CachingIconLoader.java revision e29d52aa72c96c3147fa91d83aeb8dafc6d1f578 
1/*
2 * Copyright (C) 2009 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
17package com.android.quicksearchbox;
18
19import com.android.quicksearchbox.util.CachedLater;
20import com.android.quicksearchbox.util.Consumer;
21import com.android.quicksearchbox.util.Now;
22import com.android.quicksearchbox.util.NowOrLater;
23import com.android.quicksearchbox.util.NowOrLaterWrapper;
24
25import android.graphics.drawable.Drawable;
26import android.net.Uri;
27import android.text.TextUtils;
28import android.util.Log;
29
30import java.util.WeakHashMap;
31
32/**
33 * Icon loader that caches the results of another icon loader.
34 *
35 */
36public class CachingIconLoader implements IconLoader {
37
38    private static final boolean DBG = false;
39    private static final String TAG = "QSB.CachingIconLoader";
40
41    private final IconLoader mWrapped;
42
43    private final WeakHashMap<String, Entry> mIconCache;
44
45    /**
46     * Creates a new caching icon loader.
47     *
48     * @param wrapped IconLoader whose results will be cached.
49     */
50    public CachingIconLoader(IconLoader wrapped) {
51        mWrapped = wrapped;
52        mIconCache = new WeakHashMap<String, Entry>();
53    }
54
55    public NowOrLater<Drawable> getIcon(String drawableId) {
56        if (DBG) Log.d(TAG, "getIcon(" + drawableId + ")");
57        if (TextUtils.isEmpty(drawableId) || "0".equals(drawableId)) {
58            return new Now<Drawable>(null);
59        }
60        Entry newEntry = null;
61        NowOrLater<Drawable.ConstantState> drawableState;
62        synchronized (this) {
63            drawableState = queryCache(drawableId);
64            if (drawableState == null) {
65                newEntry = new Entry();
66                storeInIconCache(drawableId, newEntry);
67            }
68        }
69        if (drawableState != null) {
70            return new NowOrLaterWrapper<Drawable.ConstantState, Drawable>(drawableState){
71                @Override
72                public Drawable get(Drawable.ConstantState value) {
73                    return value == null ? null : value.newDrawable();
74                }};
75        }
76        NowOrLater<Drawable> drawable = mWrapped.getIcon(drawableId);
77        newEntry.set(drawable);
78        storeInIconCache(drawableId, newEntry);
79        return drawable;
80    }
81
82    public Uri getIconUri(String drawableId) {
83        return mWrapped.getIconUri(drawableId);
84    }
85
86    private synchronized NowOrLater<Drawable.ConstantState> queryCache(String drawableId) {
87        NowOrLater<Drawable.ConstantState> cached = mIconCache.get(drawableId);
88        if (DBG) {
89            if (cached != null) Log.d(TAG, "Found icon in cache: " + drawableId);
90        }
91        return cached;
92    }
93
94    private synchronized void storeInIconCache(String resourceUri, Entry drawable) {
95        if (drawable != null) {
96            mIconCache.put(resourceUri, drawable);
97        }
98    }
99
100    private static class Entry extends CachedLater<Drawable.ConstantState>
101            implements Consumer<Drawable>{
102        private NowOrLater<Drawable> mDrawable;
103        private boolean mGotDrawable;
104        private boolean mCreateRequested;
105
106        public Entry() {
107        }
108
109        public synchronized void set(NowOrLater<Drawable> drawable) {
110            if (mGotDrawable) throw new IllegalStateException("set() may only be called once.");
111            mGotDrawable = true;
112            mDrawable = drawable;
113            if (mCreateRequested) {
114                getLater();
115            }
116        }
117
118        @Override
119        protected synchronized void create() {
120            if (!mCreateRequested) {
121                mCreateRequested = true;
122                if (mGotDrawable) {
123                    getLater();
124                }
125            }
126        }
127
128        private void getLater() {
129            NowOrLater<Drawable> drawable = mDrawable;
130            mDrawable = null;
131            drawable.getLater(this);
132        }
133
134        public boolean consume(Drawable value) {
135            store(value == null ? null : value.getConstantState());
136            return true;
137        }
138    }
139
140}
141