Android4.0 以后不允許在主線程進行網絡連接，否則會出現?android.os.NetworkOnMainThreadException。因此，必須另起一個線程進行網絡連接方面的操作。

package com.lujinhong.irmcdc.dao;import java.io.IOException; import java.net.Socket; import java.net.UnknownHostException; import java.util.Scanner;public class ResourceDao {String returnLine = "hi";public String getAllContentByName() {Runnable r = new NetWorkHandler();Thread thread = new Thread(r);thread.start();try {Thread.sleep(15000);} catch (InterruptedException e) {e.printStackTrace();}return returnLine;}private class NetWorkHandler implements Runnable {String line = "line";Socket socket = null;Scanner scanner = null;@Overridepublic void run() {try {socket = new Socket("time-A.timefreq.bldrdoc.gov", 13);scanner = new Scanner(socket.getInputStream());while (scanner.hasNextLine()) {line = scanner.nextLine();returnLine += line;}} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {scanner.close();try {socket.close();} catch (IOException e) {e.printStackTrace();}}}} }

1、由于網絡連接需要一定時間，為了在主界面上進行網絡信息的展現，暫時用sleep()方法簡單實現，使主線程等待網絡信息讀取完成。

Thread.sleep(5000);

修改以下 問題，使用wai()及nofifyAll處理。

package com.ljh.irmcdc.dao;import java.io.IOException; import java.net.Socket; import java.net.UnknownHostException; import java.util.Scanner;public class ResourceDao {String returnLine = "";public String getAllContentByName() {Runnable r = new NetWorkHandler();Thread thread = new Thread(r);thread.start();synchronized (this) {try {wait(20000);} catch (InterruptedException e) {e.printStackTrace(); } }return returnLine;}private class NetWorkHandler implements Runnable {String line = "line";Socket socket = null;Scanner scanner = null;@Overridepublic void run() {try {// socket = new Socket("time-A.timefreq.bldrdoc.gov", 13);socket = new Socket("192.168.136.44", 8179);scanner = new Scanner(socket.getInputStream());returnLine = "";while (scanner.hasNextLine()) {line = scanner.nextLine();returnLine += line;} //不要直接使用this，否則nofity的對象不是上面wait所鎖定的對象。synchronized (ResourceDao.this) {ResourceDao.this.notifyAll();}} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {scanner.close();try {socket.close();} catch (IOException e) {e.printStackTrace();}}}} }
注意：

1、在內部類中引用外部類對象的方法：

ResourceDao.this.notifyAll();
2、wai()及nofity()必須放在synchronized塊里面。

尤其注意在內部類中notify()外部類對象時，不要使用this，而應該是上述所表。

總結

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