[英]How to to reference an activity that implements an interface?
它说了错误的第三个参数,我已经在mainActivity中实现了LoaderManager.LoaderCallbacks。
getSupportLoaderManager().initLoader(LOADER_ID,getUrlBundle(),this);
为什么会这样呢?
public class MainActivity extends AppCompatActivity implements MovieAdapter.movieAdapterClickHandler,LoaderManager.LoaderCallbacks<List<Movie>> {
...
@Override
protected void onCreate(Bundle savedInstanceState) {
...
getSupportLoaderManager().initLoader(LOADER_ID,getUrlBundle(),this);
}
...
@Override
public Loader<List<Movie>> onCreateLoader(int i, final Bundle bundle) {
return new AsyncTaskLoader<List<Movie>>(this) {
@Override
protected void onStartLoading() {
if(bundle==null)
return;
progressBar.setVisibility(View.VISIBLE);
errorMessage.setVisibility(View.INVISIBLE);
forceLoad();
}
@Override
public List<Movie> loadInBackground() {
/* Extract the url from the args using our constant */
String UrlString = bundle.getString(URL_EXTRA);
/* If the user didn't enter anything, there's nothing to search for */
if (UrlString == null || TextUtils.isEmpty(UrlString)) {
return null;
}
return QueryUtils.fetchMovieData(UrlString);
}
@Override
public void deliverResult(List<Movie> data) {
super.deliverResult(data);
}
};
}
@Override
public void onLoadFinished(Loader<List<Movie>> loader, List<Movie> movies) {
if (movies != null && !movies.isEmpty()) {
movieAdapter.MovieAdapterUpdate(movies);
progressBar.setVisibility(View.INVISIBLE);
} else {
progressBar.setVisibility(View.INVISIBLE);
errorMessage.setText("No data returned");
errorMessage.setVisibility(View.VISIBLE);
}
}
@Override
public void onLoaderReset(Loader<List<Movie>> loader) {
}
}
如果对使用的Loader类使用了错误的导入,则可能会发生这种情况。 例如,如果您使用
import android.support.v4.content.AsyncTaskLoader;
import android.support.v4.content.Loader;
import android.support.v7.app.AppCompatActivity;
随着
import android.app.LoaderManager;
那么在将支持依赖项与非支持依赖项混合在一起时,您会收到错误的第三个参数警告。 鉴于此可行:
import android.support.v4.app.LoaderManager;
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