Android Loader vs AsyncTask on button click
I have an activity that does not require data from the server on boot - just a simple init for the ui
The user interface has several buttons.
The user clicks on one of them, and the application sends a request to the server (call rest) While the request is being processed, the counter shows (about 10 seconds)
It currently uses AsyncTask - so if the app changes portrait to album - the activity restarts and I lose the process
The second option is to use a Loader - the problem is that it starts when the button is pressed - not when the activity starts
This leads to many exceptions - when the LoaderManager dispatches events to an unloaded element
Is there any solution?
a few comments: - 10 seconds for example - blocking the user to one orientation is not an option - the service is overkill for a simple rest call
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public class TestActivity extends FragmentActivity {
private Button one;
private Button two;
private final int ONE_ID = 0;
private final int TWO_ID = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
one = (Button) findViewById(R.id.one);
two = (Button) findViewById(R.id.two);
one.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
getLoaderManager().restartLoader(ONE_ID, null, callbacks);
}
});
two.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
getLoaderManager().restartLoader(ONE_ID, null, callbacks);
}
});
Loader<AsyncTaskLoaderResult<Result>> loader = getLoaderManager().getLoader(ONE_ID);
if (loader != null) {
getLoaderManager().initLoader(ONE_ID, null, callbacks);
}
loader = getLoaderManager().getLoader(TWO_ID);
if (loader != null) {
getLoaderManager().initLoader(TWO_ID, null, callbacks);
}
}
public static class AsyncTaskLoaderResult<E> {
public E data;
public Bundle args;
}
public static class Result {
}
private LoaderManager.LoaderCallbacks<AsyncTaskLoaderResult<Result>> callbacks = new LoaderManager.LoaderCallbacks<AsyncTaskLoaderResult<Result>>() {
@Override
public Loader<AsyncTaskLoaderResult<Result>> onCreateLoader(int id, Bundle args) {
/**
* according different Id, create different AsyncTaskLoader
*/
switch (id) {
case ONE_ID:
return new OneAsyncTaskLoader(TestActivity.this);
case TWO_ID:
return new TwoAsyncTaskLoader(TestActivity.this);
}
return null;
}
@Override
public void onLoadFinished(Loader<AsyncTaskLoaderResult<Result>> loader, AsyncTaskLoaderResult<Result> data) {
/**
* handle result
*/
switch (loader.getId()) {
}
getLoaderManager().destroyLoader(loader.getId());
}
@Override
public void onLoaderReset(Loader<AsyncTaskLoaderResult<Result>> loader) {
}
};
public static class OneAsyncTaskLoader extends AsyncTaskLoader<AsyncTaskLoaderResult<Result>> {
private AsyncTaskLoaderResult<Result> result;
public OneAsyncTaskLoader(Context context) {
super(context);
}
@Override
protected void onStartLoading() {
super.onStartLoading();
if (result != null) {
deliverResult(result);
} else {
forceLoad();
}
}
@Override
public AsyncTaskLoaderResult<Result> loadInBackground() {
/**
* send request to server
*/
result = new AsyncTaskLoaderResult<Result>();
result.data = null; // result.data comes from server response
return result;
}
}
public static class TwoAsyncTaskLoader extends AsyncTaskLoader<AsyncTaskLoaderResult<Result>> {
private AsyncTaskLoaderResult<Result> result;
public TwoAsyncTaskLoader(Context context) {
super(context);
}
@Override
protected void onStartLoading() {
super.onStartLoading();
if (result != null) {
deliverResult(result);
} else {
forceLoad();
}
}
@Override
public AsyncTaskLoaderResult<Result> loadInBackground() {
/**
* send request to server
*/
result = new AsyncTaskLoaderResult<Result>();
result.data = null; // result.data comes from server response
return result;
}
}
}
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First, you can fix the orientation change issue by declaring
android:configChanges="orientation"
But the real problem is that the user looks at the counter for 10 seconds. Most users won't be patient enough for this. I don’t know what your application does, so it’s difficult to give an exact suggestion, but I can say that you need to do your web content in AsyncTask
, but let the user do other things.
You can allow the user to do other things while AsyncTask
completing or putting this code in [Service ( http://developer.android.com/guide/components/services.html ). Anyway, don't force your users to look at screen for 10 seconds of rotation ... they won't be YOUR users for a long time
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If you use AsyncTask
to do this, you can use Service
or use onRetainNonConfigurationInstance instead or Fragment.setRetainInstance
to allow the AsyncTask
configuration changes to live.
Or disable config changes: I've used this in the past with some success.
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Here's a good article on the topic:
http://www.javacodegeeks.com/2013/01/android-loaders-versus-asynctask.html
Anyway, as @codeMagic mentioned, AsyncTask
s android:configChanges="orientation|screenSize"
should be enough for you (it prevents the activity from being recreated when the config changes)
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