/**
* Created by jesse on 15-7-17.
*/
public class MyApplication extends Application{
private final String TAG = MyApplication.class.getSimpleName();
@Override
public void onCreate() {
super.onCreate();
Log.i(TAG + ", onCreate " + this.getApplicationContext().getClass().getSimpleName());
}
} 而且在DeskClock的入口Activity,DeskClock处也print出该程序眼下ApplicationContext的名字用于兴许Proxy后的对照. <application android:name="cn.jesse.MyApplication"
android:label="@string/app_label"
android:icon="@mipmap/ic_launcher_alarmclock"
android:requiredForAllUsers="true"
android:supportsRtl="true"> 过滤后的执行Log: 简单的流程就是先启动自己定义MyApplication 之后再launch DeskClock，同一时候都打印出来ApplicationContext的名字
<application android:name="cn.jesse.MyProxyApplication"
android:label="@string/app_label"
android:icon="@mipmap/ic_launcher_alarmclock"
android:requiredForAllUsers="true"
android:supportsRtl="true">
<meta-data
android:name="DELEGATE_APPLICATION_CLASS_NAME"
android:value="cn.jesse.MyApplication" >
</meta-data>
</application>
* Created by jesse on 15-7-17.
*/
public abstract class ProxyApplication extends Application{
protected abstract void initProxyApplication();
} 当我们要替换当前ProxyApplication的ClassLoader为父类的ClassLoader,所以这个替换的动作要足够得早(要保证在app Context最早被构建的入口处替换ClassLoader),要不然就会出现替换不干净的情况,就会有程序中大部分使用的DelegateApplication的ClassLoader,而一小部分是使用的ProxyApplication的ClassLoader,这样可能会出现一些意想不到的bug. /**
* Set the base context for this ContextWrapper. All calls will then be
* delegated to the base context. Throws
* IllegalStateException if a base context has already been set.
*
* @param base The new base context for this wrapper.
*/
protected void attachBaseContext(Context base) {
if (mBase != null) {
throw new IllegalStateException("Base context already set");
}
mBase = base;
} 转换ClassLoader的入口也确定之后就能够自己定义一个MyProxyApplication,继承自ProxyApplication而且复写attachBaseContext方法,print相关信息/**
* Created by jesse on 15-7-17.
*/
public class MyProxyApplication extends ProxyApplication {
private final String TAG = MyProxyApplication.class.getSimpleName();
private Context mContext;
@Override
protected void attachBaseContext(Context base) {
super.attachBaseContext(base);
Log.i(TAG + ", attachBaseContext");
mContext = base;
this.initProxyApplication();
}
@Override
public void onCreate() {
super.onCreate();
Log.i(TAG + ", onCreate" + this.getApplicationContext().getClass().getSimpleName());
BootLoader.boot(mContext);
}
@Override
protected void initProxyApplication() {
Log.i(TAG + ", initProxyApplication");
BootLoader.resetClassLoader(mContext);
}
} Log执行的顺序,先进入attachBaseContext->initProxyApplication->onCreate->DeskClock:onCreate (这里DeskClock的onCreate获取到的ApplicationContext的名字是(MyProxyApplication)
String className = CLASS_NAME;
ApplicationInfo appInfo = getPackageManager().getApplicationInfo(super.getPackageName(), PackageManager.GET_META_DATA);
Bundle bundle = appInfo.metaData;
if (bundle != null && bundle.containsKey(KEY)) {
className = bundle.getString(KEY);
if (className.startsWith("."))
className = super.getPackageName() + className;
} 依据className反射得到MyApplication,创建MyApplication实例而且取得MyProxyApplication的实例 Class delegateClass = Class.forName(className, true, getClassLoader());
Application delegate = (Application) delegateClass.newInstance();
Application proxyApplication = (Application)getApplicationContext(); 使用反射更换MyProxyApplication context成员中的mOuterContext属性 Class contextImplClass = Class.forName("android.app.ContextImpl");
Field mOuterContext = contextImplClass.getDeclaredField("mOuterContext");
mOuterContext.setAccessible(true);
mOuterContext.set(mContext, delegate);
Field mPackageInfoField = contextImplClass.getDeclaredField("mPackageInfo");
mPackageInfoField.setAccessible(true);
Object mPackageInfo = mPackageInfoField.get(mContext);
Class loadedApkClass = Class.forName("android.app.LoadedApk");
Field mApplication = loadedApkClass.getDeclaredField("mApplication");
mApplication.setAccessible(true);
mApplication.set(mPackageInfo, delegate);
Class activityThreadClass = Class.forName("android.app.ActivityThread");
Field mAcitivityThreadField = loadedApkClass.getDeclaredField("mActivityThread");
mAcitivityThreadField.setAccessible(true);
Object mActivityThread = mAcitivityThreadField.get(mPackageInfo);
Field mInitialApplicationField = activityThreadClass.getDeclaredField("mInitialApplication");
mInitialApplicationField.setAccessible(true);
mInitialApplicationField.set(mActivityThread, delegate);
Field mAllApplicationsField = activityThreadClass.getDeclaredField("mAllApplications");
mAllApplicationsField.setAccessible(true);
ArrayList<Application> al = (ArrayList<Application>)mAllApplicationsField.get(mActivityThread);
al.add(delegate);
al.remove(proxyApplication);
Method attach = Application.class.getDeclaredMethod("attach", Context.class);
attach.setAccessible(true);
attach.invoke(delegate, mContext);
delegate.onCreate(); 完毕这些步骤之后再又一次执行查看Log,观察DeskClock处获取的ApplicationContext的名字已经变成MyApplication.
private IActivityManager.ContentProviderHolder installProvider(Context context,
IActivityManager.ContentProviderHolder holder, ProviderInfo info,
boolean noisy, boolean noReleaseNeeded, boolean stable) {
ContentProvider localProvider = null;
IContentProvider provider;
if (holder == null || holder.provider == null) {
if (DEBUG_PROVIDER || noisy) {
Slog.d(TAG, "Loading provider " + info.authority + ": "
+ info.name);
}
Context c = null;
ApplicationInfo ai = info.applicationInfo;
if (context.getPackageName().equals(ai.packageName)) {
c = context;
} else if (mInitialApplication != null &&
mInitialApplication.getPackageName().equals(ai.packageName)) {
c = mInitialApplication;
} else {
try {
c = context.createPackageContext(ai.packageName,
Context.CONTEXT_INCLUDE_CODE);
} catch (PackageManager.NameNotFoundException e) {
// Ignore
}
}转载请注明出处:http://blog.csdn.net/l2show/article/details/46914881
Android源代码之DeskClock (三) Proxy/Delegate Application 框架应用
原文：http://www.cnblogs.com/jzdwajue/p/7123677.html