攜程DynamicAPK插件化框架源碼分析
攜程DynamicAPK插件化框架源碼分析
Author：莫川
插件核心思想
1.aapt的改造
分別對不同的插件項目分配不同的packageId，然后對各個插件的資源進行編譯，生成R文件，然后與宿主項目的R文件進行id的合并。
要求：由于最終會將所有的資源文件id進行合并，因此，所有的資源名稱均不能相同。
2.運行ClassLoader加載各Bundle
和MultiDex的思路是一樣的，所有的插件都被加載到同一個ClassLoader當中，因此，不同插件中的Class必須保持包名和類名的唯一。否則，加載過的類不會再次被加載。
優缺點：各個Bundle之間完全可以相互調用，但是這也造成了各個Bundle之間ClassLoader的非隔離性。并且隨著數組的加長，每次findClass的時間會變長，對性能照成一定長度的影響。
讓我們在熟悉一下這張圖：
在DynamicAPK框架中，每個Bundle被加載到ClassLoader的調用棧如下：
Bundle的Application：BundleBaseApplication
->BundleBaseApplication(onCreate)
->BundleCore(run)
->BundleImpl(optDexFile)
->BundleArchiveRevision(optDexFile)
->BundlePathLoader(installBundleDexs)
->…
如下圖所示：
3.熱修復
由于所有的插件都被加載到同一個ClassLoader當中，因為，熱修復的方案都是從dexElements數組的順序入手，修改expandFieldArray方法的實現，將修復的類放到dexElements的前方。核心代碼如下（詳見BundlePathLoader）：
private static void expandFieldArray(Object instance, String fieldName,
Object[] extraElements,boolean isHotFix) throws NoSuchFieldException, IllegalArgumentException,
IllegalAccessException {
synchronized (BundlePathLoader.class) {
Field jlrField = findField(instance, fieldName);
Object[] original = (Object[]) jlrField.get(instance);
Object[] combined = (Object[]) Array.newInstance(
original.getClass().getComponentType(), original.length + extraElements.length);
if(isHotFix) {
System.arraycopy(extraElements, 0, combined, 0, extraElements.length);
System.arraycopy(original, 0, combined, extraElements.length, original.length);
}else {
System.arraycopy(original, 0, combined, 0, original.length);
System.arraycopy(extraElements, 0, combined, original.length, extraElements.length);
}
jlrField.set(instance, combined);
}
} 調用的關鍵代碼如下(HotPatchItem.class)：
public void optDexFile() throws Exception{
List<File> files = new ArrayList<File>();
files.add(this.hotFixFile);
BundlePathLoader.installBundleDexs(RuntimeArgs.androidApplication.getClassLoader(), storageDir, files, false);
}
public void optHotFixDexFile() throws Exception{
List<File> files = new ArrayList<File>();
files.add(this.hotFixFile);
BundlePathLoader.installBundleDexs(RuntimeArgs.androidApplication.getClassLoader(), storageDir, files, true);
} 4.運行時資源的加載
所有插件的資源都加載到DelegateResources中，關鍵代碼如下：
DelegateResources.class
...
public static void newDelegateResources(Application application, Resources resources) throws Exception {
List<Bundle> bundles = Framework.getBundles();
if (bundles != null && !bundles.isEmpty()) {
Resources delegateResources;
List<String> arrayList = new ArrayList();
arrayList.add(application.getApplicationInfo().sourceDir);
for (Bundle bundle : bundles) {
arrayList.add(((BundleImpl) bundle).getArchive().getArchiveFile().getAbsolutePath());
}
AssetManager assetManager = AssetManager.class.newInstance();
for (String str : arrayList) {
SysHacks.AssetManager_addAssetPath.invoke(assetManager, str);
}
//處理小米UI資源
if (resources == null || !resources.getClass().getName().equals("android.content.res.MiuiResources")) {
delegateResources = new DelegateResources(assetManager, resources);
} else {
Constructor declaredConstructor = Class.forName("android.content.res.MiuiResources").getDeclaredConstructor(new Class[]{AssetManager.class, DisplayMetrics.class, Configuration.class});
declaredConstructor.setAccessible(true);
delegateResources = (Resources) declaredConstructor.newInstance(new Object[]{assetManager, resources.getDisplayMetrics(), resources.getConfiguration()});
}
RuntimeArgs.delegateResources = delegateResources;
AndroidHack.injectResources(application, delegateResources);
StringBuffer stringBuffer = new StringBuffer();
stringBuffer.append("newDelegateResources [");
for (int i = 0; i < arrayList.size(); i++) {
if (i > 0) {
stringBuffer.append(",");
}
stringBuffer.append(arrayList.get(i));
}
stringBuffer.append("]");
log.log(stringBuffer.toString(), Logger.LogLevel.DBUG);
}
}
...
上述代碼就是將所有Bundle中的資源，通過調用AssetManager的addAssetPath方法，加載到assetManager對象中，然后再用assetManager對象，創建delegateResources對象，并保存在RuntimeArgs.delegateResources當中，然后調用AndroidHack.injectResources方法，對Application和LoadedApk中的mResources成員變量進行注入，代碼如下：
public static void injectResources(Application application, Resources resources) throws Exception {
Object activityThread = getActivityThread();
if (activityThread == null) {
throw new Exception("Failed to get ActivityThread.sCurrentActivityThread");
}
Object loadedApk = getLoadedApk(activityThread, application.getPackageName());
if (loadedApk == null) {
throw new Exception("Failed to get ActivityThread.mLoadedApk");
}
SysHacks.LoadedApk_mResources.set(loadedApk, resources);
SysHacks.ContextImpl_mResources.set(application.getBaseContext(), resources);
SysHacks.ContextImpl_mTheme.set(application.getBaseContext(), null);
} 其中，上述獲取LoadedApk的代碼，也是通過反射，獲取運行時ActivityThread類的LoadedApk對象.
5.運行時動態替換Resource對象
ContextImplHook,動態替換getResources
為了控制startActivity的時候，能夠及時替換Activity的Resource和AssetsManager對象，使用ContextImplHook類對Comtext進行替換，然后動態的返回上一步加載的RuntimeArgs.delegateResources委托資源對象。ContextImplHook的核心代碼如下：
@Override
public Resources getResources() {
log.log("getResources is invoke", Logger.LogLevel.INFO);
return RuntimeArgs.delegateResources;
}
@Override
public AssetManager getAssets() {
log.log("getAssets is invoke", Logger.LogLevel.INFO);
return RuntimeArgs.delegateResources.getAssets();
} 如何在Activity跳轉過程中，動態的替換呢
通過反射替換ActivityThread的mInstrumentation對象，替換成InstrumentationHook.class,然后就可以在執行startActivity時，攔截其newActivity和callActivityOnCreate方法，在newActivity方法中，動態的替換newActivity的mResources對象。在callActivityOnCreate方法中將ContextImplHook注入到新創建的Activity中。核心代碼如下：
@Override
public Activity newActivity(Class<?> cls, Context context, IBinder iBinder, Application application, Intent intent, ActivityInfo activityInfo, CharSequence charSequence, Activity activity, String str, Object obj) throws InstantiationException, IllegalAccessException {
Activity newActivity = this.mBase.newActivity(cls, context, iBinder, application, intent, activityInfo, charSequence, activity, str, obj);
if (RuntimeArgs.androidApplication.getPackageName().equals(activityInfo.packageName) && SysHacks.ContextThemeWrapper_mResources != null) {
SysHacks.ContextThemeWrapper_mResources.set(newActivity, RuntimeArgs.delegateResources);
}
return newActivity;
}
@Override
public Activity newActivity(ClassLoader classLoader, String str, Intent intent) throws InstantiationException, IllegalAccessException, ClassNotFoundException {
Activity newActivity;
try {
newActivity = this.mBase.newActivity(classLoader, str, intent);
if (SysHacks.ContextThemeWrapper_mResources != null) {
SysHacks.ContextThemeWrapper_mResources.set(newActivity, RuntimeArgs.delegateResources);
}
} catch (ClassNotFoundException e) {
String property = Framework.getProperty("ctrip.android.bundle.welcome", "ctrip.android.view.home.CtripSplashActivity");
if (StringUtil.isEmpty(property)) {
throw e;
} else {
List runningTasks = ((ActivityManager) this.context.getSystemService(Context.ACTIVITY_SERVICE)).getRunningTasks(1);
if (runningTasks != null && runningTasks.size() > 0 && ((ActivityManager.RunningTaskInfo) runningTasks.get(0)).numActivities > 1) {
if (intent.getComponent() == null) {
intent.setClassName(this.context, str);
}
}
log.log("Could not find activity class: " + str, Logger.LogLevel.WARN);
log.log("Redirect to welcome activity: " + property, Logger.LogLevel.WARN);
newActivity = this.mBase.newActivity(classLoader, property, intent);
}
}
return newActivity;
}
@Override
public void callActivityOnCreate(Activity activity, Bundle bundle) {
if (RuntimeArgs.androidApplication.getPackageName().equals(activity.getPackageName())) {
ContextImplHook contextImplHook = new ContextImplHook(activity.getBaseContext());
if (!(SysHacks.ContextThemeWrapper_mBase == null || SysHacks.ContextThemeWrapper_mBase.getField() == null)) {
SysHacks.ContextThemeWrapper_mBase.set(activity, contextImplHook);
}
SysHacks.ContextWrapper_mBase.set(activity, contextImplHook);
}
this.mBase.callActivityOnCreate(activity, bundle);
} 總結如下圖,Resource的加載和動態替換：
6.插件Activity在宿主AndroidManifest中的預注冊
每個插件的Activity，必須在宿主的AndroidManifest.xml中進行注冊。
DynamicAPK源碼導讀：
源代碼的目錄結構圖
- framework
管理各個Bundle以及各個Bundle的封裝、版本控制等。
- hack
通過反射的形式，hack類，方法，成員變量等
- hotpatch
熱修復相關的封裝
- loader
對MultiDex的修改，各Bundle加載到ClassLoader，熱修復。
- log
日志管理
- runtime
運行時，對Resources進行動態替換
- util
工具類
博客相關Demo的Github地址
參考
1.AssetManager源碼
2.LoadedApk源碼
3.ActivityThread源碼
4.DynamicAPK源碼
來自： http://blog.csdn.net/nupt123456789/article/details/50531709