is);//如果消息池中沒有消息，new一個，如果有，復(fù)用這條空閑消息Message msg = handler.obtainMessage();msg.obj = text;handler.sendMessage(msg);}}catch(Exception e){e.printStackTrace();}}};t.start();} }

添加權(quán)限：

運行結(jié)果：

如果html文件為gbk編碼：

那么Tools.java中代碼只要進行如下修改即可：

新聞客戶端布局

res\layout\item_listview.xml

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="wrap_content" ><ImageView android:id="@+id/iv"android:layout_width="90dp"android:layout_height="70dp"android:src="@drawable/ic_launcher"android:layout_centerVertical="true"/><!-- android:singleLine是為了讓過長的標題不會導(dǎo)致?lián)Q行，影響美觀 --><TextView android:id="@+id/tv_title"android:layout_width="wrap_content"android:layout_height="wrap_content"android:textSize="22sp"android:text="這是標題"android:singleLine="true"android:layout_toRightOf="@+id/iv"/><!-- android:lines表示如果文本過長，最多顯示幾行 --><TextView android:id="@+id/tv_detail"android:layout_width="wrap_content"android:layout_height="wrap_content"android:textSize="15sp"android:text="這是詳細"android:lines="2"android:textColor="@android:color/darker_gray"android:layout_toRightOf="@+id/iv"android:layout_below="@id/tv_title"/><TextView android:id="@+id/tv_comment"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="12345條評論"android:textColor="#ff0000"android:layout_alignParentRight="true"android:layout_below="@id/tv_detail"/></RelativeLayout>

效果：

獲取新聞信息，將news.xml和images文件夾存放在Tomcat服務(wù)器中。

News.xml

<?xml version="1.0" encoding="UTF-8" ?> <newslist><news><title>西安一期就業(yè)快報</title><detail>熱烈祝賀西安一期平均薪水突破13k</detail><comment>15687</comment><image>http://192.168.1.100:8080/images/6.jpg</image></news><news><title>程序員因?qū)懘a太亂被殺害</title><detail>兇手是死者同事，維護死者代碼時完全看不懂而痛下殺手</detail><comment>16359</comment><image>http://192.168.1.100:8080/images/7.jpg</image></news><news><title>產(chǎn)品經(jīng)理因頻繁改需求被殺害</title><detail>兇手是一名程序員，因死者對項目需求頻繁改動而痛下殺手</detail><comment>14112</comment><image>http://192.168.1.100:8080/images/7.jpg</image></news><news><title>3Q大戰(zhàn)宣判: 騰訊獲賠500萬</title><detail>最高法駁回360上訴, 維持一審宣判.</detail><comment>6427</comment><image>http://192.168.1.100:8080/images/1.jpg</image></news><news><title>今日之聲:北大雕塑被戴口罩</title><detail>市民: 因霧霾起訴環(huán)保局; 公務(wù)員談"緊日子": 堅決不出去.</detail><comment>681</comment><image>http://192.168.1.100:8080/images/2.jpg</image></news><news><title>奧巴馬見達賴是裝蒜</title><detail>外文局: 國際民眾認可中國大國地位;法院: "流量清零"未侵權(quán).</detail><comment>1359</comment><image>http://192.168.1.100:8080/images/3.jpg</image></news><news><title>輕松一刻: 我要沉迷學(xué)習(xí)不自拔</title><detail>放假時我醒了不代表我起床了, 如今我起床了不代表我醒了!</detail><comment>11616</comment><image>http://192.168.1.100:8080/images/4.jpg</image></news><news><title>男女那些事兒</title><detail>"媽, 我在東莞被抓, 要2萬保釋金, 快匯錢到xxx!"</detail><comment>10339</comment><image>http://192.168.1.100:8080/images/5.jpg</image></news><news><title>趙帥哥語錄一</title><detail>少壯不努力，老大做IT</detail><comment>14612</comment><image>http://192.168.1.100:8080/images/8.jpg</image></news><news><title>趙帥哥語錄二</title><detail>問君能有幾多愁，恰似調(diào)完代碼改需求</detail><comment>13230</comment><image>http://192.168.1.100:8080/images/8.jpg</image></news><news><title>趙帥哥語錄三</title><detail>覺得我?guī)浀娜斯べY一般都比較高</detail><comment>9928</comment><image>http://192.168.1.100:8080/images/8.jpg</image></news><news><title>今日之聲:北大雕塑被戴口罩</title><detail>市民: 因霧霾起訴環(huán)保局; 公務(wù)員談"緊日子": 堅決不出去.</detail><comment>681</comment><image>http://192.168.1.100:8080/images/2.jpg</image></news><news><title>奧巴馬見達賴是裝蒜</title><detail>外文局: 國際民眾認可中國大國地位;法院: "流量清零"未侵權(quán).</detail><comment>1359</comment><image>http://192.168.1.100:8080/images/3.jpg</image></news> </newslist> src/cn.itcast.news.domain/News.java package cn.itcast.news.domain;public class News {private String title; private String detail;private String comment;private String imageUrl;public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getDetail() {return detail;}public void setDetail(String detail) {this.detail = detail;}public String getComment() {return comment;}public void setComment(String comment) {this.comment = comment;}public String getImageUrl() {return imageUrl;}public void setImageUrl(String imageUrl) {this.imageUrl = imageUrl;} } src/cn.itcast.news/MainActivity.java package cn.itcast.news;import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL; import java.util.ArrayList; import java.util.List;import org.xmlpull.v1.XmlPullParser;import android.app.Activity; import android.os.Bundle; import android.util.Xml; import cn.itcast.news.domain.News;public class MainActivity extends Activity {List<News> newsList;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);getNewsInfo();}private void getNewsInfo(){Thread t = new Thread(){public void run(){String path = "http://192.168.1.100:8080/news.xml";try{URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection)url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(8000);conn.setReadTimeout(8000);if(conn.getResponseCode() == 200){//獲取服務(wù)器返回的流，流里就是xml文件InputStream is = conn.getInputStream();parserNewsInfo(is);}}catch(Exception e){e.printStackTrace();}}};t.start();}private void parserNewsInfo(InputStream is){XmlPullParser xp = Xml.newPullParser();try{xp.setInput(is,"utf-8"); int type = xp.getEventType(); News news = null; while(type != XmlPullParser.END_DOCUMENT){switch(type){case XmlPullParser.START_TAG:if("newslist".equals(xp.getName())){newsList = new ArrayList<News>();}else if("news".equals(xp.getName())){news = new News();}else if("title".equals(xp.getName())){String title = xp.nextText();news.setTitle(title);}else if("detail".equals(xp.getName())){String detail = xp.nextText();news.setDetail(detail);}else if("comment".equals(xp.getName())){String comment = xp.nextText();news.setComment(comment);}else if("image".equals(xp.getName())){String image = xp.nextText();news.setImageUrl(image);}break;case XmlPullParser.END_TAG:if("news".equals(xp.getName())){newsList.add(news);}break;}type = xp.next();}}catch(Exception e){e.printStackTrace();}} }

把新聞信息顯示至界面
修改res\layout\item_listview.xml中的ImageView標簽為SmartImageView標簽，便于顯示圖片。

src/cn.itcast.news/MainActivity.java package cn.itcast.news;import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL; import java.util.ArrayList; import java.util.List; import org.xmlpull.v1.XmlPullParser; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.util.Xml; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ListView; import android.widget.TextView; import cn.itcast.news.domain.News;import com.loopj.android.image.SmartImageView;public class MainActivity extends Activity {List<News> newsList;Handler handler = new Handler(){@Overridepublic void handleMessage(Message msg) {ListView lv = (ListView)findViewById(R.id.lv);lv.setAdapter(new MyAdapter());}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);getNewsInfo();//由于getNewsInfo方法中是開啟了一個子線程，與主線程并行。所以當(dāng)listview顯示內(nèi)容時，newsList還沒來得及創(chuàng)建，所以lv設(shè)置顯示內(nèi)容的代碼不能運行在這里。要保證運行在xml解析完畢之后。//ListView lv = (ListView)findViewById(R.id.lv);//lv.setAdapter(new MyAdapter());}class MyAdapter extends BaseAdapter{@Overridepublic int getCount() {//之所以系統(tǒng)需要知道條目數(shù)量，是因為屏幕右側(cè)的控制條顯示基于此數(shù)據(jù)而定return newsList.size();}@Overridepublic Object getItem(int position) {return null;}@Overridepublic long getItemId(int position) {return 0;}//視圖保存器class ViewHolder{TextView tv_title;TextView tv_detail;TextView tv_comment;SmartImageView siv;}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {View v = null;ViewHolder vh = null;News news = newsList.get(position);if(convertView == null){v = View.inflate(MainActivity.this, R.layout.item_listview, null);vh = new ViewHolder();//如果緩存為空，那么需要填充新的View對象，同時找到布局文件中的所有組件，并封裝至ViewHolder對象中vh.tv_title = (TextView)v.findViewById(R.id.tv_title);vh.tv_detail = (TextView)v.findViewById(R.id.tv_detail);vh.tv_comment = (TextView)v.findViewById(R.id.tv_comment);vh.siv = (SmartImageView) v.findViewById(R.id.iv);//把ViewHolder對象存入View對象中，緩存View對象，同時緩存了ViewHolder對象v.setTag(vh);}else{v = convertView;//從緩存中取出ViewHolder對象，這個對象中就封裝了布局文件中所有的組件對象，那么就不需要再次findViewById了vh = (ViewHolder)v.getTag();}vh.tv_title.setText(news.getTitle());vh.tv_detail.setText(news.getDetail());vh.tv_comment.setText(news.getComment() + "條評論");vh.siv.setImageUrl(news.getImageUrl());return v;}}private void getNewsInfo(){Thread t = new Thread(){public void run(){String path = "http://192.168.1.100:8080/news.xml";try{URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection)url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(8000);conn.setReadTimeout(8000);if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();parserNewsInfo(is);}}catch(Exception e){e.printStackTrace();}}};t.start();}private void parserNewsInfo(InputStream is){XmlPullParser xp = Xml.newPullParser();try{xp.setInput(is,"utf-8");int type = xp.getEventType();News news = null;while(type != XmlPullParser.END_DOCUMENT){switch(type){case XmlPullParser.START_TAG:if("newslist".equals(xp.getName())){newsList = new ArrayList<News>();}else if("news".equals(xp.getName())){news = new News();}else if("title".equals(xp.getName())){String title = xp.nextText();news.setTitle(title);}else if("detail".equals(xp.getName())){String detail = xp.nextText();news.setDetail(detail);}else if("comment".equals(xp.getName())){String comment = xp.nextText();news.setComment(comment);}else if("image".equals(xp.getName())){String image = xp.nextText();news.setImageUrl(image);}break;case XmlPullParser.END_TAG:if("news".equals(xp.getName())){newsList.add(news);}break;}type = xp.next();}}catch(Exception e){e.printStackTrace();}//xml解析完畢，發(fā)送消息，通知主線程，設(shè)置lv的顯示內(nèi)容handler.sendEmptyMessage(1);} }

添加權(quán)限：

運行結(jié)果：

使用get方式提交表單

使用MyEclipse，新建一個Servlet：Login.java，把該Web項目部署到Tomcat服務(wù)器上。

src/cn.itcast.login/Login.java

package cn.itcast.login;import java.io.IOException;import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;public class Login extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String name = request.getParameter("name");String pass = request.getParameter("pass");ServletOutputStream os = response.getOutputStream();if("asd".equals(name)&&"123".equals(pass)){os.write("登陸成功".getBytes("utf-8"));}else{os.write("登陸失敗".getBytes("utf-8"));}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);} }

WebRoot/index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html><head></head><body><form action="/Web/servlet/Login" method=get>賬號：<input type="text" name="name"><br/>密碼：<input type="text" name="pass"><br/><input type="submit" value="登陸"/></form></body> </html>

打開瀏覽器，輸入地址，然后輸入用戶名和密碼，提交。

將瀏覽器編碼改為UTF-8。

結(jié)果如下：

Android之Get方式提交數(shù)據(jù)： res\layout\activity_main.xml <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity" android:orientation="vertical"><EditText android:id="@+id/et_name"android:layout_width="match_parent"android:layout_height="wrap_content"/><EditText android:id="@+id/et_pass"android:layout_width="match_parent"android:layout_height="wrap_content"/><Button android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="登陸"android:onClick="click"/> </LinearLayout> src/cn.itcast.getmethod.tool/Tools.java package cn.itcast.getmethod.tool;import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream;public class Tools {public static String getTextFromStream(InputStream is){try{byte[] b = new byte[1024];int len;ByteArrayOutputStream bos = new ByteArrayOutputStream();while((len = is.read(b)) != -1){bos.write(b,0,len);}//把輸出流里的內(nèi)容轉(zhuǎn)換成字節(jié)數(shù)組String text = new String(bos.toByteArray());return text;}catch(IOException e){e.printStackTrace();}return null;} } src/cn.itcast.getmethod/MainActivity.java package cn.itcast.getmethod;import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL;import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.EditText; import android.widget.Toast; import cn.itcast.getmethod.tool.Tools;public class MainActivity extends Activity {Handler handler = new Handler(){@Overridepublic void handleMessage(Message msg) {Toast.makeText(MainActivity.this, (String)msg.obj, 0).show();}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){EditText et_name = (EditText)findViewById(R.id.et_name);EditText et_pass = (EditText)findViewById(R.id.et_pass);String name = et_name.getText().toString();String pass = et_pass.getText().toString();//在url后面拼接要提交的數(shù)據(jù)final String path = "http://localhost:8080/Web/servlet/Login?name=" + name + "&pass=" + pass;Thread t = new Thread(){public void run(){URL url;try {url = new URL(path);HttpURLConnection conn = (HttpURLConnection)url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(8000);conn.setReadTimeout(8000);if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();String text = Tools.getTextFromStream(is);Message msg = handler.obtainMessage();msg.obj = text;handler.sendMessage(msg);}} catch (Exception e) {e.printStackTrace();}}};t.start();} }

添加權(quán)限：

運行結(jié)果：

提交表單的亂碼問題

將Login.java中“zhangsan”修改為“張三”，并且打印出接收到的用戶名及密碼。

src/cn.itcast.login/Login.java

package cn.itcast.login;import java.io.IOException;import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;public class Login extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String name = request.getParameter("name");String pass = request.getParameter("pass");System.out.println(name);System.out.println(pass);ServletOutputStream os = response.getOutputStream();if("張三".equals(name)&&"123".equals(pass)){os.write("登陸成功".getBytes("utf-8"));}else{os.write("登陸失敗".getBytes("utf-8"));}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);} }

重新部署，運行。結(jié)果如下：

將瀏覽器編碼調(diào)整為UTF-8。

可以看到，打印出來的為亂碼。原因在于瀏覽器提交表單的時候，會把“張三”用UTF-8編碼變成字節(jié)數(shù)組，然后傳給服務(wù)器。服務(wù)器拿到這些字節(jié)以后，因為getParameter默認使用iso8859-1編碼把讀取到的字節(jié)數(shù)組構(gòu)造成字符串，導(dǎo)致亂碼。因此，解決方案為，首先使用iso8859-1把字符串重新轉(zhuǎn)換成字節(jié)數(shù)組，然后再用utf-8構(gòu)造成字符串即可。

重新部署，運行，結(jié)果如下：

嘗試通過手機端發(fā)送中文的情況，如下：輸入中文，首先選擇谷歌拼音輸入法。

由上面的圖片可以看到，依然存在亂碼問題。原因在于瀏覽器提交的數(shù)據(jù)都是經(jīng)過URL編碼的，所以，通過代碼提交的數(shù)據(jù)就需要手動編碼。

修改后，運行結(jié)果：

使用post方式提交表單，修改表單為post提交方式：

通過代碼實現(xiàn)post提交請求，一方面通過流的方式將數(shù)據(jù)傳輸給服務(wù)器，一方面是給post請求頭添加額外屬性。

src/cn.itcast.postmethod/MainActivity.java

package cn.itcast.postmethod;import java.io.InputStream; import java.io.OutputStream; import java.net.HttpURLConnection; import java.net.URL; import java.net.URLEncoder;import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.EditText; import android.widget.Toast; import cn.itcast.getmethod.tool.Tools;public class MainActivity extends Activity {Handler handler = new Handler(){@Overridepublic void handleMessage(Message msg) {Toast.makeText(MainActivity.this, (String)msg.obj, 0).show();}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){EditText et_name = (EditText)findViewById(R.id.et_name);EditText et_pass = (EditText)findViewById(R.id.et_pass);final String name = et_name.getText().toString();final String pass = et_pass.getText().toString();final String path = "http://192.168.1.100:8080/Web/servlet/Login";Thread t = new Thread(){public void run(){URL url;try {url = new URL(path);HttpURLConnection conn = (HttpURLConnection)url.openConnection();conn.setRequestMethod("POST");conn.setConnectTimeout(8000);conn.setReadTimeout(8000);//post請求頭需要添加額外屬性conn.setRequestProperty("Content-type", "application/x-www-form-urlencoded");String content = "name=" + URLEncoder.encode(name) + "&pass=" + pass;conn.setRequestProperty("Content-Length", content.length() + "");//開啟請求頭的流，把要提交的數(shù)據(jù)寫入流中//設(shè)置打開連接對象輸出流conn.setDoOutput(true);OutputStream os = conn.getOutputStream();os.write(content.getBytes());if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();String text = Tools.getTextFromStream(is);Message msg = handler.obtainMessage();msg.obj = text;handler.sendMessage(msg);}} catch (Exception e) {e.printStackTrace();}}};t.start();} }

運行結(jié)果：

---

1. 網(wǎng)絡(luò)圖片查看器

• 確定圖片的網(wǎng)址
• 發(fā)送http請求

URL url = new URL(address); //獲取連接對象，并沒有建立連接 HttpURLConnection conn = (HttpURLConnection) url.openConnection(); //設(shè)置連接和讀取超時 conn.setConnectTimeout(5000); conn.setReadTimeout(5000); //設(shè)置請求方法，注意必須大寫 conn.setRequestMethod("GET"); //建立連接，發(fā)送get請求 //conn.connect(); //建立連接，然后獲取響應(yīng)嗎，200說明請求成功 conn.getResponseCode();

• 服務(wù)器的圖片是以流的形式返回給瀏覽器的

//拿到服務(wù)器返回的輸入流 InputStream is = conn.getInputStream(); //把流里的數(shù)據(jù)讀取出來，并構(gòu)造成圖片 Bitmap bm = BitmapFactory.decodeStream(is);

• 把圖片設(shè)置為ImageView的顯示內(nèi)容

ImageView iv = (ImageView) findViewById(R.id.iv); iv.setImageBitmap(bm);

• 添加網(wǎng)絡(luò)權(quán)限

1.1 主線程不能被阻塞

• 在Android中，主線程被阻塞會導(dǎo)致應(yīng)用不能刷新ui界面，不能響應(yīng)用戶操作，用戶體驗將非常差
• 主線程阻塞時間過長，系統(tǒng)會拋出ANR異常
• ANR：Application Not Response；應(yīng)用無響應(yīng)
• 任何耗時操作都不可以寫在主線程
• 因為網(wǎng)絡(luò)交互屬于耗時操作，如果網(wǎng)速很慢，代碼會阻塞，所以網(wǎng)絡(luò)交互的代碼不能運行在主線程

1.2 只有主線程能刷新ui

• 刷新ui的代碼只能運行在主線程，運行在子線程是沒有任何效果的
• 如果需要在子線程中刷新ui，使用消息隊列機制

1.3 消息隊列

• Looper一旦發(fā)現(xiàn)Message Queue中有消息，就會把消息取出，然后把消息扔給Handler對象，Handler會調(diào)用自己的handleMessage方法來處理這條消息
• handleMessage方法運行在主線程
• 主線程創(chuàng)建時，消息隊列和輪詢器對象就會被創(chuàng)建，但是消息處理器對象，需要使用時，自行創(chuàng)建

//消息隊列 Handler handler = new Handler(){//主線程中有一個消息輪詢器looper，不斷檢測消息隊列中是否有新消息，//如果發(fā)現(xiàn)有新消息，自動調(diào)用此方法，注意此方法是在主線程中運行的public void handleMessage(android.os.Message msg) {} };

• 在子線程中往消息隊列里發(fā)消息

//創(chuàng)建消息對象 Message msg = new Message(); //消息的obj屬性可以賦值任何對象，通過這個屬性可以攜帶數(shù)據(jù) msg.obj = bm; //what屬性相當(dāng)于一個標簽，用于區(qū)分出不同的消息，從而運行不能的代碼 msg.what = 1; //發(fā)送消息 handler.sendMessage(msg);

• 通過switch語句區(qū)分不同的消息

public void handleMessage(android.os.Message msg) {switch (msg.what) {//如果是1，說明屬于請求成功的消息case 1:ImageView iv = (ImageView) findViewById(R.id.iv);Bitmap bm = (Bitmap) msg.obj;iv.setImageBitmap(bm);break;case 2:Toast.makeText(MainActivity.this, "請求失敗", 0).show();break;} } public class MainActivity extends Activity {static ImageView iv;static MainActivity ma;static Handler handler = new Handler(){//此方法在主線程中調(diào)用，可以用來刷新uipublic void handleMessage(android.os.Message msg) {//處理消息時，需要知道到底是成功的消息，還是失敗的消息switch (msg.what) {case 1://把位圖對象顯示至imageviewiv.setImageBitmap((Bitmap)msg.obj);break;case 0:Toast.makeText(ma, "請求失敗", 0).show();break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);iv = (ImageView) findViewById(R.id.iv);ma = this;}public void click(View v){Thread t = new Thread(){@Overridepublic void run() {//下載圖片//1.確定網(wǎng)址String path = "http://192.168.13.13:8080/dd.jpg";try {//2.把網(wǎng)址封裝成一個url對象URL url = new URL(path);//3.獲取客戶端和服務(wù)器的連接對象，此時還沒有建立連接HttpURLConnection conn = (HttpURLConnection) url.openConnection();//4.對連接對象進行初始化//設(shè)置請求方法，注意大寫conn.setRequestMethod("GET");//設(shè)置連接超時conn.setConnectTimeout(5000);//設(shè)置讀取超時conn.setReadTimeout(5000);//5.發(fā)送請求，與服務(wù)器建立連接conn.connect();//如果響應(yīng)碼為200，說明請求成功if(conn.getResponseCode() == 200){//獲取服務(wù)器響應(yīng)頭中的流，流里的數(shù)據(jù)就是客戶端請求的數(shù)據(jù)InputStream is = conn.getInputStream();//讀取出流里的數(shù)據(jù)，并構(gòu)造成位圖對象Bitmap bm = BitmapFactory.decodeStream(is);// ImageView iv = (ImageView) findViewById(R.id.iv); // //把位圖對象顯示至imageview // iv.setImageBitmap(bm);Message msg = new Message();//消息對象可以攜帶數(shù)據(jù)msg.obj = bm;msg.what = 1;//把消息發(fā)送至主線程的消息隊列handler.sendMessage(msg);}else{ // Toast.makeText(MainActivity.this, "請求失敗", 0).show();Message msg = handler.obtainMessage();msg.what = 0;handler.sendMessage(msg);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();} }

1.4 案例1：網(wǎng)絡(luò)圖片查看器

public class MainActivity extends Activity {static ImageView iv;static MainActivity ma;static Handler handler = new Handler(){//此方法在主線程中調(diào)用，可以用來刷新uipublic void handleMessage(android.os.Message msg) {//處理消息時，需要知道到底是成功的消息，還是失敗的消息switch (msg.what) {case 1://把位圖對象顯示至imageviewiv.setImageBitmap((Bitmap)msg.obj);break;case 0:Toast.makeText(ma, "請求失敗", 0).show();break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);iv = (ImageView) findViewById(R.id.iv);ma = this;}public void click(View v){Thread t = new Thread(){@Overridepublic void run() {//下載圖片//1.確定網(wǎng)址String path = "http://192.168.13.13:8080/dd.jpg";try {//2.把網(wǎng)址封裝成一個url對象URL url = new URL(path);//3.獲取客戶端和服務(wù)器的連接對象，此時還沒有建立連接HttpURLConnection conn = (HttpURLConnection) url.openConnection();//4.對連接對象進行初始化//設(shè)置請求方法，注意大寫conn.setRequestMethod("GET");//設(shè)置連接超時conn.setConnectTimeout(5000);//設(shè)置讀取超時conn.setReadTimeout(5000);//5.發(fā)送請求，與服務(wù)器建立連接conn.connect();//如果響應(yīng)碼為200，說明請求成功if(conn.getResponseCode() == 200){//獲取服務(wù)器響應(yīng)頭中的流，流里的數(shù)據(jù)就是客戶端請求的數(shù)據(jù)InputStream is = conn.getInputStream();//讀取出流里的數(shù)據(jù)，并構(gòu)造成位圖對象Bitmap bm = BitmapFactory.decodeStream(is);// ImageView iv = (ImageView) findViewById(R.id.iv); // //把位圖對象顯示至imageview // iv.setImageBitmap(bm);Message msg = new Message();//消息對象可以攜帶數(shù)據(jù)msg.obj = bm;msg.what = 1;//把消息發(fā)送至主線程的消息隊列handler.sendMessage(msg);}else{ // Toast.makeText(MainActivity.this, "請求失敗", 0).show();Message msg = handler.obtainMessage();msg.what = 0;handler.sendMessage(msg);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();} }

1.5 加入緩存圖片的功能

• 把服務(wù)器返回的流里的數(shù)據(jù)讀取出來，然后通過文件輸入流寫至本地文件

//1.拿到服務(wù)器返回的輸入流 InputStream is = conn.getInputStream(); //2.把流里的數(shù)據(jù)讀取出來，并構(gòu)造成圖片FileOutputStream fos = new FileOutputStream(file); byte[] b = new byte[1024]; int len = 0; while((len = is.read(b)) != -1){fos.write(b, 0, len); }

• 創(chuàng)建bitmap對象的代碼改成

Bitmap bm = BitmapFactory.decodeFile(file.getAbsolutePath());

• 每次發(fā)送請求前檢測一下在緩存中是否存在同名圖片，如果存在，則讀取緩存

public class MainActivity extends Activity {static ImageView iv;static MainActivity ma;static Handler handler = new Handler(){//此方法在主線程中調(diào)用，可以用來刷新uipublic void handleMessage(android.os.Message msg) {//處理消息時，需要知道到底是成功的消息，還是失敗的消息switch (msg.what) {case 1://把位圖對象顯示至imageviewiv.setImageBitmap((Bitmap)msg.obj);break;case 0:Toast.makeText(ma, "請求失敗", 0).show();break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);iv = (ImageView) findViewById(R.id.iv);ma = this;}public void click(View v){//下載圖片//1.確定網(wǎng)址final String path = "http://192.168.13.13:8080/dd.jpg";final File file = new File(getCacheDir(), getFileName(path));//判斷，緩存中是否存在該文件if(file.exists()){//如果緩存存在，從緩存讀取圖片System.out.println("從緩存讀取的");Bitmap bm = BitmapFactory.decodeFile(file.getAbsolutePath());iv.setImageBitmap(bm);}else{//如果緩存不存在，從網(wǎng)絡(luò)下載System.out.println("從網(wǎng)上下載的");Thread t = new Thread(){@Overridepublic void run() {try {//2.把網(wǎng)址封裝成一個url對象URL url = new URL(path);//3.獲取客戶端和服務(wù)器的連接對象，此時還沒有建立連接HttpURLConnection conn = (HttpURLConnection) url.openConnection();//4.對連接對象進行初始化//設(shè)置請求方法，注意大寫conn.setRequestMethod("GET");//設(shè)置連接超時conn.setConnectTimeout(5000);//設(shè)置讀取超時conn.setReadTimeout(5000);//5.發(fā)送請求，與服務(wù)器建立連接conn.connect();//如果響應(yīng)碼為200，說明請求成功if(conn.getResponseCode() == 200){//獲取服務(wù)器響應(yīng)頭中的流，流里的數(shù)據(jù)就是客戶端請求的數(shù)據(jù)InputStream is = conn.getInputStream();//讀取服務(wù)器返回的流里的數(shù)據(jù)，把數(shù)據(jù)寫到本地文件，緩存起來FileOutputStream fos = new FileOutputStream(file);byte[] b = new byte[1024];int len = 0;while((len = is.read(b)) != -1){fos.write(b, 0, len);}fos.close();//讀取出流里的數(shù)據(jù)，并構(gòu)造成位圖對象//流里已經(jīng)沒有數(shù)據(jù)了 // Bitmap bm = BitmapFactory.decodeStream(is);Bitmap bm = BitmapFactory.decodeFile(file.getAbsolutePath());Message msg = new Message();//消息對象可以攜帶數(shù)據(jù)msg.obj = bm;msg.what = 1;//把消息發(fā)送至主線程的消息隊列handler.sendMessage(msg);}else{ // Toast.makeText(MainActivity.this, "請求失敗", 0).show();Message msg = handler.obtainMessage();msg.what = 0;handler.sendMessage(msg);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();}}public String getFileName(String path){int index = path.lastIndexOf("/");return path.substring(index + 1);}}

1.6 案例2：帶緩存的網(wǎng)絡(luò)圖片查看器

public class MainActivity extends Activity {static ImageView iv;static MainActivity ma;static Handler handler = new Handler(){//此方法在主線程中調(diào)用，可以用來刷新uipublic void handleMessage(android.os.Message msg) {//處理消息時，需要知道到底是成功的消息，還是失敗的消息switch (msg.what) {case 1://把位圖對象顯示至imageviewiv.setImageBitmap((Bitmap)msg.obj);break;case 0:Toast.makeText(ma, "請求失敗", 0).show();break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);iv = (ImageView) findViewById(R.id.iv);ma = this;}public void click(View v){//下載圖片//1.確定網(wǎng)址final String path = "http://192.168.13.13:8080/dd.jpg";final File file = new File(getCacheDir(), getFileName(path));//判斷，緩存中是否存在該文件if(file.exists()){//如果緩存存在，從緩存讀取圖片System.out.println("從緩存讀取的");Bitmap bm = BitmapFactory.decodeFile(file.getAbsolutePath());iv.setImageBitmap(bm);}else{//如果緩存不存在，從網(wǎng)絡(luò)下載System.out.println("從網(wǎng)上下載的");Thread t = new Thread(){@Overridepublic void run() {try {//2.把網(wǎng)址封裝成一個url對象URL url = new URL(path);//3.獲取客戶端和服務(wù)器的連接對象，此時還沒有建立連接HttpURLConnection conn = (HttpURLConnection) url.openConnection();//4.對連接對象進行初始化//設(shè)置請求方法，注意大寫conn.setRequestMethod("GET");//設(shè)置連接超時conn.setConnectTimeout(5000);//設(shè)置讀取超時conn.setReadTimeout(5000);//5.發(fā)送請求，與服務(wù)器建立連接conn.connect();//如果響應(yīng)碼為200，說明請求成功if(conn.getResponseCode() == 200){//獲取服務(wù)器響應(yīng)頭中的流，流里的數(shù)據(jù)就是客戶端請求的數(shù)據(jù)InputStream is = conn.getInputStream();//讀取服務(wù)器返回的流里的數(shù)據(jù)，把數(shù)據(jù)寫到本地文件，緩存起來FileOutputStream fos = new FileOutputStream(file);byte[] b = new byte[1024];int len = 0;while((len = is.read(b)) != -1){fos.write(b, 0, len);}fos.close();//讀取出流里的數(shù)據(jù)，并構(gòu)造成位圖對象//流里已經(jīng)沒有數(shù)據(jù)了 // Bitmap bm = BitmapFactory.decodeStream(is);Bitmap bm = BitmapFactory.decodeFile(file.getAbsolutePath());Message msg = new Message();//消息對象可以攜帶數(shù)據(jù)msg.obj = bm;msg.what = 1;//把消息發(fā)送至主線程的消息隊列handler.sendMessage(msg);}else{ // Toast.makeText(MainActivity.this, "請求失敗", 0).show();Message msg = handler.obtainMessage();msg.what = 0;handler.sendMessage(msg);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();}}public String getFileName(String path){int index = path.lastIndexOf("/");return path.substring(index + 1);}}

1.7 案例3：開源圖片查看器

public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){//下載圖片//1.確定網(wǎng)址String path = "http://192.168.13.13:8080/dd.jpg";//2.找到智能圖片查看器對象SmartImageView siv = (SmartImageView) findViewById(R.id.iv);//3.下載并顯示圖片siv.setImageUrl(path);}}

2. 獲取開源代碼的網(wǎng)站

• code.google.com
• github.com
• 在github搜索smart-image-view
• 下載開源項目smart-image-view
• 使用自定義組件時，標簽名字要寫包名

<com.loopj.android.image.SmartImageView/>

• SmartImageView的使用

SmartImageView siv = (SmartImageView) findViewById(R.id.siv); siv.setImageUrl("http://192.168.1.102:8080/dd.jpg");

3. 新聞客戶端

public class MainActivity extends Activity {List<News> newsList;Handler handler = new Handler(){public void handleMessage(android.os.Message msg) {ListView lv = (ListView) findViewById(R.id.lv);lv.setAdapter(new MyAdapter());}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);getNewsInfo(); // ListView lv = (ListView) findViewById(R.id.lv); // //要保證在設(shè)置適配器時，新聞xml文件已經(jīng)解析完畢了 // lv.setAdapter(new MyAdapter());}class MyAdapter extends BaseAdapter{//得到模型層中元素的數(shù)量，用來確定listview需要有多少個條目@Overridepublic int getCount() {// TODO Auto-generated method stubreturn newsList.size();}@Override//返回一個View對象，作為listview的條目顯示至界面public View getView(int position, View convertView, ViewGroup parent) {News news = newsList.get(position);View v = null;ViewHolder mHolder;if(convertView == null){v = View.inflate(MainActivity.this, R.layout.item_listview, null);mHolder = new ViewHolder();//把布局文件中所有組件的對象封裝至ViewHolder對象中mHolder.tv_title = (TextView) v.findViewById(R.id.tv_title);mHolder.tv_detail = (TextView) v.findViewById(R.id.tv_detail);mHolder.tv_comment = (TextView) v.findViewById(R.id.tv_comment);mHolder.siv = (SmartImageView) v.findViewById(R.id.iv);//把ViewHolder對象封裝至View對象中v.setTag(mHolder);}else{v = convertView;mHolder = (ViewHolder) v.getTag();}//給三個文本框設(shè)置內(nèi)容mHolder.tv_title.setText(news.getTitle());mHolder.tv_detail.setText(news.getDetail());mHolder.tv_comment.setText(news.getComment() + "條評論");//給新聞圖片imageview設(shè)置內(nèi)容mHolder.siv.setImageUrl(news.getImageUrl());return v;}class ViewHolder{//條目的布局文件中有什么組件，這里就定義什么屬性TextView tv_title;TextView tv_detail;TextView tv_comment;SmartImageView siv;}@Overridepublic Object getItem(int position) {return null;}@Overridepublic long getItemId(int position) {return 0;}}private void getNewsInfo() {Thread t = new Thread(){@Overridepublic void run() {String path = "http://192.168.13.13:8080/news.xml";try {URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(5000);conn.setReadTimeout(5000);//發(fā)送http GET請求，獲取相應(yīng)碼if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();//使用pull解析器，解析這個流parseNewsXml(is);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();}private void parseNewsXml(InputStream is) {XmlPullParser xp = Xml.newPullParser();try {xp.setInput(is, "utf-8");//對節(jié)點的事件類型進行判斷，就可以知道當(dāng)前節(jié)點是什么節(jié)點int type = xp.getEventType();News news = null;while(type != XmlPullParser.END_DOCUMENT){switch (type) {case XmlPullParser.START_TAG:if("newslist".equals(xp.getName())){newsList = new ArrayList<News>();}else if("news".equals(xp.getName())){news = new News();}else if("title".equals(xp.getName())){String title = xp.nextText();news.setTitle(title);}else if("detail".equals(xp.getName())){String detail = xp.nextText();news.setDetail(detail);}else if("comment".equals(xp.getName())){String comment = xp.nextText();news.setComment(comment);}else if("image".equals(xp.getName())){String image = xp.nextText();news.setImageUrl(image);}break;case XmlPullParser.END_TAG:if("news".equals(xp.getName())){newsList.add(news);}break;}//解析完當(dāng)前節(jié)點后，把指針移動至下一個節(jié)點，并返回它的事件類型type = xp.next();}//發(fā)消息，讓主線程設(shè)置listview的適配器，如果消息不需要攜帶數(shù)據(jù)，可以發(fā)送空消息handler.sendEmptyMessage(1);// for (News n : newsList) { // System.out.println(n.toString()); // }} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

3.1 案例5：新聞客戶端

public class MainActivity extends Activity {List<News> newsList;Handler handler = new Handler(){public void handleMessage(android.os.Message msg) {ListView lv = (ListView) findViewById(R.id.lv);lv.setAdapter(new MyAdapter());}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);getNewsInfo(); // ListView lv = (ListView) findViewById(R.id.lv); // //要保證在設(shè)置適配器時，新聞xml文件已經(jīng)解析完畢了 // lv.setAdapter(new MyAdapter());}class MyAdapter extends BaseAdapter{//得到模型層中元素的數(shù)量，用來確定listview需要有多少個條目@Overridepublic int getCount() {// TODO Auto-generated method stubreturn newsList.size();}@Override//返回一個View對象，作為listview的條目顯示至界面public View getView(int position, View convertView, ViewGroup parent) {News news = newsList.get(position);View v = null;ViewHolder mHolder;if(convertView == null){v = View.inflate(MainActivity.this, R.layout.item_listview, null);mHolder = new ViewHolder();//把布局文件中所有組件的對象封裝至ViewHolder對象中mHolder.tv_title = (TextView) v.findViewById(R.id.tv_title);mHolder.tv_detail = (TextView) v.findViewById(R.id.tv_detail);mHolder.tv_comment = (TextView) v.findViewById(R.id.tv_comment);mHolder.siv = (SmartImageView) v.findViewById(R.id.iv);//把ViewHolder對象封裝至View對象中v.setTag(mHolder);}else{v = convertView;mHolder = (ViewHolder) v.getTag();}//給三個文本框設(shè)置內(nèi)容mHolder.tv_title.setText(news.getTitle());mHolder.tv_detail.setText(news.getDetail());mHolder.tv_comment.setText(news.getComment() + "條評論");//給新聞圖片imageview設(shè)置內(nèi)容mHolder.siv.setImageUrl(news.getImageUrl());return v;}class ViewHolder{//條目的布局文件中有什么組件，這里就定義什么屬性TextView tv_title;TextView tv_detail;TextView tv_comment;SmartImageView siv;}@Overridepublic Object getItem(int position) {return null;}@Overridepublic long getItemId(int position) {return 0;}}private void getNewsInfo() {Thread t = new Thread(){@Overridepublic void run() {String path = "http://192.168.13.13:8080/news.xml";try {URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(5000);conn.setReadTimeout(5000);//發(fā)送http GET請求，獲取相應(yīng)碼if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();//使用pull解析器，解析這個流parseNewsXml(is);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();}private void parseNewsXml(InputStream is) {XmlPullParser xp = Xml.newPullParser();try {xp.setInput(is, "utf-8");//對節(jié)點的事件類型進行判斷，就可以知道當(dāng)前節(jié)點是什么節(jié)點int type = xp.getEventType();News news = null;while(type != XmlPullParser.END_DOCUMENT){switch (type) {case XmlPullParser.START_TAG:if("newslist".equals(xp.getName())){newsList = new ArrayList<News>();}else if("news".equals(xp.getName())){news = new News();}else if("title".equals(xp.getName())){String title = xp.nextText();news.setTitle(title);}else if("detail".equals(xp.getName())){String detail = xp.nextText();news.setDetail(detail);}else if("comment".equals(xp.getName())){String comment = xp.nextText();news.setComment(comment);}else if("image".equals(xp.getName())){String image = xp.nextText();news.setImageUrl(image);}break;case XmlPullParser.END_TAG:if("news".equals(xp.getName())){newsList.add(news);}break;}//解析完當(dāng)前節(jié)點后，把指針移動至下一個節(jié)點，并返回它的事件類型type = xp.next();}//發(fā)消息，讓主線程設(shè)置listview的適配器，如果消息不需要攜帶數(shù)據(jù)，可以發(fā)送空消息handler.sendEmptyMessage(1);// for (News n : newsList) { // System.out.println(n.toString()); // }} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

4. Html源文件查看器

• 發(fā)送GET請求

URL url = new URL(path); //獲取連接對象 HttpURLConnection conn = (HttpURLConnection) url.openConnection(); //設(shè)置連接屬性 conn.setRequestMethod("GET"); conn.setConnectTimeout(5000); conn.setReadTimeout(5000); //建立連接，獲取響應(yīng)嗎 if(conn.getResponseCode() == 200){}

• 獲取服務(wù)器返回的流，從流中把html源碼讀取出來

byte[] b = new byte[1024]; int len = 0; ByteArrayOutputStream bos = new ByteArrayOutputStream(); while((len = is.read(b)) != -1){//把讀到的字節(jié)先寫入字節(jié)數(shù)組輸出流中存起來bos.write(b, 0, len); } //把字節(jié)數(shù)組輸出流中的內(nèi)容轉(zhuǎn)換成字符串 //默認使用utf-8 text = new String(bos.toByteArray());

4.1 亂碼的處理

• 亂碼的出現(xiàn)是因為服務(wù)器和客戶端碼表不一致導(dǎo)致

//手動指定碼表 text = new String(bos.toByteArray(), "gb2312");

4.2 案例4：HTML源文件查看器

public class MainActivity extends Activity {Handler handler = new Handler(){public void handleMessage(android.os.Message msg) {TextView tv = (TextView) findViewById(R.id.tv);tv.setText((String)msg.obj);}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View v){Thread t = new Thread(){@Overridepublic void run() {String path = "http://192.168.13.13:8080/baidu.html";try {URL url = new URL(path);//獲取連接對象，此時還未建立連接HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(5000);conn.setReadTimeout(5000);//先建立連接，然后獲取響應(yīng)碼if(conn.getResponseCode() == 200){//拿到服務(wù)器返回的輸入流，流里的數(shù)據(jù)就是html的源文件InputStream is = conn.getInputStream();//從流里把文本數(shù)據(jù)取出來String text = Utils.getTextFromStream(is);//發(fā)送消息，讓主線程刷新ui，顯示源文件Message msg = handler.obtainMessage();msg.obj = text;handler.sendMessage(msg);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();}}

5. 提交數(shù)據(jù)

5.1 GET方式提交數(shù)據(jù)

• get方式提交的數(shù)據(jù)是直接拼接在url的末尾

final String path = "http://192.168.1.104/Web/servlet/CheckLogin?name=" + name + "&pass=" + pass;

• 發(fā)送get請求，代碼和之前一樣

URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET"); conn.setReadTimeout(5000); conn.setConnectTimeout(5000); if(conn.getResponseCode() == 200){}

• 瀏覽器在發(fā)送請求攜帶數(shù)據(jù)時會對數(shù)據(jù)進行URL編碼，我們寫代碼時也需要為中文進行URL編碼

String path = "http://192.168.1.104/Web/servlet/CheckLogin?name=" + URLEncoder.encode(name) + "&pass=" + pass;

5.2 案例6：使用get方式提交數(shù)據(jù)

public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}Handler handler = new Handler(){public void handleMessage(android.os.Message msg) {Toast.makeText(MainActivity.this, (String)msg.obj, 0).show();}};public void click(View v){EditText et_name = (EditText) findViewById(R.id.et_name);EditText et_pass = (EditText) findViewById(R.id.et_pass);final String name = et_name.getText().toString();final String pass = et_pass.getText().toString();Thread t = new Thread(){@Overridepublic void run() {//提交的數(shù)據(jù)需要經(jīng)過url編碼，英文和數(shù)字編碼后不變@SuppressWarnings("deprecation")String path = "http://192.168.13.13/Web2/servlet/LoginServlet?name=" + URLEncoder.encode(name) + "&pass=" + pass;try {URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(5000);conn.setReadTimeout(5000);if(conn.getResponseCode() == 200){InputStream is =conn.getInputStream();String text = Utils.getTextFromStream(is);Message msg = handler.obtainMessage();msg.obj = text;handler.sendMessage(msg);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();}} public class Utils {public static String getTextFromStream(InputStream is){byte[] b = new byte[1024];int len = 0;//創(chuàng)建字節(jié)數(shù)組輸出流，讀取輸入流的文本數(shù)據(jù)時，同步把數(shù)據(jù)寫入數(shù)組輸出流ByteArrayOutputStream bos = new ByteArrayOutputStream();try {while((len = is.read(b)) != -1){bos.write(b, 0, len);}//把字節(jié)數(shù)組輸出流里的數(shù)據(jù)轉(zhuǎn)換成字節(jié)數(shù)組String text = new String(bos.toByteArray());return text;} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}return null;} }

5.3 POST方式提交數(shù)據(jù)

• post提交數(shù)據(jù)是用流寫給服務(wù)器的
• 協(xié)議頭中多了兩個屬性
  
  • Content-Type: application/x-www-form-urlencoded，描述提交的數(shù)據(jù)的mimetype
  • Content-Length: 32，描述提交的數(shù)據(jù)的長度

//給請求頭添加post多出來的兩個屬性 String data = "name=" + URLEncoder.encode(name) + "&pass=" + pass; conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); conn.setRequestProperty("Content-Length", data.length() + "");

• 設(shè)置允許打開post請求的流

conn.setDoOutput(true);

• 獲取連接對象的輸出流，往流里寫要提交給服務(wù)器的數(shù)據(jù)

OutputStream os = conn.getOutputStream(); os.write(data.getBytes());

5.4 案例7：使用post方式提交數(shù)據(jù)

public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}Handler handler = new Handler(){public void handleMessage(android.os.Message msg) {Toast.makeText(MainActivity.this, (String)msg.obj, 0).show();}};public void click(View v){EditText et_name = (EditText) findViewById(R.id.et_name);EditText et_pass = (EditText) findViewById(R.id.et_pass);final String name = et_name.getText().toString();final String pass = et_pass.getText().toString();Thread t = new Thread(){@Overridepublic void run() {//提交的數(shù)據(jù)需要經(jīng)過url編碼，英文和數(shù)字編碼后不變@SuppressWarnings("deprecation")String path = "http://192.168.13.13/Web2/servlet/LoginServlet";try {URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("POST");conn.setConnectTimeout(5000);conn.setReadTimeout(5000);//拼接出要提交的數(shù)據(jù)的字符串String data = "name=" + URLEncoder.encode(name) + "&pass=" + pass;//添加post請求的兩行屬性conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");conn.setRequestProperty("Content-Length", data.length() + "");//設(shè)置打開輸出流conn.setDoOutput(true);//拿到輸出流OutputStream os = conn.getOutputStream();//使用輸出流往服務(wù)器提交數(shù)據(jù)os.write(data.getBytes());if(conn.getResponseCode() == 200){InputStream is = conn.getInputStream();String text = Utils.getTextFromStream(is);Message msg = handler.obtainMessage();msg.obj = text;handler.sendMessage(msg);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}};t.start();} }

6. 網(wǎng)絡(luò)請求

6.1 主線程阻塞

• UI停止刷新，應(yīng)用無法響應(yīng)用戶操作
• 耗時操作不應(yīng)該在主線程進行

• ANR

  • application not responding
  • 應(yīng)用無響應(yīng)異常
  • 主線程阻塞時間過長，就會拋出ANR

• 主線程又稱UI線程，因為只有在主線程中，才能刷新UI

6.2 消息隊列機制

• 主線程創(chuàng)建時，系統(tǒng)會同時創(chuàng)建消息隊列對象（MessageQueue）和消息輪詢器對象（Looper）
• 輪詢器的作用，就是不停的檢測消息隊列中是否有消息（Message）
• 消息隊列一旦有消息，輪詢器會把消息對象傳給消息處理器（Handler），處理器會調(diào)用handleMessage方法來處理這條消息，handleMessage方法運行在主線程中，所以可以刷新ui
• 總結(jié)：只要消息隊列有消息，handleMessage方法就會調(diào)用
• 子線程如果需要刷新ui，只需要往消息隊列中發(fā)一條消息，觸發(fā)handleMessage方法即可
• 子線程使用處理器對象的sendMessage方法發(fā)送消息

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