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/*
* Copyright (C) 2013 Google Inc.
* Licensed to The Android Open Source Project.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.mail.ui;
import android.content.AsyncTaskLoader;
import android.content.Context;
/**
* This class fills in some boilerplate for AsyncTaskLoader to actually load things.
*
* Subclasses need to implement {@link MailAsyncTaskLoader#loadInBackground()} to perform the actual
* background task, and {@link MailAsyncTaskLoader#onDiscardResult(T)} to clean up previously loaded
* results.
*/
public abstract class MailAsyncTaskLoader<T> extends AsyncTaskLoader<T> {
private T mResult;
public MailAsyncTaskLoader(final Context context) {
super(context);
}
@Override
protected void onStartLoading() {
if (mResult != null) {
deliverResult(mResult);
}
if (takeContentChanged() || mResult == null) {
forceLoad();
}
}
@Override
protected void onStopLoading() {
cancelLoad();
}
@Override
public void deliverResult(final T data) {
if (isReset()) {
if (data != null) {
onDiscardResult(data);
}
return;
}
final T oldResult = mResult;
mResult = data;
if (isStarted()) {
super.deliverResult(data);
}
if (oldResult != null && oldResult != mResult) {
onDiscardResult(oldResult);
}
}
@Override
protected void onReset() {
super.onReset();
onStopLoading();
if (mResult != null) {
onDiscardResult(mResult);
}
mResult = null;
}
@Override
public void onCanceled(final T data) {
super.onCanceled(data);
if (data != null) {
onDiscardResult(data);
}
}
/**
* Called when discarding the load results so subclasses can take care of clean-up or
* recycling tasks. This is not called if the same result (by way of pointer equality) is
* returned again by a subsequent call to loadInBackground, or if result is null.
*
* Note that this may be called concurrently with loadInBackground(), and in some circumstances
* may be called more than once for a given object.
*
* @param result The value returned from {@link MailAsyncTaskLoader#loadInBackground()} which
* is to be discarded.
*/
protected abstract void onDiscardResult(final T result);
}
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