AsyncTask的简单例子

package com.archer.rainbow.AsyncTaskDemo; import android.app.Activity; import android.app.AlertDialog; import android.content.DialogInterface; import android.os.AsyncTask; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.ProgressBar; import android.widget.TextView; public class AsyncTaskDemoActivity extends Activity { private Button writeLog; private TextView log; // 滚动条 private ProgressBar dlProgress; private Button positiveBtn; private Button negativeBtn; private MyAsyncTask mat; private boolean taskOver = false; private OnClickListener btnListener = new OnClickListener() { @Override public void onClick(View v) { mat = new MyAsyncTask(); // 从download.xml加载画面 LayoutInflater factory = LayoutInflater .from(AsyncTaskDemoActivity.this); final View downloadView = factory.inflate(R.layout.download, null); log = (TextView) downloadView.findViewById(R.id.log); dlProgress = (ProgressBar) downloadView .findViewById(R.id.dlProgress); AlertDialog dialog = new AlertDialog.Builder( AsyncTaskDemoActivity.this) .setTitle("DownLoad Info") .setView(downloadView) .setPositiveButton("OK", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { } }) .setNegativeButton("Cancel", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int whichButton) { if (!taskOver) { mat.cancel(true); } ((AlertDialog)dialog).show(); } }).create(); dialog.show(); // 此处获取 Button 的代码必须写在 show() 方法之后，否则会报 空指针 异常， // 这可能是系统Bug，请参见 // http://code.google.com/p/android/issues/detail?id=6360 positiveBtn = dialog.getButton(AlertDialog.BUTTON1); positiveBtn.setEnabled(false); negativeBtn = dialog.getButton(AlertDialog.BUTTON2); mat.execute(10); } }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); writeLog = (Button) findViewById(R.id.writeLog); writeLog.setOnClickListener(btnListener); } private class MyAsyncTask extends AsyncTask<Integer, Integer, Boolean> { @Override protected void onPreExecute() { super.onPreExecute(); updateLog("AsyncTask started"); } @Override protected Boolean doInBackground(Integer... params) { int max = params[0]; for (int i = 0; i < max; i++) { try { publishProgress((int) (((i + 1.0) / max) * 100)); // 每隔一秒钟执行一次，模拟下载文件 Thread.sleep(1000); } catch (InterruptedException e) { return false; } } return true; } @Override protected void onProgressUpdate(Integer... values) { super.onProgressUpdate(values); dlProgress.setProgress(values[0]); updateLog(log.getText() + "."); } @Override protected void onPostExecute(Boolean result) { super.onPostExecute(result); taskOver = true; positiveBtn.setEnabled(true); negativeBtn.setEnabled(false); if (result) { updateLog("AsyncTask ended. Download successfully"); } else { updateLog("AsyncTask ended. Download failed"); } } @Override protected void onCancelled() { super.onCancelled(); taskOver = true; positiveBtn.setEnabled(true); negativeBtn.setEnabled(false); updateLog("AsyncTask cancelled"); } } private void updateLog(String text) { log.setText(text); } }