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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.settingslib.utils;
     18 
     19 import android.content.AsyncTaskLoader;
     20 import android.content.Context;
     21 
     22 /**
     23  * This class fills in some boilerplate for AsyncTaskLoader to actually load things.
     24  *
     25  * Subclasses need to implement {@link AsyncLoader#loadInBackground()} to perform the actual
     26  * background task, and {@link AsyncLoader#onDiscardResult(T)} to clean up previously loaded
     27  * results.
     28  *
     29  * This loader is based on the MailAsyncTaskLoader from the AOSP EmailUnified repo.
     30  *
     31  * @param <T> the data type to be loaded.
     32  * @deprecated Framework loader is deprecated, use the compat version instead.
     33  */
     34 @Deprecated
     35 public abstract class AsyncLoader<T> extends AsyncTaskLoader<T> {
     36     private T mResult;
     37 
     38     public AsyncLoader(final Context context) {
     39         super(context);
     40     }
     41 
     42     @Override
     43     protected void onStartLoading() {
     44         if (mResult != null) {
     45             deliverResult(mResult);
     46         }
     47 
     48         if (takeContentChanged() || mResult == null) {
     49             forceLoad();
     50         }
     51     }
     52 
     53     @Override
     54     protected void onStopLoading() {
     55         cancelLoad();
     56     }
     57 
     58     @Override
     59     public void deliverResult(final T data) {
     60         if (isReset()) {
     61             if (data != null) {
     62                 onDiscardResult(data);
     63             }
     64             return;
     65         }
     66 
     67         final T oldResult = mResult;
     68         mResult = data;
     69 
     70         if (isStarted()) {
     71             super.deliverResult(data);
     72         }
     73 
     74         if (oldResult != null && oldResult != mResult) {
     75             onDiscardResult(oldResult);
     76         }
     77     }
     78 
     79     @Override
     80     protected void onReset() {
     81         super.onReset();
     82 
     83         onStopLoading();
     84 
     85         if (mResult != null) {
     86             onDiscardResult(mResult);
     87         }
     88         mResult = null;
     89     }
     90 
     91     @Override
     92     public void onCanceled(final T data) {
     93         super.onCanceled(data);
     94 
     95         if (data != null) {
     96             onDiscardResult(data);
     97         }
     98     }
     99 
    100     /**
    101      * Called when discarding the load results so subclasses can take care of clean-up or
    102      * recycling tasks. This is not called if the same result (by way of pointer equality) is
    103      * returned again by a subsequent call to loadInBackground, or if result is null.
    104      *
    105      * Note that this may be called concurrently with loadInBackground(), and in some circumstances
    106      * may be called more than once for a given object.
    107      *
    108      * @param result The value returned from {@link AsyncLoader#loadInBackground()} which
    109      *               is to be discarded.
    110      */
    111     protected abstract void onDiscardResult(T result);
    112 }
    113