1 package com.android.settings.intelligence.utils;
2 
3 import android.content.AsyncTaskLoader;
4 import android.content.Context;
5 
6 /**
7  * This class fills in some boilerplate for AsyncTaskLoader to actually load things.
8  *
9  * Subclasses need to implement {@link AsyncLoader#loadInBackground()} to perform the actual
10  * background task, and {@link AsyncLoader#onDiscardResult(T)} to clean up previously loaded
11  * results.
12  *
13  * This loader is based on the MailAsyncTaskLoader from the AOSP EmailUnified repo.
14  */
15 public abstract class AsyncLoader<T> extends AsyncTaskLoader<T> {
16     private T mResult;
17 
AsyncLoader(final Context context)18     public AsyncLoader(final Context context) {
19         super(context);
20     }
21 
22     @Override
onStartLoading()23     protected void onStartLoading() {
24         if (mResult != null) {
25             deliverResult(mResult);
26         }
27 
28         if (takeContentChanged() || mResult == null) {
29             forceLoad();
30         }
31     }
32 
33     @Override
onStopLoading()34     protected void onStopLoading() {
35         cancelLoad();
36     }
37 
38     @Override
deliverResult(final T data)39     public void deliverResult(final T data) {
40         if (isReset()) {
41             if (data != null) {
42                 onDiscardResult(data);
43             }
44             return;
45         }
46 
47         final T oldResult = mResult;
48         mResult = data;
49 
50         if (isStarted()) {
51             super.deliverResult(data);
52         }
53 
54         if (oldResult != null && oldResult != mResult) {
55             onDiscardResult(oldResult);
56         }
57     }
58 
59     @Override
onReset()60     protected void onReset() {
61         super.onReset();
62 
63         onStopLoading();
64 
65         if (mResult != null) {
66             onDiscardResult(mResult);
67         }
68         mResult = null;
69     }
70 
71     @Override
onCanceled(final T data)72     public void onCanceled(final T data) {
73         super.onCanceled(data);
74 
75         if (data != null) {
76             onDiscardResult(data);
77         }
78     }
79 
80     /**
81      * Called when discarding the load results so subclasses can take care of clean-up or
82      * recycling tasks. This is not called if the same result (by way of pointer equality) is
83      * returned again by a subsequent call to loadInBackground, or if result is null.
84      *
85      * Note that this may be called concurrently with loadInBackground(), and in some circumstances
86      * may be called more than once for a given object.
87      *
88      * @param result The value returned from {@link AsyncLoader#loadInBackground()} which
89      *               is to be discarded.
90      */
onDiscardResult(final T result)91     protected abstract void onDiscardResult(final T result);
92 }