你真的会用AsyncTask吗?(一) 你真的会用AsyncTask吗?(一)

【你真的会用AsyncTask吗?(一)】2019独角兽企业重金招聘Python工程师标准>>>
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一个典型AsyncTask的。

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 {@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(); } }

转载于:https://my.oschina.net/dingbuoyi/blog/61626