Android AsyncTask 結果回調 Activity：接口回調模式實現解耦

定義回調接口

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

AsyncTask 實現

public class MyTask extends AsyncTask {
    private AsyncCallback callback;

    public MyTask(AsyncCallback callback) {
        this.callback = callback;
    }

    @Override
    protected String doInBackground(Void... voids) {
        // 耗時操作
        return "Result from background";
    }

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

Activity 實現接口

public class MainActivity extends AppCompatActivity implements AsyncCallback {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        new MyTask(this).execute();
    }

    @Override
    public void onTaskComplete(String result) {
        // 更新 UI
        textView.setText(result);
    }
}

現代替代：協程 / LiveData / RxJava

// 協程
lifecycleScope.launch {
    val result = withContext(Dispatchers.IO) { doBackgroundWork() }
    textView.text = result // 自動切回主線程
}

協程代碼更線性，生命周期感知自動取消，避免內存洩漏。