续 Android APK免安装启动

续 Android APK免安装启动

此文章描述了通过不替换系统的ClassLoader方式，只是将我们所动态释放的dex文件放入系统的ClassLoader中这种方式实现免安装启动插件APK

有疑问的可以先参看
http://blog.youkuaiyun.com/happyst1990/article/details/51146301

 51     @Override
 52     protected Class<?> findClass(String name) throws ClassNotFoundException {
 53         List<Throwable> suppressedExceptions = new ArrayList<Throwable>();
 54         Class c = pathList.findClass(name, suppressedExceptions);
 55         if (c == null) {
 56             ClassNotFoundException cnfe = new ClassNotFoundException("Didn't find class \"" + name + "\" on path: " + pathList);
 57             for (Throwable t : suppressedExceptions) {
 58                 cnfe.addSuppressed(t);
 59             }
 60             throw cnfe;
 61         }
 62         return c;
 63     }

昨天在翻看的时候，无意中留意了一下BaseDexClassLoader的查找类的过程，其中有一个变量

private final DexPathList pathList;

进入看了一下，

304     /**
305      * Finds the named class in one of the dex files pointed at by
306      * this instance. This will find the one in the earliest listed
307      * path element. If the class is found but has not yet been
308      * defined, then this method will define it in the defining
309      * context that this instance was constructed with.
310      *
311      * @param name of class to find
312      * @param suppressed exceptions encountered whilst finding the class
313      * @return the named class or {@code null} if the class is not
314      * found in any of the dex files
315      */
316     public Class findClass(String name, List<Throwable> suppressed) {
317         for (Element element : dexElements) {
318             DexFile dex = element.dexFile;
319 
320             if (dex != null) {
321                 Class clazz = dex.loadClassBinaryName(name, definingContext, suppressed);
322                 if (clazz != null) {
323                     return clazz;
324                 }
325             }
326         }
327         if (dexElementsSuppressedExceptions != null) {
328             suppressed.addAll(Arrays.asList(dexElementsSuppressedExceptions));
329         }
330         return null;
331     }

可以发现寻找类的过程是遍历dexElements对象去寻找的。

说道此处可能大家已经明白我想说的是什么，没错，就是让我们手动释放出来的dex加入到此处。

如何获取到dexElements变量，并将其合并，然后设置到PathClassLoader中的过程就不写了，具体如何做请参考上一篇中的通过反射获取变量。