从零开始分析 InstantRun 源码 (1)，最新精心整理 Android 面试题
####Gradle4.1 的 Instant Run
源码分析是基于 Gradle4.1 版本研究的 Instant Run，但是这个版本的 Instant Run 功能已经削减很多了，下面还会介绍其他版本的 Gradle
运行后反编译 app-debug.apk 会找到多个 dex(一般是两个)，一开始是通过 dex2jar-2.0 和 jd-gui，但是有时候有些方法无法进行反编译而是依旧显示初始的字节码，很不方便阅读，后来使用了 jadx-gui 进行直接反编译 apk，使用很方便，但依旧还是会有些方法还是显示字节码，所以我是两者交叉着看，但是有时候甚至两者都是字节码，只能上网上直接找别人的博客代码了。
因为我研究的版本是基于 Gradle4.1 的，仅仅剩下可怜的热插拔和处理资源补丁,而且我还找不到 intant-run.zip 了，所以我找不到项目中的代码了，不在 dex 文件中，原本这玩意解压 apk 之后就有了，所以暂时只能在 build 下的目录里面寻找了，后面再看看这些文件时如何弄到 apk 当中。
InstantRunContentProvider 的 onCreate 方法中初始化 Socket
public boolean onCreate() {if (isMainProcess()) { //只支持主进程 Log.i("InstantRun", "starting instant run server: is main process");Server.create(getContext());return true;}Log.i("InstantRun", "not starting instant run server: not main process");return true;}
然后启动一个 socket 监听 Android Studio 推送的消息
private class SocketServerThread extends Thread {private SocketServerThread() {}
public void run() {while (true) {try {LocalServerSocket localServerSocket = Server.this.serverSocket;if (localServerSocket == null)return;LocalSocket localSocket = localServerSocket.accept();if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Received connection from IDE: spawning connection thread");(new Server.SocketServerReplyThread(localSocket)).run();if (wrongTokenCount > 50) {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Stopping server: too many wrong token connections");Server.this.serverSocket.close();return;}} catch (Throwable throwable) {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Fatal error accepting connection on local socket", throwable);}}}}
然后在 SocketServerReplyThread 的 run 方法值接受数据并处理
//处理补丁 private int handlePatches(List<ApplicationPatch> paramList, boolean paramBoolean, int paramInt) {if (paramBoolean)FileManager.startUpdate();for (ApplicationPatch applicationPatch : paramList) {String str = applicationPatch.getPath();if (str.equals("classes.dex.3")) { //如果有 classes.dex.3 处理热插拔 paramInt = handleHotSwapPatch(paramInt, applicationPatch);continue;}if (isResourcePath(str))//处理资源补丁 paramInt = handleResourcePatch(paramInt, applicationPatch, str);}if (paramBoolean)FileManager.finishUpdate(true);return paramInt;}
这里先来看看 ApplicationPatch 是什么
public static List<ApplicationPatch> read(DataInputStream paramDataInputStream) throws IOException {int j = paramDataInputStream.readInt();if (Log.logging != null && Log.logging.isLoggable(Level.FINE))Log.logging.log(Level.FINE, "Receiving " + j + " changes");ArrayList<ApplicationPatch> arrayList = new ArrayList(j);for (int i = 0; i < j; i++) {String str = paramDataInputStream.readUTF();byte[] arrayOfByte = new byte[paramDataInputStream.readInt()];paramDataInputStream.readFully(arrayOfByte);arrayList.add(new ApplicationPatch(str, arrayOfByte));}return arrayList;}
可以看到 ApplicationPatch 是从 Socket 接收到的数据输入流中调用 readFully 来读取的，关于 readFully 的使用 while 循环判断 byte 数组是否已经读满所有数据，如果没有读满则继续读取补充直到读满为止，从而改善输入流出现空档，造成 read 方法直接跳出的问题。即通过缓冲来保证数量的完整，也算是常用的一种方法。所以以后若要读取特定长度的数据，使用 readFully 读取更加安全。
#####1.处理热插拔
下面来看看是如何处理热插拔的
//处理热插拔 private int handleHotSwapPatch(int paramInt, ApplicationPatch paramApplicationPatch) {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Received incremental code patch");try {//创建或获取“data/data/applicationid/files/instant-run/dex”文件路径 String str1 = FileManager.writeTempDexFile(paramApplicationPatch.getBytes());if (str1 == null) {Log.e("InstantRun", "No file to write the code to");return paramInt;}if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Reading live code from " + str1);
String str2 = FileManager.getNativeLibraryFolder().getPath();//反射构造 AppPatchesLoaderImpl 实例 Class<?> clazz = Class.forName("com.android.tools.fd.runtime.AppPatchesLoaderImpl", true, (ClassLoader)new DexClassLoader(str1, this.context.getCacheDir().getPath(), str2, getClass().getClassLoader()));try {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Got the patcher class " + clazz);PatchesLoader patchesLoader = (PatchesLoader)clazz.newInstance();if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Got the patcher instance " + patchesLoader);//获取热修复所要替换的类的 classnameString[] arrayOfString = (String[])clazz.getDeclaredMethod("getPatchedClasses", new Class[0]).invoke(patchesLoader, new Object[0]);if (Log.isLoggable("InstantRun", 2)) {Log.v("InstantRun", "Got the list of classes ");int j = arrayOfString.length;for (int i = 0; i < j; i++) {String str = arrayOfString[i];Log.v("InstantRun", "class " + str);}}//执行 AppPatchesLoaderImpl 的 load 方法进行类修复 boolean bool = patchesLoader.load();if (!bool)paramInt = 3;} catch (Exception exception) {}} catch (Throwable throwable) {Log.e("InstantRun", "Couldn't apply code changes", throwable);paramInt = 3;}return paramInt;}//AppPatchesLoaderImpl 实现抽象类 AbstractPatchesLoaderImpl，重写 getPatchedClasses 方法，重写方法中有提供需要热更新的类 public abstract class AbstractPatchesLoaderImpl implements PatchesLoader {public abstract String[] getPatchedClasses();
public boolean load() {try {//《《《《《《最关键的方法，一个个替换类中要替换的方法》》》》》》for (String str : getPatchedClasses()) {ClassLoader classLoader = getClass().getClassLoader();Object object1 = classLoader.loadClass(str + "change");field.setAccessible(true);Object object2 = field.get(null);if (object2 != null) {object2 = object2.getClass().getDeclaredField("$obsolete");if (object2 != null)object2.set(null, Boolean.valueOf(true));}field.set(null, object1);if (Log.logging != null && Log.logging.isLoggable(Level.FINE))Log.logging.log(Level.FINE, String.format("patched %s", new Object[] { str }));}} catch (Exception exception) {if (Log.logging != null)Log.logging.log(Level.SEVERE, String.format("Exception while patching %s", new Object[] { "foo.bar" }), exception);return false;}return true;}}//AppPatchesLoaderImpl 继承 AbstractPatchesLoaderImpl,真正的实现类，这里我们只要求 change 的 MainActivity 这个类里面的方法 public class AppPatchesLoaderImpl extends AbstractPatchesLoaderImpl {public static final long BUILD_ID = 1597285889481L;
public AppPatchesLoaderImpl() {}
public String[] getPatchedClasses() {return new String[]{"com.example.jackie.instantrundemo.MainActivity"};}}
其中 DexClassLoader 的构造方法定义
//dexPath:被解压的 apk 路径，不能为空。//optimizedDirectory：解压后的.dex 文件的存储路径，不能为空。这个路径强烈建议使用应用程序的私有路径，不要放到 sdcard 上，否则代码容易被注入攻击。//libraryPath：os 库的存放路径，可以为空，若有 os 库，必须填写。//parent：父类加载器，一般为 context.getClassLoader(),使用当前上下文的类加载器。DexClassLoader(String dexPath, String optimizedDirectory, String librarySearchPath, ClassLoader parent)
我们的 MainActivity 会被修改成这样
public class MainActivity extends AppCompatActivity {public static final long serialVersionUID = 2158910920756968252L;
//重写空构造方法，方便于替换该方法的实现 public MainActivity() {IncrementalChange var1 = change;if(var1 != null) {Object[] var10001 = (Object[])var1.accessdispatch("initdispatch("init$body.(Lcom/example/jackie/instantrundemo/MainActivity;[Ljava/lang/Object;)V", var2);} else {super();}}
public void onCreate(Bundle savedInstanceState) {IncrementalChange var2 = change;if(var2 != null) {var2.accessdispatch("onCreate.(Landroid/os/Bundle;)V", new Object[]{this, savedInstanceState});} else {super.onCreate(savedInstanceState);this.setContentView(2130968603);if(this.test(30) > 20333005) {Log.d("jackie", "==4444099994==sf=dd=ddecf==999=abc==");} else {Log.d("jackie", "==999999999999=");}
byte b = 0;Toast.makeText(this, "hellodd4fdddd", 1).show();Log.d("jackie", "===d=666==dd=dddd==abc==" + b);}}
public int test(int a) {IncrementalChange var2 = change;if(var2 != null) {return ((Number)var2.accessdispatch("test.(I)I", new Object[]{this, new Integer(a)})).intValue();} else {byte age = 100;int b = 300189 + age;
for(int i = 0; i < b + 9; ++i) {a += b;}
return 20 + a;}}//增加类的构造方法，方便与修改类的任何构造方法 MainActivity(Object[] var1, InstantReloadException var2) {String var3 = (String)var1[1];switch(var3.hashCode()) {case -2089128195:super();return;case 173992496:this();return;default:throw new InstantReloadException(String.format("String switch could not find '%s' with hashcode %s in %s", new Object[]{var3, Integer.valueOf(var3.hashCode()), "com/example/jackie/instantrundemo/MainActivity"}));}}}
在 MainActivity 中做个小修改，点击小闪电执行 Instant Run，可以看到 build 下面文件夹 4000 中会找一个 MainActivity$override.class 和 AppPatchesLoaderImpl.class
要替换的 MainActivity$override 实现了 IncrementalChange，从这里面进行方法的替换，所有的方法都会被替换，因为change值不为空
public class MainActivityoverride implements IncrementalChange {public MainActivityoverride() {}
public static Object init$args(MainActivity[] var0, Object[] var1) {Object[] var2 = new Object[]{new Object[]{var0, new Object[0]}, "android/support/v7/app/AppCompatActivity.()V"};return var2;}
public static void initthis, Object[] var1) {AndroidInstantRuntime.setPrivateField($this, new Integer(100), MainActivity.class, "cmd");}
public static void onCreate(MainActivity this, Bundle savedInstanceState) {Object[] var2 = new Object[]{savedInstanceState};MainActivity.accesssuper(this.setContentView(2130968603);if($this.test(30) > 20333005) {Log.d("jackie", "==44440999940==sf=dd=ddecf==999=abc==");} else {Log.d("jackie", "==999999999999=");}
byte b = 0;//因为修改了全局变量的值，所以进行处理 AndroidInstantRuntime.setPrivateField(this, MainActivity.class, "cmd")).intValue() + 100), MainActivity.class, "cmd");Toast.makeText($this, "hellodd4fdddd", 1).show();Log.d("jackie", "===d=666==dd=dddd==abc==" + b);}
public static int test(MainActivity this, int a) {int ageabc = 100 + ((Number)AndroidInstantRuntime.getPrivateField(this, MainActivity.class, "cmd")).intValue();int b = 300189 + ageabc;
for(int i = 0; i < b + 9; ++i) {a += b;}
return 20 + a;}
//替换相对应的方法,最后两个方法我估计是前面 MainActivity 类里面的 copypublic Object accessdispatch(String var1, Object... var2) {switch(var1.hashCode()) {case -1227667971:return new Integer(test((MainActivity)var2[0], ((Number)var2[1]).intValue()));case -641568046:onCreate((MainActivity)var2[0], (Bundle)var2[1]);return null;case 435530788:return initargs((MainActivity[])var2[0], (Object[])var2[1]);case 1043612718:init$body((MainActivity)var2[0], (Object[])var2[1]);return null;default:throw new InstantReloadException(String.format("String switch could not find '%s' with hashcode %s in %s", new Object[]{var1, Integer.valueOf(var1.hashCode()), "com/example/jackie/instantrundemo/MainActivity"}));}}}
#####2.处理资源补丁(温插拔)
下面来看看是如何处理资源补丁的，但是设计到资源的处理需要重启当前界面，我们先来看看重启 App 这种状况下的逻辑
//Server 类的 handle()case 5:if (authenticate(param1DataInputStream)) {Activity activity1 = Restarter.getForegroundActivity(Server.this.context);if (activity1 != null) {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Restarting activity per user request");Restarter.restartActivityOnUiThread(activity1);}continue;}return;case 1:if (authenticate(param1DataInputStream)) {List<ApplicationPatch> list = ApplicationPatch.read(param1DataInputStream);if (list != null) {bool = Server.hasResources(list);i = param1DataInputStream.readInt();//处理 acitivity 或者把资源写到文件中 i = Server.this.handlePatches(list, bool, i);boolean bool1 = param1DataInputStream.readBoolean();param1DataOutputStream.writeBoolean(true);//重启 ActivityServer.this.restart(i, bool, bool1);}continue;}
我们先来看看 handlePatches 里面的 handleResourcePatch 是如何处理资源的
//Server.class//处理资源补丁 private static int handleResourcePatch(int paramInt, ApplicationPatch paramApplicationPatch, String paramString) {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Received resource changes (" + paramString + ")");FileManager.writeAaptResources(paramString, paramApplicationPatch.getBytes());return Math.max(paramInt, 2);}//FileManager.class//writeAaptResourcespublic static void writeAaptResources(String paramString, byte[] paramArrayOfbyte) {File file1 = getResourceFile(getWriteFolder(false)); //获取资源文件 File file2 = file1.getParentFile();if (!file2.isDirectory() && !file2.mkdirs()) {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Cannot create local resource file directory " + file2);return;}//把内容写到 resources.ap_资源中 if (paramString.equals("resources.ap_")) {writeRawBytes(file1, paramArrayOfbyte);return;}//把 raw 资源写入 writeRawBytes(file1, paramArrayOfbyte);}//getWriteFolderpublic static File getWriteFolder(boolean paramBoolean) {String str;if (leftIsActive()) {str = "right";} else {str = "left";}File file = new File(getDataFolder(), str);if (paramBoolean && file.exists()) {delete(file);if (!file.mkdirs())Log.e("InstantRun", "Failed to create folder " + file);}return file;}//getResourceFileprivate static File getResourceFile(File paramFile) { return new File(paramFile, "resources.ap_"); }
//writeRawBytespublic static boolean writeRawBytes(File paramFile, byte[] paramArrayOfbyte) {try {BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(paramFile));try {bufferedOutputStream.write(paramArrayOfbyte);bufferedOutputStream.flush();return true;} finally {bufferedOutputStream.close();}} catch (IOException iOException) {Log.wtf("InstantRun", "Failed to write file, clean project and rebuild " + paramFile, iOException);throw new RuntimeException(String.format("InstantRun could not write file %1$s, clean project and rebuild ", new Object[] { paramFile }));}}public static String writeTempDexFile(byte[] paramArrayOfbyte) {File file = getTempDexFile();if (file != null) {writeRawBytes(file, paramArrayOfbyte);return file.getPath();}Log.e("InstantRun", "No file to write temp dex content to");return null;}
下面来看看Server.this.restart(i, bool, bool1)是如何处理的，不必拘泥于细节是如何启动的，在里面找到一行关键代码
MonkeyPatcher.monkeyPatchExistingResources(this.context, str, list);
具体实现如下
public static void monkeyPatchExistingResources(Context context, String externalResourceFile, Collection<Activity> activities) {Collection<WeakReference<Resources>> references;if (externalResourceFile != null) {//通过反射获取 AssetManagerAssetManager newAssetManager = AssetManager.class.getConstructor(new Class[0]).newInstance(new Object[0]);Method mAddAssetPath = AssetManager.class.getDeclaredMethod("addAssetPath", new Class[]{String.class});mAddAssetPath.setAccessible(true);//将当前的资源文件路径添加到 AssetManager 中 if (((Integer) mAddAssetPath.invoke(newAssetManager, new Object[]{externalResourceFile})).intValue() == 0) {throw new IllegalStateException("Could not create new AssetManager");}Method mEnsureStringBlocks = AssetManager.class.getDeclaredMethod("ensureStringBlocks", new Class[0]);mEnsureStringBlocks.setAccessible(true);//进行资源初始化 StringBlock 对象 mEnsureStringBlocks.invoke(newAssetManager, new Object[0]);if (activities != null) {for (Activity activity : activities) {Resources resources = activity.getResources();try {Field mAssets = Resources.class.getDeclaredField("mAssets");mAssets.setAccessible(true);mAssets.set(resources, newAssetManager);} catch (Throwable e) {throw new IllegalStateException(e);}Resources.Theme theme = activity.getTheme();try {Field ma = Resources.Theme.class.getDeclaredField("mAssets");ma.setAccessible(true);ma.set(theme, newAssetManager);} catch (NoSuchFieldException e2) {Field themeField = Resources.Theme.class.getDeclaredField("mThemeImpl");themeField.setAccessible(true);Object impl = themeField.get(theme);Field ma2 = impl.getClass().getDeclaredField("mAssets");ma2.setAccessible(true);ma2.set(impl, newAssetManager);} catch (Throwable e3) {Log.e(Logging.LOG_TAG, "Failed to update existing theme for activity " + activity, e3);}Field mt = ContextThemeWrapper.class.getDeclaredField("mTheme");mt.setAccessible(true);mt.set(activity, (Object) null);Method mtm = ContextThemeWrapper.class.getDeclaredMethod("initializeTheme", new Class[0]);mtm.setAccessible(true);mtm.invoke(activity, new Object[0]);if (Build.VERSION.SDK_INT < 24) {Method mCreateTheme = AssetManager.class.getDeclaredMethod("createTheme", new Class[0]);mCreateTheme.setAccessible(true);Object internalTheme = mCreateTheme.invoke(newAssetManager, new Object[0]);Field mTheme = Resources.Theme.class.getDeclaredField("mTheme");mTheme.setAccessible(true);mTheme.set(theme, internalTheme);}pruneResourceCaches(resources);}}//获取当前 JVM 中的 ResourcesManager 的 final ArrayMap<ResourcesKey, WeakReference<Resources> > mActiveResourcesif (Build.VERSION.SDK_INT >= 19) {Class<?> resourcesManagerClass = Class.forName("android.app.ResourcesManager");Method mGetInstance = resourcesManagerClass.getDeclaredMethod("getInstance", new Class[0]);mGetInstance.setAccessible(true);Object resourcesManager = mGetInstance.invoke((Object) null, new Object[0]);try {Field fMActiveResources = resourcesManagerClass.getDeclaredField("mActiveResources");fMActiveResources.setAccessible(true);references = ((ArrayMap) fMActiveResources.get(resourcesManager)).values();} catch (NoSuchFieldException e4) {Field mResourceReferences = resourcesManagerClass.getDeclaredField("mResourceReferences");mResourceReferences.setAccessible(true);references = (Collection) mResourceReferences.get(resourcesManager);}} else {Class<?> activityThread = Class
.forName("android.app.ActivityThread");Field fMActiveResources2 = activityThread.getDeclaredField("mActiveResources");fMActiveResources2.setAccessible(true);references = ((HashMap) fMActiveResources2.get(getActivityThread(context, activityThread))).values();}//循环便利当前 Resources，将其成员变量 mAssets 指向自定义的 newAssetManagerfor (WeakReference<Resources> wr : references) {Resources resources2 = (Resources) wr.get();if (resources2 != null) {try {Field mAssets2 = Resources.class.getDeclaredField("mAssets");mAssets2.setAccessible(true);mAssets2.set(resources2, newAssetManager);} catch (Throwable th) {Field mResourcesImpl = Resources.class.getDeclaredField("mResourcesImpl");mResourcesImpl.setAccessible(true);Object resourceImpl = mResourcesImpl.get(resources2);Field implAssets = resourceImpl.getClass().getDeclaredField("mAssets");implAssets.setAccessible(true);implAssets.set(resourceImpl, newAssetManager);}//更新资源 resources2.updateConfiguration(resources2.getConfiguration(), resources2.getDisplayMetrics());}}}}
在研究过程中，本来想基于退出 gradle4.1 然后在 gradle2.2.3 重新再搞一下，后面想想不把 4.1 研究透再去搞 2.2.3 总是心有不甘，网上也基本找不到 gradle 4.1 的研究的，其实在 2.3.0 之后就没有 instant-run.zip 包了，但是好像所有人都没有提到这点，难道他们都是基于 2.2.3 或者更早的？
####找不到的项目代码去哪里了
下面来看看我们的 MainActivity,MyApplication 等文件在去哪里了，找到之前的 Server(SocketServerThread)，明白我们是从 AS 端接受这些文件的，接受这些 dex 文件后，存储在 app 的 cache 文件中(getWriteFolder)，并进行处理，
private class SocketServerThread extends Thread {private SocketServerThread() {}
public void run() {while (true) {try {LocalServerSocket localServerSocket = Server.this.serverSocket;if (localServerSocket == null)return;//接受 AS 发过来的文件 LocalSocket localSocket = localServerSocket.accept();if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Received connection from IDE: spawning connection thread");(new Server.SocketServerReplyThread(localSocket)).run();if (wrongTokenCount > 50) {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Stopping server: too many wrong token connections");Server.this.serverSocket.close();return;}} catch (Throwable throwable) {if (Log.isLoggable("InstantRun", 2))Log.v("InstantRun", "Fatal error accepting connection on local socket", throwable);}}}}
下面可以使用我们一开始下载的源码，在 instant-run 下面的 intant-run-client，InstantClient 类中，将文件发送到设备中
private void transferBuildIdToDevice(@NonNull IDevice device, @NonNull String buildId) {try {String remoteIdFile = getDeviceIdFolder(mPackageName);//noinspection SSBasedInspection This should workFile local = File.createTempFile("build-id", "txt");local.deleteOnExit();Files.write(buildId, local, Charsets.UTF_8);device.pushFile(local.getPath(), remoteIdFile);} catch (IOException ioe) {mLogger.warning("Couldn't write build id file: %s", ioe);} catch (AdbCommandRejectedException | TimeoutException | SyncException e) {mLogger.warning("%s", Throwables.getStackTraceAsString(e));}}
我们回看之前的 handleHotSwapPatch 方法中读取文件的方式，可以看到在 cache 文件中
private int handleHotSwapPatch(int updateMode, @NonNull ApplicationPatch patch) {···try {String dexFile = FileManager.writeTempDexFile(patch.getBytes());···String nativeLibraryPath = FileManager.getNativeLibraryFolder().getPath();DexClassLoader dexClassLoader = new DexClassLoader(dexFile,context.getCacheDir().getPath(), nativeLibraryPath,getClass().getClassLoader());
####使用 InstantRun 更新的文件去哪里了
下面来看看我们的MainActivity$override,MyApplication$override,AppPatchesLoaderImpl 等文件在去哪里了,我们进入应用内部的/data/data/com.example.jackie.instantrundemo/files/instant-run/dex-temp中会发现一个 reload0x0000.dex 文件，里面就有提供更新的内容，instant-run 里面中的 right 是用于存储 resource.ap_。
其他一些 Gradle 版本
Gradle2.2.3
在当前版本中，我们可以看到 instant-run.zip 包，里面包含的项目的代码和要替换的代码。解压后可以看到 AndroidManifest.xml 文件，从 AndroidManifest.xml 中我们看到了MyApplication 被 BootstrapApplication 替代，那么我们可以想象当 Application 为 Instant-run 自己的时，那么它至少可以像加载插件一样在应用启动的时候（程序入口）加载替换自己的 dex 和资源文件，从而达到修改运行程序的目的。
@Overrideprotected void attachBaseContext(Context context) {// As of Marshmallow, we use APK splits and don't need to rely on// reflection to inject classes and resources for coldswap//noinspection PointlessBooleanExpression//是否使用了 apk 分裂安装 if (!AppInfo.usingApkSplits) {String apkFile = context.getApplicationInfo().sourceDir;long apkModified = apkFile != null ? new File(apkFile).lastModified() : 0L;//判断资源 resource.ap_是否进行了修改，将其路径保存在 externalResourcePathcreateResources(apkModified);//创建 classloade//delegateClassLoader->PathClassLoader->IncrementalClassLoader->BootClassLoadersetupClassLoaders(context, context.getCacheDir().getPath(), apkModified);}//创建正真的 ApplicationcreateRealApplication();
// This is called from ActivityThread#handleBindApplication() -> LoadedApk#makeApplication().// Application#mApplication is changed right after this call, so we cannot do the monkey// patching here. So just forward this method to the real Application instance.super.attachBaseContext(context);
if (realApplication != null) {try {Method attachBaseContext =ContextWrapper.class.getDeclaredMethod("attachBaseContext", Context.class);attachBaseContext.setAccessible(true);//执行自己的 Application 的 attachBaseContext 方法 attachBaseContext.invoke(realApplication, context);} catch (Exception e) {throw new IllegalStateException(e);}}}
该方法的主要目的在于，创建自定义的 ClassLoader 和真正的 Application 实例。而 BootstrapApplication 只起到一个壳子的作用。
替换 Application 的时候我们可以看看 MonkeyPatcher 中是如何替换的
public class MonkeyPatcher {public static void monkeyPatchApplication(Context context, Application bootstrap, Application realApplication, String externalResourceFile) {Class<?> activityThread;Class<?> loadedApkClass;try {//获取 ActivityThread 实例 activityThread = Class.forName("android.app.ActivityThread");Object currentActivityThread = getActivityThread(context, activityThread);Field mInitialApplication = activityThread.getDeclaredField("mInitialApplication");mInitialApplication.setAccessible(true);
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