异步任务还可以取消，在Activity或者Fragment销毁等状态后，耗时任务便需要停止。
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public class DialogTestActivity extends
Activity { private
Button button1; private
Task task; @Override public
void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); this.button1 = (Button) findViewById(R.id.button1); button1.setOnClickListener(new
View.OnClickListener() { @Override public
void onClick(View v) { if
(task != null
&& task.getStatus() == AsyncTask.Status.RUNNING) { Toast.makeText(DialogTestActivity.this, "task 正在运行", Toast.LENGTH_SHORT).show(); //task.cancel(true); // 如果Task还在运行，则先取消它 } else
{ task = new
Task(); task.execute(); } } }); } @Override protected
void onDestroy() { super.onDestroy(); // 用户按回退的时候要取消正在进行的任务 task.cancel(true); } private
class Task extends
AsyncTask<Void, Void, Void> { @Override protected
void onPreExecute() { super.onPreExecute(); Toast.makeText(DialogTestActivity.this, "task 开始运行", Toast.LENGTH_SHORT).show(); } @Override protected
Void doInBackground(Void... params) { try
{ // 模拟耗时操作 比如网络连接等 Thread.sleep(5000); } catch
(InterruptedException e) { e.printStackTrace(); } // 判断如果task已经cancel就没有必须继续进行下面的操作 if
(!isCancelled()) { System.out.println("task 如果被cancel,就不会显示"); } return
null; } @Override protected
void onPostExecute(Void result) { super.onPostExecute(result); Toast.makeText(DialogTestActivity.this, "task 完成", Toast.LENGTH_SHORT).show(); // 所有调用当前context的对象要注意判断activity是否还存在 // 典型的比如弹窗 if
(!isFinishing()) { try
{ createAlertDialog().show(); } catch
(Exception e) { } } } @Override protected
void onCancelled() { super.onCancelled(); System.out.println("task 取消"); } } private
AlertDialog createAlertDialog() { return
new AlertDialog.Builder(DialogTestActivity.this).setTitle("fadfasdf") .setPositiveButton("OK", new
DialogInterface.OnClickListener() { public
void onClick(DialogInterface dialog, int
whichButton) { } }).setNegativeButton("Cancel", new
DialogInterface.OnClickListener() { public
void onClick(DialogInterface dialog, int
whichButton) { } }).create(); }} |
超时处理
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import java.util.Timer;import java.util.TimerTask;import android.app.Activity;import android.os.AsyncTask;import android.os.Bundle;import android.widget.Toast;public class TimeoutTestActivity extends
Activity { private
final static int TIME_OUT = 3
* 1000; private
final static int SLEEP_TIME = 2
* 1000; @Override public
void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //new TimeOutTask().execute(); new
CancelSelfWhenTimeOutTask().execute(); } private
class CancelSelfWhenTimeOutTask extends
AsyncTask<Void, Void, Void> { private
boolean done = false; @Override protected
Void doInBackground(Void... params) { cancelSelfWhenTimeOut(); sleep(); return
null; } @Override protected
void onPostExecute(Void result) { super.onPostExecute(result); Toast.makeText(TimeoutTestActivity.this, "任务完成", Toast.LENGTH_SHORT) .show(); } private
void cancelSelfWhenTimeOut() { new
Timer().schedule(new
TimerTask() { @Override public
void run() { if
(!done) { CancelSelfWhenTimeOutTask.this.cancel(true); } } }, TIME_OUT); } private
void sleep() { try
{ Thread.sleep(SLEEP_TIME); done = true; } catch
(InterruptedException e) { } } } private
class TimeOutTask extends
AsyncTask<Void, Void, Void> { private
boolean done = false; private
boolean isTimeOut = false; @Override protected
Void doInBackground(Void... params) { try
{ throwTimeOutException(); } catch
(Exception e) { isTimeOut = true; } sleep(); return
null; } @Override protected
void onPostExecute(Void result) { super.onPostExecute(result); if
(isTimeOut) { Toast.makeText(TimeoutTestActivity.this, "任务超时", Toast.LENGTH_SHORT).show(); } else
{ Toast.makeText(TimeoutTestActivity.this, "任务完成", Toast.LENGTH_SHORT).show(); } } private
void throwTimeOutException() { new
Timer().schedule(new
TimerTask() { @Override public
void run() { if
(!done) { isTimeOut = true; } } }, TIME_OUT); } private
void sleep() { try
{ Thread.sleep(SLEEP_TIME); done = true; } catch
(InterruptedException e) { } } }} |
原文：http://www.cnblogs.com/weixiao870428/p/3543871.html