0、背景
自从Android 9.0后，Android就已经开始着手阻止app开发调用非sdk的api，也就是被标记为@hide的变量、函数、类不可以通过反射调用，否则会提示NoSuchMethod异常
1、对atlas影响
atlas有许多调用都是通过反射系统api来完成的，其中不乏被标记为@hide的类，比如用来处理插件资源的android.content.res.AssetManager#addAssetPath，还有用来处理动态部署的启动新activity的android.app.ActivityThread
/**
* Add an additional set of assets to the asset manager. This can be
* either a directory or ZIP file. Not for use by applications. Returns
* the cookie of the added asset, or 0 on failure.
* {@hide} WARM，该方法被标记为隐藏
*/
public final int addAssetPath(String path) {
synchronized (this) {
int res = addAssetPathNative(path);
makeStringBlocks(mStringBlocks);
return res;
}
}
/**
* This manages the execution of the main thread in an
* application process, scheduling and executing activities,
* broadcasts, and other operations on it as the activity
* manager requests.
*
* {@hide} 高能，整个类都标记为隐藏
*/
public final class ActivityThread {
如果android.content.res.AssetManager#addAssetPath不能用，资源在插件中就无法使用，如果android.app.ActivityThread整个类不让反射，那动态部署中无法添加新的activity、service
2、android p 处理非sdk调用
但情况并没有想象的糟糕，android p 阻止调用非sdk并不是绝对的，并不是标记了hide就一定会抛异常。还有个X因素——light-greylist，如果被hide的api在里面列出，就允许被反射调用。该列表如下：
https://github.com/aosp-mirror/platform_frameworks_base/blob/master/config/hiddenapi-p-light-greylist.txt
https://github.com/aosp-mirror/platform_frameworks_base/blob/master/config/hiddenapi-light-greylist.txt
乍一看addAssetPath和ActivityThread都在里面，看来atlas还是有希望的，不过atlas用的反射有许多，让我们在Android p模拟器上运行下atlas试一试
3、死而后生，atlas的适配
现在官网默认的master分支上的demo还没法运行，那是因为demo里反射调用了hide api且light-greylist没生命的api——android.app.ActivityThread#performRestartActivity，所以现在要运行demo请clone分支android_p
git clone https://github.com/alibaba/atlas.git -b android_p
运行后发现没有了之前的异常，但会有如下提示
05-27 04:37:31.077 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ApplicationPackageManager;->mPM:Landroid/content/pm/IPackageManager; (light greylist, reflection)
05-27 04:37:31.077 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/content/pm/ParceledListSlice;-><init>(Ljava/util/List;)V (light greylist, linking)
05-27 04:37:31.115 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/content/pm/PackageParser;-><init>()V (light greylist, reflection)
05-27 04:37:31.115 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/content/res/StringBlock;-><init>(JZ)V (light greylist, reflection)
05-27 04:37:31.115 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ActivityThread;->mInstrumentation:Landroid/app/Instrumentation; (light greylist, reflection)
05-27 04:37:31.115 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ActivityThread;->mAllApplications:Ljava/util/ArrayList; (light greylist, reflection)
05-27 04:37:31.115 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ActivityThread;->mInitialApplication:Landroid/app/Application; (light greylist, reflection)
05-27 04:37:31.115 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ActivityThread;->mPackages:Landroid/util/ArrayMap; (light greylist, reflection)
05-27 04:37:31.115 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ActivityThread;->sPackageManager:Landroid/content/pm/IPackageManager; (light greylist, reflection)
05-27 04:37:31.116 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/LoadedApk;->mApplication:Landroid/app/Application; (light greylist, reflection)
05-27 04:37:31.116 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/LoadedApk;->mResources:Landroid/content/res/Resources; (light greylist, reflection)
05-27 04:37:31.116 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/LoadedApk;->mResDir:Ljava/lang/String; (light greylist, reflection)
05-27 04:37:31.116 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/LoadedApk;->mClassLoader:Ljava/lang/ClassLoader; (light greylist, reflection)
05-27 04:37:31.116 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/LoadedApk;->mBaseClassLoader:Ljava/lang/ClassLoader; (light greylist, reflection)
05-27 04:37:31.116 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/LoadedApk;->mAppDir:Ljava/lang/String; (light greylist, reflection)
05-27 04:37:31.116 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ContextImpl;->mResources:Landroid/content/res/Resources; (light greylist, reflection)
05-27 04:37:31.117 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ContextImpl;->mTheme:Landroid/content/res/Resources$Theme; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/view/ContextThemeWrapper;->mTheme:Landroid/content/res/Resources$Theme; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/view/ContextThemeWrapper;->mResources:Landroid/content/res/Resources; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/ContextWrapper;->mBase:Landroid/content/Context; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$Component;->intents:Ljava/util/ArrayList; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$Package;->activities:Ljava/util/ArrayList; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$Package;->services:Ljava/util/ArrayList; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$Package;->receivers:Ljava/util/ArrayList; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$Package;->providers:Ljava/util/ArrayList; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$Package;->applicationInfo:Landroid/content/pm/ApplicationInfo; (light greylist, reflection)
05-27 04:37:31.118 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$Package;->packageName:Ljava/lang/String; (light greylist, reflection)
05-27 04:37:31.119 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$ActivityIntentInfo;->activity:Landroid/content/pm/PackageParser$Activity; (light greylist, reflection)
05-27 04:37:31.119 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$ServiceIntentInfo;->service:Landroid/content/pm/PackageParser$Service; (light greylist, reflection)
05-27 04:37:31.119 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$ProviderIntentInfo;->provider:Landroid/content/pm/PackageParser$Provider; (light greylist, reflection)
05-27 04:37:31.119 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/content/pm/PackageParser$Provider;->info:Landroid/content/pm/ProviderInfo; (light greylist, reflection)
05-27 04:37:31.119 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ActivityManager;->IActivityManagerSingleton:Landroid/util/Singleton; (light greylist, reflection)
05-27 04:37:31.119 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/util/Singleton;->mInstance:Ljava/lang/Object; (light greylist, reflection)
05-27 04:37:31.120 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ActivityThread$AppBindData;->providers:Ljava/util/List; (light greylist, reflection)
05-27 04:37:31.120 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ActivityThread;->mBoundApplication:Landroid/app/ActivityThread$AppBindData; (light greylist, reflection)
05-27 04:37:31.120 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden field Landroid/app/ContextImpl;->mPackageInfo:Landroid/app/LoadedApk; (light greylist, reflection)
05-27 04:37:31.121 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/app/ActivityThread;->currentActivityThread()Landroid/app/ActivityThread; (light greylist, reflection)
05-27 04:37:31.121 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/content/res/AssetManager;->addAssetPath(Ljava/lang/String;)I (light greylist, reflection)
05-27 04:37:31.121 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/content/res/AssetManager;->addAssetPathAsSharedLibrary(Ljava/lang/String;)I (light greylist, reflection)
05-27 04:37:31.121 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/app/Application;->attach(Landroid/content/Context;)V (light greylist, reflection)
05-27 04:37:31.121 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/content/pm/PackageParser$Component;->getComponentName()Landroid/content/ComponentName; (light greylist, reflection)
05-27 04:37:31.121 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/app/ContextImpl;->setOuterContext(Landroid/content/Context;)V (light greylist, reflection)
05-27 04:37:31.122 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/content/res/AssetManager;->getResourceIdentifier(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)I (light greylist, reflection)
05-27 04:37:31.122 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/app/ActivityThread;->installContentProviders(Landroid/content/Context;Ljava/util/List;)V (light greylist, reflection)
05-27 04:37:31.122 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/app/ActivityThread;->installProvider(Landroid/content/Context;Landroid/app/ContentProviderHolder;Landroid/content/pm/ProviderInfo;ZZZ)Landroid/app/ContentProviderHolder; (light greylist, reflection)
05-27 04:37:31.122 2972-2972/com.taobao.demo W/com.taobao.dem: Accessing hidden method Landroid/app/Service;->attach(Landroid/content/Context;Landroid/app/ActivityThread;Ljava/lang/String;Landroid/os/IBinder;Landroid/app/Application;Ljava/lang/Object;)V (light greylist, reflection)
hide api在light greylist中，调用时都会有警告，但还好大部分都可以被反射调用了
当然也有失败的情况：
0 = {Hack$HackDeclaration$HackAssertionException@5211} "android.taobao.atlas.hack.Hack$HackDeclaration$HackAssertionException: java.lang.NoSuchFieldException: No field mStringBlocks in class Landroid/content/res/AssetManager; (declaration of 'android.content.res.AssetManager' appears in /system/framework/framework.jar)"
1 = {Hack$HackDeclaration$HackAssertionException@5212} "android.taobao.atlas.hack.Hack$HackDeclaration$HackAssertionException: java.lang.NoSuchMethodException: ensureStringBlocks []"
2 = {Hack$HackDeclaration$HackAssertionException@5213} "android.taobao.atlas.hack.Hack$HackDeclaration$HackAssertionException: java.lang.NoSuchMethodException: addAssetPathNative [class java.lang.String]"
3 = {Hack$HackDeclaration$HackAssertionException@5214} "android.taobao.atlas.hack.Hack$HackDeclaration$HackAssertionException: java.lang.NoSuchMethodException: addAssetPathNative [class java.lang.String, boolean]"
4 = {Hack$HackDeclaration$HackAssertionException@5215} "android.taobao.atlas.hack.Hack$HackDeclaration$HackAssertionException: java.lang.NoSuchMethodException: addAssetPathNative [class java.lang.String, int]"
5 = {Hack$HackDeclaration$HackAssertionException@5216} "android.taobao.atlas.hack.Hack$HackDeclaration$HackAssertionException: java.lang.NoSuchMethodException: getStringBlockCount []"
6 = {Hack$HackDeclaration$HackAssertionException@5217} "android.taobao.atlas.hack.Hack$HackDeclaration$HackAssertionException: java.lang.NoSuchMethodException: getNativeStringBlock [int]"
不过这些都是一些兼容性处理的反射调用，不会影响到整个atlas的框架。
所以从目前来看atlas在Android不会因为hide api限制而作废
4、hide api 自相矛盾的现状
为什么Android会开放出light greylist来运行反射调用hide api呢？为什么没法立即执行这个限制呢？
原因很可能还是Android studio中需要使用，Instant Run是主要使用者，而Instant Run这种机制还主要是用的插件化的思想来完成的(不清楚的自行百度instant run原理)，atlas中调用的大部分还是Instant Run需要用的，如果Android一刀切，可能自己的工具也会遭殃，所以这个是Android hide api中矛盾的现状。
5、未来，未知...
如果Android未来删除了light greylist、如果Android p正式版的限制更加严格、甚至Android更改了activity的启动源码，这都不好说，有许多未知问题，不过这不是因为Android自身问题，而是这些api本身就是隐藏的。但是，插件话加载的核心还是DexClassLoader的使用。
6、未来，猜测
就算Android屏蔽了所有的hide api，只要DexClassLoader可以使用，我们还是可以实现插件化开发，以后减少对Android系统组件依赖，使用weex、rn解耦可能是趋势，而阿里巴巴现在本身一直都在推广weex，集团下app大都也是插件化和weex并用，所以我们就等待安心等待Android p的到来、未来的到来。
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