1 /* 2 * Copyright (C) 2015 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.tv.settings.util; 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 SettingsAsyncTaskLoader#loadInBackground()} to perform the 26 * actual background task, and {@link SettingsAsyncTaskLoader#onDiscardResult(T)} to clean up 27 * previously loaded results. 28 */ 29 30 public abstract class SettingsAsyncTaskLoader<T> extends AsyncTaskLoader<T> { 31 private T mResult; 32 SettingsAsyncTaskLoader(final Context context)33 public SettingsAsyncTaskLoader(final Context context) { 34 super(context); 35 } 36 37 @Override onStartLoading()38 protected void onStartLoading() { 39 if (mResult != null) { 40 deliverResult(mResult); 41 } 42 43 if (takeContentChanged() || mResult == null) { 44 forceLoad(); 45 } 46 } 47 48 @Override onStopLoading()49 protected void onStopLoading() { 50 cancelLoad(); 51 } 52 53 @Override deliverResult(final T data)54 public void deliverResult(final T data) { 55 if (isReset()) { 56 if (data != null) { 57 onDiscardResult(data); 58 } 59 return; 60 } 61 62 final T oldResult = mResult; 63 mResult = data; 64 65 if (isStarted()) { 66 super.deliverResult(data); 67 } 68 69 if (oldResult != null && oldResult != mResult) { 70 onDiscardResult(oldResult); 71 } 72 } 73 74 @Override onReset()75 protected void onReset() { 76 super.onReset(); 77 78 onStopLoading(); 79 80 if (mResult != null) { 81 onDiscardResult(mResult); 82 } 83 mResult = null; 84 } 85 86 @Override onCanceled(final T data)87 public void onCanceled(final T data) { 88 super.onCanceled(data); 89 90 if (data != null) { 91 onDiscardResult(data); 92 } 93 } 94 95 /** 96 * Called when discarding the load results so subclasses can take care of clean-up or 97 * recycling tasks. This is not called if the same result (by way of pointer equality) is 98 * returned again by a subsequent call to loadInBackground, or if result is null. 99 * 100 * Note that this may be called concurrently with loadInBackground(), and in some circumstances 101 * may be called more than once for a given object. 102 * 103 * @param result The value returned from {@link SettingsAsyncTaskLoader#loadInBackground()} which 104 * is to be discarded. 105 */ onDiscardResult(final T result)106 protected abstract void onDiscardResult(final T result); 107 } 108