Android4.2_Launcher_IconCache

在LauncherApplication中用到了 IconCache,用来保存应用程序图标的缓存。

类设计：

这个类主要是提供了访问图标的接口，外界提供 组件名即可获得对应的图标。这里图标是缓存在内存中。核心是cacheLocked 这个函数。

类结构

public Drawable getFullResIcon(Resources resources, int iconId)public Drawable getFullResIcon(String packageName, int iconId)public Drawable getFullResIcon(ResolveInfo info)public Drawable getFullResIcon(ActivityInfo info)public Bitmap getIcon(Intent intent)public Bitmap getIcon(ComponentName component, ResolveInfo resolveInfo,<span style="white-space:pre"></span>HashMap<Object, CharSequence> labelCache)private CacheEntry cacheLocked(ComponentName componentName,<span style="white-space:pre"></span>ResolveInfo info, HashMap<Object, CharSequence> labelCache)

CacheEntry 对应一个应用，包括应用程序名称和图标。

INITIAL_ICON_CACHE_CAPACITY 缓存队列的长度。

mIconDpi 用来显示控制图标的大小。在构造函数中确定。

mDefaultIcon 如果应用程序没有自己的图标就使用默认的图标。对应的id 为com.android.internal.R.mipmap.sym_def_app_icon。在构造函数中实现。

publicvoid getTitleAndIcon(ApplicationInfo application, ResolveInfo info, HashMap<Object, CharSequence>labelCache)publicBitmap getIcon(ComponentName component, ResolveInfo resolveInfo,HashMap<Object,CharSequence>labelCache)publicBitmap getIcon(Intent intent)

  这几个函数都是用来获取特定应用对应的图标或标题。他们最后都是调用cacheLocked从mCache中获得CacheEntry结构，然后从中获得需要的信息。

<span style="font-size:24px;">privateCacheEntry cacheLocked(ComponentName componentName, ResolveInfo info,HashMap<Object,CharSequence>labelCache)</span>

    componentname用来从哈希表mCache中获得CacheEntry结构。如果mCache中没有匹配项。会从info中获取到应用相应的信息填充到哈希表中。

源码：

/* * Copyright (C) 2008 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.launcher2;import android.app.ActivityManager;import android.content.ComponentName;import android.content.Context;import android.content.Intent;import android.content.pm.ActivityInfo;import android.content.pm.PackageManager;import android.content.pm.ResolveInfo;import android.content.res.Resources;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.drawable.Drawable;import java.util.HashMap;/** * Cache of application icons.  Icons can be made from any thread. */public class IconCache {    @SuppressWarnings("unused")    private static final String TAG = "Launcher.IconCache";    private static final int INITIAL_ICON_CACHE_CAPACITY = 50;    private static class CacheEntry {        public Bitmap icon;        public String title;    }    private final Bitmap mDefaultIcon;    private final LauncherApplication mContext;    private final PackageManager mPackageManager;    private final HashMap<ComponentName, CacheEntry> mCache =            new HashMap<ComponentName, CacheEntry>(INITIAL_ICON_CACHE_CAPACITY);    private int mIconDpi;    public IconCache(LauncherApplication context) {        ActivityManager activityManager =                (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);        mContext = context;        mPackageManager = context.getPackageManager();        mIconDpi = activityManager.getLauncherLargeIconDensity();        // need to set mIconDpi before getting default icon        mDefaultIcon = makeDefaultIcon();    }    public Drawable getFullResDefaultActivityIcon() {        return getFullResIcon(Resources.getSystem(),                android.R.mipmap.sym_def_app_icon);    }    public Drawable getFullResIcon(Resources resources, int iconId) {        Drawable d;        try {            d = resources.getDrawableForDensity(iconId, mIconDpi);        } catch (Resources.NotFoundException e) {            d = null;        }        return (d != null) ? d : getFullResDefaultActivityIcon();    }    public Drawable getFullResIcon(String packageName, int iconId) {        Resources resources;        try {            resources = mPackageManager.getResourcesForApplication(packageName);        } catch (PackageManager.NameNotFoundException e) {            resources = null;        }        if (resources != null) {            if (iconId != 0) {                return getFullResIcon(resources, iconId);            }        }        return getFullResDefaultActivityIcon();    }    public Drawable getFullResIcon(ResolveInfo info) {        return getFullResIcon(info.activityInfo);    }    public Drawable getFullResIcon(ActivityInfo info) {        Resources resources;        try {            resources = mPackageManager.getResourcesForApplication(                    info.applicationInfo);        } catch (PackageManager.NameNotFoundException e) {            resources = null;        }        if (resources != null) {            int iconId = info.getIconResource();            if (iconId != 0) {                return getFullResIcon(resources, iconId);            }        }        return getFullResDefaultActivityIcon();    }    private Bitmap makeDefaultIcon() {        Drawable d = getFullResDefaultActivityIcon();        Bitmap b = Bitmap.createBitmap(Math.max(d.getIntrinsicWidth(), 1),                Math.max(d.getIntrinsicHeight(), 1),                Bitmap.Config.ARGB_8888);        Canvas c = new Canvas(b);        d.setBounds(0, 0, b.getWidth(), b.getHeight());        d.draw(c);        c.setBitmap(null);        return b;    }    /**     * Remove any records for the supplied ComponentName.     */    public void remove(ComponentName componentName) {        synchronized (mCache) {            mCache.remove(componentName);        }    }    /**     * Empty out the cache.     */    public void flush() {        synchronized (mCache) {            mCache.clear();        }    }    /**     * Fill in "application" with the icon and label for "info."     */    public void getTitleAndIcon(ApplicationInfo application, ResolveInfo info,            HashMap<Object, CharSequence> labelCache) {        synchronized (mCache) {            CacheEntry entry = cacheLocked(application.componentName, info, labelCache);            application.title = entry.title;            application.iconBitmap = entry.icon;        }    }    public Bitmap getIcon(Intent intent) {        synchronized (mCache) {            final ResolveInfo resolveInfo = mPackageManager.resolveActivity(intent, 0);            ComponentName component = intent.getComponent();            if (resolveInfo == null || component == null) {                return mDefaultIcon;            }            CacheEntry entry = cacheLocked(component, resolveInfo, null);            return entry.icon;        }    }    public Bitmap getIcon(ComponentName component, ResolveInfo resolveInfo,            HashMap<Object, CharSequence> labelCache) {        synchronized (mCache) {            if (resolveInfo == null || component == null) {                return null;            }            CacheEntry entry = cacheLocked(component, resolveInfo, labelCache);            return entry.icon;        }    }    public boolean isDefaultIcon(Bitmap icon) {        return mDefaultIcon == icon;    }    private CacheEntry cacheLocked(ComponentName componentName, ResolveInfo info,            HashMap<Object, CharSequence> labelCache) {        CacheEntry entry = mCache.get(componentName);        if (entry == null) {            entry = new CacheEntry();            mCache.put(componentName, entry);            ComponentName key = LauncherModel.getComponentNameFromResolveInfo(info);            if (labelCache != null && labelCache.containsKey(key)) {                entry.title = labelCache.get(key).toString();            } else {                entry.title = info.loadLabel(mPackageManager).toString();                if (labelCache != null) {                    labelCache.put(key, entry.title);                }            }            if (entry.title == null) {                entry.title = info.activityInfo.name;            }            entry.icon = Utilities.createIconBitmap(                    getFullResIcon(info), mContext);        }        return entry;    }    public HashMap<ComponentName,Bitmap> getAllIcons() {        synchronized (mCache) {            HashMap<ComponentName,Bitmap> set = new HashMap<ComponentName,Bitmap>();            for (ComponentName cn : mCache.keySet()) {                final CacheEntry e = mCache.get(cn);                set.put(cn, e.icon);            }            return set;        }    }}