Chen's Notes
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Android动态化容器框架Atlas启动过程(下)

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概述

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接上篇 ,继续 6-10 步的启动过程。

6. onCreate

AtlasBridgeApplication.java

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@Override
public void onCreate() {
	super.onCreate();
	Method method = mBridgeApplicationDelegate.getClass().getDeclaredMethod("onCreate");
	method.invoke(mBridgeApplicationDelegate);       
}

直接反射调用mBridgeApplicationDelegate的onCreate方法.

7. BridgeApplicationDelegate.onCreate

BridgeApplicationDelegate.java

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public void onCreate(){
   // 7.1 实例application
	mRealApplication = (Application) mRawApplication.getBaseContext()
		.getClassLoader().loadClass(mRealApplicationName).newInstance();
    
    //7.2 replace xxx
    AtlasHacks.ContextImpl_setOuterContext.invoke(
    	mRawApplication.getBaseContext(), mRealApplication);
    //...
    
    //7.3 mRealApplication.attach
    AtlasHacks.Application_attach
   		.invoke(mRealApplication,mRawApplication.getBaseContext());
   
    //7.4 install content providers
    Object mBoundApplication = AtlasHacks.ActivityThread_mBoundApplication.get(activityThread);
    AtlasHacks.ActivityThread$AppBindData_providers.set(mBoundApplication,mBoundApplication_provider);
    AtlasHacks.ActivityThread_installContentProviders.invoke(activityThread,mRealApplication,mBoundApplication_provider);
    
    //7.5. startup
    Atlas.getInstance().startup(mRealApplication,mIsUpdated);
    
    //7.6 onCreate
    mRealApplication.onCreate();
}

函数有点长，不过内容大概分为6块

  1. 实例化app工程中指定的mRealApplication
  2. 替换application
  3. 反射执行mRealApplication的attach方法
  4. 加载provider
  5. Atlas.startup
  6. 调用mRealApplication.onCreate方法

##7.1 实例application

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mRealApplication = (Application) mRawApplication.getBaseContext()
		.getClassLoader().loadClass(mRealApplicationName).newInstance();

mRealApplicationName实际上是指com.taobao.demo.DemoApplication。在这里，构造出了app工程中指定application的对象实例。

##7.2 替换application

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//replace baseContext.mOuterContext
AtlasHacks.ContextImpl_setOuterContext.invoke(mRawApplication.getBaseContext(), mRealApplication);

//replace baseContext.mPackageInfo.mApplication
Object mPackageInfo = AtlasHacks.ContextImpl_mPackageInfo.get(mRawApplication.getBaseContext());

//...

7.2部分，为了保证DemoApplication能够像正常声明的application一样正常工作，做了大量的hook。这里不关注具体hook实现，只给出hook后的映射，感兴趣的童鞋可以自行研究。

替换点 实现类
ContextImpl.mOuterContextt DemoApplication
ContextImp.mPackageInfo DemoApplication
ActivityThread.mInitialApplication DemoApplication
ActivityThread.mAllApplications DemoApplication

##7.3 Application.attach

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AtlasHacks.Application_attach.invoke(mRealApplication,mRawApplication.getBaseContext());

mRealApplication实际上就是DemoApplication,反射执行application的attach方法,即第8步。

##7.4 加载provider

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Object mBoundApplication = AtlasHacks.ActivityThread_mBoundApplication.get(activityThread);

AtlasHacks.ActivityThread$AppBindData_providers.set(mBoundApplication,mBoundApplication_provider);

AtlasHacks.ActivityThread_installContentProviders.invoke(activityThread,mRealApplication,mBoundApplication_provider);

在Atlas启动过程(上)的2.4小节中，为了防止在主dex中找不到bundle中的class,不得已延迟了对provider的加载。而在第5步中，atlas完成了对classloader等关键地方的hook。由于DelegateClassLoader的存在，此时进行加载provider，是不会出现问题的。

#8. DemoApplication.attach

DemoApplication.java

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final void attach(Context context) {
	attachBaseContext(context);
	mLoadedApk = ContextImpl.getImpl(context).mPackageInfo;
}

由7.3可知，mRealApplication实际上就是DemoApplication

  • 调用DemoApplication的attachBaseContext方法
  • 为DemoApplication创建一个LoadedApk对象

#9. startUp

在startup整个函数周期内，做的事情非常之多，重要的是第3、4、6、7和8步。

##9.3 

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public void init(Context context, boolean hookedJavaVM) {
	if(VMUtil.IS_VM_ART) {
		success = Boolean.valueOf(ARTUtils.init(context, hookedJavaVM));
	} else {
       success = Boolean.valueOf(DalvikUtils.init());
   }
}

看函数名，是针对art和dalvik工具类进行初始化。 

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//DalvikUtils.java
public static boolean init() {
	System.loadLibrary("dalvikhack");
	nativeInit();
}
    
//ARTUtils.java
public static boolean init(Context context, boolean hookedJavaVM) {
	System.loadLibrary("dexinterpret");
	nativeInit(...);
}

9.4

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public static int patchIfPossible() {
	System.loadLibrary("dalvikpatch");
	if(isDalvik()) {
   		int ingored = adjustLinearAlloc();
    }
    return 0;
}

首先加载dalvikpatchso,用途： todo

接着执行 adjustLinearAlloc方法 ，用途 todo

9.7

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private synchronized void InitBundleInfoByVersionIfNeed(){
	String bundleInfoStr = (String)RuntimeVariables.getFrameworkProperty("bundleInfo");
	if(!TextUtils.isEmpty(bundleInfoStr)) {
		LinkedHashMap<String,BundleListing.BundleInfo> infos = BundleListingUtil.parseArray(bundleInfoStr);
		BundleListing listing = new BundleListing();
		listing.setBundles(infos);
		mCurrentBundleListing = listing;
    }
}

可以看到，函数是从RuntimeVariables读取字符串，之后解析成对象存储。很明显，这个字符串应该是配置之类的信息。在atals从gradle到apk中，我们提到过，atlas会在编译期间会分析bundle和gradle配置，将一些配置写入RuntimeVariables中。

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package android.taobao.atlas.framework;

public class FrameworkProperties
{
  public static String autoStartBundles;
  public static String bundleInfo = "[{\"activities\":[\"com.taobao.firstbundle.FirstBundleActivity\"],\"contentProviders\":[],\"dependency\":[],\"isInternal\":true,\"pkgName\":\"com.taobao.firstbundle\",\"receivers\":[],\"services\":[\"com.taobao.firstbundle.FirstBundleService\"],\"version\":\"1.0.0@unspecified\"},{\"activities\":[\"com.taobao.secondbundle.SecondBundleActivity\",\"com.taobao.secondbundlelibrary.SecondbundleShareActivity\"],\"contentProviders\":[],\"dependency\":[],\"isInternal\":true,\"pkgName\":\"com.taobao.secondbundle\",\"receivers\":[],\"services\":[],\"version\":\"1.0.0@unspecified\"},{\"activities\":[\"com.taobao.remotebunle.RemoteBundleActivity\"],\"contentProviders\":[],\"dependency\":[],\"isInternal\":false,\"pkgName\":\"com.taobao.remotebunle\",\"receivers\":[],\"services\":[],\"version\":\"1.0.0@unspecified\"},{\"activities\":[],\"contentProviders\":[],\"dependency\":[],\"isInternal\":true,\"pkgName\":\"com.taobao.publicBundle\",\"receivers\":[],\"services\":[],\"version\":\"1.0.0@unspecified\"}]";
 
  static
  {
    autoStartBundles = "com.taobao.firstbundle";
  }
}

可以看到，bundleInfo 字段是一堆json字段，解析后格式BundleInfo,保存着bundle的信息。

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public static class BundleInfo{
	private String pkgName;
	private String applicationName；
	private List<String> dependency;
	private HashMap<String,Boolean> activities;
	private HashMap<String,Boolean> services;
	private HashMap<String,Boolean> receivers;
	private HashMap<String,Boolean> contentProviders;
	//...
}

也就是说，在这一步， atlas获得了所有bundle的信息 。

9.8

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private void started(){
	//读取配置
	String autoStartBundle = (String) RuntimeVariables.getFrameworkProperty("autoStartBundles");
	String[] bundles = autoStartBundle.split(",");
	
	//异步安装bundle
	for (int x = 0; x < bundles.length; x++) {
		final String bundleName = bundles[x];
		BundleInstaller.startDelayInstall(bundleName, ...);
	}                        
}

简化了大部分代码，只关注核心逻辑。代码读取RuntimeVariables上的字段autoStartBundles,这个值是在gradle中配置的com.taobao.firstbundle，然后开始异步加载firstbundle

bundle的加载过程和加载触发时机请参考 atlas之bundle加载过程(正在准备中)，这里不在讨论。

10. DemoApplication.onCreate

DemoApplication.java

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public void onCreate() {
	super.onCreate();
	//...
}

执行app工程定义的DemoApplication的onCreate方法。

至此，Atlas启动过程的分析完成。