Android热修复学习之旅HotFix完全解析.doc

Android热修复学习之旅——HotFix完全解析 Android dex分包原理介绍 QQ空间热修复方案基于Android dex分包基础之上，简单概述android dex分包的原理就是：就是把多个dex文件塞入到app的classloader之中，但是android dex拆包方案中的类是没有重复的，如果classes.dex和classes1.dex中有重复的类，当classes.dex和classes1.dex中都具有同一个类的时候，那么classloader会选择加载哪个类呢？这要从classloader的源码入手，加载类是通过classloader的loadClass方法实现的，所以我们看一下loadClass的源码： /** * Loads the class with the specified name. Invoking this method is * equivalent to calling {@code loadClass(className, false)}. * p * strongNote:/strong In the Android reference implementation, the * second parameter of {@link #loadClass(String, boolean)} is ignored * anyway. * /p * * @return the {@code Class} object. * @param className * the name of the class to look for. * @throws ClassNotFoundException * if the class can not be found. */ public Class? loadClass(String className) throws ClassNotFoundException { return loadClass(className, false); } protected Class? loadClass(String className, boolean resolve) throws ClassNotFoundException { Class? clazz = findLoadedClass(className); if (clazz == null) { ClassNotFoundException suppressed = null; try { clazz = parent.loadClass(className, false); } catch (ClassNotFoundException e) { suppressed = e; } if (clazz == null) { try { clazz = findClass(className); } catch (ClassNotFoundException e) { e.addSuppressed(suppressed); throw e; } } } return clazz; } 简单来说就是ClassLoader用loadClass方法调用了findClass方法，点进去发现findClass是抽象方法，而这个方法的实现是在它的子类BaseDexClassLoader中，而BaseDexClassLoader重载了这个方法，得到BaseDexClassLoader，进入到BaseDexClassLoader类的findClass方法中 #BaseDexClassLoader @Override protected Class? findClass(String name) throws ClassNotFoundException { Class clazz = pathList.findClass(name); if (clazz == null) { throw new ClassNotFoundException(name); } return clazz; } #DexPathList publi