android - 从 AsyncTaskLoader 更新进度条？

Question

当使用 AsyncTaskLoader 时，您将如何更新显示状态的进度条，因为它正在被更新？通常你会等待回调在完成后移除，但是如何运行更新呢？您会让主线程 (ui) 在设置数据时轮询数据吗？

编辑:我说的是AsyncTaskLoader，看看加载器部分。这是类(class)链接:http://developer.android.com/reference/android/content/AsyncTaskLoader.html

我想使用它，因为它是 future :)，我知道如何使用 AsyncTask 来做到这一点。

Answer 1

您可以使用加载器来做到这一点，但您需要在您的 Activity 上保留和更新 WeakReference:

public class LoaderTestActivity extends FragmentActivity implements LoaderCallbacks<Void> {
    private static final int MAX_COUNT = 100;

    private ProgressBar progressBar;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_async_task_test);

        progressBar = (ProgressBar) findViewById(R.id.progressBar1);
        progressBar.setMax(MAX_COUNT);
        AsyncTaskCounter.mActivity = new WeakReference<LoaderTestActivity>(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_async_task_test, menu);
        return true;
    }

    public void onStartButtonClick(View v) {
        startWork();
    }

    void startWork() {
        getSupportLoaderManager().initLoader(0, (Bundle) null, this);
    }

    static class AsyncTaskCounter extends AsyncTaskLoader<Void> {
        static WeakReference<LoaderTestActivity> mActivity;

        AsyncTaskCounter(LoaderTestActivity activity) {
            super(activity);
            mActivity = new WeakReference<LoaderTestActivity>(activity);
        }

        private static final int SLEEP_TIME = 200;

        @Override
        public Void loadInBackground() {
            for (int i = 0; i < MAX_COUNT; i++) {
                try {
                    Thread.sleep(SLEEP_TIME);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                Log.d(getClass().getSimpleName(), "Progress value is " + i);
                Log.d(getClass().getSimpleName(), "getActivity is " + getContext());
                Log.d(getClass().getSimpleName(), "this is " + this);

                final int progress = i;
                if (mActivity.get() != null) {
                    mActivity.get().runOnUiThread(new Runnable() {

                        @Override
                        public void run() {
                            mActivity.get().progressBar.setProgress(progress);
                        }
                    });
                }
            }
            return null;
        }

    }

    @Override
    public Loader<Void> onCreateLoader(int id, Bundle args) {
        AsyncTaskLoader<Void> asyncTaskLoader = new AsyncTaskCounter(this);
        asyncTaskLoader.forceLoad();
        return asyncTaskLoader;
    }

    @Override
    public void onLoadFinished(Loader<Void> arg0, Void arg1) {

    }

    @Override
    public void onLoaderReset(Loader<Void> arg0) {

    }

}