插件化

Classloader 分为三种： 1: pathClassloader: Android 用来加载系统文件 和 应用的主文件 2: DexClassloader: Android 用来加载 jar/apk/dex 文件 3: URLClassloader: 可以加载java的jar包,但是Dalvik 虚拟机不支持这种加载方式

public class ProxyActivity extends AppCompatActivity {

    private ProxyActivityInterface pluginObj;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //在这里拿到了真实跳转的activity 拿出来 再去启动真实的activity

        String className = getIntent().getStringExtra("ClassName");

        //通过反射在去启动一个真实的activity 拿到Class对象
        try {
            Class<?> plugClass = getClassLoader().loadClass(className);
            Constructor<?> pluginConstructor = plugClass.getConstructor(new Class[]{});
            //因为插件的activity实现了我们的标准
            pluginObj = (ProxyActivityInterface) pluginConstructor.newInstance(new Object[]{});
            pluginObj.attach(this);//注入上下文
            pluginObj.onCreate(new Bundle());//一定要调用onCreate 
        } catch (Exception e) {
            if (e.getClass().getSimpleName() .equals("ClassCastException")){
                //我这里是直接拿到异常判断的 ，也可的 拿到上面的plugClass对象判断有没有实现我们的接口
                finish();
                Toast.makeText(this,"非法页面",Toast.LENGTH_LONG).show();
                return;
            }
            e.printStackTrace();
        }
    }
]
    //为什么要重写这个呢 因为这个是插件内部startactivity调用的 将真正要开启的activity的类名穿过来
    //然后取出来，启动我们的占坑的activity 在我们真正要启动的赛进去
    @Override
    public void startActivity(Intent intent) {
        String className1=intent.getStringExtra("ClassName");
        Intent intent1 = new Intent(this, ProxyActivity.class);
        intent1.putExtra("ClassName", className1);
        super.startActivity(intent1);
    }

    //重写classLoader
    @Override
    public ClassLoader getClassLoader() {
        return HookManager.getInstance().getClassLoader();
    }

    //重写Resource
    @Override
    public Resources getResources() {
        return HookManager.getInstance().getResource();
    }

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

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

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

public class HookManager {
    private static final HookManager ourInstance = new HookManager();
    private Resources resources;
    private DexClassLoader loader;
    public PackageInfo packageInfo;

    public static HookManager getInstance() {
        return ourInstance;
    }

    private HookManager() {
    }


    //用来加载插件
    public void loadPlugin(Activity activity) {
        // 假如这里是从网络获取的插件 我们直接从sd卡获取 然后读取到我们的cache目录
        String pluginName = "plugin.apk";
        File filesDir = activity.getDir("plugin", activity.MODE_PRIVATE);
        String filePath = new File(filesDir, pluginName).getAbsolutePath();
        File file = new File(filePath);
        if (file.exists()) {
            file.delete();
        }
        FileInputStream is = null;
        FileOutputStream os = null;
        //读取的目录
        try {
            is = new FileInputStream(new File(Environment.getExternalStorageDirectory(), pluginName));
            //要输入的目录
            os = new FileOutputStream(filePath);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        try {
            int len = 0;
            byte[] buffer = new byte[1024];
            while ((len = is.read(buffer)) != -1) {
                os.write(buffer, 0, len);
            }
            File f = new File(filePath);
            if (f.exists()) {
                Toast.makeText(activity, "dex overwrite", Toast.LENGTH_SHORT).show();
            }
            loadPathToPlugin(activity);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            try {
                os.close();
                is.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }


    }

    private void loadPathToPlugin(Activity activity) {
        File filesDir = activity.getDir("plugin", activity.MODE_PRIVATE);
        String name = "plugin.apk";
        String path = new File(filesDir, name).getAbsolutePath();

        //然后我们开始加载我们的apk 使用DexClassLoader
        File dexOutDir = activity.getDir("dex", activity.MODE_PRIVATE);
        loader = new DexClassLoader(path, dexOutDir.getAbsolutePath(), null, activity.getClassLoader());

        //通过PackAgemanager 来获取插件的第一个activity是哪一个
        PackageManager packageManager = activity.getPackageManager();
        packageInfo = packageManager.getPackageArchiveInfo(path, PackageManager.GET_ACTIVITIES);


        //然后开始加载我们的资源 肯定要使用Resource 但是它是AssetManager创建出来的 就是AssertManager 有一个addAssertPath 这个方法 但是私有的 所有使用反射
        Class<?> assetManagerClass = AssetManager.class;
        try {
            AssetManager assertManagerObj = (AssetManager) assetManagerClass.newInstance();
            Method addAssetPathMethod = assetManagerClass.getMethod("addAssetPath", String.class);
            addAssetPathMethod.setAccessible(true);
            addAssetPathMethod.invoke(assertManagerObj, path);
            //在创建一个Resource
            resources = new Resources(assertManagerObj, activity.getResources().getDisplayMetrics(), activity.getResources().getConfiguration());
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
    //对外提供插件的classLoader
    public ClassLoader getClassLoader() {
        return loader;
    }

    //插件中的Resource
    public Resources getResource() {
        return resources;
    }
}