Android使用hook来做热修复的原理，都需要用到类的加载器来dex，将出bug的dex替换掉，来达到热修复的目的，至于热修复的原理，在《你值得知道的Android 热修复，以及热修复原理》这篇文章中已经做过详细的介绍，那么tinker的dex补丁加载过程是否也是使用同样的原理呢?本文就是要为读者解剖tinker的dex补丁加载过程。
如果读者没有将tinker接入过项目的，可以阅读《Android tinker热修复——实战接入项目》这篇文章，该文章带领读者将tinker接入到自己的项目，实现热修复，并且本文也是从《Android tinker热修复——实战接入项目》这篇文章的基础上做一个深入的探究，因此建议读者阅读下我之前写过的热修复系列的文章：
《Android tinker热修复——从运行demo开始》
同时希望读者关注我的专题Android热修复和插件化，我将会为读者更新一些列有关热修复和插件化的技术文章，也希望大家来投稿，一起交流这系列的技术。
TinkerApplication
在使用tinker的时候，首先需要在AndroidManifest.xml的application标签指定自定义的application，而这个application需要继承TinkerApplication。那么首先就要看下TinkerApplication的attachBaseContext方法，因为application的方法执行顺序如下：
所以首先会调用TinkerApplication的attachBaseContext。
setDefaultUncaughtExceptionHandler方法是用来收集crash的，我们这里不分析crash，主要分析dex补丁加载过程，所以我们继续往下看，执行的是该类的内部方法onBaseContextAttached。
首先调用loadTinker：
这里的loaderClassName也就是从MyApplication的构造方法super过来的com.tencent.tinker.loader.TinkerLoader
因此loadTinker方法中最终通过反射调用TinkerLoader类的tryLoad方法。而在onBaseContextAttached方法中调用的ensureDelegate方法，其实就是初始化MyTestApplicationLike类，然后调用其onBaseContextAttached方法来进行tinker的install过程，初始化tinker的一些配置。
关于该过程，可以参考上一篇文章《tinker热修复——install过程》，那么热修复过程显然是在TinkerLoader的tryLoad中进行的。
tryLoad方法的注释说明，只能在主线程中处理补丁版本的更改，在tryLoad方法中直接调用tryLoadPatchFilesInternal方法完成补丁的热修复。
private void tryLoadPatchFilesInternal(TinkerApplication app, Intent resultIntent) {
final int tinkerFlag = app.getTinkerFlags();
//判断是否开启热修复
if (!ShareTinkerInternals.isTinkerEnabled(tinkerFlag)) {
Log.w(TAG, "tryLoadPatchFiles: tinker is disable, just return");
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_DISABLE);
return;
}
//是否在patch进程
if (ShareTinkerInternals.isInPatchProcess(app)) {
Log.w(TAG, "tryLoadPatchFiles: we don't load patch with :patch process itself, just return");
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_DISABLE);
return;
}
//tinker，补丁的文件目录是否为null
File patchDirectoryFile = SharePatchFileUtil.getPatchDirectory(app);
if (patchDirectoryFile == null) {
Log.w(TAG, "tryLoadPatchFiles:getPatchDirectory == null");
//treat as not exist
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_DIRECTORY_NOT_EXIST);
return;
}
String patchDirectoryPath = patchDirectoryFile.getAbsolutePath();
//check patch directory whether exist，补丁的路径是否存在
if (!patchDirectoryFile.exists()) {
Log.w(TAG, "tryLoadPatchFiles:patch dir not exist:" + patchDirectoryPath);
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_DIRECTORY_NOT_EXIST);
return;
}
//tinker/patch.info
File patchInfoFile = SharePatchFileUtil.getPatchInfoFile(patchDirectoryPath);
//check patch info file whether exist 检查补丁信息的文件是否存在
if (!patchInfoFile.exists()) {
Log.w(TAG, "tryLoadPatchFiles:patch info not exist:" + patchInfoFile.getAbsolutePath());
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_INFO_NOT_EXIST);
return;
}
//old = 641e634c5b8f1649c75caf73794acbdf
//new = 2c150d8560334966952678930ba67fa8
File patchInfoLockFile = SharePatchFileUtil.getPatchInfoLockFile(patchDirectoryPath);
//补丁信息
patchInfo = SharePatchInfo.readAndCheckPropertyWithLock(patchInfoFile, patchInfoLockFile);
if (patchInfo == null) {
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_INFO_CORRUPTED);
return;
}
String oldVersion = patchInfo.oldVersion;//旧版本
String newVersion = patchInfo.newVersion;//新版本
String oatDex = patchInfo.oatDir;
if (oldVersion == null || newVersion == null || oatDex == null) {
//it is nice to clean patch
Log.w(TAG, "tryLoadPatchFiles:onPatchInfoCorrupted");
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_INFO_CORRUPTED);
return;
}
//将新旧版本的put到intent中去
resultIntent.putExtra(ShareIntentUtil.INTENT_PATCH_OLD_VERSION, oldVersion);
resultIntent.putExtra(ShareIntentUtil.INTENT_PATCH_NEW_VERSION, newVersion);
boolean mainProcess = ShareTinkerInternals.isInMainProcess(app);
boolean versionChanged = !(oldVersion.equals(newVersion));
boolean oatModeChanged = oatDex.equals(ShareConstants.CHANING_DEX_OPTIMIZE_PATH) && mainProcess;
oatDex = ShareTinkerInternals.getCurrentOatMode(app, oatDex);
resultIntent.putExtra(ShareIntentUtil.INTENT_PATCH_OAT_DIR, oatDex);
String version = oldVersion;
if (versionChanged && mainProcess) {
version = newVersion;
}
if (ShareTinkerInternals.isNullOrNil(version)) {
Log.w(TAG, "tryLoadPatchFiles:version is blank, wait main process to restart");
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_INFO_BLANK);
return;
}
//如果获取不到补丁，那么就需要删掉补丁的信息
//patch-641e634c
String patchName = SharePatchFileUtil.getPatchVersionDirectory(version);
if (patchName == null) {
Log.w(TAG, "tryLoadPatchFiles:patchName is null");
//we may delete patch info file
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_VERSION_DIRECTORY_NOT_EXIST);
return;
}
//tinker/patch.info/patch-641e634c
String patchVersionDirectory = patchDirectoryPath + "/" + patchName;
File patchVersionDirectoryFile = new File(patchVersionDirectory);
//检查补丁是否存在
if (!patchVersionDirectoryFile.exists()) {
Log.w(TAG, "tryLoadPatchFiles:onPatchVersionDirectoryNotFound");
//we may delete patch info file
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_VERSION_DIRECTORY_NOT_EXIST);
return;
}
//tinker/patch.info/patch-641e634c/patch-641e634c.apk
File patchVersionFile = new File(patchVersionDirectoryFile.getAbsolutePath(), SharePatchFileUtil.getPatchVersionFile(version));
//检查补丁文件是否存在
if (!SharePatchFileUtil.isLegalFile(patchVersionFile)) {
Log.w(TAG, "tryLoadPatchFiles:onPatchVersionFileNotFound");
//we may delete patch info file
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_VERSION_FILE_NOT_EXIST);
return;
}
ShareSecurityCheck securityCheck = new ShareSecurityCheck(app);
int returnCode = ShareTinkerInternals.checkTinkerPackage(app, tinkerFlag, patchVersionFile, securityCheck);
if (returnCode != ShareConstants.ERROR_PACKAGE_CHECK_OK) {
Log.w(TAG, "tryLoadPatchFiles:checkTinkerPackage");
resultIntent.putExtra(ShareIntentUtil.INTENT_PATCH_PACKAGE_PATCH_CHECK, returnCode);
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_PACKAGE_CHECK_FAIL);
return;
}
resultIntent.putExtra(ShareIntentUtil.INTENT_PATCH_PACKAGE_CONFIG, securityCheck.getPackagePropertiesIfPresent());
final boolean isEnabledForDex = ShareTinkerInternals.isTinkerEnabledForDex(tinkerFlag);
if (isEnabledForDex) {
//tinker/patch.info/patch-641e634c/dex
boolean dexCheck = TinkerDexLoader.checkComplete(patchVersionDirectory, securityCheck, oatDex, resultIntent);
if (!dexCheck) {
//file not found, do not load patch
Log.w(TAG, "tryLoadPatchFiles:dex check fail");
return;
}
}
//检查lib库
final boolean isEnabledForNativeLib = ShareTinkerInternals.isTinkerEnabledForNativeLib(tinkerFlag);
if (isEnabledForNativeLib) {
//tinker/patch.info/patch-641e634c/lib
boolean libCheck = TinkerSoLoader.checkComplete(patchVersionDirectory, securityCheck, resultIntent);
if (!libCheck) {
//file not found, do not load patch
Log.w(TAG, "tryLoadPatchFiles:native lib check fail");
return;
}
}
//检查资源
//check resource
final boolean isEnabledForResource = ShareTinkerInternals.isTinkerEnabledForResource(tinkerFlag);
Log.w(TAG, "tryLoadPatchFiles:isEnabledForResource:" + isEnabledForResource);
if (isEnabledForResource) {
boolean resourceCheck = TinkerResourceLoader.checkComplete(app, patchVersionDirectory, securityCheck, resultIntent);
if (!resourceCheck) {
//file not found, do not load patch
Log.w(TAG, "tryLoadPatchFiles:resource check fail");
return;
}
}
//only work for art platform oat，because of interpret, refuse 4.4 art oat
//android o use quicken default, we don't need to use interpret mode
boolean isSystemOTA = ShareTinkerInternals.isVmArt()
&& ShareTinkerInternals.isSystemOTA(patchInfo.fingerPrint)
&& Build.VERSION.SDK_INT >= 21 && !ShareTinkerInternals.isAfterAndroidO();
resultIntent.putExtra(ShareIntentUtil.INTENT_PATCH_SYSTEM_OTA, isSystemOTA);
//we should first try rewrite patch info file, if there is a error, we can't load jar
if ((mainProcess && versionChanged)
|| oatModeChanged) {
patchInfo.oldVersion = version;
patchInfo.oatDir = oatDex;
//update old version to new
if (!SharePatchInfo.rewritePatchInfoFileWithLock(patchInfoFile, patchInfo, patchInfoLockFile)) {
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_REWRITE_PATCH_INFO_FAIL);
Log.w(TAG, "tryLoadPatchFiles:onReWritePatchInfoCorrupted");
return;
}
if (oatModeChanged) {
// delete interpret odex
// for android o, directory change. Fortunately, we don't need to support android o interpret mode any more
Log.i(TAG, "tryLoadPatchFiles:oatModeChanged, try to delete interpret optimize files");
SharePatchFileUtil.deleteDir(patchVersionDirectory + "/" + ShareConstants.INTERPRET_DEX_OPTIMIZE_PATH);
}
}
if (!checkSafeModeCount(app)) {
resultIntent.putExtra(ShareIntentUtil.INTENT_PATCH_EXCEPTION, new TinkerRuntimeException("checkSafeModeCount fail"));
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_UNCAUGHT_EXCEPTION);
Log.w(TAG, "tryLoadPatchFiles:checkSafeModeCount fail");
return;
}
//now we can load patch jar
if (isEnabledForDex) {
boolean loadTinkerJars = TinkerDexLoader.loadTinkerJars(app, patchVersionDirectory, oatDex, resultIntent, isSystemOTA);
if (isSystemOTA) {
// update fingerprint after load success
patchInfo.fingerPrint = Build.FINGERPRINT;
patchInfo.oatDir = loadTinkerJars ? ShareConstants.INTERPRET_DEX_OPTIMIZE_PATH : ShareConstants.DEFAULT_DEX_OPTIMIZE_PATH;
// reset to false
oatModeChanged = false;
if (!SharePatchInfo.rewritePatchInfoFileWithLock(patchInfoFile, patchInfo, patchInfoLockFile)) {
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_PATCH_REWRITE_PATCH_INFO_FAIL);
Log.w(TAG, "tryLoadPatchFiles:onReWritePatchInfoCorrupted");
return;
}
// update oat dir
resultIntent.putExtra(ShareIntentUtil.INTENT_PATCH_OAT_DIR, patchInfo.oatDir);
}
if (!loadTinkerJars) {
Log.w(TAG, "tryLoadPatchFiles:onPatchLoadDexesFail");
return;
}
}
//now we can load patch resource
if (isEnabledForResource) {
boolean loadTinkerResources = TinkerResourceLoader.loadTinkerResources(app, patchVersionDirectory, resultIntent);
if (!loadTinkerResources) {
Log.w(TAG, "tryLoadPatchFiles:onPatchLoadResourcesFail");
return;
}
}
// Init component hotplug support.
if (isEnabledForDex && isEnabledForResource) {
ComponentHotplug.install(app, securityCheck);
}
// kill all other process if oat mode change
if (oatModeChanged) {
ShareTinkerInternals.killAllOtherProcess(app);
Log.i(TAG, "tryLoadPatchFiles:oatModeChanged, try to kill all other process");
}
//all is ok!
ShareIntentUtil.setIntentReturnCode(resultIntent, ShareConstants.ERROR_LOAD_OK);
Log.i(TAG, "tryLoadPatchFiles: load end, ok!");
return;
}
复制代码tryLoadPatchFilesInternal方法，代码量很大，但是逻辑还是非常的清晰的，首先要经过一层层的检查，包括检查是否开启热修复、是否在patch进程和补丁的文件目录是否为null等等，具体可以看上面代码的注释。经过这么多的判断之后，在后面我们终于找到加载补丁的jar方法了，那就是TinkerDexLoader的loadTinkerJars方法。而在《你值得知道的Android 热修复，以及热修复原理》中介绍过类加载器可以加载dex、jar、zip和apk文件。
而在调用loadTinkerJars方法之前调用了TinkerDexLoader的checkComplete方法。
/**
* all the dex files in meta file exist?
* fast check, only check whether exist
*
* @return boolean
*/
public static boolean checkComplete(String directory, ShareSecurityCheck securityCheck, String oatDir, Intent intentResult) {
//DEX_MEAT_FILE:assets/dex_meta.txt
String meta = securityCheck.getMetaContentMap().get(DEX_MEAT_FILE);
//not found dex
if (meta == null) {
return true;
}
//清空loadDexList
loadDexList.clear();
//清空classNDexInfo
classNDexInfo.clear();
ArrayList<ShareDexDiffPatchInfo> allDexInfo = new ArrayList<>();
//读取dex_meta.txt文件信息
ShareDexDiffPatchInfo.parseDexDiffPatchInfo(meta, allDexInfo);
if (allDexInfo.isEmpty()) {
return true;
}
HashMap<String, String> dexes = new HashMap<>();
ShareDexDiffPatchInfo testInfo = null;
for (ShareDexDiffPatchInfo info : allDexInfo) {
//for dalvik, ignore art support dex
if (isJustArtSupportDex(info)) {
continue;
}
if (!ShareDexDiffPatchInfo.checkDexDiffPatchInfo(info)) {
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_PACKAGE_PATCH_CHECK, ShareConstants.ERROR_PACKAGE_CHECK_DEX_META_CORRUPTED);
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_PACKAGE_CHECK_FAIL);
return false;
}
if (isVmArt && info.rawName.startsWith(ShareConstants.TEST_DEX_NAME)) {
testInfo = info;
} else if (isVmArt && ShareConstants.CLASS_N_PATTERN.matcher(info.realName).matches()) {
classNDexInfo.add(info);
} else {
dexes.put(info.realName, getInfoMd5(info));
loadDexList.add(info);
}
}
if (isVmArt
&& (testInfo != null || !classNDexInfo.isEmpty())) {
if (testInfo != null) {
classNDexInfo.add(ShareTinkerInternals.changeTestDexToClassN(testInfo, classNDexInfo.size() + 1));
}
dexes.put(ShareConstants.CLASS_N_APK_NAME, "");
}
//tinker/patch.info/patch-641e634c/dex
String dexDirectory = directory + "/" + DEX_PATH + "/";
File dexDir = new File(dexDirectory);
if (!dexDir.exists() || !dexDir.isDirectory()) {
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_DIRECTORY_NOT_EXIST);
return false;
}
String optimizeDexDirectory = directory + "/" + oatDir + "/";
File optimizeDexDirectoryFile = new File(optimizeDexDirectory);
//fast check whether there is any dex files missing
for (String name : dexes.keySet()) {
File dexFile = new File(dexDirectory + name);
if (!SharePatchFileUtil.isLegalFile(dexFile)) {
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_MISSING_DEX_PATH, dexFile.getAbsolutePath());
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_FILE_NOT_EXIST);
return false;
}
//check dex opt whether complete also
File dexOptFile = new File(SharePatchFileUtil.optimizedPathFor(dexFile, optimizeDexDirectoryFile));
if (!SharePatchFileUtil.isLegalFile(dexOptFile)) {
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_MISSING_DEX_PATH, dexOptFile.getAbsolutePath());
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_OPT_FILE_NOT_EXIST);
return false;
}
// // find test dex
// if (dexOptFile.getName().startsWith(ShareConstants.TEST_DEX_NAME)) {
// testOptDexFile = dexOptFile;
// }
}
//if is ok, add to result intent
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_DEXES_PATH, dexes);
return true;
}
复制代码就像注释说明的那样，checkComplete只是检查在assets/dex_meta.txt文件中dex文件，而且快速的检查，只是检查是否存在，并将解析得到的信息，存储到一个ShareDexDiffPatchInfo的对象，然后将对象存放到loadDexList或者classNDexInfo中。
接下来我们看loadTinkerJars方法的实现
/**
* Load tinker JARs and add them to
* the Application ClassLoader.
*
* @param application The application.
*/
@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public static boolean loadTinkerJars(final TinkerApplication application, String directory, String oatDir, Intent intentResult, boolean isSystemOTA) {
//通过TinkerDexLoader的checkComplete方法，得到loadDexList和classNDexInfo
if (loadDexList.isEmpty() && classNDexInfo.isEmpty()) {
Log.w(TAG, "there is no dex to load");
return true;
}
//the Application ClassLoader
PathClassLoader classLoader = (PathClassLoader) TinkerDexLoader.class.getClassLoader();
if (classLoader != null) {
Log.i(TAG, "classloader: " + classLoader.toString());
} else {
Log.e(TAG, "classloader is null");
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_CLASSLOADER_NULL);
return false;
}
String dexPath = directory + "/" + DEX_PATH + "/";
//补丁文件队列
ArrayList<File> legalFiles = new ArrayList<>();
for (ShareDexDiffPatchInfo info : loadDexList) {
//for dalvik, ignore art support dex
if (isJustArtSupportDex(info)) {
continue;
}
String path = dexPath + info.realName;
File file = new File(path);
if (application.isTinkerLoadVerifyFlag()) {
long start = System.currentTimeMillis();
String checkMd5 = getInfoMd5(info);
if (!SharePatchFileUtil.verifyDexFileMd5(file, checkMd5)) {
//it is good to delete the mismatch file
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_MD5_MISMATCH);
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_MISMATCH_DEX_PATH,
file.getAbsolutePath());
return false;
}
Log.i(TAG, "verify dex file:" + file.getPath() + " md5, use time: " + (System.currentTimeMillis() - start));
}
//将文件加入队列
legalFiles.add(file);
}
// verify merge classN.apk
if (isVmArt && !classNDexInfo.isEmpty()) {
File classNFile = new File(dexPath + ShareConstants.CLASS_N_APK_NAME);
long start = System.currentTimeMillis();
if (application.isTinkerLoadVerifyFlag()) {
for (ShareDexDiffPatchInfo info : classNDexInfo) {
if (!SharePatchFileUtil.verifyDexFileMd5(classNFile, info.rawName, info.destMd5InArt)) {
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_MD5_MISMATCH);
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_MISMATCH_DEX_PATH,
classNFile.getAbsolutePath());
return false;
}
}
}
Log.i(TAG, "verify dex file:" + classNFile.getPath() + " md5, use time: " + (System.currentTimeMillis() - start));
//将文件加入队列
legalFiles.add(classNFile);
}
//优化补丁的目录
File optimizeDir = new File(directory + "/" + oatDir);
if (isSystemOTA) {
final boolean[] parallelOTAResult = {true};
final Throwable[] parallelOTAThrowable = new Throwable[1];
String targetISA;
try {
targetISA = ShareTinkerInternals.getCurrentInstructionSet();
} catch (Throwable throwable) {
Log.i(TAG, "getCurrentInstructionSet fail:" + throwable);
// try {
// targetISA = ShareOatUtil.getOatFileInstructionSet(testOptDexFile);
// } catch (Throwable throwable) {
// don't ota on the front
deleteOutOfDateOATFile(directory);
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_INTERPRET_EXCEPTION, throwable);
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_GET_OTA_INSTRUCTION_SET_EXCEPTION);
return false;
// }
}
deleteOutOfDateOATFile(directory);
Log.w(TAG, "systemOTA, try parallel oat dexes, targetISA:" + targetISA);
// change dir
optimizeDir = new File(directory + "/" + INTERPRET_DEX_OPTIMIZE_PATH);
TinkerDexOptimizer.optimizeAll(
legalFiles, optimizeDir, true, targetISA,
new TinkerDexOptimizer.ResultCallback() {
long start;
@Override
public void onStart(File dexFile, File optimizedDir) {
start = System.currentTimeMillis();
Log.i(TAG, "start to optimize dex:" + dexFile.getPath());
}
@Override
public void onSuccess(File dexFile, File optimizedDir, File optimizedFile) {
// Do nothing.
Log.i(TAG, "success to optimize dex " + dexFile.getPath() + ", use time " + (System.currentTimeMillis() - start));
}
@Override
public void onFailed(File dexFile, File optimizedDir, Throwable thr) {
parallelOTAResult[0] = false;
parallelOTAThrowable[0] = thr;
Log.i(TAG, "fail to optimize dex " + dexFile.getPath() + ", use time " + (System.currentTimeMillis() - start));
}
}
);
if (!parallelOTAResult[0]) {
Log.e(TAG, "parallel oat dexes failed");
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_INTERPRET_EXCEPTION, parallelOTAThrowable[0]);
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_OTA_INTERPRET_ONLY_EXCEPTION);
return false;
}
}
try {
SystemClassLoaderAdder.installDexes(application, classLoader, optimizeDir, legalFiles);
} catch (Throwable e) {
Log.e(TAG, "install dexes failed");
// e.printStackTrace();
intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_EXCEPTION, e);
ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_LOAD_EXCEPTION);
return false;
}
return true;
}
复制代码首先判断loadDexList和classNDexInfo有没有元素，在TinkerDexLoader的checkComplete方法，里面已经添加完成了元素。然后通过TinkerDexLoader的class.getClassLoader()方法拿到Application的ClassLoader，接下来将补丁文件添加到legalFiles队列，最重要的就是通过SystemClassLoaderAdder的installDexes方法安装dex，也就是通过该方法来完成热修复。
这里会根据不同的版本调用不同版本的install方法，这里看Build.VERSION.SDK_INT >= 19这个版本的install方法。
首先通过调用ShareReflectUtil的findField方法，也就是通过反射来获取得到PathClassLoader的pathList属性。
/**
* Locates a given field anywhere in the class inheritance hierarchy.
*
* @param instance an object to search the field into.
* @param name field name
* @return a field object
* @throws NoSuchFieldException if the field cannot be located
*/
public static Field findField(Object instance, String name) throws NoSuchFieldException {
for (Class<?> clazz = instance.getClass(); clazz != null; clazz = clazz.getSuperclass()) {
try {
Field field = clazz.getDeclaredField(name);
if (!field.isAccessible()) {
field.setAccessible(true);
}
return field;
} catch (NoSuchFieldException e) {
// ignore and search next
}
}
throw new NoSuchFieldException("Field " + name + " not found in " + instance.getClass());
}
复制代码接着V19的install方法，得到PathClassLoader的pathList属性之后，通过pathListField.get(loader)得到DexPathList对象，接着调用ShareReflectUtil的expandFieldArray方法。
/**
* Replace the value of a field containing a non null array, by a new array containing the
* elements of the original array plus the elements of extraElements.
*
* @param instance the instance whose field is to be modified.
* @param fieldName the field to modify.
* @param extraElements elements to append at the end of the array.
*/
public static void expandFieldArray(Object instance, String fieldName, Object[] extraElements)
throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
Field jlrField = findField(instance, fieldName);
Object[] original = (Object[]) jlrField.get(instance);
Object[] combined = (Object[]) Array.newInstance(original.getClass().getComponentType(), original.length + extraElements.length);
// NOTE: changed to copy extraElements first, for patch load first
System.arraycopy(extraElements, 0, combined, 0, extraElements.length);
System.arraycopy(original, 0, combined, extraElements.length, original.length);
jlrField.set(instance, combined);
}
复制代码方法内，首先调用findField方法得到pathListField的dexElements数组。
/**
* Locates a given field anywhere in the class inheritance hierarchy.
*
* @param instance an object to search the field into.
* @param name field name
* @return a field object
* @throws NoSuchFieldException if the field cannot be located
*/
public static Field findField(Object instance, String name) throws NoSuchFieldException {
for (Class<?> clazz = instance.getClass(); clazz != null; clazz = clazz.getSuperclass()) {
try {
Field field = clazz.getDeclaredField(name);
if (!field.isAccessible()) {
field.setAccessible(true);
}
return field;
} catch (NoSuchFieldException e) {
// ignore and search next
}
}
throw new NoSuchFieldException("Field " + name + " not found in " + instance.getClass());
}
复制代码在《你值得知道的Android 热修复，以及热修复原理》这篇文章中已经介绍过了通过反射得到dexElements这些原理了，毫无疑问，tinker也是使用了相同的原理来进行热修复。
在expandFieldArray方法中，new了一个数据类型为object的数组combined，其长度是：原本dexElements的长度+通过dexPathList对象的makeDexElements方法创建的长度，通过System.arraycopy将补丁插入dex插入到combined最前面的位置，也就是0的位置，然后通过jlrField.set(instance, combined)，用combined将就的dexElements替换掉。替换掉之后，每次加载dex，都是从新的dexElements开始查找，因为修复好的dex在最前面，一旦找到新的dex，就不会再从dexElements往下查找旧dex，这样子就达到了热修复的目的。
通过以上的分析，希望能够提升大家对tinker源码和热修复原理的理解。