handleHotSwapPatch 方法的具体实现:
private int handleHotSwapPatch(int updateMode, ApplicationPatch patch)
{
if (Log.isLoggable("InstantRun", 2)) {
Log.v("InstantRun", "Received incremental code patch");
}
try
{
String dexFile = FileManager.writeTempDexFile(patch.getBytes());
if (dexFile == null)
{
Log.e("InstantRun", "No file to write the code to");
return updateMode;
}
if (Log.isLoggable("InstantRun", 2)) {
Log.v("InstantRun", "Reading live code from " + dexFile);
}
String nativeLibraryPath = FileManager.getNativeLibraryFolder().getPath();
DexClassLoader dexClassLoader = new DexClassLoader(dexFile, this.context.getCacheDir().getPath(), nativeLibraryPath, getClass().getClassLoader());
Class<?> aClass = Class.forName("com.android.tools.fd.runtime.AppPatchesLoaderImpl", true, dexClassLoader);
try
{
if (Log.isLoggable("InstantRun", 2)) {
Log.v("InstantRun", "Got the patcher class " + aClass);
}
PatchesLoader loader = (PatchesLoader)aClass.newInstance();
if (Log.isLoggable("InstantRun", 2)) {
Log.v("InstantRun", "Got the patcher instance " + loader);
}
String[] getPatchedClasses = (String[])aClass.getDeclaredMethod("getPatchedClasses", new Class[0]).invoke(loader, new Object[0]);
if (Log.isLoggable("InstantRun", 2))
{
Log.v("InstantRun", "Got the list of classes ");
for (String getPatchedClass : getPatchedClasses) {
Log.v("InstantRun", "class " + getPatchedClass);
}
}
if (!loader.load()) {
updateMode = 3;
}
}
catch (Exception e)
{
Log.e("InstantRun", "Couldn't apply code changes", e);
e.printStackTrace();
updateMode = 3;
}
}
catch (Throwable e)
{
Log.e("InstantRun", "Couldn't apply code changes", e);
updateMode = 3;
}
return updateMode;
}
首先将 patch 数据保存到文件, 根据 patch
保存路径创建一个DexClassLoader 对象, 这样就可以通过该 DexClassLoader 对象获取 patch 中的类信息并实例化相应对象, 首先实例化 patch 中的 AppPatchesLoaderImpl 对象, 前面笔记中可以看到 AppPatchesLoaderImpl 是继承 AbstractPatchesLoaderImpl, AppPatchesLoaderImpl 只是复写了 getPatchedClasses 方法, 在 Demo 项目中返回 "org.demo.example.MainActivity$1", 然后调用 AppPatchesLoaderImpl 的 load 方法, 具体实现是在父类 AbstractPatchesLoaderImpl 中:
public boolean load()
{
try
{
for (String className : getPatchedClasses())
{
ClassLoader cl = getClass().getClassLoader();
Class<?> aClass = cl.loadClass(className + "$override");
Object o = aClass.newInstance();
Class<?> originalClass = cl.loadClass(className);
Field changeField = originalClass.getDeclaredField("$change");
changeField.setAccessible(true);
Object previous = changeField.get(null);
if (previous != null)
{
Field isObsolete = previous.getClass().getDeclaredField("$obsolete");
if (isObsolete != null) {
isObsolete.set(null, Boolean.valueOf(true));
}
}
changeField.set(null, o);
if ((Log.logging != null) && (Log.logging.isLoggable(Level.FINE))) {
Log.logging.log(Level.FINE, String.format("patched %s", new Object[] { className }));
}
}
}
catch (Exception e)
{
if (Log.logging != null) {
Log.logging.log(Level.SEVERE, String.format("Exception while patching %s", new Object[] { "foo.bar" }), e);
}
return false;
}
return true;
}
首先创建具体补丁 MainActivity$override 对象, 并将该对象复制给 MainActivity 类的 $change 变量, 到此根据之前的分析, 在 MainActivity 对象中调用方法都会走到 MainActivity$override 对象的对应方法, 修改代码后不需要重新安装 APP 就能生效.
替换资源文件
上面说的都是源码补丁, 如果修改了图片或布局, 就通过创建 一个新的AssetManager 对象, 并调用其 addAssetPath 方法加载变更的资源数据, 并替换已经创建的 Activity 对象中的 resource.mAssets 变量为新的 AssetManager 对象, 然后重启 Activity 就可以生效了, 具体实现源码在 MonkeyPatcher 类中, 有兴趣的童鞋可以了解一下
