之前写过一片：与Android热更新方案Amigo的初次接触，主要是记叙了Amigo的接入和使用。
最近读了一下Amigo的源码，而且看了看网上其他讲Amigo源码的文章，它们所针对的代码都和最新的Amigo代码有所出路，所以针对最新的代码，浅浅的分析一下。
Amigo的最近更新已经是8个月之前了。我最近更新了Android Studio3.0，gradle版本3.1.1。但是Amigo使用的gradle版本2.3.1。如果项目还是要使用gradle3.x版本的话，会报错。所以我更新了Amigo插件使用的gradle版本（因为的gradle3.0比起2.0有一些修改，所以也修改了部分Amigo插件代码），如果有使用Amigo的老铁同时用的是gradle3.x版本的话，可以找我要代码。
Amigo主要有两个部分，在Github上可以看到，amigo-lib和buildSrc。
amigo-lib对应：
dependencies {
...
compile 'me.ele:amigo-lib:0.6.7'
}
复制代码buildSrc对应插件：
dependencies {
......
classpath 'me.ele:amigo:0.6.8'
}
复制代码apply plugin: 'me.ele.amigo'
复制代码先说插件，这个插件的作用就是修改AndroidManifest.xml，将项目原本的Application替换称Amigo.java，并且将原来的 application 的 name 保存在了一个名为acd的类中。AndroidManifest.xml 中将原来的 application 做为一个 Activity。
再说amigo-lib，这个是热更新的重点。我们从更新的入口开始说起：
button.setOnClickListener {
var file = File(Environment.getExternalStorageDirectory().path + File.separator + "test.apk")
if(file.exists()){
Amigo.workLater(this, file) {
if(it){
toast("更新成功！")
val intent = packageManager.getLaunchIntentForPackage(packageName)
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
startActivity(intent)
android.os.Process.killProcess(android.os.Process.myPid())
}
}
}
}
复制代码本地已经有了一个新的APK，直接调用Amigo.workLater()开始更新。
private static void workLater(Context context, File patchFile, boolean checkSignature,
WorkLaterCallback callback) {
String patchChecksum = PatchChecker.checkPatchAndCopy(context, patchFile, checkSignature);
if (checkWithWorkingPatch(context, patchChecksum)) return;
if (patchChecksum == null) {
Log.e(TAG, "#workLater: empty checksum");
return;
}
if (callback != null) {
AmigoService.startReleaseDex(context, patchChecksum, callback);
} else {
AmigoService.startReleaseDex(context, patchChecksum);
}
}
复制代码第一步
第二步
释放Dex。在 AmigoService.startReleaseDex()中主要是启动了AmigoService。在AmigoService.java中会调用：
private synchronized void handleReleaseDex(Intent intent) {
String checksum = intent.getStringExtra(EXTRA_APK_CHECKSUM);
if (apkReleaser == null) {
apkReleaser = new ApkReleaser(getApplicationContext());
}
apkReleaser.release(checksum, msgHandler);
}
复制代码具体的释放Dex在ApkReleaser的release()中：
public void release(final String checksum, final Handler msgHandler) {
if (isReleasing) {
Log.w(TAG, "release : been busy now, skip release " + checksum);
return;
}
Log.d(TAG, "release: start release " + checksum);
try {
this.amigoDirs = AmigoDirs.getInstance(context);
this.patchApks = PatchApks.getInstance(context);
} catch (Exception e) {
Log.e(TAG,
"release: unable to create amigo dir and patch apk dir, abort release dex files",
e);
handleDexOptFailure(checksum, msgHandler);
return;
}
isReleasing = true;
service.submit(new Runnable() {
@Override
public void run() {
if (!new DexExtractor(context, checksum).extractDexFiles()) {
Log.e(TAG, "releasing dex failed");
handleDexOptFailure(checksum, msgHandler);
isReleasing = false;
FileUtils.removeFile(amigoDirs.dexDir(checksum), false);
return;
}
// todo
// just create a link point to /data/app/{package_name}/libs
// if none of the native libs are changed
int errorCode;
if ((errorCode =
NativeLibraryHelperCompat.copyNativeBinaries(patchApks.patchFile(checksum),
amigoDirs.libDir(checksum))) < 0) {
Log.e(TAG, "coping native binaries failed, errorCode = " + errorCode);
handleDexOptFailure(checksum, msgHandler);
FileUtils.removeFile(amigoDirs.dexDir(checksum), false);
FileUtils.removeFile(amigoDirs.libDir(checksum), false);
isReleasing = false;
return;
}
final boolean dexOptimized = Build.VERSION.SDK_INT >= 21 ? dexOptimizationOnArt(checksum)
: dexOptimizationOnDalvik(checksum);
if (dexOptimized) {
Log.e(TAG, "optimize dex succeed");
handleDexOptSuccess(checksum, msgHandler);
isReleasing = false;
return;
}
Log.e(TAG, "optimize dex failed");
FileUtils.removeFile(amigoDirs.dexDir(checksum), false);
FileUtils.removeFile(amigoDirs.libDir(checksum), false);
FileUtils.removeFile(amigoDirs.dexOptDir(checksum), false);
handleDexOptFailure(checksum, msgHandler);
isReleasing = false;
}
});
}
复制代码这里又分了3小步：1.释放dex；2.释放lib中的so；3.优化dex。
在DexExtractor(context, checksum).extractDexFiles()中是具体的释放dex过程：
public boolean extractDexFiles() {
if (Build.VERSION.SDK_INT >= 21) {
return true; // art supports multi-dex natively
}
return performExtractions(PatchApks.getInstance(context).patchFile(checksum),
AmigoDirs.getInstance(context).dexDir(checksum));
}
//把patchApk（新包）中的dex解压到dexDir:/data/data/{package_name}/files/amigo/{checksum}/dexes
private boolean performExtractions(File patchApk, File dexDir) {
ZipFile apk = null;
try {
apk = new ZipFile(patchApk);
int dexNum = 0;
ZipEntry dexFile = apk.getEntry("classes.dex");
for (; dexFile != null; dexFile = apk.getEntry("classes" + dexNum + ".dex")) {
String fileName = dexFile.getName().replace("dex", "zip");
File extractedFile = new File(dexDir, fileName);
extract(apk, dexFile, extractedFile);
verifyZipFile(extractedFile);
if (dexNum == 0) ++dexNum;
++dexNum;
}
return dexNum > 0;
} catch (IOException ioe) {
ioe.printStackTrace();
return false;
} finally {
try {
apk.close();
} catch (IOException var16) {
Log.w("DexExtractor", "Failed to close resource", var16);
}
}
}
复制代码这里有个extract()方法，进去看一下：
private void extract(ZipFile patchApk, ZipEntry dexFile, File extractTo) throws IOException {
boolean reused = reusePreExistedODex(patchApk, dexFile);
Log.d(TAG, "extracted: "
+ dexFile.getName() + " success ? "
+ reused
+ ", by reusing pre-existed secondary dex");
//可以如果复用旧dex
if (reused) {
return;
}
//不能复用，就执行拷贝
InputStream in = null;
File tmp = null;
ZipOutputStream out = null;
try {
in = patchApk.getInputStream(dexFile);
tmp = File.createTempFile(extractTo.getName(), ".tmp", extractTo.getParentFile());
try {
out = new ZipOutputStream(new BufferedOutputStream(new FileOutputStream(tmp)));
ZipEntry classesDex = new ZipEntry("classes.dex");
classesDex.setTime(dexFile.getTime());
out.putNextEntry(classesDex);
if (buffer == null) {
buffer = new byte[16384];
}
for (int length = in.read(buffer); length != -1; length = in.read(buffer)) {
out.write(buffer, 0, length);
}
} finally {
if (out != null) {
out.closeEntry();
out.close();
}
}
if (!tmp.renameTo(extractTo)) {
throw new IOException("Failed to rename \""
+ tmp.getAbsolutePath()
+ "\" to \""
+ extractTo.getAbsolutePath()
+ "\"");
}
} finally {
closeSilently(in);
if (tmp != null) tmp.delete();
}
}
复制代码在这里我们看到了具体的拷贝过程，先是拷贝到了tmp文件，然后改的名。但是在拷贝之前有一个操作reusePreExistedODex()，在这个方法中判断了当前运行的App的dex与更新包的dex是否一致，如果一致做了一个link，把当前APP的dex文件link到了我们需要拷贝的目录dexDir:/data/data/{package_name}/files/amigo/{checksum}/dexes，如果不一致再做拷贝操作。
到此dex释放完毕，下一步释放so文件。NativeLibraryHelperCompat.copyNativeBinaries()这里就是判断，根据不同的系统版本（比如是64位还32位系统），调用了不同拷贝方法。具体的这篇文章有详细说。
然后就是优化dex了。final boolean dexOptimized = Build.VERSION.SDK_INT >= 21 ? dexOptimizationOnArt(checksum) : dexOptimizationOnDalvik(checksum)这里针对系统版本调用了不同的方法。
第三步
保存标志，然后重启：
private void handleDexOptSuccess(String checksum, Handler msgHandler) {
saveDexAndSoChecksum(checksum);
PatchInfoUtil.updateDexFileOptStatus(context, checksum, true);
PatchInfoUtil.setWorkingChecksum(context, checksum);
if (msgHandler != null) {
msgHandler.sendEmptyMessage(AmigoService.MSG_ID_DEX_OPT_SUCCESS);
}
}
复制代码到此释放阶段结束。
下面是重启后，读取资源。代码在Amigo.java中，先看看attachApplication(). 在attachApplication()中先做了一系列判断，主要是判断是否需要读取释放后的文件(比如是否有更新文件，是否需要更新)，我们直接进入读取文件的地方attachPatchApk(workingChecksum);
private void attachPatchApk(String checksum) throws LoadPatchApkException {
try {
if (isPatchApkFirstRun(checksum)
|| !AmigoDirs.getInstance(this).isOptedDexExists(checksum)) {
PatchInfoUtil.updateDexFileOptStatus(this, checksum, false);
releasePatchApk(checksum);
} else {
PatchChecker.checkDexAndSo(this, checksum);
}
setAPKClassLoader(AmigoClassLoader.newInstance(this, checksum));
setApkResource(checksum);
revertBitFlag |= getClassLoader() instanceof AmigoClassLoader ? 1 : 0;
attachPatchedApplication(checksum);
PatchCleaner.clearOldPatches(this, checksum);
shouldHookAmAndPm = true;
Log.i(TAG, "#attachPatchApk: success");
} catch (Exception e) {
throw new LoadPatchApkException(e);
}
}
复制代码这里有两个地方setAPKClassLoader(AmigoClassLoader.newInstance(this, checksum)); setApkResource(checksum); 分别是设置 ClassLoader 和加载资源。
先说ClassLoader，这里Hook了一个ClassLoader，使用了自己的AmigoClassLoader。
public static AmigoClassLoader newInstance(Context context, String checksum) {
return new AmigoClassLoader(PatchApks.getInstance(context).patchPath(checksum),
getDexPath(context, checksum),
AmigoDirs.getInstance(context).dexOptDir(checksum).getAbsolutePath(),
getLibraryPath(context, checksum),
AmigoClassLoader.class.getClassLoader().getParent());
}
复制代码通过上面的代码可以看出AmigoClassLoader使用了我们之前释放的资源的目录，也就是dex，libs等。
private void setApkResource(String checksum) throws Exception {
PatchResourceLoader.loadPatchResources(this, checksum);
Log.i(TAG, "hook Resources success");
}
static void loadPatchResources(Context context, String checksum) throws Exception {
AssetManager newAssetManager = AssetManager.class.newInstance();
invokeMethod(newAssetManager, "addAssetPath", PatchApks.getInstance(context).patchPath(checksum));
invokeMethod(newAssetManager, "ensureStringBlocks");
replaceAssetManager(context, newAssetManager);
}
复制代码replaceAssetManager(context, newAssetManager)中Hook了一些其他AssetManager用到的地方。
然后把shouldHookAmAndPm设成了true。 到这里attachApplication()执行完成。然后走onCreate()
public void onCreate() {
super.onCreate();
try {
setAPKApplication(realApplication);
} catch (Exception e) {
// should not happen, if it does happen, we just let it die
throw new RuntimeException(e);
}
if(shouldHookAmAndPm) {
try {
installAndHook();
} catch (Exception e) {
try {
clear(this);
attachOriginalApplication();
} catch (Exception e1) {
throw new RuntimeException(e1);
}
}
}
realApplication.onCreate();
}
复制代码这里有个：
private void installAndHook() throws Exception {
boolean gotNewActivity = ActivityFinder.newActivityExistsInPatch(this);
if (gotNewActivity) {
setApkInstrumentation();
revertBitFlag |= 1 << 1;
setApkHandlerCallback();
revertBitFlag |= 1 << 2;
} else {
Log.d(TAG, "installAndHook: there is no any new activity, skip hooking " +
"instrumentation & mH's callback");
}
installHookFactory();
dynamicRegisterNewReceivers();
installPatchContentProviders();
}
复制代码首先判断是否有新的Activity，如果有，就需要HookmInstrumentation。 installHookFactory()中替换了ClassLoader，动态注册了Receiver，安装ContentProvider。
最后调用attachOriginalApplication()，把之前的Application替换回来，然后走正常的流程。
【2018/10/11】
最近，适配了Android O。有需要的，拿去-> github。