如何在Android的后台线程中更新UI元素？

// 在主线程中创建Handler
Handler handler = new Handler(Looper.getMainLooper()) {
    @Override
    public void handleMessage(Message msg) {
        // 更新UI
        TextView textView = findViewById(R.id.textView);
        textView.setText((String) msg.obj);
    }
};

// 在后台线程中发送消息
new Thread(new Runnable() {
    @Override
    public void run() {
        try {
            Thread.sleep(2000); // 模拟耗时操作
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Message message = handler.obtainMessage();
        message.obj = "更新后的文本";
        handler.sendMessage(message);
    }
}).start();

new Thread(new Runnable() {
    @Override
    public void run() {
        try {
            Thread.sleep(2000); // 模拟耗时操作
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                TextView textView = findViewById(R.id.textView);
                textView.setText("更新后的文本");
            }
        });
    }
}).start();

class MyAsyncTask extends AsyncTask<Void, Void, String> {
    @Override
    protected String doInBackground(Void... voids) {
        try {
            Thread.sleep(2000); // 模拟耗时操作
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "更新后的文本";
    }

    @Override
    protected void onPostExecute(String result) {
        TextView textView = findViewById(R.id.textView);
        textView.setText(result);
    }
}

// 执行AsyncTask
new MyAsyncTask().execute();