Android 下拉刷新
一、實現(xiàn)分析
????? 實現(xiàn)原理：
? ? ?(1)下拉，顯示提示頭部界面，這個過程提示用戶"下拉刷新"
? ? ? ? a. 下拉的操作，首先是監(jiān)聽滾動，ListView提供了onScroll()方法
? ? ? ? b. 與下拉類似一個動作向下飛滑，所以ListView的scrollState有3種值:SCROLL_STATE_IDLE,?SCROLL_STATE_TOUCH_SCROLL,?SCROLL_STATE_FLING,意思容易理解，而我們要下拉的觸發(fā)條件是SCROLL_STATE_TOUCH_SCROLL。判斷當(dāng)前的下拉操作狀態(tài)，ListView提供了public void onScrollStateChanged(AbsListView view, int scrollState) {}。
? ????? c. 下拉的過程中，我們可能還需要下拉到多少的邊界值處理，重寫onTouchEvent(MotionEvent ev){}方法，可依據(jù)ACTION_DOWN，ACTION_MOVE，ACTION_UP實現(xiàn)更精細的判斷。
? ? (2)下拉到一定程度，超出了刷新最基本的下拉界限，我們認為達到了刷新的條件，提示用戶可以"松手刷新"了，效果上允許用戶繼續(xù)下拉
? ? ? ? a. 達到下拉刷新界限，一般指達到header的高度的，所以有兩步，第一，獲取header的高度，第二，當(dāng)header.getBottom()>=header的高度時，我們認為就達到了刷新界限值
? ? ? ? b. 繼續(xù)允許用戶下拉，當(dāng)header完全下拉后，默認無法繼續(xù)下拉，但是可以增加header的PaddingTop實現(xiàn)這種效果
? ? (3) 用戶松手，可能用戶下拉遠遠不止提示頭部界面，所以這一步，先反彈回僅顯示提示頭部界面，然后提示用戶"正在加載"。
? ? ? ? a. 松手后反彈，這個不能一下子彈回去，看上去太突然，需要一步一步柔性的彈回去，像彈簧一樣，我們可以new一個Thread循環(huán)計算減少PaddingTop，直到PaddingTop為0，反彈結(jié)束。
? ? ? ? b. 正在加載，在子線程里處理后臺任務(wù)
? ? (4) 加載完成后，隱藏提示頭部界面。
? ? ? ? a. 后臺任務(wù)完成后，我們需要隱藏header,setSelection(1)即實現(xiàn)了從第2項開始顯示，間接隱藏了header。
上面我們分析了實現(xiàn)過程的輪廓，接下來，我們通過細節(jié)說明和代碼具體實現(xiàn)。
二、 初始化
? ? 一切狀態(tài)顯示都是用HeaderView顯示的，所以我們需要一個HeaderView的layout，使用addHeaderView方法添加到ListView中。
? ? 同時，默認狀態(tài)下，HeaderView是不顯示的，只是在下拉后才顯示，所以我們需要隱藏HeaderView且不影響后續(xù)的下拉顯示，用setSelection(1)。
? ? refresh_list_header.xml布局如下:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
??? android:layout_width="fill_parent"
??? android:layout_height="wrap_content"
??? android:gravity="center">
??? <ProgressBar android:id="@+id/refresh_list_header_progressbar"
??????? android:layout_width="wrap_content"
??????? android:layout_height="wrap_content"
??????? android:layout_gravity="center"
??????? style="?android:attr/progressBarStyleSmall"
????? ??android:visibility="gone">
??? </ProgressBar>
??? <ImageView android:id="@+id/refresh_list_header_pull_down"
??????? android:layout_width="9dip"
??????? android:layout_height="25dip"
??????? android:layout_gravity="center"
??????? android:src="@drawable/refresh_list_pull_down" />
??? <ImageView android:id="@+id/refresh_list_header_release_up"
??????? android:layout_width="9dip"
??????? android:layout_height="25dip"
??????? android:layout_gravity="center"
??????? android:src="@drawable/refresh_list_release_up"
??????? android:visibility="gone" />
??? <RelativeLayout android:layout_width="180dip"
??????? android:layout_height="wrap_content">
??????? <TextView android:id="@+id/refresh_list_header_text"
??????????? android:layout_width="fill_parent"
????????? ??android:layout_height="wrap_content"
??????????? android:gravity="center"
??????????? android:layout_alignParentTop="true"
??????????? android:textSize="12dip"
??????????? android:textColor="#192F06"
??????????? android:paddingTop="8dip"
??????????? android:text="@string/app_list_header_refresh_down"/>
??????? <TextView android:id="@+id/refresh_list_header_last_update"
??????????? android:layout_width="fill_parent"
??????????? android:layout_height="wrap_content"
??????????? android:gravity="center"
???? ???????android:layout_below="@id/refresh_list_header_text"
??????????? android:textSize="12dip"
??????????? android:textColor="#192F06"
??????????? android:paddingBottom="8dip"
??????????? android:text="@string/app_list_header_refresh_last_update"/>
??? </RelativeLayout>
</LinearLayout>
?
代碼中在構(gòu)造函數(shù)中添加init()方法加載如下:
private LinearLayout mHeaderLinearLayout = null;
private TextView mHeaderTextView = null;
private TextView mHeaderUpdateText = null;
private ImageView mHeaderPullDownImageView = null;
private ImageView mHeaderReleaseDownImageView = null;
private ProgressBar mHeaderProgressBar = null;
?
public RefreshListView(Context context) {
??? this(context, null);
}
public RefreshListView(Context context, AttributeSet attrs) {
??? super(context, attrs);
??? init(context);
}
?
void init(final Context context) {
??? mHeaderLinearLayout = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.refresh_list_header, null);
??? addHeaderView(mHeaderLinearLayout);
??? mHeaderTextView = (TextView) findViewById(R.id.refresh_list_header_text);
??? mHeaderUpdateText = (TextView) findViewById(R.id.refresh_list_header_last_update);
??? mHeaderPullDownImageView = (ImageView) findViewById(R.id.refresh_list_header_pull_down);
??? mHeaderReleaseDownImageView = (ImageView) findViewById(R.id.refresh_list_header_release_up);
??? mHeaderProgressBar = (ProgressBar) findViewById(R.id.refresh_list_header_progressbar);
?
??? setSelection(1);
}默認就顯示完成了。
三、?HeaderView的默認高度測量
? ? 因為下拉到HeaderView全部顯示出來，就由提示"下拉刷新"變?yōu)?#34;松手刷新",全部顯示的出來的測量標(biāo)準就是header.getBottom()>=header的高度。
? ? 所以，首先我們需要測量HeaderView的默認高度。
//因為是在構(gòu)造函數(shù)里測量高度，應(yīng)該先measure一下
private void measureView(View child) {
??? ViewGroup.LayoutParams p = child.getLayoutParams();
??? if (p == null) {
??????? p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,
??????????????? ViewGroup.LayoutParams.WRAP_CONTENT);
??? }
?
??? int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);
??? int lpHeight = p.height;
??? int childHeightSpec;
??? if (lpHeight > 0) {
??????? childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,
??????????????? MeasureSpec.EXACTLY);
??? } else {
??????? childHeightSpec = MeasureSpec.makeMeasureSpec(0,
????? ??????????MeasureSpec.UNSPECIFIED);
??? }
??? child.measure(childWidthSpec, childHeightSpec);
}?
然后在init的上述代碼后面加上調(diào)用measureView后，使用getMeasureHeight()方法獲取header的高度：
private?int?mHeaderHeight;
void?init(final?Context context) {
????... ...
????measureView(mHeaderLinearLayout);
????mHeaderHeight = mHeaderLinearLayout.getMeasuredHeight();
}
后面我們就會用到這個mHeaderHeight.
四、?scrollState監(jiān)聽記錄
scrollState有3種，使用onScrollStateChanged()方法監(jiān)聽記錄。
private?int?mCurrentScrollState;
@Override
public?void?onScrollStateChanged(AbsListView view, int?scrollState) {
????mCurrentScrollState = scrollState;
}
然后即可使用mCurrentScrollState作為后面判斷的條件了。
五、?刷新狀態(tài)分析
? ? 因為一些地方需要知道我們處在正常狀態(tài)下還是進入下拉刷新狀態(tài)還是松手反彈狀態(tài)，比如，
? ? (1). 在非正常的狀態(tài)下，我們不小心飛滑了一下(松手的瞬間容易出現(xiàn)這種情況),我們不能setSelection(1)的，否則總是松手后header跳的一下消失掉了。
? ? (2). 下拉后要做一個下拉效果的特殊處理，需要用到OVER_PULL_REFRESH(松手刷新狀態(tài)下)
? ? (3). 松手反彈后要做一個反彈效果的特殊處理，需要用到OVER_PULL_REFRESH和ENTER_PULL_REFRESH。
private final static int NONE_PULL_REFRESH = 0;?? //正常狀態(tài)
private final static int ENTER_PULL_REFRESH = 1;? //進入下拉刷新狀態(tài)
private final static int OVER_PULL_REFRESH = 2;?? //進入松手刷新狀態(tài)
private final static int EXIT_PULL_REFRESH = 3;???? //松手后反彈后加載狀態(tài)
private int mPullRefreshState = 0;???????????????????????? //記錄刷新狀態(tài)
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
??? if (mCurrentScrollState ==SCROLL_STATE_TOUCH_SCROLL
??????????? && firstVisibleItem == 0
??????????? && (mHeaderLinearLayout.getBottom() >= 0 && mHeaderLinearLayout.getBottom() < mHeaderHeight)) {
??????? //進入且僅進入下拉刷新狀態(tài)
??????? if (mPullRefreshState == NONE_PULL_REFRESH) {
??????????? mPullRefreshState = ENTER_PULL_REFRESH;
??????? }
??? } else if (mCurrentScrollState ==SCROLL_STATE_TOUCH_SCROLL
??????????? && firstVisibleItem == 0
??????????? && (mHeaderLinearLayout.getBottom() >= mHeaderHeight)) {
??????? //下拉達到界限，進入松手刷新狀態(tài)
??????? if (mPullRefreshState == ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
??????????? mPullRefreshState = OVER_PULL_REFRESH;
??????????? //下面是進入松手刷新狀態(tài)需要做的一個顯示改變
????? ??????mDownY = mMoveY;//用于后面的下拉特殊效果
??????????? mHeaderTextView.setText("松手刷新");
??????????? mHeaderPullDownImageView.setVisibility(View.GONE);
??????????? mHeaderReleaseDownImageView.setVisibility(View.VISIBLE);
??????? }
??? } else if (mCurrentScrollState ==SCROLL_STATE_TOUCH_SCROLL && firstVisibleItem != 0) {
??????? //不刷新了
??????? if (mPullRefreshState == ENTER_PULL_REFRESH) {
??????????? mPullRefreshState = NONE_PULL_REFRESH;
??????? }
??? } else if (mCurrentScrollState == SCROLL_STATE_FLING && firstVisibleItem == 0) {
??????? //飛滑狀態(tài)，不能顯示出header，也不能影響正常的飛滑
??????? //只在正常情況下才糾正位置
??????? if (mPullRefreshState == NONE_PULL_REFRESH) {
??????????? setSelection(1);
??????? }
??? }
}
mPullRefreshState將是后面我們處理邊界的重要變量。
六、下拉效果的特殊處理
所謂的特殊處理，當(dāng)header完全顯示后，下拉只按下拉1/3的距離下拉，給用戶一種艱難下拉，該松手的彈簧感覺。
這個在onTouchEvent里處理比較方便：
private float mDownY;
private float mMoveY;
@Override
public boolean onTouchEvent(MotionEvent ev) {
??? switch (ev.getAction()) {
??????? case MotionEvent.ACTION_DOWN:
??????????? //記下按下位置
??????? ????//改變
??????????? mDownY = ev.getY();
??????????? break;
??????? case MotionEvent.ACTION_MOVE:
??????????? //移動時手指的位置
??????????? mMoveY = ev.getY();
??????????? if (mPullRefreshState == OVER_PULL_REFRESH) {
??????????????? //注意下面的mDownY在onScroll的第二個else中被改變了
??????????????? mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
??????????????????????? (int)((mMoveY - mDownY)/3), //1/3距離折扣
??????????????????????? mHeaderLinearLayout.getPaddingRight(),
??????????????????????? mHeaderLinearLayout.getPaddingBottom());
??????????? }
??????????? break;
??????? case MotionEvent.ACTION_UP:
??????????? ... ...
??????????? break;
??? }
??? return super.onTouchEvent(ev);
}
?
//重復(fù)貼出下面這段需要注意的代碼
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
??? ... ...
??? else if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
??????????? && firstVisibleItem == 0
??????????? && (mHeaderLinearLayout.getBottom() >= mHeaderHeight)) {
??????? //下拉達到界限，進入松手刷新狀態(tài)
??????? if (mPullRefreshState == ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
??????????? mPullRefreshState = OVER_PULL_REFRESH;
??????????? mDownY = mMoveY; //為下拉1/3折扣效果記錄開始位置
??????????? mHeaderTextView.setText("松手刷新");//顯示松手刷新
??????????? mHeaderPullDownImageView.setVisibility(View.GONE);//隱藏"下拉刷新"
??????????? mHeaderReleaseDownImageView.setVisibility(View.VISIBLE);//顯示向上的箭頭
??????? }
??? }
??? ... ...
}
onScroll里監(jiān)聽到了進入松手刷新狀態(tài)，onTouchEvent就開始在ACTION_MOVE中處理1/3折扣問題。
六、 反彈效果的特殊處理
松手后我們需要一個柔性的反彈效果，意味著我們彈回去的過程需要分一步步走,我的解決方案是：
在子線程里計算PaddingTop，并減少到原來的3/4，循環(huán)通知主線程，直到PaddingTop小于1(這個值取一個小值，合適即可)。
松手后，當(dāng)然是在onTouchEvent的ACTION_UP條件下處理比較方便：
//因為涉及到handler數(shù)據(jù)處理，為方便我們定義如下常量
private final static int REFRESH_BACKING = 0;????? //反彈中
private final static int REFRESH_BACED = 1;??????? //達到刷新界限，反彈結(jié)束后
private final static int REFRESH_RETURN = 2;?????? //沒有達到刷新界限，返回
private final static int REFRESH_DONE = 3;???????? //加載數(shù)據(jù)結(jié)束
?
@Override
public boolean onTouchEvent(MotionEvent ev) {
??? switch (ev.getAction()) {
??????? ... ...
??????? case MotionEvent.ACTION_UP:
??????????? //when you action up, it will do these:
??????????? //1. roll back util header topPadding is 0
??????????? //2. hide the header by setSelection(1)
??????????? if (mPullRefreshState == OVER_PULL_REFRESH || mPullRefreshState == ENTER_PULL_REFRESH) {
??????????????? new Thread() {
??????????????????? public void run() {
??????????????????????? Message msg;
??????????????????????? while(mHeaderLinearLayout.getPaddingTop() > 1) {
??????????????????????????? msg = mHandler.obtainMessage();
??????????????????????????? msg.what = REFRESH_BACKING;
??????????????????????????? mHandler.sendMessage(msg);
??????????????????????????? try {
??????????????????????????????? sleep(5);//慢一點反彈，別一下子就彈回去了
??????????????????????????? } catch (InterruptedException e) {
??????????????????????????????? e.printStackTrace();
??????????????????????????? }
??????????????????????? }
??????????????????????? msg = mHandler.obtainMessage();
?????????????????? ?????if (mPullRefreshState == OVER_PULL_REFRESH) {
??????????????????????????? msg.what = REFRESH_BACED;//加載數(shù)據(jù)完成，結(jié)束返回
??????????????????????? } else {
??????????????????????????? msg.what = REFRESH_RETURN;//未達到刷新界限，直接返回
??????????????????????? }
????????? ??????????????mHandler.sendMessage(msg);
??????????????????? };
??????????????? }.start();
??????????? }
??????????? break;
??? }
??? return super.onTouchEvent(ev);
}
?
private Handler mHandler = new Handler(){
??? @Override
??? public void handleMessage(Message msg) {
??????? switch (msg.what) {
??????? case REFRESH_BACKING:
??????????? mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
??????????????????? (int) (mHeaderLinearLayout.getPaddingTop()*0.75f),
??????????????????? mHeaderLinearLayout.getPaddingRight(),
??????????????????? mHeaderLinearLayout.getPaddingBottom());
??????????? break;
??????? case REFRESH_BACED:
??????????? mHeaderTextView.setText("正在加載...");
??????????? mHeaderProgressBar.setVisibility(View.VISIBLE);
??????????? mHeaderPullDownImageView.setVisibility(View.GONE);
??????????? mHeaderReleaseDownImageView.setVisibility(View.GONE);
??????????? mPullRefreshState = EXIT_PULL_REFRESH;
??????????? new Thread() {
??????????????? public void run() {
??????????????????? sleep(2000);//處理后臺加載數(shù)據(jù)
??????????????????? Message msg = mHandler.obtainMessage();
??????????????????? msg.what = REFRESH_DONE;
??????????????????? //通知主線程加載數(shù)據(jù)完成
??????????????????? mHandler.sendMessage(msg);
??????????????? };
??????????? }.start();
?????????? ?break;
??????? case REFRESH_RETURN:
??????????? //未達到刷新界限，返回
??????????? mHeaderTextView.setText("下拉刷新");
??????????? mHeaderProgressBar.setVisibility(View.INVISIBLE);
??????????? mHeaderPullDownImageView.setVisibility(View.VISIBLE);
??????????? mHeaderReleaseDownImageView.setVisibility(View.GONE);
??????????? mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
??????????????????? 0,
??????????????????? mHeaderLinearLayout.getPaddingRight(),
??????????????????? mHeaderLinearLayout.getPaddingBottom());
??????????? mPullRefreshState = NONE_PULL_REFRESH;
??????????? setSelection(1);
??????????? break;
??????? case REFRESH_DONE:
??????????? //刷新結(jié)束后，恢復(fù)原始默認狀態(tài)
??????????? mHeaderTextView.setText("下拉刷新");
??????????? mHeaderProgressBar.setVisibility(View.INVISIBLE);
??????????? mHeaderPullDownImageView.setVisibility(View.VISIBLE);
??????????? mHeaderReleaseDownImageView.setVisibility(View.GONE);
??????????? mHeaderUpdateText.setText(getContext().getString(R.string.app_list_header_refresh_last_update,
??????????????????? mSimpleDateFormat.format(new Date())));
??????????? mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
??????????????????? 0,
??????????????????? mHeaderLinearLayout.getPaddingRight(),
??????????????????? mHeaderLinearLayout.getPaddingBottom());
??????????? mPullRefreshState = NONE_PULL_REFRESH;
??????????? setSelection(1);
??????????? break;
??????? default:
??????????? break;
??????? }
??? }
};
? 為了一下子看的明確，我把效果中的數(shù)據(jù)處理代碼也貼出來了。
七、切入數(shù)據(jù)加載過程
上面數(shù)據(jù)后臺處理我們用sleep(2000)來處理，實際處理中，作為公共組件，我們也不好把具體代碼直接寫在這里，我們需要一個更靈活的分離:
(1)定義接口
(2)注入接口
//定義接口
public interface RefreshListener {
??? Object refreshing();??????????????? //加載數(shù)據(jù)
??? void refreshed(Object obj);??? //外部可擴展加載完成后的操作
}
?
//注入接口
private Object mRefreshObject = null; //傳值
private RefreshListener mRefreshListener = null;
public void setOnRefreshListener(RefreshListener refreshListener) {
??? this.mRefreshListener = refreshListener;
}?
//我們需要重寫上面的mHandler如下代碼
case REFRESH_BACED:
??? ... ...
??? new Thread() {
??????? public void run() {
??????????? if (mRefreshListener != null) {
??????????????? mRefreshObject = mRefreshListener.refreshing();
??? ????????}
??????????? Message msg = mHandler.obtainMessage();
??????????? msg.what = REFRESH_DONE;
??????????? mHandler.sendMessage(msg);
??????? };
??? }.start();
??? break;
case REFRESH_DONE:
??? ... ...
??? mPullRefreshState = NONE_PULL_REFRESH;
??? setSelection(1);
??? if (mRefreshListener != null) {
??????? mRefreshListener.refreshed(mRefreshObject);
??? }
??? break;
??? 在其他地方我們就可以不修改這個listview組件的代碼，使用如下：
public xxx implements RefreshListener{?
@Override
??? protected void onCreate(Bundle savedInstanceState) {
??????? super.onCreate(savedInstanceState);
????? ??//類似如下
??????? ((RefreshListView) listView).setOnRefreshListener(this);
??? }
?
??? @Override
??? public Object refreshing() {
??????? String result = null;
??????? //result = FileUtils.readTextFile(file);
??????? return result;
??? }
?
??? @Override
?? ?public void refreshed(Object obj) {
??????? if (obj != null) {
?????????? //擴展操作
??????? }
??? };
}
很方便了。
八、?擴展"更多"功能
下拉刷新之外，我們也可以通過相同方法使用FooterView切入底部"更多"過程，這里我就不詳細說明了
九、源碼
上面的每段代碼都看做是"零部件"，需要組合一下。
因為我們上面實現(xiàn)了下拉刷新，還增加了"更多"功能，我們直接命名這個類為RefreshListView吧：
package com.tianxia.lib.baseworld.widget;
?
import java.text.SimpleDateFormat;
import java.util.Date;
?
import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
?
import com.tianxia.lib.baseworld.R;
?
/**
?* 下拉刷新，底部更多
?*/
public class RefreshListView extends ListView implements OnScrollListener{
?
??? private float mDownY;
??? private float mMoveY;
?
??? private int mHeaderHeight;?
??? private int mCurrentScrollState;
?
??? private final static int NONE_PULL_REFRESH = 0;??? //正常狀態(tài)
??? private final static int ENTER_PULL_REFRESH = 1;?? //進入下拉刷新狀態(tài)
??? private final static int OVER_PULL_REFRESH = 2;??? //進入松手刷新狀態(tài)
??? private final static int EXIT_PULL_REFRESH = 3;??? //松手后反彈和加載狀態(tài)
??? private int mPullRefreshState = 0;???????????????? //記錄刷新狀態(tài)
?
??? private final static int REFRESH_BACKING = 0;????? //反彈中
??? private final static int REFRESH_BACED = 1;??????? //達到刷新界限，反彈結(jié)束后
??? private final static int REFRESH_RETURN = 2;?????? //沒有達到刷新界限，返回
??? private final static int REFRESH_DONE = 3;???????? //加載數(shù)據(jù)結(jié)束
?
??? private LinearLayout mHeaderLinearLayout = null;
??? private LinearLayout mFooterLinearLayout = null;
??? private TextView mHeaderTextView = null;
??? private TextView mHeaderUpdateText = null;
??? private ImageView mHeaderPullDownImageView = null;
??? private ImageView mHeaderReleaseDownImageView = null;
??? private ProgressBar mHeaderProgressBar = null;
??? private TextView mFooterTextView = null;
??? private ProgressBar mFooterProgressBar = null;
?
??? private SimpleDateFormat mSimpleDateFormat;
?
??? private Object mRefreshObject = null;
??? private RefreshListener mRefreshListener = null;
??? public void setOnRefreshListener(RefreshListener refreshListener) {
??????? this.mRefreshListener = refreshListener;
??? }
?
??? public RefreshListView(Context context) {
??????? this(context, null);
??? }
?
??? public RefreshListView(Context context, AttributeSet attrs) {
??????? super(context, attrs);
??????? init(context);
??? }
?
??? void init(final Context context) {
??????? mHeaderLinearLayout = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.refresh_list_header, null);
??????? addHeaderView(mHeaderLinearLayout);
??????? mHeaderTextView = (TextView) findViewById(R.id.refresh_list_header_text);
???? ???mHeaderUpdateText = (TextView) findViewById(R.id.refresh_list_header_last_update);
??????? mHeaderPullDownImageView = (ImageView) findViewById(R.id.refresh_list_header_pull_down);
??????? mHeaderReleaseDownImageView = (ImageView) findViewById(R.id.refresh_list_header_release_up);
??????? mHeaderProgressBar = (ProgressBar) findViewById(R.id.refresh_list_header_progressbar);
?
??????? mFooterLinearLayout = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.refresh_list_footer, null);
??????? addFooterView(mFooterLinearLayout);
??????? mFooterProgressBar = (ProgressBar) findViewById(R.id.refresh_list_footer_progressbar);
??????? mFooterTextView = (TextView) mFooterLinearLayout.findViewById(R.id.refresh_list_footer_text);
??????? mFooterLinearLayout.setOnClickListener(new OnClickListener() {
??????????? @Override
??????????? public void onClick(View v) {
??????????????? if (context.getString(R.string.app_list_footer_more).equals(mFooterTextView.getText())) {
??????????????????? mFooterTextView.setText(R.string.app_list_footer_loading);
??????????????????? mFooterProgressBar.setVisibility(View.VISIBLE);
??????????????????? if (mRefreshListener != null) {
??????????????????????? mRefreshListener.more();
??????????????????? }
??????????????? }
????????? ??}
??????? });
?
??????? setSelection(1);
??????? setOnScrollListener(this);
??????? measureView(mHeaderLinearLayout);
??????? mHeaderHeight = mHeaderLinearLayout.getMeasuredHeight();
?
??????? mSimpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm");
??????? mHeaderUpdateText.setText(context.getString(R.string.app_list_header_refresh_last_update, mSimpleDateFormat.format(new Date())));
??? }
?
??? @Override
??? public boolean onTouchEvent(MotionEvent ev) {
??????? switch (ev.getAction()) {
?????????? ?case MotionEvent.ACTION_DOWN:
??????????????? mDownY = ev.getY();
??????????????? break;
??????????? case MotionEvent.ACTION_MOVE:
??????????????? mMoveY = ev.getY();
??????????????? if (mPullRefreshState == OVER_PULL_REFRESH) {
??????????????????? mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
??????????????????????????? (int)((mMoveY - mDownY)/3),
??????????????????????????? mHeaderLinearLayout.getPaddingRight(),
??????????????????????????? mHeaderLinearLayout.getPaddingBottom());
??????????????? }
??????????????? break;
??????????? case MotionEvent.ACTION_UP:
??????????????? //when you action up, it will do these:
??????????????? //1. roll back util header topPadding is 0
??????????????? //2. hide the header by setSelection(1)
???? ???????????if (mPullRefreshState == OVER_PULL_REFRESH || mPullRefreshState == ENTER_PULL_REFRESH) {
??????????????????? new Thread() {
??????????????????????? public void run() {
??????????????????????????? Message msg;
??????????????????????????? while(mHeaderLinearLayout.getPaddingTop() > 1) {
??????????????????????????????? msg = mHandler.obtainMessage();
??????????????????????????????? msg.what = REFRESH_BACKING;
??????????????????????????????? mHandler.sendMessage(msg);
??????????????????????????????? try {
??????????????????????????????????? sleep(5);
??????????????????????????????? } catch (InterruptedException e) {
??????????????????????????????????? e.printStackTrace();
??????????????????????????????? }
??????????????????????????? }
??????????????? ????????????msg = mHandler.obtainMessage();
??????????????????????????? if (mPullRefreshState == OVER_PULL_REFRESH) {
??????????????????????????????? msg.what = REFRESH_BACED;
??????????????????????????? } else {
??????????????????????????????? msg.what = REFRESH_RETURN;
??????????????????????????? }
??????????????????????????? mHandler.sendMessage(msg);
??????????????????????? };
??????????????????? }.start();
??????????????? }
??????????????? break;
??????? }
??????? return super.onTouchEvent(ev);
??? }
?
??? @Override
??? public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
??????? if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
??????????????? && firstVisibleItem == 0
??????????????? && (mHeaderLinearLayout.getBottom() >= 0 && mHeaderLinearLayout.getBottom() < mHeaderHeight)) {
??????????? //進入且僅進入下拉刷新狀態(tài)
??????????? if (mPullRefreshState == NONE_PULL_REFRESH) {
??????????????? mPullRefreshState = ENTER_PULL_REFRESH;
??????????? }
??????? } else if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
??????????????? && firstVisibleItem == 0
??????????????? && (mHeaderLinearLayout.getBottom() >= mHeaderHeight)) {
??????????? //下拉達到界限，進入松手刷新狀態(tài)
??????????? if (mPullRefreshState == ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
??????????????? mPullRefreshState = OVER_PULL_REFRESH;
??????????????? mDownY = mMoveY; //為下拉1/3折扣效果記錄開始位置
??????????????? mHeaderTextView.setText("松手刷新");//顯示松手刷新
??????????????? mHeaderPullDownImageView.setVisibility(View.GONE);//隱藏"下拉刷新"
??????????????? mHeaderReleaseDownImageView.setVisibility(View.VISIBLE);//顯示向上的箭頭
??????????? }
??????? } else if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL && firstVisibleItem != 0) {
??????????? //不刷新了
??????????? if (mPullRefreshState == ENTER_PULL_REFRESH) {
??????????????? mPullRefreshState = NONE_PULL_REFRESH;
??????????? }
??????? } else if (mCurrentScrollState == SCROLL_STATE_FLING && firstVisibleItem == 0) {
??????????? //飛滑狀態(tài)，不能顯示出header，也不能影響正常的飛滑
??????????? //只在正常情況下才糾正位置
??????????? if (mPullRefreshState == NONE_PULL_REFRESH) {
??????????????? setSelection(1);
??????????? }
??????? }
??? }
?
??? @Override
??? public void onScrollStateChanged(AbsListView view, int scrollState) {
??????? mCurrentScrollState = scrollState;
??? }
?
??? @Override
??? public void setAdapter(ListAdapter adapter) {
??????? super.setAdapter(adapter);
??????? setSelection(1);
??? }
?
??? private void measureView(View child) {
??????? ViewGroup.LayoutParams p = child.getLayoutParams();
?????? ?if (p == null) {
??????????? p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,
??????????????????? ViewGroup.LayoutParams.WRAP_CONTENT);
??????? }
?
??????? int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);
??????? int lpHeight = p.height;
??????? int childHeightSpec;
??????? if (lpHeight > 0) {
??????????? childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,
??????????????????? MeasureSpec.EXACTLY);
??????? } else {
??????????? childHeightSpec = MeasureSpec.makeMeasureSpec(0,
??????????????????? MeasureSpec.UNSPECIFIED);
??????? }
??????? child.measure(childWidthSpec, childHeightSpec);
??? }
?
??? private Handler mHandler = new Handler(){
??????? @Override
??????? public void handleMessage(Message msg) {
?????????? ?switch (msg.what) {
??????????? case REFRESH_BACKING:
??????????????? mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
??????????????????????? (int) (mHeaderLinearLayout.getPaddingTop()*0.75f),
??????????????????????? mHeaderLinearLayout.getPaddingRight(),
??????????????????????? mHeaderLinearLayout.getPaddingBottom());
??????????????? break;
??????????? case REFRESH_BACED:
??????????????? mHeaderTextView.setText("正在加載...");
??????????????? mHeaderProgressBar.setVisibility(View.VISIBLE);
??????????????? mHeaderPullDownImageView.setVisibility(View.GONE);
??????????????? mHeaderReleaseDownImageView.setVisibility(View.GONE);
??????????????? mPullRefreshState = EXIT_PULL_REFRESH;
??????????????? new Thread() {
??????????????????? public void run() {
??????????????????????? if (mRefreshListener != null) {
??????????????????????????? mRefreshObject = mRefreshListener.refreshing();
??????????????????????? }
??????????????????????? Message msg = mHandler.obtainMessage();
??????????????????????? msg.what = REFRESH_DONE;
??????????????????????? mHandler.sendMessage(msg);
??????????????????? };
??????????????? }.start();
??????????????? break;
??????????? case REFRESH_RETURN:
??????????????? mHeaderTextView.setText("下拉刷新");
??????????????? mHeaderProgressBar.setVisibility(View.INVISIBLE);
??????????????? mHeaderPullDownImageView.setVisibility(View.VISIBLE);
??????????????? mHeaderReleaseDownImageView.setVisibility(View.GONE);
??????????????? mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
??????????????????????? 0,
??????????????????????? mHeaderLinearLayout.getPaddingRight(),
??????????????????????? mHeaderLinearLayout.getPaddingBottom());
??????????????? mPullRefreshState = NONE_PULL_REFRESH;
??????????????? setSelection(1);
??? ????????????break;
??????????? case REFRESH_DONE:
??????????????? mHeaderTextView.setText("下拉刷新");
??????????????? mHeaderProgressBar.setVisibility(View.INVISIBLE);
??????????????? mHeaderPullDownImageView.setVisibility(View.VISIBLE);
??????????????? mHeaderReleaseDownImageView.setVisibility(View.GONE);
??????????????? mHeaderUpdateText.setText(getContext().getString(R.string.app_list_header_refresh_last_update,
??????????????????????? mSimpleDateFormat.format(new Date())));
??????????????? mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
??????????????????????? 0,
??????????????????????? mHeaderLinearLayout.getPaddingRight(),
??????????????????????? mHeaderLinearLayout.getPaddingBottom());
??????????????? mPullRefreshState = NONE_PULL_REFRESH;
??????????????? setSelection(1);
??????????????? if (mRefreshListener != null) {
??????????????????? mRefreshListener.refreshed(mRefreshObject);
??????????????? }
??????????????? break;
??????????? default:
??????????????? break;
??????????? }
???? ???}
??? };
??? public interface RefreshListener {
??????? Object refreshing();
??????? void refreshed(Object obj);
??????? void more();
??? }
?
??? public void finishFootView() {
??????? mFooterProgressBar.setVisibility(View.GONE);
??????? mFooterTextView.setText(R.string.app_list_footer_more);
??? }
?
??? public void addFootView() {
??????? if (getFooterViewsCount() == 0) {
??????????? addFooterView(mFooterLinearLayout);
??????? }
??? }
?
??? public void removeFootView() {
??????? removeFooterView(mFooterLinearLayout);
??? }
}
11.小結(jié)
這個只是一個原型，無論代碼風(fēng)格和邏輯處理，我覺得還有改進的空間，我會在后續(xù)逐漸改善的。
? ? 以下是例子效果
? ??https://github.com/openproject/world/blob/master/baseworld/src/com/tianxia/lib/baseworld/widget/RefreshListView.java
? ??https://github.com/openproject/world/blob/master/healthworld/src/com/tianxia/app/healthworld/infomation/InfomationTabActivity.java
? ? 期待有建設(shè)性的意見改善這個實現(xiàn)。
?
?
轉(zhuǎn)載于:https://www.cnblogs.com/zhangping/p/3514030.html
總結(jié)
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