我怎么知道后台线程什么时候完成了AsyncTask？

public class MyTask extends AsyncTask<Void, Void, String> {
    @Override
    protected String doInBackground(Void... voids) {
        // 执行后台任务
        return "任务完成";
    }

    @Override
    protected void onPostExecute(String result) {
        // 任务完成后的处理
        Log.d("MyTask", result);
    }
}

public interface TaskCompleteListener {
    void onTaskComplete(String result);
}

public class MyTask extends AsyncTask<Void, Void, String> {
    private TaskCompleteListener listener;

    public MyTask(TaskCompleteListener listener) {
        this.listener = listener;
    }

    @Override
    protected String doInBackground(Void... voids) {
        // 执行后台任务
        return "任务完成";
    }

    @Override
    protected void onPostExecute(String result) {
        if (listener != null) {
            listener.onTaskComplete(result);
        }
    }
}

MyTask task = new MyTask(new TaskCompleteListener() {
    @Override
    public void onTaskComplete(String result) {
        Log.d("MyTask", result);
    }
});
task.execute();

ExecutorService executor = Executors.newSingleThreadExecutor();
Future<String> future = executor.submit(new Callable<String>() {
    @Override
    public String call() throws Exception {
        // 执行后台任务
        return "任务完成";
    }
});

try {
    String result = future.get(); // 阻塞等待任务完成
    Log.d("MyTask", result);
} catch (Exception e) {
    e.printStackTrace();
} finally {
    executor.shutdown();
}

class MyViewModel : ViewModel() {
    private val _result = MutableLiveData<String>()
    val result: LiveData<String> get() = _result

    fun doBackgroundTask() {
        viewModelScope.launch {
            val result = withContext(Dispatchers.IO) {
                // 执行后台任务
                "任务完成"
            }
            _result.value = result
        }
    }
}

viewModel.result.observe(this, Observer { result ->
    Log.d("MyTask", result)
})