@Override
public void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); 
 setContentView(R.layout.main); 
} 
protected void dialog() { 
 AlertDialog.Builder builder = new Builder(HanderTestActivty.this); 
 builder.setMessage("确定要退出吗?"); 
 builder.setTitle("提示"); 
 builder.setPositiveButton("确认", 
  new android.content.DialogInterface.OnClickListener() { 
   @Override
   public void onClick(DialogInterface dialog, int which) { 
   dialog.dismiss(); 
   HanderTestActivty.this.finish(); 
   } 
  }); 
 builder.setNegativeButton("取消", 
  new android.content.DialogInterface.OnClickListener() { 
   @Override
   public void onClick(DialogInterface dialog, int which) { 
   dialog.dismiss(); 
   } 
  }); 
 builder.create().show(); 
} 
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) { 
 if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) { 
  dialog(); 
  return false; 
 } 
 return false; 
}