我正在使用 AsyncTaskLoader
。我的一个活动已经实现了LoaderCallbacks
(支持库)。
我设置了断点和日志,发现加载器成功返回结果,但第二次回调时onLoadFinished
没有被触发。奇怪的是 - 当我再次旋转后它就奏效了,无论我从哪个方向开始,在返回时都会得到回调。
在我的活动中的onResume
方法中:
LoaderManager lm = getSupportLoaderManager();
Loader loader = lm.initLoader(0, null, new LoaderManager.LoaderCallbacks<String>() {
@Override
public Loader<String> onCreateLoader(int i, Bundle bundle) {
Loader<String> loader = new TestLoader(MainActivity.this);
return loader;
}
@Override
public void onLoadFinished(Loader<String> stringLoader, String s) {
Log.d(Application.TAG, "OnLoadFinished " + s);
doStuff(s);
}
@Override
public void onLoaderReset(Loader<String> stringLoader) {
// NOP
}
});
在我的加载器中:
public class TestLoader extends AsyncTaskLoader<String> {
private String mData;
public TestLoader(Context context) {
super(context);
}
// This get's called after a loader is initialized or a loader
// that is alive still is reset
@Override
public void onStartLoading() {
if (mData != null) { // Have our data loaded, just deliver it!
deliverResult(mData);
}
if (takeContentChanged() || mData == null) {
forceLoad();
}
}
// This is called when an Activity or Fragment requests a loader
// to be reset because they want new data
@Override
public void onReset() {
mData = null;
// Ensure that the old task is cancelled if it was running
// We do NOT have to call forceLoad here because onStartLoading
// will get called after this
cancelLoad();
}
// Here we just want to store our own data we got and reset our boolean
@Override
public void deliverResult(String data) {
Log.d(Application.TAG, "deliverResult " + data);
mData = data;
super.deliverResult(mData);
}
@Override
public String loadInBackground() {
// returns content from a content provider ...
}
}
这个问题让我十分困惑,我是 Android 新手,也许对其他人来说很明显 :)