换肤-插件化

--摘自《android插件化开发指南》

fork了强哥的github代码到自己的github下 https://github.com/king1039/Dynamic3

将代码跑起来，Plugin1和Plugin2打成apk放到HostApp的assets下

贴下主要代码

public class BaseActivity extends Activity {

    private AssetManager mAssetManager;
    private Resources mResources;
    private Resources.Theme mTheme;

    protected HashMap<String, PluginInfo> plugins = new HashMap<String, PluginInfo>();

    @Override
    protected void attachBaseContext(Context newBase) {
        super.attachBaseContext(newBase);

        Utils.extractAssets(newBase, "plugin1.apk");
        Utils.extractAssets(newBase, "plugin2.apk");
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        genegatePluginInfo("plugin1.apk");
        genegatePluginInfo("plugin2.apk");
    }

    protected void genegatePluginInfo(String pluginName) {
        File extractFile = this.getFileStreamPath(pluginName);
        File fileRelease = getDir("dex", 0);
        String dexpath = extractFile.getPath();
        DexClassLoader classLoader = new DexClassLoader(dexpath, fileRelease.getAbsolutePath(), null, getClassLoader());

        plugins.put(pluginName, new PluginInfo(dexpath, classLoader));
    }

    protected void loadResources(String dexPath) {
        try {
            AssetManager assetManager = AssetManager.class.newInstance();
            Method addAssetPath = assetManager.getClass().getMethod("addAssetPath", String.class);
            addAssetPath.invoke(assetManager, dexPath);
            mAssetManager = assetManager;
        } catch (Exception e) {
            e.printStackTrace();
        }
        Resources superRes = super.getResources();
        mResources = new Resources(mAssetManager, superRes.getDisplayMetrics(), superRes.getConfiguration());
        mTheme = mResources.newTheme();
        mTheme.setTo(super.getTheme());
    }

    @Override
    public AssetManager getAssets() {
        return mAssetManager == null ? super.getAssets() : mAssetManager;
    }

    @Override
    public Resources getResources() {
        return mResources == null ? super.getResources() : mResources;
    }

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

public class ResourceActivity extends BaseActivity {

    /**
     * 需要替换主题的控件
     * 这里就列举三个：TextView,ImageView,LinearLayout
     */
    private TextView textV;
    private ImageView imgV;
    private LinearLayout layout;

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

        textV = (TextView) findViewById(R.id.text);
        imgV = (ImageView) findViewById(R.id.imageview);
        layout = (LinearLayout) findViewById(R.id.layout);

        findViewById(R.id.btn1).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0) {
                PluginInfo pluginInfo = plugins.get("plugin1.apk");

                loadResources(pluginInfo.getDexPath());

                doSomething(pluginInfo.getClassLoader());
            }
        });

        findViewById(R.id.btn2).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                PluginInfo pluginInfo = plugins.get("plugin2.apk");

                loadResources(pluginInfo.getDexPath());

                doSomething(pluginInfo.getClassLoader());
            }
        });
    }

    private void doSomething(ClassLoader cl) {
        try {
            Class clazz = cl.loadClass("jianqiang.com.plugin1.UIUtil");

            String str = (String) RefInvoke.invokeStaticMethod(clazz, "getTextString", Context.class, this);
            textV.setText(str);

            Drawable drawable = (Drawable) RefInvoke.invokeStaticMethod(clazz, "getImageDrawable", Context.class, this);
            imgV.setBackground(drawable);

            layout.removeAllViews();
            View view = (View) RefInvoke.invokeStaticMethod(clazz, "getLayout", Context.class, this);
            layout.addView(view);

        } catch (Exception e) {
            Log.e("DEMO", "msg:" + e.getMessage());
        }
    }
}

简单来说，就是针对不同的apk生成不同的ClassLoader，然后通过反射框架取出相应的资源，最终加载显示

doSomething还有另外一个种写法，直接访问R.java的内部类drawable/string/layout中的相应字段对应的十六进制值（这个好屌）

private void doSomething(ClassLoader cl) {
    try {
        Class stringClass = cl.loadClass("jianqiang.com.plugin1.R$string");
        int resId1 = (int) RefInvoke.getStaticFieldObject(stringClass, "hello_message");
        textV.setText(getResources().getString(resId1));


        Class drawableClass = cl.loadClass("jianqiang.com.plugin1.R$drawable");
        int resId2 = (int) RefInvoke.getStaticFieldObject(drawableClass, "robert");
        imgV.setBackground(getResources().getDrawable(resId2));

        Class layoutClazz = cl.loadClass("jianqiang.com.plugin1.R$layout");
        int resId3 = (int) RefInvoke.getStaticFieldObject(layoutClazz, "main_activity");
        View view = (View) LayoutInflater.from(this).inflate(resId3, null);
        layout.removeAllViews();
        layout.addView(view);

    } catch (Exception e) {
        Log.e("DEMO", "msg:" + e.getMessage());
    }
}

总的来说，资源插件化就是通过反射AssetManager和addAssetPath来加载插件资源

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