VirtualAPK插件化方案原理探索
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*本篇文章已授权微信公众号 guolin_blog (郭霖)独家发布
一、前言
最近刚好在看任玉刚的《安卓开发艺术探索》,学到了不少东西。前面刚写完四大组件的原理分析,算是对Android组件进一步了解。趁热打铁,了解一下滴滴出品的VirtualAPK插件化方案,同样是刚哥参与的,站在巨人的肩膀来看看。
插件化、热更新在国内近段时间相当火热,我们也得跟上啊。学习插件化不仅仅只有”插件化”这么简单而已,涉及到相当多的知识,对我们提升还是有一定帮助的。之前也看过鸿洋的文章,写的很简练、直击要害,过不对刚了解插件化的同学们不太友好,我这里就稍微详细谈谈。不过同样,阅读本文之前需要先了解四大组件启动原理。网上资源很多,我这里不要脸的推荐一下我的文章:
【Android源码系列】Activity启动源码解析
【Android源码系列】Service启动源码解析
【Android源码系列】BroadcastReceiver启动源码解析
【Android源码系列】ContentProvider启动源码解析
同时插件化还会涉及到Binder、classLoader、Hook、反射、动态代理等知识,先了解一波会有助于阅读本文,建议大家学习一波。废话不多说,进入正题。
二、VirtualAPK使用
具体使用方案可以参见VirtualAPK的wiki,里面也有推荐第三方文章,写的都很详细。我这里就简单的说一下,不详细的讲怎样引入之类的了。我们都知道插件化分为宿主工程和插件工程,首先需要重写宿主工程Application里的attachBaseContext方法:
@Overrideprotected void attachBaseContext(Context base) { super.attachBaseContext(base); PluginManager.getInstance(base).init();}
然后再加载插件:
private void loadPlugin(Context base) { PluginManager pluginManager = PluginManager.getInstance(base); //这里加载插件APK,可以看出,需要把APK放到手机根文件夹下(可自定义). File apk = new File(Environment.getExternalStorageDirectory(), "Test.apk"); if (apk.exists()) { try { pluginManager.loadPlugin(apk); } catch (Exception e) { e.printStackTrace(); } } }
调用了pluginManager.loadPlugin(apk),PluginManager这个类是VirtualAPK的核心类,我们跟进方法看看
public void loadPlugin(File apk) throws Exception { if (null == apk) { throw new IllegalArgumentException("error : apk is null."); } if (!apk.exists()) { throw new FileNotFoundException(apk.getAbsolutePath()); } //这里解析APK,并保存到LoadedPlugin对象中 LoadedPlugin plugin = LoadedPlugin.create(this, this.mContext, apk); if (null != plugin) { //放到mPlugins这个map里保存 this.mPlugins.put(plugin.getPackageName(), plugin); // 启动pluginAPK plugin.invokeApplication(); } else { throw new RuntimeException("Can't load plugin which is invalid: " + apk.getAbsolutePath()); } }
这个方法将插件APK进行解析、启动、保存,具体如何解析的这里就不详细分析,有兴趣的童鞋可以看看LoadedPlugin 这个类的实现。
这样初始工作就做完了(当然还需要gradle配置),可以直接在插件工程里码代码了~没什么不一样,和平时一样码就行,还是很方便的。
三、Activity支持原理
我们之前看到PluginManager.getInstance(base)的初始化,现在我们来看看如何实现。
getInstance是我们熟悉的单例,接着发现在构造方法里调用了prepare方法
private void prepare() { Systems.sHostContext = getHostContext(); this.hookInstrumentationAndHandler(); if (Build.VERSION.SDK_INT >= 26) { this.hookAMSForO(); } else { this.hookSystemServices(); } }
先来看看this.hookInstrumentationAndHandler();
private void hookInstrumentationAndHandler() { try { Instrumentation baseInstrumentation = ReflectUtil.getInstrumentation(this.mContext); if (baseInstrumentation.getClass().getName().contains("lbe")) { // reject executing in paralell space, for example, lbe. System.exit(0); } final VAInstrumentation instrumentation = new VAInstrumentation(this, baseInstrumentation); Object activityThread = ReflectUtil.getActivityThread(this.mContext); ReflectUtil.setInstrumentation(activityThread, instrumentation); ReflectUtil.setHandlerCallback(this.mContext, instrumentation); this.mInstrumentation = instrumentation; } catch (Exception e) { e.printStackTrace(); } }
1、先是利用反射获取到context里的Instrumentation对象
2、然后把他保存到自定义的VAInstrumentation里
3、利用反射获取到ActivityThread的对象,将原来的Instrumentation对象用新的VAInstrumentation替换掉。
这样就VAInstrumentation就可以工作了,我们都知道Activity启动时,需要调用Instrumentation的execStartActivity方法(以下都默认读者已经了解过四大组件启动原理),所以…嘿嘿,我们看VAInstrumentation里面果然重写了execStartActivity
public ActivityResult execStartActivity( Context who, IBinder contextThread, IBinder token, Activity target, Intent intent, int requestCode, Bundle options) { mPluginManager.getComponentsHandler().transformIntentToExplicitAsNeeded(intent); // null component is an implicitly intent if (intent.getComponent() != null) { Log.i(TAG, String.format("execStartActivity[%s : %s]", intent.getComponent().getPackageName(), intent.getComponent().getClassName())); // resolve intent with Stub Activity if needed this.mPluginManager.getComponentsHandler().markIntentIfNeeded(intent); } ActivityResult result = realExecStartActivity(who, contextThread, token, target, intent, requestCode, options); return result; }
1、调用transformIntentToExplicitAsNeeded方法,注释:transform intent from implicit to explicit(将隐式启动的Activity转为显示启动),代码就不贴了,可以自己看(其实我一直推荐阅读类似源码文章时,一定要把源码打开跟着走,效果最佳)
2、接着,依然调用ComponentsHandler的方法:markIntentIfNeeded,这个方法将intent的偷换成我们的,达到欺骗系统的作用(下文分析)。
3、最后调用realExecStartActivity返回结果,其实点进去发现,就是调用了真正的Instrumentation的方法。
接下来详细解析一下步骤2。
public void markIntentIfNeeded(Intent intent) { if (intent.getComponent() == null) { return; } String targetPackageName = intent.getComponent().getPackageName(); String targetClassName = intent.getComponent().getClassName(); // search map and return specific launchmode stub activity if (!targetPackageName.equals(mContext.getPackageName()) && mPluginManager.getLoadedPlugin(targetPackageName) != null) { intent.putExtra(Constants.KEY_IS_PLUGIN, true); intent.putExtra(Constants.KEY_TARGET_PACKAGE, targetPackageName); intent.putExtra(Constants.KEY_TARGET_ACTIVITY, targetClassName); dispatchStubActivity(intent); } }
这段代码很简单,将包名、类名、插件标记保存在intent里,然后调用dispatchStubActivity
private void dispatchStubActivity(Intent intent) { ComponentName component = intent.getComponent(); String targetClassName = intent.getComponent().getClassName(); LoadedPlugin loadedPlugin = mPluginManager.getLoadedPlugin(intent); ActivityInfo info = loadedPlugin.getActivityInfo(component); if (info == null) { throw new RuntimeException("can not find " + component); } int launchMode = info.launchMode; Resources.Theme themeObj = loadedPlugin.getResources().newTheme(); themeObj.applyStyle(info.theme, true); String stubActivity = mStubActivityInfo.getStubActivity(targetClassName, launchMode, themeObj); Log.i(TAG, String.format("dispatchStubActivity,[%s -> %s]", targetClassName, stubActivity)); intent.setClassName(mContext, stubActivity); }
我们都知道,Activity必须在Manifest里注册,所以这里将Intent里ComponentName替换为提前在Manifest“占坑”的Activity,这样就骗过了系统检测,而检测是在AMS(ActivityManagerService)端完成的,最后一句intent.setClassName(mContext, stubActivity);就是这个作用。
我们再来看看,stubActivity这个名字是如何替换的:
public static final String corePackage = "com.didi.virtualapk.core"; public static final String STUB_ACTIVITY_STANDARD = "%s.A$%d"; public static final String STUB_ACTIVITY_SINGLETOP = "%s.B$%d"; public static final String STUB_ACTIVITY_SINGLETASK = "%s.C$%d"; public static final String STUB_ACTIVITY_SINGLEINSTANCE = "%s.D$%d"; public final int usedStandardStubActivity = 1; public int usedSingleTopStubActivity = 0; public int usedSingleTaskStubActivity = 0; public int usedSingleInstanceStubActivity = 0;public String getStubActivity(String className, int launchMode, Theme theme) { String stubActivity= mCachedStubActivity.get(className); if (stubActivity != null) { return stubActivity; } TypedArray array = theme.obtainStyledAttributes(new int[]{ android.R.attr.windowIsTranslucent, android.R.attr.windowBackground }); boolean windowIsTranslucent = array.getBoolean(0, false); array.recycle(); if (Constants.DEBUG) { Log.d("StubActivityInfo", "getStubActivity, is transparent theme ? " + windowIsTranslucent); } stubActivity = String.format(STUB_ACTIVITY_STANDARD, corePackage, usedStandardStubActivity); switch (launchMode) { case ActivityInfo.LAUNCH_MULTIPLE: { stubActivity = String.format(STUB_ACTIVITY_STANDARD, corePackage, usedStandardStubActivity); if (windowIsTranslucent) { stubActivity = String.format(STUB_ACTIVITY_STANDARD, corePackage, 2); } break; } case ActivityInfo.LAUNCH_SINGLE_TOP: { usedSingleTopStubActivity = usedSingleTopStubActivity % MAX_COUNT_SINGLETOP + 1; stubActivity = String.format(STUB_ACTIVITY_SINGLETOP, corePackage, usedSingleTopStubActivity); break; } case ActivityInfo.LAUNCH_SINGLE_TASK: { usedSingleTaskStubActivity = usedSingleTaskStubActivity % MAX_COUNT_SINGLETASK + 1; stubActivity = String.format(STUB_ACTIVITY_SINGLETASK, corePackage, usedSingleTaskStubActivity); break; } case ActivityInfo.LAUNCH_SINGLE_INSTANCE: { usedSingleInstanceStubActivity = usedSingleInstanceStubActivity % MAX_COUNT_SINGLEINSTANCE + 1; stubActivity = String.format(STUB_ACTIVITY_SINGLEINSTANCE, corePackage, usedSingleInstanceStubActivity); break; } default:break; } mCachedStubActivity.put(className, stubActivity); return stubActivity; }
很明显,根据Activity的启动方式分别取名,这里我们看看标准的standard模式。
stubActivity = String.format(STUB_ACTIVITY_STANDARD, corePackage, usedStandardStubActivity); if (windowIsTranslucent) { stubActivity = String.format(STUB_ACTIVITY_STANDARD, corePackage, 2); }
是以”%s.A$%d”的格式取名,可以预见我们的Activity名字大概是:
“com.didi.virtualapk.core.A\$1”,有转场动画的为2。好的我们去看看Manifest里的占坑Activity
<!-- Stub Activities --> <activity android:name=".A$1" android:launchMode="standard"/> <activity android:name=".A$2" android:launchMode="standard" android:theme="@android:style/Theme.Translucent" />
没错了,和我们预想的一样。其他启动模式也差不多,读者可自行查看。
这样就完成了”欺骗”启动的效果,但是这样启动的不就是占坑Activity而已吗?所以还需要在AMS工作后,将启动Activity变回目标Activity。
我们知道真正创建Activity实例是在Instrumentation里的newActivity,Virtual就选择从这里下手。
@Override public Activity newActivity(ClassLoader cl, String className, Intent intent) throws InstantiationException, IllegalAccessException, ClassNotFoundException { try { cl.loadClass(className); } catch (ClassNotFoundException e) { LoadedPlugin plugin = this.mPluginManager.getLoadedPlugin(intent); String targetClassName = PluginUtil.getTargetActivity(intent); Log.i(TAG, String.format("newActivity[%s : %s]", className, targetClassName)); if (targetClassName != null) { Activity activity = mBase.newActivity(plugin.getClassLoader(), targetClassName, intent); activity.setIntent(intent); try { // for 4.1+ ReflectUtil.setField(ContextThemeWrapper.class, activity, "mResources", plugin.getResources()); } catch (Exception ignored) { // ignored. } return activity; } } return mBase.newActivity(cl, className, intent); }
上诉代码比较简单,先用我们保存好的className替代掉占坑的Name,然后用真正的Instrumentation调用newActivity,最后再讲Intent替换掉,一顿操作行云流水….咳咳,同时还重写了callActivityOnCreate方法
public void callActivityOnCreate(Activity activity, Bundle icicle) { final Intent intent = activity.getIntent(); if (PluginUtil.isIntentFromPlugin(intent)) { Context base = activity.getBaseContext(); try { LoadedPlugin plugin = this.mPluginManager.getLoadedPlugin(intent); ReflectUtil.setField(base.getClass(), base, "mResources", plugin.getResources()); ReflectUtil.setField(ContextWrapper.class, activity, "mBase", plugin.getPluginContext()); ReflectUtil.setField(Activity.class, activity, "mApplication", plugin.getApplication()); ReflectUtil.setFieldNoException(ContextThemeWrapper.class, activity, "mBase", plugin.getPluginContext()); // set screenOrientation ActivityInfo activityInfo = plugin.getActivityInfo(PluginUtil.getComponent(intent)); if (activityInfo.screenOrientation != ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED) { activity.setRequestedOrientation(activityInfo.screenOrientation); } } catch (Exception e) { e.printStackTrace(); } } mBase.callActivityOnCreate(activity, icicle); }
这个方法主要是利用反射替换掉了resource、context等对象,resource就不说了,context也就是我们的上下文,保存了很多Activity信息,替换掉也就意味着我们的Activity很多配置被支持了。具体实现类是PluginContext,这个类用了Context一族的装饰模式来写,非常巧妙的完成了他的工作,有兴趣的童鞋可以自行查看PluginContext源码。
到这Activity算是插入了,接下来是Service。
四、Service的插入原理
刚刚我们分析到PluginManager的prepare方法
private void prepare() { Systems.sHostContext = getHostContext(); this.hookInstrumentationAndHandler(); if (Build.VERSION.SDK_INT >= 26) { this.hookAMSForO(); } else { this.hookSystemServices(); } }
前面是Activity相关,后面就是Service了,只不过有两个方法,因为Android O改动了AMS/AMN的实现(我粗略看了看AMN整个类好像被干掉了),所以Virtual做了适配,不过原理上都是一样的,所以我们只看hookSystemServices方法
/** * hookSystemServices, but need to compatible with Android O in future. */ private void hookSystemServices() { try { Singleton<IActivityManager> defaultSingleton = (Singleton<IActivityManager>) ReflectUtil.getField(ActivityManagerNative.class, null, "gDefault"); IActivityManager activityManagerProxy = ActivityManagerProxy.newInstance(this, defaultSingleton.get()); // Hook IActivityManager from ActivityManagerNative ReflectUtil.setField(defaultSingleton.getClass().getSuperclass(), defaultSingleton, "mInstance", activityManagerProxy); if (defaultSingleton.get() == activityManagerProxy) { this.mActivityManager = activityManagerProxy; } } catch (Exception e) { e.printStackTrace(); } }
这个方法大概做了几件事
1、利用反射获取了ActivityManagerNative的静态成员gDefault。了解源码的童鞋应该知道,这个gDefault其实就是AMS的代理对象,具体实现如下
2、自定义了ActivityManagerProxy类,用动态代理获取一个IActivityManager的代理对象,newInstance实现如下
public static IActivityManager newInstance(PluginManager pluginManager, IActivityManager activityManager) { return (IActivityManager) Proxy.newProxyInstance(activityManager.getClass().getClassLoader(), new Class[] { IActivityManager.class }, new ActivityManagerProxy(pluginManager, activityManager)); }
3、用生成的代理对象替换掉原来的,并保存起来。
其实,看到这里,Service的插入已经很明朗了。
我们都知道startService的逻辑会走到AMS的startService里,就像这样
private ComponentName startServiceCommon(Intent service, UserHandle user) { try { validateServiceIntent(service); service.prepareToLeaveProcess(); ComponentName cn = ActivityManagerNative.getDefault().startService( mMainThread.getApplicationThread(), service, service.resolveTypeIfNeeded(getContentResolver()), user.getIdentifier()); //省略部分代码 return cn; } catch (RemoteException e) { return null; } }
我们把ActivityManagerNative.getDefault()代理掉了,让我们自己的方法实现startService,让我们来看看代理类ActivityManagerProxy是怎么处理的。
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { if ("startService".equals(method.getName())) { try { return startService(proxy, method, args); } catch (Throwable e) { Log.e(TAG, "Start service error", e); } } else if ("stopService".equals(method.getName())) { try { return stopService(proxy, method, args); } catch (Throwable e) { Log.e(TAG, "Stop Service error", e); } } //省略巨量代码......... }
拦截了startService、bindService等等方法,我们就不一一分析了,这里拿startService来当案例
private Object startService(Object proxy, Method method, Object[] args) throws Throwable { IApplicationThread appThread = (IApplicationThread) args[0]; Intent target = (Intent) args[1]; 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); }
先取出Service信息,判断是不是宿主工程的Service,如果是就按原来的逻辑,如果是插件的就走startDelegateServiceForTarget
private ComponentName startDelegateServiceForTarget(Intent target, ServiceInfo serviceInfo, Bundle extras, int command) { Intent wrapperIntent = wrapperTargetIntent(target, serviceInfo, extras, command); return mPluginManager.getHostContext().startService(wrapperIntent); }
很明显,在wrapperTargetIntent里处理了intent,然后启动了Service
private Intent wrapperTargetIntent(Intent target, ServiceInfo serviceInfo, Bundle extras, int command) { // fill in service with ComponentName target.setComponent(new ComponentName(serviceInfo.packageName, serviceInfo.name)); String pluginLocation = mPluginManager.getLoadedPlugin(target.getComponent()).getLocation(); // start delegate service to run plugin service inside boolean local = PluginUtil.isLocalService(serviceInfo); Class<? extends Service> delegate = local ? LocalService.class : RemoteService.class; 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; }
将原来的intent当做参数,新建了一个intent,目标Service是LocalService或RemoteService,RemoteService继承了LocalService,他主要负责在多进程的时候新加一个LoadedPlugin保存起来。主要工作还是在LocalService里实现
public int onStartCommand(Intent intent, int flags, int startId) { if (null == intent || !intent.hasExtra(EXTRA_TARGET) || !intent.hasExtra(EXTRA_COMMAND)) { return START_STICKY; } Intent target = intent.getParcelableExtra(EXTRA_TARGET); int command = intent.getIntExtra(EXTRA_COMMAND, 0); if (null == target || command <= 0) { return START_STICKY; } ComponentName component = target.getComponent(); LoadedPlugin plugin = mPluginManager.getLoadedPlugin(component); // ClassNotFoundException when unmarshalling in Android 5.1 target.setExtrasClassLoader(plugin.getClassLoader()); switch (command) { case EXTRA_COMMAND_START_SERVICE: { ActivityThread mainThread = (ActivityThread)ReflectUtil.getActivityThread(getBaseContext()); IApplicationThread appThread = mainThread.getApplicationThread(); Service service; if (this.mPluginManager.getComponentsHandler().isServiceAvailable(component)) { service = this.mPluginManager.getComponentsHandler().getService(component); } else { try { 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(); attach.invoke(service, plugin.getPluginContext(), mainThread, component.getClassName(), token, app, am); service.onCreate(); this.mPluginManager.getComponentsHandler().rememberService(component, service); } catch (Throwable t) { return START_STICKY; } } service.onStartCommand(target, 0, this.mPluginManager.getComponentsHandler().getServiceCounter(service).getAndIncrement()); break; } //省略bind等方法.... } return START_STICKY; }
通过intent、PluginManager获取到Service信息,再通过command判断执行的方法(这里所有方法都在startCommand执行了),这里我们只看start方法。
其实就是模拟了service的启动:反射获取service实例,然后调用他的attach、onCreate、onStartCommand等方法。如果已经启动过,那直接调用onStartCommand方法。
五、BroadcastReceiver
这个实现就方便了,直接全部动态注册一下就好了。代码位于LoadedPlugin的构造方法内
// Register broadcast receivers dynamically Map<ComponentName, ActivityInfo> receivers = new HashMap<ComponentName, ActivityInfo>(); for (PackageParser.Activity receiver : this.mPackage.receivers) { receivers.put(receiver.getComponentName(), receiver.info); try { BroadcastReceiver br = BroadcastReceiver.class.cast(getClassLoader().loadClass(receiver.getComponentName().getClassName()).newInstance()); for (PackageParser.ActivityIntentInfo aii : receiver.intents) { this.mHostContext.registerReceiver(br, aii); } } catch (Exception e) { e.printStackTrace(); } } this.mReceiverInfos = Collections.unmodifiableMap(receivers); this.mPackageInfo.receivers = receivers.values().toArray(new ActivityInfo[receivers.size()]);
通过classLoader获取到Receiver对象,注册即可。
六、ContentProvider
终于到了最后了,相信(假装相信)大家还记得前面提到过PluginContext这个类,他”代理”了Context,而我们使用ContentProvider会是这样
getContentResolver().query(bookUri, new String[]{"_id", "name"}, null, null, null);
熟悉ContentProvider源码后,我们知道getContentResolver会获取一个ContentResolver对象,操作都在它里面执行,而这个对象保存在ContextImpl里面,而Virtual巧妙的用PluginContext”装饰了”ContextImpl,使得获取到的ContentResolver变成我们自定义的ContentResolver:PluginContentResolver。这里可能有点绕,不清楚的童鞋建议了解Context一族的实现方式,PluginContext的实现和他们一样一样的!~为了便于理解,画了两张图
Context原来的逻辑
Hook后的逻辑
好了,我接着看PluginContext的getContentResolver
public ContentResolver getContentResolver() { return new PluginContentResolver(getHostContext()); }
上文也提到了,自定义了PluginContentResolver来实现。我们知道,增删改查会调用acquireProvider类方法来获取IContentProvider的binder对象实现IPC通信。
protected IContentProvider acquireProvider(Context context, String auth) { try { if (mPluginManager.resolveContentProvider(auth, 0) != null) { return mPluginManager.getIContentProvider(); } return (IContentProvider) sAcquireProvider.invoke(mBase, context, auth); } catch (Exception e) { e.printStackTrace(); } return null; }
接着getIContentProvider的实现
public synchronized IContentProvider getIContentProvider() { if (mIContentProvider == null) { hookIContentProviderAsNeeded(); } return mIContentProvider; }
看方法名都知道hook点在这了,继续
private void hookIContentProviderAsNeeded() { Uri uri = Uri.parse(PluginContentResolver.getUri(mContext)); mContext.getContentResolver().call(uri, "wakeup", null, null); try { Field authority = null; Field mProvider = null; ActivityThread activityThread = (ActivityThread) ReflectUtil.getActivityThread(mContext); Map mProviderMap = (Map) ReflectUtil.getField(activityThread.getClass(), activityThread, "mProviderMap"); Iterator iter = mProviderMap.entrySet().iterator(); while (iter.hasNext()) { Map.Entry entry = (Map.Entry) iter.next(); Object key = entry.getKey(); Object val = entry.getValue(); String auth; if (key instanceof String) { auth = (String) key; } else { if (authority == null) { authority = key.getClass().getDeclaredField("authority"); authority.setAccessible(true); } auth = (String) authority.get(key); } if (auth.equals(PluginContentResolver.getAuthority(mContext))) { if (mProvider == null) { mProvider = val.getClass().getDeclaredField("mProvider"); mProvider.setAccessible(true); } IContentProvider rawProvider = (IContentProvider) mProvider.get(val); IContentProvider proxy = IContentProviderProxy.newInstance(mContext, rawProvider); mIContentProvider = proxy; Log.d(TAG, "hookIContentProvider succeed : " + mIContentProvider); break; } } } catch (Exception e) { e.printStackTrace(); } }
首先前两句,是找到占坑Provider,然后通过call方法,是Provider启动起来(调用任意方法都可以),”wakeup”也算是一个提示了,其实Provider根本没有这个方法。
之后获取到ActivityThread,通过他获取mProviderMap,然后就能获取到占坑的Provider啦。然后动态代理这个Provider,返回回去,这样我们拿到的provider就被代理了。主要是这三句代码实现的
IContentProvider rawProvider = (IContentProvider) mProvider.get(val); IContentProvider proxy = IContentProviderProxy.newInstance(mContext, rawProvider); mIContentProvider = proxy;
我们接着看如何实现代理
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Log.v(TAG, method.toGenericString() + " : " + Arrays.toString(args)); wrapperUri(method, args); try { return method.invoke(mBase, args); } catch (InvocationTargetException e) { throw e.getTargetException(); } }
这里provider的所有操作都会先执行一遍wrapperUri方法,然后按原逻辑走。那这个wrapperUri是干嘛的?
private void wrapperUri(Method method, Object[] args) { Uri uri = null; int index = 0; if (args != null) { //获取Uri for (int i = 0; i < args.length; i++) { if (args[i] instanceof Uri) { uri = (Uri) args[i]; index = i; break; } } } Bundle bundleInCallMethod = null; if (method.getName().equals("call")) { bundleInCallMethod = getBundleParameter(args); if (bundleInCallMethod != null) { String uriString = bundleInCallMethod.getString(KEY_WRAPPER_URI); if (uriString != null) { uri = Uri.parse(uriString); } } } if (uri == null) { return; } PluginManager pluginManager = PluginManager.getInstance(mContext); ProviderInfo info = pluginManager.resolveContentProvider(uri.getAuthority(), 0); if (info != null) { String pkg = info.packageName; LoadedPlugin plugin = pluginManager.getLoadedPlugin(pkg); String pluginUri = Uri.encode(uri.toString()); StringBuilder builder = new StringBuilder(PluginContentResolver.getUri(mContext)); builder.append("/?plugin=" + plugin.getLocation()); builder.append("&pkg=" + pkg); builder.append("&uri=" + pluginUri); Uri wrapperUri = Uri.parse(builder.toString()); if (method.getName().equals("call")) { bundleInCallMethod.putString(KEY_WRAPPER_URI, wrapperUri.toString()); } else { args[index] = wrapperUri; } } }
其实就是把uri处理一下,将APK位置、包名、真正的uri信息都放到占坑Uri的后面当做参数,后面应该会通过这个进行判断吧,其实到这里Hook已经结束了。嗯,为了验证我们的猜测,去看看占坑Provider怎么实现的吧
首先我们在Manifest里找到了他
<provider android:name="com.didi.virtualapk.delegate.RemoteContentProvider" android:authorities="${applicationId}.VirtualAPK.Provider" android:process=":daemon" />
看看query方法吧,其他的都类似
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { ContentProvider provider = getContentProvider(uri); Uri pluginUri = Uri.parse(uri.getQueryParameter(KEY_URI)); if (provider != null) { return provider.query(pluginUri, projection, selection, selectionArgs, sortOrder); } return null; }
主要是getContentProvider方法
private ContentProvider getContentProvider(final Uri uri) { final PluginManager pluginManager = PluginManager.getInstance(getContext()); Uri pluginUri = Uri.parse(uri.getQueryParameter(KEY_URI)); final String auth = pluginUri.getAuthority(); ContentProvider cachedProvider = sCachedProviders.get(auth); if (cachedProvider != null) { return cachedProvider; } synchronized (sCachedProviders) { LoadedPlugin plugin = pluginManager.getLoadedPlugin(uri.getQueryParameter(KEY_PKG)); if (plugin == null) { try { pluginManager.loadPlugin(new File(uri.getQueryParameter(KEY_PLUGIN))); } catch (Exception e) { e.printStackTrace(); } } final ProviderInfo providerInfo = pluginManager.resolveContentProvider(auth, 0); if (providerInfo != null) { RunUtil.runOnUiThread(new Runnable() { @Override public void run() { try { LoadedPlugin loadedPlugin = pluginManager.getLoadedPlugin(uri.getQueryParameter(KEY_PKG)); ContentProvider contentProvider = (ContentProvider) Class.forName(providerInfo.name).newInstance(); contentProvider.attachInfo(loadedPlugin.getPluginContext(), providerInfo); sCachedProviders.put(auth, contentProvider); } catch (Exception e) { e.printStackTrace(); } } }, true); return sCachedProviders.get(auth); } } return null; }
1、通过key拿到我们的pluginUri,auth
2、用auth当做key,做了一个缓存Map
3、通过反射获取provider对象并启动,放入缓存,所以占坑的provider不仅仅只是占坑作用,还成为了所有插件Provider的”容器”。
七、总结
VirtualAPK不仅仅是这里的内容,他还有很多细节需要去摸索,笔者也有些地方持有疑惑,想要更了解VirtualAPK,或者说更了解插件化,就需要很清楚Android源码的实现方式,这是一个积累的过程。
可以这么说,你如果很擅长插件化,那你对Android的理解一定很深刻,所以还不快行动?
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