title: Atlas之启动过程(二)

date: 2017-05-03 15:00:00

概述

接上篇 Atlasz之启动过程(一) ,继续 6-10 步的启动过程。

Atlas之启动过程(二) - 图1

6. onCreate

AtlasBridgeApplication.java

  1. @Override
  2. public void onCreate() {
  3.     super.onCreate();
  4.     Method method = mBridgeApplicationDelegate.getClass().getDeclaredMethod("onCreate");
  5.     method.invoke(mBridgeApplicationDelegate);       
  6. }

直接反射调用mBridgeApplicationDelegate的onCreate方法.

7. BridgeApplicationDelegate.onCreate

BridgeApplicationDelegate.java

  1. public void onCreate(){
  2.    // 7.1 实例application
  3.     mRealApplication = (Application) mRawApplication.getBaseContext()
  4.         .getClassLoader().loadClass(mRealApplicationName).newInstance();
  6.     //7.2 replace xxx
  7.     AtlasHacks.ContextImpl_setOuterContext.invoke(
  8.         mRawApplication.getBaseContext(), mRealApplication);
  9.     //...
  11.     //7.3 mRealApplication.attach
  12.     AtlasHacks.Application_attach
  13.            .invoke(mRealApplication,mRawApplication.getBaseContext());
  15.     //7.4 install content providers
  16.     Object mBoundApplication = AtlasHacks.ActivityThread_mBoundApplication.get(activityThread);
  17.     AtlasHacks.ActivityThread$AppBindData_providers.set(mBoundApplication,mBoundApplication_provider);
  18.     AtlasHacks.ActivityThread_installContentProviders.invoke(activityThread,mRealApplication,mBoundApplication_provider);
  20.     //7.5. startup
  21.     Atlas.getInstance().startup(mRealApplication,mIsUpdated);
  23.     //7.6 onCreate
  24.     mRealApplication.onCreate();
  25. }

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

  1. mRealApplication = (Application) mRawApplication.getBaseContext()
  2.         .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

  1. //replace baseContext.mOuterContext
  2. AtlasHacks.ContextImpl_setOuterContext.invoke(mRawApplication.getBaseContext(), mRealApplication);
  4. //replace baseContext.mPackageInfo.mApplication
  5. Object mPackageInfo = AtlasHacks.ContextImpl_mPackageInfo.get(mRawApplication.getBaseContext());
  7. //...

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

  1. 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

  1. Object mBoundApplication = AtlasHacks.ActivityThread_mBoundApplication.get(activityThread);
  3. AtlasHacks.ActivityThread$AppBindData_providers.set(mBoundApplication,mBoundApplication_provider);
  5. 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

  1. final void attach(Context context) {
  2.     attachBaseContext(context);
  3.     mLoadedApk = ContextImpl.getImpl(context).mPackageInfo;
  4. }

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

Atlas之启动过程(二) - 图2

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

  1. public void init(Context context, boolean hookedJavaVM) {
  2.     if(VMUtil.IS_VM_ART) {
  3.         success = Boolean.valueOf(ARTUtils.init(context, hookedJavaVM));
  4.     } else {
  5.        success = Boolean.valueOf(DalvikUtils.init());
  6.    }
  7. }

看函数名，是针对art和dalvik工具类进行初始化。 

  1. //DalvikUtils.java
  2. public static boolean init() {
  3.     System.loadLibrary("dalvikhack");
  4.     nativeInit();
  5. }
  7. //ARTUtils.java
  8. public static boolean init(Context context, boolean hookedJavaVM) {
  9.     System.loadLibrary("dexinterpret");
  10.     nativeInit(...);
  11. }

9.4

  1. public static int patchIfPossible() {
  2.     System.loadLibrary("dalvikpatch");
  3.     if(isDalvik()) {
  4.            int ingored = adjustLinearAlloc();
  5.     }
  6.     return 0;
  7. }

首先加载dalvikpatchso,用途： todo

接着执行 adjustLinearAlloc方法 ，用途 todo

9.7

  1. private synchronized void InitBundleInfoByVersionIfNeed(){
  2.     String bundleInfoStr = (String)RuntimeVariables.getFrameworkProperty("bundleInfo");
  3.     if(!TextUtils.isEmpty(bundleInfoStr)) {
  4.         LinkedHashMap<String,BundleListing.BundleInfo> infos = BundleListingUtil.parseArray(bundleInfoStr);
  5.         BundleListing listing = new BundleListing();
  6.         listing.setBundles(infos);
  7.         mCurrentBundleListing = listing;
  8.     }
  9. }

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。

  1. package android.taobao.atlas.framework;
  3. public class FrameworkProperties
  4. {
  5.   public static String autoStartBundles;
  6.   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\"}]";
  8.   static
  9.   {
  10.     autoStartBundles = "com.taobao.firstbundle";
  11.   }
  12. }

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。

  1. public static class BundleInfo{
  2.     private String pkgName;
  3.     private String applicationName；
  4.     private List<String> dependency;
  5.     private HashMap<String,Boolean> activities;
  6.     private HashMap<String,Boolean> services;
  7.     private HashMap<String,Boolean> receivers;
  8.     private HashMap<String,Boolean> contentProviders;
  9.     //...
  10. }

也就是说，在这一步， atlas获得了所有bundle的信息 。

9.8

  1. private void started(){
  2.     //读取配置
  3.     String autoStartBundle = (String) RuntimeVariables.getFrameworkProperty("autoStartBundles");
  4.     String[] bundles = autoStartBundle.split(",");
  6.     //异步安装bundle
  7.     for (int x = 0; x < bundles.length; x++) {
  8.         final String bundleName = bundles[x];
  9.         BundleInstaller.startDelayInstall(bundleName, ...);
  10.     }                        
  11. }

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，这里不在讨论。

10. DemoApplication.onCreate

DemoApplication.java

  1. public void onCreate() {
  2.     super.onCreate();
  3.     //...
  4. }

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。