Android進階（十）資源和Service的插件化
1、系統資源加載
一、資源類別
- res目錄下存放的資源文件。編譯時會在R文件中生成資源文件的十六進制值。res目錄下資源經過Context.getResource方法獲取到Resource對象，而後經過getXXX獲取資源。
- assets目錄下存放的原始文件，編譯時不會被編譯。經過AssetManager的open方法獲取目錄下文件資源，AssetManager來源於Resources類的getAssets方法
二、Resources
（1）AssetManager
android
- AssetManage有一個addAssetPath方法，將apk路徑傳入，Resources就能訪問當前apk的全部資源。能夠經過反射的方式將插件apk路徑傳入addAssetPath方法。
- AssetManager內部有一個NDK方法，用來訪問文件。apk打包時會生成一個resources.arsc文件，是一個Hash表，存放着十六進制和資源的對應關係
2、VirtualApk插件資源加載
資源插件化實現方式：bash
- 合併資源：將插件的資源合併到宿主的Resources中，能夠訪問宿主的資源。可能存在插件和宿主的資源id重複的狀況。
解決方式：
（1）修改Android打包流程中使用到的aapt命令，爲插件的資源id指定前綴，避免與宿主資源id衝突。
（2）在Android打包生成resources.arsc文件以後，對這個resources.arsc文件進行修改。 - 單獨加載插件資源：每一個插件都會構造單獨的Resources去加載插件資源，不能訪問宿主資源
一、Resources建立
#LoadedPlugin
public LoadedPlugin(PluginManager pluginManager, Context context, File apk) throws Exception {
......
this.mResources = createResources(context, getPackageName(), apk);
......
}
protected Resources createResources(Context context, String packageName, File apk) throws Exception {
if (Constants.COMBINE_RESOURCES) {
//插件資源合併到宿主中，插件可訪問宿主資源
return ResourcesManager.createResources(context, packageName, apk);
} else {
//插件建立獨立的Resources，不與宿主關聯
Resources hostResources = context.getResources();
AssetManager assetManager = createAssetManager(context, apk);
return new Resources(assetManager, hostResources.getDisplayMetrics(), hostResources.getConfiguration());
}
}
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二、插件資源獨立
主要經過反射建立新的AssetManager對象，經過addAssetPath加載插件資源。適用於資源獨立的狀況，沒法調用宿主資源cookie
protected AssetManager createAssetManager(Context context, File apk) throws Exception {
//經過反射建立新的AssetManager對象，經過addAssetPath加載插件資源
AssetManager am = AssetManager.class.newInstance();
Reflector.with(am).method("addAssetPath", String.class).call(apk.getAbsolutePath());
return am;
}
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三、插件資源合併
先獲取到宿主資源的AssetManager，再經過反射調用AssetManager的addAssetPath添加插件資源，返回新的Resourcesapp
#ResourcesManager
public static synchronized Resources createResources(Context hostContext, String packageName, File apk) throws Exception {
//根據版本建立Resources對象
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
//（1）
return createResourcesForN(hostContext, packageName, apk);
}
//（2）
Resources resources = ResourcesManager.createResourcesSimple(hostContext, apk.getAbsolutePath());
ResourcesManager.hookResources(hostContext, resources);
return resources;
}
//建立Resource對象
private static Resources createResourcesSimple(Context hostContext, String apk) throws Exception {
//宿主Resources對象
Resources hostResources = hostContext.getResources();
Resources newResources = null;
AssetManager assetManager;
Reflector reflector = Reflector.on(AssetManager.class).method("addAssetPath", String.class);
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
//經過反射建立AssetManager
assetManager = AssetManager.class.newInstance();
reflector.bind(assetManager);
final int cookie1 = reflector.call(hostContext.getApplicationInfo().sourceDir);;
if (cookie1 == 0) {
throw new RuntimeException("createResources failed, can't addAssetPath for " + hostContext.getApplicationInfo().sourceDir);
}
} else {
//獲取到宿主的AssetManager
assetManager = hostResources.getAssets();
reflector.bind(assetManager);
}
final int cookie2 = reflector.call(apk);
if (cookie2 == 0) {
throw new RuntimeException("createResources failed, can't addAssetPath for " + apk);
}
List<LoadedPlugin> pluginList = PluginManager.getInstance(hostContext).getAllLoadedPlugins();
for (LoadedPlugin plugin : pluginList) {
final int cookie3 = reflector.call(plugin.getLocation());
if (cookie3 == 0) {
throw new RuntimeException("createResources failed, can't addAssetPath for " + plugin.getLocation());
}
}
//經過不一樣的手機品牌建立Resources對象
if (isMiUi(hostResources)) {
newResources = MiUiResourcesCompat.createResources(hostResources, assetManager);
} else if (isVivo(hostResources)) {
newResources = VivoResourcesCompat.createResources(hostContext, hostResources, assetManager);
} else if (isNubia(hostResources)) {
newResources = NubiaResourcesCompat.createResources(hostResources, assetManager);
} else if (isNotRawResources(hostResources)) {
newResources = AdaptationResourcesCompat.createResources(hostResources, assetManager);
} else {
// is raw android resources
newResources = new Resources(assetManager, hostResources.getDisplayMetrics(), hostResources.getConfiguration());
}
// lastly, sync all LoadedPlugin to newResources
for (LoadedPlugin plugin : pluginList) {
plugin.updateResources(newResources);
}
return newResources;
}
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Hook住了ContextImpl的mResources和LoadedApk的mResourceside
public static void hookResources(Context base, Resources resources) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
return;
}
try {
Reflector reflector = Reflector.with(base);
//hook mResources
reflector.field("mResources").set(resources);
Object loadedApk = reflector.field("mPackageInfo").get();
//hook mResources
Reflector.with(loadedApk).field("mResources").set(resources);
Object activityThread = ActivityThread.currentActivityThread();
Object resManager;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
resManager = android.app.ResourcesManager.getInstance();
} else {
resManager = Reflector.with(activityThread).field("mResourcesManager").get();
}
Map<Object, WeakReference<Resources>> map = Reflector.with(resManager).field("mActiveResources").get();
Object key = map.keySet().iterator().next();
map.put(key, new WeakReference<>(resources));
} catch (Exception e) {
Log.w(TAG, e);
}
}
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四、Activity啓動資源處理
#VAInstrumentation
@Override
public Activity newActivity(ClassLoader cl, String className, Intent intent) throws InstantiationException, IllegalAccessException, ClassNotFoundException {
try {
cl.loadClass(className);
Log.i(TAG, String.format("newActivity[%s]", className));
} catch (ClassNotFoundException e) {
......
// 經過反射將Resources賦值給Activity的mResources
Reflector.QuietReflector.with(activity).field("mResources").set(plugin.getResources());
return newActivity(activity);
}
return newActivity(mBase.newActivity(cl, className, intent));
}
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3、so的插件化
so的插件化，有兩種方案：基於System.Load和基於System.LoadLibrary。函數
一、VirtualApk的實現
#LoadedPlugin
protected ClassLoader createClassLoader(Context context, File apk, File libsDir, ClassLoader parent) throws Exception {
File dexOutputDir = getDir(context, Constants.OPTIMIZE_DIR);
String dexOutputPath = dexOutputDir.getAbsolutePath();
DexClassLoader loader = new DexClassLoader(apk.getAbsolutePath(), dexOutputPath, libsDir.getAbsolutePath(), parent);
if (Constants.COMBINE_CLASSLOADER) {
DexUtil.insertDex(loader, parent, libsDir);
}
return loader;
}
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建立了一個DexClassLoader，解析出每一個插件apk中的so文件，解壓到某個位置，把這些路徑用逗號鏈接起來成爲一個字符串，放到DexClassLoader的構造函數的第3個參數中。這樣插件中的so，就和宿主App中jniLib目錄下的so同樣，經過System.loadLibrary方法來加載。ui
#DexUtil
public static void insertDex(DexClassLoader dexClassLoader, ClassLoader baseClassLoader, File nativeLibsDir) throws Exception {
Object baseDexElements = getDexElements(getPathList(baseClassLoader));
Object newDexElements = getDexElements(getPathList(dexClassLoader));
//將宿主和插件的DexElements合併獲得allDexElements
Object allDexElements = combineArray(baseDexElements, newDexElements);
Object pathList = getPathList(baseClassLoader);
//經過反射將dexElements替換爲allDexElements
Reflector.with(pathList).field("dexElements").set(allDexElements);
insertNativeLibrary(dexClassLoader, baseClassLoader, nativeLibsDir);
}
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so插件化核心代碼this
private static synchronized void insertNativeLibrary(DexClassLoader dexClassLoader, ClassLoader baseClassLoader, File nativeLibsDir) throws Exception {
if (sHasInsertedNativeLibrary) {
return;
}
sHasInsertedNativeLibrary = true;
Context context = ActivityThread.currentApplication();
//獲取宿主的PathList
Object basePathList = getPathList(baseClassLoader);
if (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP_MR1) {
Reflector reflector = Reflector.with(basePathList);
List<File> nativeLibraryDirectories = reflector.field("nativeLibraryDirectories").get();
nativeLibraryDirectories.add(nativeLibsDir);
//獲取到宿主的so集合
Object baseNativeLibraryPathElements = reflector.field("nativeLibraryPathElements").get();
final int baseArrayLength = Array.getLength(baseNativeLibraryPathElements);
Object newPathList = getPathList(dexClassLoader);
//獲取到插件的so集合
Object newNativeLibraryPathElements = reflector.get(newPathList);
Class<?> elementClass = newNativeLibraryPathElements.getClass().getComponentType();
Object allNativeLibraryPathElements = Array.newInstance(elementClass, baseArrayLength + 1);
//將原來宿主的so集合拷貝到新集合中
System.arraycopy(baseNativeLibraryPathElements, 0, allNativeLibraryPathElements, 0, baseArrayLength);
Field soPathField;
if (Build.VERSION.SDK_INT >= 26) {
soPathField = elementClass.getDeclaredField("path");
} else {
soPathField = elementClass.getDeclaredField("dir");
}
soPathField.setAccessible(true);
//將插件的so集合拷貝到新集合中
final int newArrayLength = Array.getLength(newNativeLibraryPathElements);
for (int i = 0; i < newArrayLength; i++) {
Object element = Array.get(newNativeLibraryPathElements, i);
String dir = ((File)soPathField.get(element)).getAbsolutePath();
if (dir.contains(Constants.NATIVE_DIR)) {
Array.set(allNativeLibraryPathElements, baseArrayLength, element);
break;
}
}
//將宿主和插件so的合集替換上去
reflector.set(allNativeLibraryPathElements);
} else {
Reflector reflector = Reflector.with(basePathList).field("nativeLibraryDirectories");
File[] nativeLibraryDirectories = reflector.get();
final int N = nativeLibraryDirectories.length;
File[] newNativeLibraryDirectories = new File[N + 1];
System.arraycopy(nativeLibraryDirectories, 0, newNativeLibraryDirectories, 0, N);
newNativeLibraryDirectories[N] = nativeLibsDir;
reflector.set(newNativeLibraryDirectories);
}
}
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獲取宿主so集合，獲取插件so集合，兩者合併後經過反射替換原so集合，插件so文件就能正常被加載了spa
4、VirtualApk的Service插件化
一、Service啓動分析
- Service啓動跟Instrumentation不要緊，不能經過Hook Instrumentation來處理
- 在Standard模式下屢次啓動佔位Activity可建立多個Activity，可是屢次啓動佔位Service並不會建立多個Service實例
- 經過代理分發實現：啓動一個代理Service統一管理，攔截全部Service方法，修改成startService到代理Service，在代理Service的onStartCommond統一管理，建立/中止目標service。
二、Hook IActivityManager
VirtualApk初始化時經過ActivityManagerProxy Hook了IActivityManager。啓動服務時，經過ActivityManagerProxy攔截到了startService的操做插件
public class ActivityManagerProxy implements InvocationHandler {
protected Object startService(Object proxy, Method method, Object[] args) throws Throwable {
IApplicationThread appThread = (IApplicationThread) args[0];
//跳轉的intent
Intent target = (Intent) args[1];
//檢查Service信息
ResolveInfo resolveInfo = this.mPluginManager.resolveService(target, 0);
if (null == resolveInfo || null == resolveInfo.serviceInfo) {
// is host service
return method.invoke(this.mActivityManager, args);
}
return startDelegateServiceForTarget(target, resolveInfo.serviceInfo, null, RemoteService.EXTRA_COMMAND_START_SERVICE);
}
protected ComponentName startDelegateServiceForTarget(Intent target, ServiceInfo serviceInfo, Bundle extras, int command) {
Intent wrapperIntent = wrapperTargetIntent(target, serviceInfo, extras, command);
return mPluginManager.getHostContext().startService(wrapperIntent);
}
protected Intent wrapperTargetIntent(Intent target, ServiceInfo serviceInfo, Bundle extras, int command) {
// 將目標Service的相關信息存儲起來
target.setComponent(new ComponentName(serviceInfo.packageName, serviceInfo.name));
String pluginLocation = mPluginManager.getLoadedPlugin(target.getComponent()).getLocation();
// 根據processName判斷是否爲遠程服務
boolean local = PluginUtil.isLocalService(serviceInfo);
// 判斷交給LocalService仍是RemoteService進行處理
Class<? extends Service> delegate = local ? LocalService.class : RemoteService.class;
// 參數傳遞
Intent intent = new Intent();
intent.setClass(mPluginManager.getHostContext(), delegate);
intent.putExtra(RemoteService.EXTRA_TARGET, target);
intent.putExtra(RemoteService.EXTRA_COMMAND, command);
intent.putExtra(RemoteService.EXTRA_PLUGIN_LOCATION, pluginLocation);
if (extras != null) {
intent.putExtras(extras);
}
return intent;
}
}
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三、LocalService
public class LocalService extends Service {
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
......
switch (command) {
case EXTRA_COMMAND_START_SERVICE: {
//獲取ActivityThread
ActivityThread mainThread = ActivityThread.currentActivityThread();
IApplicationThread appThread = mainThread.getApplicationThread();
Service service;
if (this.mPluginManager.getComponentsHandler().isServiceAvailable(component)) {
//獲取Service
service = this.mPluginManager.getComponentsHandler().getService(component);
} else {
try {
//經過DexClassLoader加載Service
service = (Service) plugin.getClassLoader().loadClass(component.getClassName()).newInstance();
Application app = plugin.getApplication();
IBinder token = appThread.asBinder();
Method attach = service.getClass().getMethod("attach", Context.class, ActivityThread.class, String.class, IBinder.class, Application.class, Object.class);
IActivityManager am = mPluginManager.getActivityManager();
//經過attach方法綁定Context
attach.invoke(service, plugin.getPluginContext(), mainThread, component.getClassName(), token, app, am);
//調用Service的onCreate方法
service.onCreate();
this.mPluginManager.getComponentsHandler().rememberService(component, service);
} catch (Throwable t) {
return START_STICKY;
}
}
//調用service的onStartCommand方法
service.onStartCommand(target, 0, this.mPluginManager.getComponentsHandler().getServiceCounter(service).getAndIncrement());
break;
}
......
}
}
}
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四、RemoteService
public class RemoteService extends LocalService {
private static final String TAG = Constants.TAG_PREFIX + "RemoteService";
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
if (intent == null) {
return super.onStartCommand(intent, flags, startId);
}
//獲取目標service的intent
Intent target = intent.getParcelableExtra(EXTRA_TARGET);
if (target != null) {
//獲取插件路徑
String pluginLocation = intent.getStringExtra(EXTRA_PLUGIN_LOCATION);
ComponentName component = target.getComponent();
LoadedPlugin plugin = PluginManager.getInstance(this).getLoadedPlugin(component);
if (plugin == null && pluginLocation != null) {
try {
//加載apk插件文件
PluginManager.getInstance(this).loadPlugin(new File(pluginLocation));
} catch (Exception e) {
Log.w(TAG, e);
}
}
}
return super.onStartCommand(intent, flags, startId);
}
}
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啓動遠程服務多了一步加載其餘插件的Service的操做
五、Service插件化總結
- 初始化時經過ActivityManagerProxy Hook住了IActivityManager。
- 服務啓動時經過ActivityManagerProxy攔截，判斷是否爲遠程服務，若是爲遠程服務，啓動RemoteService，若是爲同進程服務則啓動LocalService。
- 若是爲LocalService，則經過DexClassLoader加載目標Service，而後反射調用attach方法綁定Context，而後執行Service的onCreate、onStartCommand方法
- 若是爲RemoteService，則先加載插件的遠程Service，後續跟LocalService一致。
參考資料:
- VirtualAPK 資源篇
- 《Android插件化開發指南》
- 《Android進階解密》
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