点击一个应用的时候,会加载其对应的base.apk,我们在AssetManager类的addAssetPath方法中添加堆栈打印,
其调用堆栈为
android.content.res.AssetManager.addAssetPath(AssetManager.java:653)
android.app.ResourcesManager.getTopLevelResources(ResourcesManager.java:221)
android.app.ActivityThread.getTopLevelResources(ActivityThread.java:1854)
android.app.LoadedApk.getResources(LoadedApk.java:558)
android.app.ContextImpl.
android.app.ContextImpl.createPackageContextAsUser(ContextImpl.java:1733)
android.app.ContextImpl.createPackageContextAsUser(ContextImpl.java:1718)
com.android.server.AttributeCache.get(AttributeCache.java:114)
com.android.server.am.ActivityRecord.
com.android.server.am.ActivityStackSupervisor.startActivityMayWait(ActivityStackSupervisor.java:1153)
com.android.server.am.ActivityManagerService.startActivityAsUser(ActivityManagerService.java:4271)
com.android.server.am.ActivityManagerService.startActivity(ActivityManagerService.java:4258)
android.app.ActivityManagerNative.onTransact(ActivityManagerNative.java:168)
com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:2703)
分析这个堆栈信息,我们来追根溯源的查看AssetManager对象的创建过程。
第一次打开应用的时候,调到ActivityManagerService的startActivityAsUser方法,
后来调到com.android.server.am.ActivityRecord.
564 AttributeCache.Entry ent = AttributeCache.instance().get(packageName,
565 realTheme,com.android.internal.R.styleable.Window, userId);
继续调用
com.android.server.AttributeCache.get(AttributeCache.java:114)
查看AttributeCache.java
112 Context context;
113 try {
114 context =mContext.createPackageContextAsUser(packageName, 0,
115 new UserHandle(userId));
116 if (context == null) {
117 return null;
118 }
119 } catch (PackageManager.NameNotFoundExceptione) {
120 return null;
121 }
122 pkg = new Package(context);
123 mPackages.put(packageName, pkg);
在这里,mPackages是一个map,其定义为
private final WeakHashMap
newWeakHashMap
在Android 7上,修改为了
private finalArrayMap
在114行,变量context指向了mContext.createPackageContextAsUser(packageName, 0, newUserHandle(userId));的返回值
在122行对context进行了引用。
114行调用到android.app.ContextImpl.createPackageContextAsUser(ContextImpl.java:1718)
继续调用到
android.app.ContextImpl.createPackageContextAsUser(ContextImpl.java:1733)
查看ContextImpl.java
1733 ContextImpl c = new ContextImpl(this,mMainThread, pi, mActivityToken,
1734 user, restricted, mDisplay, null,Display.INVALID_DISPLAY, themePackageName);
1733行又调用到
android.app.ContextImpl.
查看ContextImpl.java
1884 Resources resources =packageInfo.getResources(mainThread);
1906 mResources = resources;
新创建的ContextImpl对象的成员变量mResources对resources进行了引用。
1884行继续调用
android.app.LoadedApk.getResources(LoadedApk.java:558)
android.app.ActivityThread.getTopLevelResources(ActivityThread.java:1854)
android.app.ResourcesManager.getTopLevelResources(ResourcesManager.java:221)
查看ResourcesManager.java
211 AssetManager assets = newAssetManager();
218 // already.
219 if (resDir != null) {
220
221 if (assets.addAssetPath(resDir) ==0) {
222 return null;
223 }
224 }
301 r = new Resources(assets, dm, config,compatInfo);
319 return r;
终于,找到了AssetManager创建的地方了,然后创建了C++层的AssetManager对象,再调用addAssetPath方法加载了base.apk
在Resources.java中有
public Resources(AssetManager assets, DisplayMetrics metrics,Configuration config, CompatibilityInfocompatInfo) {
mAssets = assets;
mMetrics.setToDefaults();
if (compatInfo != null) {
mCompatibilityInfo = compatInfo;
}
updateConfiguration(config, metrics);
assets.recreateStringBlocks();//Modified for ThemeManager
}
Resources中的mAssets对新创建的AssetManager对象进行了引用