广播退出多个Activity

public class BaseActivity extends Activity {
 protected BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {

  @Override
  public void onReceive(Context context, Intent intent) {
   finish();
  }
 };
 
 @Override
 public void onResume() {
  super.onResume();
  // 在当前的activity中注册广播
  IntentFilter filter = new IntentFilter();
  filter.addAction("ExitApp");
  this.registerReceiver(this.broadcastReceiver, filter);
 }
 
 @Override
 protected void onDestroy() {
  // TODO Auto-generated method stub
  super.onDestroy();
  this.unregisterReceiver(this.broadcastReceiver);  
 }
}

public class Activity1 extends BaseActivity {
 private Button btn1;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  // TODO Auto-generated method stub
  super.onCreate(savedInstanceState);
  setContentView(R.layout.a1);
 
  btn1 = (Button)findViewById(R.id.btn1);
        btn1.setOnClickListener(new View.OnClickListener() {
   
   @Override
   public void onClick(View v) {
    Intent i = new Intent(Activity1.this, Activity2.class);
    startActivity(i);
   }
  });
 }
 /**
  * 捕获手机物理菜单键
  */
 private long exitTime = 0;

 @Override
 public boolean onKeyDown(int keyCode, KeyEvent event) {
  if(keyCode == KeyEvent.KEYCODE_BACK){//&& event.getAction() == KeyEvent.ACTION_DOWN

      if((System.currentTimeMillis()-exitTime) > 2000){
          Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();

          exitTime = System.currentTimeMillis();
   } else {
    myExit();
   }
      return true;
     }
  return super.onKeyDown(keyCode, event);
 }
 
 protected void myExit() {
  Intent intent = new Intent();
  intent.setAction("ExitApp");
  this.sendBroadcast(intent);
  super.finish();
 }
}