is your activity running?

[wymaweiyue]

程序报如下异常：
android.view.WindowManager$BadTokenException: Unable to add window -- token android.os.BinderProxy@41a068c8 is not valid; is your activity running?

程序结构如下：

class ParentActivity extends Activity{
    .......
    private class ReadThread extends Thread {
		@Override
		public void run() {
			super.run();
			while (!isInterrupted()) {
				......
				try {
					onDataReceived(buffer, size);
				} catch (IOException e) {
					e.printStackTrace();
					return;
				}
			}
		}
	}
    
    protected abstract void onDataReceived(final byte[] buffer, final int size);

    protected void DisplayError(int resourceId, Activity activity) {
		AlertDialog.Builder b = new AlertDialog.Builder(activity);
		b.setTitle("Error");
		b.setMessage(resourceId);
		b.setPositiveButton("OK", new OnClickListener() {
			public void onClick(DialogInterface dialog, int which) {
				//SerialPortActivity.this.finish();
			}
		});
		b.show();
	}
}

class SubA extends ParentActivity {
    @Override
    protected void onDataReceived(byte[] buffer, int size) {
        ....
        Message msg = mHandler.obtainMessage();
		msg.what = 1;
		mHandler.sendMessage(msg);
	}

	private Handler mHandler = new Handler() {
		@Override
		public synchronized void handleMessage(Message msg) {
			switch (msg.what) {
			case 1: {
				DisplayError(R.string.error_op, TagFunctionActivity.this);
				break;
			}
			case 2: {
				DisplayError(R.string.success_op, TagFunctionActivity.this);
				break;
			}
		}
	}
	};
}

class SubB extends ParentActivity {
    @Override
    protected void onDataReceived(byte[] buffer, int size) {
        ....
        Message msg = mHandler.obtainMessage();
		msg.what = 1;
		mHandler.sendMessage(msg);
	}

	private Handler mHandler = new Handler() {
		@Override
		public synchronized void handleMessage(Message msg) {
			switch (msg.what) {
			case 1: {
				......
			}
		}
	}
	};
}

操作流程如下：
1、SubA有个按钮，点击后启动父类中的线程ReadThread ，然后再回调本类中的onDataReceived()方法做一些事情。
2、SubB中也有个按钮，点击后启动父类中的线程ReadThread ，然后再回调本类中的onDataReceived()方法做一些事情。

问题如下：
首先进入SubA，点击按钮，执行到SubA的onDataReceived()方法，并通过Handler弹出提示消息(调用DisplayError(R.string.error_op, SubA.this)方法)。然后返回主界面，再进入SubB界面。
进入SubB界面，点击按钮，此时会发现时SubB的onDataReceived()方法和SubA的onDataReceived()都会执行，此时SubA中再去通过Handler弹出提示消息框就报错了。

如果SubA中不弹出消息提示框(不调用DisplayError(R.string.error_op, SubA.this)方法)，则在SubB界面中不会报错。

本人菜鸟，百度也没能百度出个名目来，望各路大侠指教。

[Hare_]

显示对话框之前检测,对话框依附的Activity是否已经finish