一个典型AsyncTask的。
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public class DialogTestActivity extends Activity { |
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private Button button1; |
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private Task task; |
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@Override |
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public void onCreate(Bundle savedInstanceState) { |
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super.onCreate(savedInstanceState); |
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setContentView(R.layout.main); |
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this.button1 = (Button) findViewById(R.id.button1); |
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button1.setOnClickListener(new View.OnClickListener() { |
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@Override |
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public void onClick(View v) { |
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if (task != null && task.getStatus() == AsyncTask.Status.RUNNING) { |
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Toast.makeText(DialogTestActivity.this, "task 正在运行", Toast.LENGTH_SHORT).show(); |
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//task.cancel(true); // 如果Task还在运行，则先取消它 |
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} else { |
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task = new Task(); |
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task.execute(); |
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} |
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} |
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}); |
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} |
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@Override |
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protected void onDestroy() { |
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super.onDestroy(); |
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// 用户按回退的时候要取消正在进行的任务 |
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task.cancel(true); |
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} |
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private class Task extends AsyncTask<Void, Void, Void> { |
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|
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@Override |
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protected void onPreExecute() { |
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super.onPreExecute(); |
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Toast.makeText(DialogTestActivity.this, "task 开始运行", Toast.LENGTH_SHORT).show(); |
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} |
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|
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@Override |
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protected Void doInBackground(Void... params) { |
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try { |
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// 模拟耗时操作 比如网络连接等 |
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Thread.sleep(5000); |
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} catch (InterruptedException e) { |
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e.printStackTrace(); |
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} |
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// 判断如果task已经cancel就没有必须继续进行下面的操作 |
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if (!isCancelled()) { |
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System.out.println("task 如果被cancel,就不会显示"); |
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} |
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return null; |
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} |
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@Override |
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protected void onPostExecute(Void result) { |
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super.onPostExecute(result); |
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Toast.makeText(DialogTestActivity.this, "task 完成", Toast.LENGTH_SHORT).show(); |
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// 所有调用当前context的对象要注意判断activity是否还存在 |
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// 典型的比如弹窗 |
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if (!isFinishing()) { |
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try { |
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createAlertDialog().show(); |
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} catch (Exception e) { |
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} |
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} |
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} |
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@Override |
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protected void onCancelled() { |
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super.onCancelled(); |
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System.out.println("task 取消"); |
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} |
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} |
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private AlertDialog createAlertDialog() { |
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return new AlertDialog.Builder(DialogTestActivity.this).setTitle("fadfasdf") |
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.setPositiveButton("OK", new DialogInterface.OnClickListener() { |
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public void onClick(DialogInterface dialog, int whichButton) { |
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} |
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}).setNegativeButton("Cancel", new DialogInterface.OnClickListener() { |
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public void onClick(DialogInterface dialog, int whichButton) { |
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} |
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}).create(); |
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} |
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} |