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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@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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@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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} |