Android 插件化处理方案详解

插件化启动Activity的过程

在宿主里面的AndroidManifest.xml里面注册一个空的activity

从开始执行execStartActivity到最终将Activity对象new出来这个过程，系统层会去校验需要启动的activity的合法性[就是是否有在某个应用的AndroidManifest.xml里面注册]以及按启动要求创建activity对象。清晰了这点我们就可以很好的绕过系统的约束，达到我们的目的：【插件中的组件拥有真正生命周期，完全交由系统管理、非反射代理】。 简单来说方案就两步： Step1、在开始startActivity的时候将需要启动的插件组件替换成宿主预先声明号的。

public ActivityResult execStartActivity(Context who, IBinder contextThread, IBinder token, Activity target, Intent intent, int requestCode, Bundle options) { //如果启动的是插件的activity组件，这里面将会被替换成宿主预先声明的 PluginIntentResolver.resolveActivity(intent); return hackInstrumentation.execStartActivity(who, contextThread, token, target, intent, requestCode, ptions);}

Step2、在最终创建activity对象的时候改回成插件组件的。

@Overridepublic Activity newActivity(ClassLoader cl, String className, Intent intent) throws InstantiationException, IllegalAccessException, ClassNotFoundException { ClassLoader orignalCl = cl; String orginalClassName = className; String orignalIntent = intent.toString(); if (ProcessUtil.isPluginProcess()) { // 将PluginStubActivity替换成插件中的activity if (PluginManagerHelper.isStub(className)) { String action = intent.getAction(); if (action != null && action.contains(PluginIntentResolver.CLASS_SEPARATOR)) {String[] targetClassName = action.split(PluginIntentResolver.CLASS_SEPARATOR);String pluginClassName = targetClassName[0];final String pid = intent.getStringExtra(PluginIntentResolver.INTENT_EXTRA_PID).trim();PluginDescriptor pluginDescriptor = TextUtils.isEmpty(pid) ? PluginManagerHelper.getPluginDescriptorByClassName(pluginClassName) : PluginManagerHelper.getPluginDescriptorByPluginId(pid);Class<?> clazz = PluginLoader.loadPluginClassByName(pluginDescriptor, pluginClassName);if (clazz != null) { className = pluginClassName; cl = clazz.getClassLoader(); intent.setExtrasClassLoader(cl); if (targetClassName.length > 1) { // 之前为了传递classNae，intent的action被修改过 // 这里再把Action还原到原始的Action intent.setAction(targetClassName[1]); } else { intent.setAction(null); } // 添加一个标记符 intent.addCategory(RELAUNCH_FLAG + className);} else { throw new ClassNotFoundException('pluginClassName : ' + pluginClassName, new Throwable());} } else if (PluginManagerHelper.isExact(className, PluginDescriptor.ACTIVITY)) {// 这个逻辑是为了支持外部app唤起配置了stub_exact的插件ActivityPluginDescriptor pluginDescriptor = PluginManagerHelper.getPluginDescriptorByClassName(className);if (pluginDescriptor != null) { boolean isRunning = PluginLauncher.instance().isRunning(pluginDescriptor.getPackageName()); if (!isRunning) { return waitForLoading(pluginDescriptor); }}Class<?> clazz = PluginLoader.loadPluginClassByName(pluginDescriptor, className);if (clazz != null) { cl = clazz.getClassLoader();} else { throw new ClassNotFoundException('className : ' + className, new Throwable());} } else {// 进入这个分支可能是因为activity重启了，比如横竖屏切换，由于上面的分支已经把Action还原到原始到Action了// 这里只能通过之前添加的标记符来查找classNameboolean found = false;Set<String> category = intent.getCategories();if (category != null) { Iterator<String> itr = category.iterator(); while (itr.hasNext()) { String cate = itr.next(); if (cate.startsWith(RELAUNCH_FLAG)) { className = cate.replace(RELAUNCH_FLAG, ''); PluginDescriptor pluginDescriptor = PluginManagerHelper.getPluginDescriptorByClassName(className); if (pluginDescriptor != null) {boolean isRunning = PluginLauncher.instance().isRunning( pluginDescriptor.getPackageName());if (!isRunning) { return waitForLoading(pluginDescriptor);} } Class<?> clazz = PluginLoader.loadPluginClassByName(pluginDescriptor, className); cl = clazz.getClassLoader(); found = true; break; } }}if (!found) { throw new ClassNotFoundException( 'className : ' + className + ', intent : ' + intent.toString(), new Throwable());} } } else { if (cl instanceof PluginClassLoader) {PluginIntentResolver.resolveActivity(intent); } else {// Do Nothing } } } try { Activity activity = super.newActivity(cl, className, intent); if (activity instanceof PluginContainer) { ((PluginContainer) activity).setPluginId(intent.getStringExtra(PluginContainer.FRAGMENT_PLUGIN_ID)); } return activity; } catch (ClassNotFoundException e) { // 收集状态，便于异常分析 throw new ClassNotFoundException(' orignalCl : ' + orignalCl.toString() + ', orginalClassName : '+ orginalClassName + ', orignalIntent : ' + orignalIntent + ', currentCl : ' + cl.toString()+ ', currentClassName : ' + className + ', currentIntent : ' + intent.toString() + ', process : '+ ProcessUtil.isPluginProcess() + ', isStubActivity : '+ PluginManagerHelper.isStub(orginalClassName) + ', isExact : '+ PluginManagerHelper.isExact(orginalClassName, PluginDescriptor.ACTIVITY), e); }}

方案确实很简单，不过还有一些收尾工作，就是将创建好的[插件]组件进行一些必要的init操作，比如：在声明周期onCreate之前进行上下文替换等操作，这些都在插件框架提供的PluginInstrumentionWrapper里面进行完成的，看一下代码片段：

@Overridepublic void callActivityOnCreate(Activity activity, Bundle icicle) { PluginInjector.injectActivityContext(activity); Intent intent = activity.getIntent(); if (intent != null) { intent.setExtrasClassLoader(activity.getClassLoader()); } if (icicle != null) { icicle.setClassLoader(activity.getClassLoader()); } if (ProcessUtil.isPluginProcess()) { installPluginViewFactory(activity); if (activity instanceof WaitForLoadingPluginActivity) { // NOTHING } else { } if (activity.isChild()) { // 修正TabActivity中的Activity的ContextImpl的packageName Context base = activity.getBaseContext(); while (base instanceof ContextWrapper) {base = ((ContextWrapper) base).getBaseContext(); } if (HackContextImpl.instanceOf(base)) {HackContextImpl impl = new HackContextImpl(base);String packageName = PluginLoader.getApplication().getPackageName();// String packageName1 = activity.getPackageName();impl.setBasePackageName(packageName);impl.setOpPackageName(packageName); } } } super.callActivityOnCreate(activity, icicle); monitor.onActivityCreate(activity);}

到这插件activity组件就被顺序的启动起来了，并且是系统在维护具备完整的生命周期。 组件service、Receiver也是一样的，只是这两个组件的拦截点在ActivityThread的Handler成员的回调Callback里面进行的。Application和provider在插件启动的时候进行加载。

资源冲突的解决方案resources.arsc资源描述符详解

packageId: 包名id 资源类型id：string,drawable,layout,color 偏移：某一种类型的偏移值 解决冲突的方案

由于每个插件的包名是不一致的，可以事先规定某个插件的packageId的值固定，然后修改aapt对其进行编译固定，就可以保证每个插件分配的值不一样了。

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