android架構師之路——插件化換膚

簡介

模塊化：將一個項目的可以共享的部分抽取出來，形成獨立的lib
組件化：組件化本來就是模塊化的概念。核心是模塊角色的可轉化換性，在打包時，是library；調試時，時application
插件化：將一個完整的工程，按業務劃分爲不同的插件，來化整爲零，相互配合。插件化的單位是apk(一個完成的應用)。可以實現apk 的動態加載，動態更新，比組件化更靈活。

我們這裏將以插件化方式，實現一個換膚的功能，通過宿主app的ProxyActivity加載子類app的mainactivity

實現方式

項目目錄結構：

app就是宿主app，依賴lib_base_plugin
douban就是需要替換的apk，依賴lib_base_plugin
lib_base_plugin是公共方法，以及接口

app中的 PluginManager類中加載sdcard中的plugin.apk文件，得到這個文件中的資源文件resources以及dex加載方式dexClassLoader

  public void loadPath(Context context) {
        File filesDir = Environment.getExternalStorageDirectory();
        String name = "plugin.apk";
        String path = new File(filesDir, name).getAbsolutePath();
        Log.d(TAG, "--path--" + path);
        PackageManager packageManager = context.getPackageManager();
        packageInfo = packageManager.getPackageArchiveInfo(path, PackageManager.GET_ACTIVITIES);
        //activity
        File dex = new File(filesDir, "dex");
        dexClassLoader = new DexClassLoader(path, dex.getAbsolutePath(), null, context.getClassLoader());
        //resource
        try {
            AssetManager manager = AssetManager.class.newInstance();
            Method addAssetPath = AssetManager.class.getMethod("addAssetPath", String.class);
            addAssetPath.invoke(manager, path);
            resources = new Resources(manager,
                    context.getResources().getDisplayMetrics(),
                    context.getResources().getConfiguration());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

lib_base_plugin中的PayInterfaceActivity接口，所有子類需要用插件化加載的activity，都需要繼承這個接口

public interface PayInterfaceActivity {

    public void attach(Activity proxyActivity);

    /**
     *生命週期
     */
    public void onCreate(Bundle saveInstanceState);
    public void onStart();
    public void onResume();
    public void onPause();
    public void onStop();
    public void onDestroy();
    public void onSaveInstanceState(Bundle outState);
    public boolean onTouchEvent(MotionEvent event);
    public void onBackPressed();
}

在douban中用一個BaseActivity繼承PayInterfaceActivity，這裏的oncreate onStart onResume等，都是PayInterfaceActivity中的方法

public class BaseActivity extends Activity implements PayInterfaceActivity {
    protected Activity that;

    @Override
    public void attach(Activity proxyActivity) {
        this.that = proxyActivity;
    }

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

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

    @Override
    public void startActivity(Intent intent) {
        Intent m  = new Intent();
        m.putExtra("className",intent.getComponent().getClassName());
        that.startActivity(m);
    }

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

    @Override
    public void onCreate(Bundle saveInstanceState) {

    }

    @Override
    public void onStart() {

    }

    @Override
    public void onResume() {

    }

    @Override
    public void onPause() {

    }

    @Override
    public void onStop() {

    }

    @Override
    public void onDestroy() {

    }

    @Override
    public void onSaveInstanceState(Bundle outState) {

    }
}

在douban中的MainActivity我們就只寫了一個文字

public class MainActivity extends BaseActivity {

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

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="豆瓣中的MainActivity"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

我們要將douban中的MainActivity加載到ProxyActivity，我們來看一下ProxyActivity中主要的方法

重寫了activity的getClassLoader方法，返回的是子類APP的getDexClassLoader

重寫了activity的getResources方法，返回子類APP的getResources

就是通過這兩個方法，修改了宿主app的加載方式

    //重寫加載類
    @Override
    public ClassLoader getClassLoader() {
        return PluginManager.getInstance().getDexClassLoader();
    }

    //重寫加載資源
    @Override
    public Resources getResources() {
        return PluginManager.getInstance().getResources();
    }

看一下ProxyActivity完整代碼

public class ProxyActivity extends Activity {
    private static final String TAG = "ProxyActivity";
    //需要加載插件的全類名
    private String className;
    PayInterfaceActivity payInterfaceActivity;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        className = getIntent().getStringExtra("className");
        Log.e(TAG, "---className--" + className);
        try {
            //TaoMainActivity
            Class<?> aClass = getClassLoader().loadClass(className);
            Constructor constructor = aClass.getConstructor(new Class[]{});
            Object in = constructor.newInstance(new Object[]{});
            payInterfaceActivity = (PayInterfaceActivity) in;
            payInterfaceActivity.attach(this);

            //如果需要參數，可以使用Bundle
            Bundle bundle = new Bundle();
            payInterfaceActivity.onCreate(bundle);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void startActivity(Intent intent) {
        String className = intent.getStringExtra("className");
        Intent intent1 = new Intent(this, ProxyActivity.class);
        intent1.putExtra("className", className);
        super.startActivity(intent1);
    }

    //重寫加載類
    @Override
    public ClassLoader getClassLoader() {
        return PluginManager.getInstance().getDexClassLoader();
    }

    //重寫加載資源
    @Override
    public Resources getResources() {
        return PluginManager.getInstance().getResources();
    }

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

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

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

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

app中的MainActivity

public class MainActivity extends Activity {

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

        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                load();
            }
        });

    }

    public void load() {
            PluginManager.getInstance().loadPath(this);
    }

    public void click(View view) {
        Intent intent = new Intent(this, ProxyActivity.class);
        intent.putExtra("className", PluginManager.getInstance().getPackageInfo().activities[0].name);
        startActivity(intent);
    }
}

注意事項：

ProxyActivity的android:launchMode="standard"，必須是standard，因爲我們每一個activity其實都是ProxyActivity，如果設置爲singleTask，返回就沒有用了
PluginManager.getInstance().getPackageInfo().activities[0].name得到的activity是AndroidManifest.xml中你註冊的activity順序來算的
需要將子類app生成的plugin.apk放置在sdcard中，並且開啓讀取權限

demo下載地址demo下載

android架構師之路——插件化換膚

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