Android 11中不推荐使用AsyncTask API。有什么替代方案吗？

The AsyncTask API is deprecated in Android 11. What are the alternatives?(Android 11中不推荐使用AsyncTask API。有什么替代方案吗？)

问题描述

Google在Android 11中弃用Android AsyncTask API，建议使用java.util.concurrent。您可以签出提交here

 *
 * @deprecated Use the standard <code>java.util.concurrent</code> or
 *   <a href="https://developer.android.com/topic/libraries/architecture/coroutines">
 *   Kotlin concurrency utilities</a> instead.
 */
@Deprecated
public abstract class AsyncTask<Params, Progress, Result> {

如果您在Android中使用异步任务维护较旧的代码库，则很可能将来必须更改它。我的问题是，使用java.util.concurrent应该如何正确替换下面显示的代码片段。它是一个活动的静电内部类。我正在寻找可以与minSdkVersion 16

一起使用的软件

private static class LongRunningTask extends AsyncTask<String, Void, MyPojo> {
        private static final String TAG = MyActivity.LongRunningTask.class.getSimpleName();
        private WeakReference<MyActivity> activityReference;

        LongRunningTask(MyActivity context) {
            activityReference = new WeakReference<>(context);
        }

        @Override
        protected MyPojo doInBackground(String... params) {
            // Some long running task
            
        }

        @Override
        protected void onPostExecute(MyPojo data) {

            MyActivity activity = activityReference.get();
            activity.progressBar.setVisibility(View.GONE);
            populateData(activity, data) ;
        }     


    }

推荐答案

private WeakReference<MyActivity> activityReference;

幸好它已被弃用，because the WeakReference<Context> was always a hack, and not a proper solution。

现在，用户将有机会清理其代码。

---

AsyncTask<String, Void, MyPojo> 

基于此代码，实际上不需要Progress，有一个String输入+MyPojo输出。

无需使用任何AsyncTask，这实际上很容易实现。

public class TaskRunner {
    private final Executor executor = Executors.newSingleThreadExecutor(); // change according to your requirements
    private final Handler handler = new Handler(Looper.getMainLooper());

    public interface Callback<R> {
        void onComplete(R result);
    }

    public <R> void executeAsync(Callable<R> callable, Callback<R> callback) {
        executor.execute(() -> {
            final R result = callable.call();
            handler.post(() -> {
                callback.onComplete(result);
            });
        });
    }
}

如何传入字符串？如下所示：

class LongRunningTask implements Callable<MyPojo> {
    private final String input;

    public LongRunningTask(String input) {
        this.input = input;
    }

    @Override
    public MyPojo call() {
        // Some long running task
        return myPojo;
    }
}

和

// in ViewModel
taskRunner.executeAsync(new LongRunningTask(input), (data) -> {
    // MyActivity activity = activityReference.get();
    // activity.progressBar.setVisibility(View.GONE);
    // populateData(activity, data) ;

    loadingLiveData.setValue(false);
    dataLiveData.setValue(data);
});

// in Activity
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main_activity);

    viewModel = ViewModelProviders.of(this).get(MyViewModel.class);
    viewModel.loadingLiveData.observe(this, (loading) -> {
        if(loading) {
            progressBar.setVisibility(View.VISIBLE);
        } else {
            progressBar.setVisibility(View.GONE);
        }
    });

    viewModel.dataLiveData.observe(this, (data) -> {
        populateData(data);
    }); 
}

---

本例使用的单线程池非常适合DB写入(或序列化的网络请求)，但是如果您想要用于DB读取或多个请求，您可以考虑以下执行器配置：

private static final Executor THREAD_POOL_EXECUTOR =
        new ThreadPoolExecutor(5, 128, 1,
                TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());

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