最近在工作中接觸到了Android插件內(nèi)的開發(fā)，發(fā)現(xiàn)自己這種技術(shù)還缺乏最基本的了解尊惰，以至于在一些基本問題上浪費(fèi)不少時(shí)間饲嗽，如插件Context和主工程Context的區(qū)別票罐，權(quán)限必須在主工程申明等，因此花了點(diǎn)時(shí)間了解了一下插件的歷史暮胧，并寫了兩個(gè)Demo作為總結(jié)锐借。本文旨在通過兩個(gè)實(shí)例直觀的說明插件的實(shí)現(xiàn)原理以加深對插件內(nèi)開發(fā)的理解问麸，因此不會深入探討背景和原理，代碼也盡量專注于核心邏輯钞翔。

原理與背景

Android插件化從技術(shù)上來說就是如何啟動未安裝的apk（主要是四大組件）里面的類口叙，主要問題涉及如何加載類、如何加載資源嗅战、如何管理組件生命周期妄田。

類加載

Android對于外部的dex文件，主要通過DexClassLoader類加載驮捍，因此疟呐，只需要給定插件的路徑，就可以構(gòu)造對應(yīng)的類加載器：

private DexClassLoader createDexClassLoader(String apkPath) {
    File dexOutputDir = mContext.getDir("dex", Context.MODE_PRIVATE);
    DexClassLoader loader = new DexClassLoader(apkPath, dexOutputDir.getAbsolutePath(),
            null, mContext.getClassLoader());
    return loader;
}

資源加載

Android系統(tǒng)通過Resource對象加載資源,因此只需要添加資源（即apk文件）所在路徑到AssetManager中东且，即可實(shí)現(xiàn)對插件資源的訪問。

  AssetManager assetManager = AssetManager.class.newInstance();
  Method addAssetPath = assetManager.getClass().getMethod(addAssetPathMethod, String.class);
  addAssetPath.invoke(assetManager, apkPath);
  Resources pluginRes = new Resources(assetManager,
          mContext.getResources().getDisplayMetrics(),
          mContext.getResources().getConfiguration());
  pluginApk = new PluginApk(pluginRes);
  pluginApk.classLoader = createDexClassLoader(apkPath);

生命周期

插件化中較為復(fù)雜的是對生命周期的管理珊泳，其中以Activity最為復(fù)雜鲁冯。早期的dynamic-load-apk采用的是代理的方式，通過一個(gè)空殼Activity作為代理（Proxy）色查，系統(tǒng)對該Activity的回調(diào)都會映射到插件Activity薯演，如此便可以實(shí)現(xiàn)通過系統(tǒng)來管理插件的生命周期。這種方式十分直觀秧了，但是需要所有的插件Activity都繼承這個(gè)用作代理的PluginActivity（Demo中的命名）跨扮，侵入性強(qiáng)，可結(jié)合后面的例子加深理解验毡。因此衡创，如何避免這種侵入性成了第二代插件化框架的目標(biāo)，VirtualApk通過Hook少量系統(tǒng)類達(dá)到了這個(gè)目標(biāo)晶通，插件的開發(fā)和普通工程無異璃氢，接入成本極低。
了解了這些原理往往還不夠狮辽，知識往往需要經(jīng)過推導(dǎo)和實(shí)踐才能變成自己的一也，因此，接下來我們結(jié)合這些原理來實(shí)現(xiàn)一個(gè)插件化框架隘竭，不考慮兼容性和健壯性塘秦，純粹來實(shí)踐上面提及的原理。

代理實(shí)現(xiàn)

首先建立一個(gè)PluginManager類來實(shí)現(xiàn)插件的加載：

public class PluginManager {
    static class PluginMgrHolder {
        static PluginManager sManager = new PluginManager();
    }

    private static Context mContext;

    Map<String, PluginApk> sMap = new HashMap<>();

    public static PluginManager getInstance() {
        return PluginMgrHolder.sManager;
    }
    public PluginApk getPluginApk(String packageName) {
        return sMap.get(packageName);
    }

    public static void init(Context context) {
        mContext = context.getApplicationContext();
    }

    public final void loadApk(String apkPath) {
        PackageInfo packageInfo = queryPackageInfo(apkPath);
        if (packageInfo == null || TextUtils.isEmpty(packageInfo.packageName)) {
            return;
        }
        // check cache
        PluginApk pluginApk = sMap.get(packageInfo.packageName);

        if (pluginApk == null) {
            pluginApk = createApk(apkPath);
            if (pluginApk != null) {
                pluginApk.packageInfo = packageInfo;
                sMap.put(packageInfo.packageName, pluginApk);
            } else {
                throw new NullPointerException("PluginApk is null");
            }
        }
    }

    private PluginApk createApk(String apkPath) {
        String addAssetPathMethod = "addAssetPath";
        PluginApk pluginApk = null;
        try {
            AssetManager assetManager = AssetManager.class.newInstance();
            Method addAssetPath = assetManager.getClass().getMethod(addAssetPathMethod, String.class);
            addAssetPath.invoke(assetManager, apkPath);
            Resources pluginRes = new Resources(assetManager,
                    mContext.getResources().getDisplayMetrics(),
                    mContext.getResources().getConfiguration());
            pluginApk = new PluginApk(pluginRes);
            pluginApk.classLoader = createDexClassLoader(apkPath);
        } catch (IllegalAccessException
                | InstantiationException
                | NoSuchMethodException
                | InvocationTargetException e) {
            e.printStackTrace();
        }
        return pluginApk;
    }
    private PackageInfo queryPackageInfo(String apkPath) {
        PackageInfo packageInfo = mContext.getPackageManager().getPackageArchiveInfo(apkPath,
                PackageManager.GET_ACTIVITIES | PackageManager.GET_SERVICES);
        if (packageInfo == null) {
            return null;
        }
        return packageInfo;
    }

    private DexClassLoader createDexClassLoader(String apkPath) {
        File dexOutputDir = mContext.getDir("dex", Context.MODE_PRIVATE);
        DexClassLoader loader = new DexClassLoader(apkPath, dexOutputDir.getAbsolutePath(),
                null, mContext.getClassLoader());
        return loader;
    }

    public void startActivity(Intent intent) {
        Intent pluginIntent = new Intent(mContext, ProxyActivity.class);
        Bundle extra = intent.getExtras();
        // complicate if statement
        if (extra == null || !extra.containsKey(Constants.PLUGIN_CLASS_NAME) && !extra.containsKey(Constants.PACKAGE_NAME)) {
            try {
                throw new IllegalAccessException("lack class of plugin and package name");
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        pluginIntent.putExtras(intent);
        pluginIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        mContext.startActivity(pluginIntent);
    }
}

PluginApk表示一個(gè)Apk文件：

public class PluginApk {
    public PackageInfo packageInfo;
    public DexClassLoader classLoader;
    public Resources pluginRes;

    public PluginApk(Resources pluginRes) {
        this.pluginRes = pluginRes;
    }

}

所有插件Activity都要繼承一個(gè)父類PluginActivity:

public abstract class PluginActivity extends Activity implements Pluginable, Attachable<Activity> {
    public final static String TAG = PluginActivity.class.getSimpleName();
    protected Activity mProxyActivity;
    private Resources mResources;
    PluginApk mPluginApk;

    @Override
    public void attach(Activity proxy, PluginApk apk) {
        mProxyActivity = proxy;
        mPluginApk = apk;
        mResources = apk.pluginRes;
    }

    @Override
    public void setContentView(int layoutResID) {
        mProxyActivity.setContentView(layoutResID);
    }

    @Override
    public void setContentView(View view) {
        mProxyActivity.setContentView(view);
    }

    @Override
    public void setContentView(View view, ViewGroup.LayoutParams params) {
        mProxyActivity.setContentView(view, params);
    }


    @Override
    public View findViewById(int id) {
        return mProxyActivity.findViewById(id);
    }

    @Override
    public Resources getResources() {
        return mResources;
    }

    @Override
    public WindowManager getWindowManager() {
        return mProxyActivity.getWindowManager();
    }

    @Override
    public ClassLoader getClassLoader() {
        return mProxyActivity.getClassLoader();
    }

    @Override
    public Context getApplicationContext() {
        return mProxyActivity.getApplicationContext();
    }

    @Override
    public MenuInflater getMenuInflater() {
        return mProxyActivity.getMenuInflater();
    }


    @Override
    public Window getWindow() {
        return mProxyActivity.getWindow();
    }

    @Override
    public Intent getIntent() {
        return mProxyActivity.getIntent();
    }

    @Override
    public LayoutInflater getLayoutInflater() {
        return mProxyActivity.getLayoutInflater();
    }

    @Override
    public String getPackageName() {
        return mPluginApk.packageInfo.packageName;
    }


    @Override
    public void onCreate(Bundle bundle) {
        // DO NOT CALL super.onCreate(bundle)
        // following same
        VLog.log(TAG + ": onCreate");
    }

    @Override
    public void onStart() {

    }

    @Override
    public void onResume() {

    }

    @Override
    public void onStop() {

    }

    @Override
    public void onPause() {

    }

    @Override
    public void onDestroy() {
    }
}

這個(gè)類只是一個(gè)殼动看，系統(tǒng)會通過ProxyActivity觸發(fā)對應(yīng)的方法的具體實(shí)現(xiàn)：

public class ProxyActivity extends Activity {
    LifeCircleController mPluginController = new LifeCircleController(this);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mPluginController.onCreate(getIntent().getExtras());
    }

    @Override
    public Resources getResources() {
        // construct when loading apk
        Resources resources = mPluginController.getResources();
        return resources == null ? super.getResources() : resources;
    }

    @Override
    public Resources.Theme getTheme() {
        Resources.Theme theme = mPluginController.getTheme();
        return theme == null ? super.getTheme() : theme;
    }

    @Override
    public AssetManager getAssets() {
        return mPluginController.getAssets();
    }


    @Override
    protected void onStart() {
        super.onStart();
        mPluginController.onStart();
    }

    @Override
    protected void onResume() {
        super.onResume();
        mPluginController.onResume();
    }

    @Override
    protected void onStop() {
        super.onStop();
        mPluginController.onStop();
    }

    @Override
    protected void onPause() {
        super.onPause();
        mPluginController.onPause();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mPluginController.onDestroy();
    }
}

這個(gè)類是系統(tǒng)實(shí)際啟動的類尊剔，其主要邏輯由LifeCircleController負(fù)責(zé)：

public class LifeCircleController implements Pluginable {
    Activity mProxy;
    PluginActivity mPlugin;
    Resources mResources;
    Resources.Theme mTheme;
    PluginApk mPluginApk;
    String mPluginClazz;

    public LifeCircleController(Activity activity) {
        mProxy = activity;
    }

    public void onCreate(Bundle bundle) {
        mPluginClazz = bundle.getString(Constants.PLUGIN_CLASS_NAME);
        String packageName = bundle.getString(Constants.PACKAGE_NAME);
        mPluginApk = PluginManager.getInstance().getPluginApk(packageName);
        try {
            mPlugin = (PluginActivity) loadPluginable(mPluginApk.classLoader, mPluginClazz);
            mPlugin.attach(mProxy, mPluginApk);
            mResources = mPluginApk.pluginRes;
            mPlugin.onCreate(bundle);
        } catch (Exception e) {
            VLog.log("Fail in LifeCircleController onCreate");
            VLog.log(e.getMessage());
            e.printStackTrace();
        }

    }
    private Object loadPluginable(ClassLoader classLoader, String pluginActivityClass)
            throws Exception {
        Class<?> pluginClz = classLoader.loadClass(pluginActivityClass);
        Constructor<?> constructor = pluginClz.getConstructor(new Class[] {});
        constructor.setAccessible(true);
        return constructor.newInstance(new Object[] {});
    }

    @Override
    public void onStart() {
        if (mPlugin != null) {
            mPlugin.onStart();
        }
    }

    @Override
    public void onResume() {
        if (mPlugin != null) {
            mPlugin.onResume();
        }
    }

    @Override
    public void onStop() {
        mPlugin.onStop();
    }

    @Override
    public void onPause() {
        mPlugin.onPause();
    }

    @Override
    public void onDestroy() {
        mPlugin.onDestroy();
    }

    public Resources getResources() {
        return mResources;
    }

    public Resources.Theme getTheme() {
        return mTheme;
    }

    public AssetManager getAssets() {
        return mResources.getAssets();
    }

}

有點(diǎn)像Activity源碼的外觀模式，內(nèi)部的分工和職責(zé)劃分對于使用者是不可見的菱皆。
最后在主工程啟動插件：

Intent intent = new Intent();
intent.putExtra(Constants.PACKAGE_NAME, PLUGIN_PACKAGE_NAME);
intent.putExtra(Constants.PLUGIN_CLASS_NAME, PLUGIN_CLAZZ_NAME);
mPluginManager.startActivity(intent);

插件Activity如下：

public class MainActivity extends PluginActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setTitle("Plugin App");
        ((ImageView) findViewById(R.id.iv_logo)).setImageResource(R.drawable.android);
    }
}

效果：

image

Hook實(shí)現(xiàn)

Hook的方式需要基本了解系統(tǒng)啟動一個(gè)Activity的過程须误，一般來說系統(tǒng)會先檢查Activity是否注冊挨稿，然后再去生成該Activity，那么我們只需要在檢查的時(shí)候用一個(gè)已經(jīng)注冊的Activity（樁京痢，通常表示為StubActivity）來給系統(tǒng)檢查奶甘，檢查通過后在生成的時(shí)候再替換成插件的就可以了。
首先要自己實(shí)現(xiàn)一個(gè)Instrumentation祭椰，在里面做一些替換工作臭家，然后去Hook掉系統(tǒng)持有的對象：

public class HookedInstrumentation extends Instrumentation implements Handler.Callback {
    public static final String TAG = "HookedInstrumentation";
    protected Instrumentation mBase;
    private PluginManager mPluginManager;

    public HookedInstrumentation(Instrumentation base, PluginManager pluginManager) {
        mBase = base;
        mPluginManager = pluginManager;
    }

    /**
     * 覆蓋掉原始Instrumentation類的對應(yīng)方法,用于插件內(nèi)部跳轉(zhuǎn)Activity時(shí)適配
     *
     * @Override
     */
    public ActivityResult execStartActivity(
            Context who, IBinder contextThread, IBinder token, Activity target,
            Intent intent, int requestCode, Bundle options) {

        if (Constants.DEBUG) Log.e(TAG, "execStartActivity");
        mPluginManager.hookToStubActivity(intent);

        try {
            Method execStartActivity = Instrumentation.class.getDeclaredMethod(
                    "execStartActivity", Context.class, IBinder.class, IBinder.class,
                    Activity.class, Intent.class, int.class, Bundle.class);
            execStartActivity.setAccessible(true);
            return (ActivityResult) execStartActivity.invoke(mBase, who,
                    contextThread, token, target, intent, requestCode, options);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException("do not support!!!" + e.getMessage());
        }
    }

    @Override
    public Activity newActivity(ClassLoader cl, String className, Intent intent) throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        if (Constants.DEBUG) Log.e(TAG, "newActivity");

        if (mPluginManager.hookToPluginActivity(intent)) {
            String targetClassName = intent.getComponent().getClassName();
            PluginApp pluginApp = mPluginManager.getLoadedPluginApk();
            Activity activity = mBase.newActivity(pluginApp.mClassLoader, targetClassName, intent);
            activity.setIntent(intent);
            ReflectUtil.setField(ContextThemeWrapper.class, activity, Constants.FIELD_RESOURCES, pluginApp.mResources);
            return activity;
        }

        if (Constants.DEBUG) Log.e(TAG, "super.newActivity(...)");
        return super.newActivity(cl, className, intent);
    }

    @Override
    public boolean handleMessage(Message message) {
        if (Constants.DEBUG) Log.e(TAG, "handleMessage");
        return false;
    }


    @Override
    public void callActivityOnCreate(Activity activity, Bundle icicle) {
        if (Constants.DEBUG) Log.e(TAG, "callActivityOnCreate");
        super.callActivityOnCreate(activity, icicle);
    }
}

在負(fù)責(zé)啟動的execStartActivity設(shè)置為啟動已注冊的Activity，再在newActivity設(shè)置為實(shí)際要啟動的插件的Activity方淤。然后去Hook系統(tǒng)持有的該字段：

public class ReflectUtil {
    public static final String METHOD_currentActivityThread = "currentActivityThread";
    public static final String CLASS_ActivityThread = "android.app.ActivityThread";
    public static final String FIELD_mInstrumentation = "mInstrumentation";
    public static final String TAG = "ReflectUtil";


    private static Instrumentation sInstrumentation;
    private static Instrumentation sActivityInstrumentation;
    private static Field sActivityThreadInstrumentationField;
    private static Field sActivityInstrumentationField;
    private static Object sActivityThread;

    public static boolean init() {
        //獲取當(dāng)前的ActivityThread對象
        Class<?> activityThreadClass = null;
        try {
            activityThreadClass = Class.forName(CLASS_ActivityThread);
            Method currentActivityThreadMethod = activityThreadClass.getDeclaredMethod(METHOD_currentActivityThread);
            currentActivityThreadMethod.setAccessible(true);
            Object currentActivityThread = currentActivityThreadMethod.invoke(null);


            //拿到在ActivityThread類里面的原始mInstrumentation對象
            Field instrumentationField = activityThreadClass.getDeclaredField(FIELD_mInstrumentation);
            instrumentationField.setAccessible(true);
            sActivityThreadInstrumentationField = instrumentationField;

            sInstrumentation = (Instrumentation) instrumentationField.get(currentActivityThread);
            sActivityThread = currentActivityThread;


            sActivityInstrumentationField =  Activity.class.getDeclaredField(FIELD_mInstrumentation);
            sActivityInstrumentationField.setAccessible(true);
            return true;
        } catch (ClassNotFoundException
                | NoSuchMethodException
                | IllegalAccessException
                | InvocationTargetException
                | NoSuchFieldException e) {
            e.printStackTrace();
        }

        return false;
    }

    public static Instrumentation getInstrumentation() {
        return sInstrumentation;
    }

    public static Object getActivityThread() {
        return sActivityThread;
    }

    public static void setInstrumentation(Object activityThread, HookedInstrumentation hookedInstrumentation) {
        try {
            sActivityThreadInstrumentationField.set(activityThread, hookedInstrumentation);
            if (Constants.DEBUG) Log.e(TAG, "set hooked instrumentation");
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }

    public static void setActivityInstrumentation(Activity activity, PluginManager manager) {
        try {
            sActivityInstrumentation = (Instrumentation) sActivityInstrumentationField.get(activity);
            HookedInstrumentation instrumentation = new HookedInstrumentation(sActivityInstrumentation, manager);
            sActivityInstrumentationField.set(activity, instrumentation);
            if (Constants.DEBUG) Log.e(TAG, "set activity hooked instrumentation");
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }


    public static void setField(Class clazz, Object target, String field, Object object) {
        try {
            Field f = clazz.getDeclaredField(field);
            f.setAccessible(true);
            f.set(target, object);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}

PluginManager同樣負(fù)責(zé)加載插件的類和資源等：

public class PluginManager {
    private final static String TAG = "PluginManager";
    private static PluginManager sInstance;
    private Context mContext;
    private PluginApp mPluginApp;


    public static PluginManager getInstance(Context context) {
        if (sInstance == null && context != null) {
            sInstance = new PluginManager(context);
        }
        return sInstance;
    }

    private PluginManager(Context context) {
        mContext = context;
    }


    public void hookInstrumentation() {
        try {
            Instrumentation baseInstrumentation = ReflectUtil.getInstrumentation();

            final HookedInstrumentation instrumentation = new HookedInstrumentation(baseInstrumentation, this);

            Object activityThread = ReflectUtil.getActivityThread();
            ReflectUtil.setInstrumentation(activityThread, instrumentation);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void hookCurrentActivityInstrumentation(Activity activity) {
        ReflectUtil.setActivityInstrumentation(activity, sInstance);
    }


    public void hookToStubActivity(Intent intent) {
        if (Constants.DEBUG) Log.e(TAG, "hookToStubActivity");

        if (intent == null || intent.getComponent() == null) {
            return;
        }
        String targetPackageName = intent.getComponent().getPackageName();
        String targetClassName = intent.getComponent().getClassName();

        if (mContext != null
                && !mContext.getPackageName().equals(targetPackageName)
                && isPluginLoaded(targetPackageName)) {
            if (Constants.DEBUG) Log.e(TAG, "hook " +  targetClassName + " to " + Constants.STUB_ACTIVITY);

            intent.setClassName(Constants.STUB_PACKAGE, Constants.STUB_ACTIVITY);
            intent.putExtra(Constants.KEY_IS_PLUGIN, true);
            intent.putExtra(Constants.KEY_PACKAGE, targetPackageName);
            intent.putExtra(Constants.KEY_ACTIVITY, targetClassName);
        }
    }

    public boolean hookToPluginActivity(Intent intent) {
        if (Constants.DEBUG) Log.e(TAG, "hookToPluginActivity");
        if (intent.getBooleanExtra(Constants.KEY_IS_PLUGIN, false)) {
            String pkg = intent.getStringExtra(Constants.KEY_PACKAGE);
            String activity = intent.getStringExtra(Constants.KEY_ACTIVITY);
            if (Constants.DEBUG) Log.e(TAG, "hook " + intent.getComponent().getClassName() + " to " + activity);
            intent.setClassName(pkg, activity);
            return true;
        }
        return false;
    }

    private boolean isPluginLoaded(String packageName) {
        // TODO 檢查packageNmae是否匹配
        return mPluginApp != null;
    }



    public PluginApp loadPluginApk(String apkPath) {
        String addAssetPathMethod = "addAssetPath";
        PluginApp pluginApp = null;
        try {
            AssetManager assetManager = AssetManager.class.newInstance();
            Method addAssetPath = assetManager.getClass().getMethod(addAssetPathMethod, String.class);
            addAssetPath.invoke(assetManager, apkPath);
            Resources pluginRes = new Resources(assetManager,
                    mContext.getResources().getDisplayMetrics(),
                    mContext.getResources().getConfiguration());
            pluginApp = new PluginApp(pluginRes);
            pluginApp.mClassLoader = createDexClassLoader(apkPath);
        } catch (IllegalAccessException
                | InstantiationException
                | NoSuchMethodException
                | InvocationTargetException e) {
            e.printStackTrace();
        }
        return pluginApp;
    }

    private DexClassLoader createDexClassLoader(String apkPath) {
        File dexOutputDir = mContext.getDir("dex", Context.MODE_PRIVATE);
        return new DexClassLoader(apkPath, dexOutputDir.getAbsolutePath(),
                null, mContext.getClassLoader());

    }

    public boolean loadPlugin(String apkPath) {
        File apk = new File(apkPath);
        if (!apk.exists()) {
            return false;
        }
        mPluginApp = loadPluginApk(apkPath);
        return mPluginApp != null;
    }

    public PluginApp getLoadedPluginApk() {
        return mPluginApp;
    }
}

在MainActivity中初始化钉赁，注意Hook的時(shí)機(jī)：

public class MainActivity extends Activity implements View.OnClickListener {
    // https://zhuanlan.zhihu.com/p/33017826

    public static final boolean DEBUG = true;
    public static final String TAG = "MainActivity";

    private String mPluginPackageName = "top.vimerzhao.image";
    private String mPluginClassName = "top.vimerzhao.image.MainActivity";

    //讀寫權(quán)限
    private static String[] PERMISSIONS_STORAGE = {Manifest.permission.READ_EXTERNAL_STORAGE,
            Manifest.permission.WRITE_EXTERNAL_STORAGE};
    //請求狀態(tài)碼
    private static int REQUEST_PERMISSION_CODE = 1;

    private PluginManager mPluginManager;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initData();
        initView();
        initPlugin();
    }


    private void initPlugin() {
        // !! must first
        ReflectUtil.init();

        mPluginManager = PluginManager.getInstance(getApplicationContext());
        mPluginManager.hookInstrumentation();
        mPluginManager.hookCurrentActivityInstrumentation(this);
    }

    private void initData() {
        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP) {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, PERMISSIONS_STORAGE, REQUEST_PERMISSION_CODE);
            }
        }
    }

    private void initView() {
        (findViewById(R.id.tv_launch)).setOnClickListener(this);
    }

    @Override
    protected void attachBaseContext(Context newBase) {
        super.attachBaseContext(newBase);
        // !!! 不要在此Hook,看源碼發(fā)現(xiàn)mInstrumentaion會在此方法后初始化
    }

    @Override
    public void onClick(View view) {
        if (Constants.DEBUG) Log.e(TAG, "click view id: " + view.getId());
        if (view.getId() == R.id.tv_launch) {
            // TODO launch plugin app
            if (mPluginManager.loadPlugin(Constants.PLUGIN_PATH)) {
                Intent intent = new Intent();
                intent.setClassName(mPluginPackageName, mPluginClassName);
                startActivity(intent);
            }
        }

    }
}

現(xiàn)在插件Activity不會有任何限制：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    }

    @Override
    protected void onResume() {
        super.onResume();

    }
}

效果和上圖類似。

Demo地址

部分源碼無關(guān)核心邏輯携茂，沒有給到你踩，目錄結(jié)構(gòu)也沒有說明，詳見Demo源碼讳苦。
PluginDemo

總結(jié)

看著理論感覺似懂非懂带膜，實(shí)戰(zhàn)發(fā)現(xiàn)問題其實(shí)挺多的，尤其是Hook的時(shí)機(jī)鸳谜，照搬網(wǎng)上的文章發(fā)現(xiàn)根本不可行膝藕。插件化也不是一蹴而就的，而是在已有成果的基礎(chǔ)上一次一次的小創(chuàng)新積累起來的卿堂，跟著插件化發(fā)展的路徑自己動手實(shí)踐一遍還是能發(fā)現(xiàn)很多自己理解不夠深刻的地方的束莫。
以上懒棉。

參考

• 《Android源碼設(shè)計(jì)模式解析與實(shí)戰(zhàn)》
• 深入理解Android插件化技術(shù)