http://www.jianshu.com/p/f751be55d1fb
- 需求很简单 ，就是加载指定文件夹下的.so。
- 原因：android在程序运行的状态下 ，无法在 data/data/packageName/lib 下写文件，但可读。
- 还有一个引申的问题：data/app-lib/packageName/ 下的.so 和 data/data/packageName/lib 的.so 是什么关系？
1 . 获取全局的classloader
PathClassLoader pathClassLoader = (PathClassLoader)context.getClassLoader();
DexClassLoader myDexClassLoader = new DexClassLoader(str, context.getDir("dex", 0).getAbsolutePath(), str, context.getClassLoader().getParent());2 . 获取pathList
Object pathList = getPathList(pathClassLoader);3 . 添加路径
File[] file = new File[]{ new File("/data/app-lib/pakageName-1"), new File("/data/app-lib/pakageName-2"), new File("/data/data/pakageName/files"), new File("/vendor/lib"), new File("/system/lib") } ;4 . 获取当前类的属性
Object nativeLibraryDirectories=pathList.getClass().getDeclaredField("nativeLibraryDirectories"); ((Field)nativeLibraryDirectories).setAccessible(true);5 . 设置新的路径
((Field)nativeLibraryDirectories).set(pathList, file);6 . 对classloader的操作，对应于BaseDexClassLoader:
public BaseDexClassLoader(String dexPath,File optimizedDirectory,String libraryPath,ClassLoader parent){ super(parent); this.pathList=new DexPathList(this,dexPath,libraryPath,optimizedDirectory); }7 . dex,library路径对应于DexPathList, 这部分和热补丁密切相关，有兴趣可以搜下hotfix ，很多开源项目。
privatefinalElement[]dexElements; //这部分就是dex分包的了，热补丁，热补丁，热补丁 privatefinalFile[]nativeLibraryDirectories;//这部分就是 libs 加载路径了，默认有 /vendor/lib system/lib data/app-lib/packageName最后给下代码：
public static void initNativeDirectory(Application application) { if (hasDexClassLoader()) { try { createNewNativeDir(application); } catch (Exception e) { e.printStackTrace(); } } } private static void createNewNativeDir(Context context) throws Exception{ PathClassLoader pathClassLoader = (PathClassLoader) context.getClassLoader(); Object pathList = getPathList(pathClassLoader); //获取当前类的属性 Object nativeLibraryDirectories = pathList.getClass().getDeclaredField("nativeLibraryDirectories"); ((Field) nativeLibraryDirectories).setAccessible(true); //获取 DEXPATHList中的属性值 File[] files1 = (File[])((Field) nativeLibraryDirectories).get(pathList); Object filesss = Array.newInstance(File.class, files1.length + 1); //添加自定义.so路径 Array.set(filesss, 0, new File(context.getFilesDir().getAbsolutePath())); //将系统自己的追加上 for(int i = 1;i<files1.length+1;i++){ Array.set(filesss,i,files1[i-1]); } // File[] filesss = new File[file.length+ files1.length]; // filesss[0] = file[0]; // for(int i = 1;i < files1.length+1;i++){ // filesss[i] = files1[i]; // } ((Field) nativeLibraryDirectories).set(pathList, filesss); } private static Object getPathList(Object obj) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException { return getField(obj, Class.forName("dalvik.system.BaseDexClassLoader"), "pathList"); } private static Object getField(Object obj, Class cls, String str) throws NoSuchFieldException, IllegalAccessException { Field declaredField = cls.getDeclaredField(str); declaredField.setAccessible(true); return declaredField.get(obj); } /** * 仅对4.0以上做支持 * @return */ private static boolean hasDexClassLoader() { try { Class.forName("dalvik.system.BaseDexClassLoader"); return true; } catch (ClassNotFoundException var1) { return false; } }