Android插件化的一种方案

思路：打开插件包里边的activity时 统一都用 一个ProxyActivity作为代理  

1、首先宿主APP提供ProxyActivity，当宿主需要打开插件包中的Activity时，一律是启动的ProxyActivity，

在启动ProxyActivity的intent中携带我们真正需要去打开的插件包中Activity的类全名。

public class ProxyActivity extends Activity {
    private IPluginActivity mPluginActivity;//用来接收插件包所有Activity的接口对象

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        String className = getIntent().getStringExtra("className");
        try {
            Class activityClass = getClassLoader().loadClass(className);
            Constructor constructor = activityClass.getConstructor(new Class[]{});
            Object instance = constructor.newInstance(new Object[]{});
            mPluginActivity = (PluginBaseActivity) instance;
            mPluginActivity.onCreate(savedInstanceState);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

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

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

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

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

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

　　

在Activity中有很重要的两个回调方法：

@Override
    public ClassLoader getClassLoader() {
        return PluginManager.getInstance().getPluginBean().getDexClassLoader();
    }

    @Override
    public Resources getResources() {
        return PluginManager.getInstance().getPluginBean().getResources();
    }

　　

• getClassLoader返回的是ClassLoader 对象，Activity内部在使用反射new对象时，都会去使用这里返回的ClassLoader 来进行反射，所以我们ProxyActivity中需要提供的应该是当前加载插件包对应的ClassLoader 。
• getResources返回的是Resources 对象，Activity内部在使用资源文件时，都会去使用这里返回的Resources 来获取资源，所以我们ProxyActivity中需要提供的应该是当前加载插件包对应的Resources 。

　　我们宿主APP提供了一个ProxyActivity，我们打开插件包Activity其实都是打开的ProxyActivity，只不过ProxyActivity不做任何其他事情，只负责实例化插件包Activity，并且将ProxyActivity中的所有事　　件驱动通知给插件包Activity，也就是ProxyActivity调用了插件包Activity中的代码来实现插件包要实现的功能。

 

获得classLoader和resource：

            File pluginFile;//插件包文件
            PackageManager packageManager = context.getPackageManager();
            PackageInfo packageInfo = packageManager.getPackageArchiveInfo(pluginFile.getAbsolutePath(), PackageManager.GET_ACTIVITIES);

            File dexOutFile = context.getDir("dex", Context.MODE_PRIVATE);
            DexClassLoader dexClassLoader = new DexClassLoader(pluginFile.getAbsolutePath(), dexOutFile.getAbsolutePath()
                    , null, context.getClassLoader());

            AssetManager assetManager = AssetManager.class.newInstance();
            Method addAssetPath = AssetManager.class.getMethod("addAssetPath", String.class);
            addAssetPath.invoke(assetManager, pluginFile.getAbsolutePath());
            Resources resources = new Resources(assetManager, context.getResources().getDisplayMetrics(), context.getResources().getConfiguration());

　　

PackageInfo 可以获取插件包manifest中所有注册了的组件信息，例如主Activity的全类名的获取为：

 

packageInfo.activities[0].name

　　

下面是完整的

public abstract class PluginBaseActivity extends AppCompatActivity implements IPluginActivity {

    protected Activity that;//宿主Activity

    @Override
    public void attach(ProxyActivity proxyActivity) {
        if (that != null)
            throw new RuntimeException("Plugin's activity already has been attached!");
        this.that = proxyActivity;
        attachBaseContext(proxyActivity);
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        if (that == null) {
            super.onCreate(savedInstanceState);
        }
    }

    @Override
    public void onStart() {
        if (that == null) {
            super.onStart();
        }
    }

    @Override
    public void onResume() {
        if (that == null) {
            super.onResume();
        }
    }

    @Override
    public void onPause() {
        if (that == null) {
            super.onPause();
        }
    }

    @Override
    public void onStop() {
        if (that == null) {
            super.onStop();
        }
    }

    @Override
    public void onDestroy() {
        if (that == null) {
            super.onDestroy();
        }
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        if (that == null) {
            super.onSaveInstanceState(outState);
        }
    }

    @Override
    public void onRestoreInstanceState(Bundle savedInstanceState) {
        if (that == null) {
            super.onRestoreInstanceState(savedInstanceState);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (that == null) {
            return super.onTouchEvent(event);
        }
        return false;
    }

    @Override
    public void onBackPressed() {
        if (that == null) {
            super.onBackPressed();
        }
    }

    @Override
    public void setContentView(View view) {
        if (that == null) {
            super.setContentView(view);
        } else {
            that.setContentView(view);
        }
    }

    @Override
    public void setContentView(int layoutResID) {
        if (that == null) {
            super.setContentView(layoutResID);
        } else {
            that.setContentView(layoutResID);
        }
    }

    @Override
    public void startActivity(Intent intent) {
        if (that == null) {
            super.startActivity(intent);
        } else {//篡改intent打开页面为proxyActivity
            intent.putExtra("className", intent.getComponent().getClassName());
            intent.setClassName(intent.getComponent().getPackageName(), ProxyActivity.class.getName());
            that.startActivity(intent);
        }
    }

    @Override
    public ComponentName startService(Intent intent) {
        if (that == null) {
            return super.startService(intent);
        } else {
            intent.putExtra("className", intent.getComponent().getClassName());
            intent.setClassName(intent.getComponent().getPackageName(), ProxyService.class.getName());
            return that.startService(intent);
        }
    }

    @Override
    public View findViewById(int id) {
        if (that == null) {
            return super.findViewById(id);
        } else {
            return that.findViewById(id);
        }
    }


    @Override
    public Intent getIntent() {
        if (that == null) {
            return super.getIntent();
        } else {
            return that.getIntent();
        }
    }


    @Override
    public Window getWindow() {
        if (that == null) {
            return super.getWindow();
        } else {
            return that.getWindow();
        }
    }

    @Override
    public WindowManager getWindowManager() {
        if (that == null) {
            return super.getWindowManager();
        } else {
            return that.getWindowManager();
        }
    }
}

　　

public interface IPluginActivity {
    void attach(ProxyActivity proxyActivity);

    void onCreate(@Nullable Bundle savedInstanceState);

    void onStart();


    void onResume();

    void onPause();

    void onStop();

    void onDestroy();

    void onSaveInstanceState(Bundle outState);

    void onRestoreInstanceState(Bundle savedInstanceState);

    boolean onTouchEvent(MotionEvent event);

    void onBackPressed();

    void setContentView(View view);

    void setContentView(int layoutResID);

    void startActivity(Intent intent);

    ComponentName startService(Intent intent);

    View findViewById(int id);


    Intent getIntent();


    Window getWindow();

    WindowManager getWindowManager();
}

　　以上步骤实则每次新打开的插件里的页面其实都是ProxyActivity 做的代理