插件化系列之解决 so 加载异常的问题

背景

• 解决完资源加载报错的问题后，Unity 开发人员（简称 CP)又给我们反馈了另外一个问题

Process: xxx.xxx, PID: 21699
    java.lang.RuntimeException: Unable to start activity ComponentInfo{xxx.xxx.MainActivityFullScreen}: java.lang.IllegalArgumentException: Unable to find native library xgame using classloader: com.plugin.core.loader.ApkClassLoader[DexPathList[[zip file "/data/user/0/xxx.xxx.xxx/app_plugin/sq_plugin_xxxxxx.apk"],nativeLibraryDirectories=[/system/lib64]]]
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3177)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3314)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:113)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:71)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2043)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:224)
        at android.app.ActivityThread.main(ActivityThread.java:7096)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:604)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:928)
     Caused by: java.lang.IllegalArgumentException: Unable to find native library xgame using classloader: com.plugin.core.loader.ApkClassLoader[DexPathList[[zip file "/data/user/0/xxx.xxx.xxx/app_plugin/sq_plugin_xxxxxx.apk"],nativeLibraryDirectories=[/system/lib64]]]
        at android.app.NativeActivity.onCreate(NativeActivity.java:161)
        at org.evt.lib.EvtActivity.onCreate(EvtActivity.java:18)
        at android.app.Activity.performCreate(Activity.java:7271)
        at android.app.Activity.performCreate(Activity.java:7262)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3157)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3314) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:113) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:71) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2043) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:224) 
        at android.app.ActivityThread.main(ActivityThread.java:7096) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:604) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:928)

一、问题筛选过程

• 这个游戏采用的是 android.app.NativeActivity 类来加载 so 库，可以看到它是 getClassLoader （即获取到的是插件的 ApkClassLoader 对象）, 然后进行 findLibrary 的操作，但是我们 ApkClassLoader 没有重写这个方法，即表现为只会查找插件中的 so 库，如果没有找到就报错。

• 我这边又去下载了其他游戏的安装包，发现里面的 so 库是可以正常加载的，原因是它加载 so 库的时候是用了另外一种方式，System.loadLibrary（Ps：最常见加载 so 库的就是用这种方式），和前面的游戏采用的方式不同。

• 于是我写了一段测试代码，直接调用 System.loadLibrary 进行 debug，实践证明并没有问题，因为它的 ClassLoader 和宿主的 ClassLoader 对象是同一个，自然是可以找得到。

二、问题结论：这个游戏加载的 so 库所用到的 ClassLoader 是插件的 ApkClassLoader，而插件的 ApkClassLoader 并没有重写 findLibrary 方法的逻辑，所以就会导致插件的 ApkClassLoader 找不到宿主的 so 库。

三、修复方案：重写 ApkClassLoader.findLibrary 方法，优先去找插件的 so 库，找不到就去找宿主的 so 库。

public class ApkClassLoader extends DexClassLoader {

    private ClassLoader mGrandParent;
    private Method mFindLibraryMethod;

    public ApkClassLoader(String dexPath, String optimizedDirectory, String librarySearchPath, ClassLoader parent) {
        super(dexPath, optimizedDirectory, librarySearchPath, parent);
        mGrandParent = parent;
    }

    @Override
    protected Class<?> loadClass(String className, boolean resolve) throws ClassNotFoundException {
        ......
        Class<?> clazz = findLoadedClass(className);
        if (clazz == null) {
            ClassNotFoundException suppressed = null;
            try {
                clazz = findClass(className);
            } catch (ClassNotFoundException e) {
                suppressed = e;
            }

            if (clazz == null) {
                try {
                    clazz = mGrandParent.loadClass(className);
                } catch (ClassNotFoundException e) {
                    e.addSuppressed(suppressed);
                    throw e;
                }
            }
        }

        return clazz;
    }

    // 加入以下代码
    @Override
    public String findLibrary(String name) {
        String path = super.findLibrary(name);
        if (path != null) {
            return path;
        }

        if (mGrandParent instanceof BaseDexClassLoader) {
            return ((BaseDexClassLoader) mGrandParent).findLibrary(name);
        }

        try {
            if (mFindLibraryMethod == null) {
                mFindLibraryMethod = ClassLoader.class.getDeclaredMethod("findLibrary", String.class);
                mFindLibraryMethod.setAccessible(true);
            }
            // 如果插件获取不到，则交由父加载器进行获取
            return (String) mFindLibraryMethod.invoke(mGrandParent, name);
        } catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
            e.printStackTrace();
            return null;
        }
    }
}

• 加上之后问题被解决，非常 nice

完结，撒花 ✿✿ヽ(°▽°)ノ✿