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。

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。

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

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。