Android 热修复方案Tinker(三) Dex补丁加载

基于Tinker V1.7.5

• Android 热修复方案Tinker(一) Application改造
• Android 热修复方案Tinker(二) 补丁加载流程
• Android 热修复方案Tinker(三) Dex补丁加载
• Android 热修复方案Tinker(四) 资源补丁加载
• Android 热修复方案Tinker(五) SO补丁加载
• Android 热修复方案Tinker(六) Gradle插件实现
• Android 热修复方案Tinker(七) 插桩实现
• 带注释的源码

之前有说到Tinker的修复原理是跟Qzone类似,这里就详细分析一下为什么这样做可以修复补丁.虽然其他Android版本的源码实现可能不一样,但是都是基于相同的原理.所以这里就以Android 6.0的源码为例介绍原理.具体每个系统版本的不同实现下面会详细说明.

首先从加载dex文件的入口开始看, /libcore/dalvik/src/main/java/dalvik/system/DexClassLoader.java这个类很简单,只是继承了BaseDexClassLoader在构造方法中调用了父类的构造方法.

public class DexClassLoader extends BaseDexClassLoader {    public DexClassLoader(String dexPath, String optimizedDirectory,            String libraryPath, ClassLoader parent) {        super(dexPath, new File(optimizedDirectory), libraryPath, parent);    }}

继续进入/libcore/dalvik/src/main/java/dalvik/system/BaseDexClassLoader.java类中,BaseDexClassLoader在构造方法中创建出了一个很重要的对象pathList,至于为什么说他重要可以看下面的findclass方法.findclass方法是根据类名在运行时从dex文件中找出并将其返回回来,而真正的findclass是通过pathList对象的方法来操作的.

public class BaseDexClassLoader extends ClassLoader {    private final DexPathList pathList;    public BaseDexClassLoader(String dexPath, File optimizedDirectory,            String libraryPath, ClassLoader parent) {        super(parent);        this.pathList = new DexPathList(this, dexPath, libraryPath, optimizedDirectory);    }    @Override    protected Class<?> findClass(String name) throws ClassNotFoundException {        List<Throwable> suppressedExceptions = new ArrayList<Throwable>();        Class c = pathList.findClass(name, suppressedExceptions);        if (c == null) {            ClassNotFoundException cnfe = new ClassNotFoundException("Didn't find class \"" + name + "\" on path: " + pathList);            for (Throwable t : suppressedExceptions) {                cnfe.addSuppressed(t);            }            throw cnfe;        }        return c;    }}

最终在/libcore/dalvik/src/main/java/dalvik/system/DexPathList.java类中找到findclass方法,该方法是按顺序遍历dexElements,只要dexElement中的dex文件中包含有该class就加载出class然后直接return.所以利用findclass这种特性把补丁包dex插入dexElements的首位,系统在findClass的时候就优先拿到补丁包中的class,从而达到修复bug的目的.

final class DexPathList {    private final Element[] dexElements;    public Class findClass(String name, List<Throwable> suppressed) {        for (Element element : dexElements) {            DexFile dex = element.dexFile;            if (dex != null) {                Class clazz = dex.loadClassBinaryName(name, definingContext, suppressed);                if (clazz != null) {                    return clazz;                }            }        }        if (dexElementsSuppressedExceptions != null) {            suppressed.addAll(Arrays.asList(dexElementsSuppressedExceptions));        }        return null;    }}

校验Dex文件

讲过dex修复的原理,回到Tinker的dex补丁加载流程.在loadTinkerJars之后,先确保之前checkComplete时是否筛选出物理有效的dex文件以供加载,再拿到PathClassLoader供后面使用.

if (dexList.isEmpty()) {    Log.w(TAG, "there is no dex to load");    return true;}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;}

在TinkerLoader.tryLoad时只是校验了dex_meta.txt文件的签名信息,并没有校验所有的dex文件的合法性.如果在ApplicationLike处配置了tinkerLoadVerifyFlag为true, 则每次加载dex补丁之前都对文件做MD5,并对比dex_meta.txt中对应的MD5信息.

for (DexDiffPatchInfo info : dexList) {    //for dalvik, ignore art support dex    if (isJustArtSupportDex(info)) {        continue;    }    String path = dexPath + info.realName;    File file = new File(path);    if (tinkerLoadVerifyFlag) {        long start = System.currentTimeMillis();        String checkMd5 = isArtPlatForm ? info.destMd5InArt : info.destMd5InDvm;        if (!PatchFileUtil.verifyDexFileMd5(file, checkMd5)) {            //it is good to delete the mismatch file            IntentUtil.setIntentReturnCode(intentResult, Constants.ERROR_LOAD_PATCH_VERSION_DEX_MD5_MISMATCH);            intentResult.putExtra(IntentUtil.INTENT_PATCH_MISMATCH_DEX_PATH,                    file.getAbsolutePath());            return false;        }        Log.i(TAG, "verify dex file:" + file.getPath() + " md5, use time: " + (System.currentTimeMillis() - start));    }    legalFiles.add(file);}

OTA在特定情况下重新load Dex

在v1.7.5的版本开始有了isSystemOTA判断,只要用户是ART环境并且做了OTA升级则在加载dex补丁的时候就会先把最近一次的补丁全部DexFile.loadDex一遍.这么做的原因是有些场景做了OTA后,oat的规则可能发生变化,在这种情况下去加载上个系统版本oat过的dex就会出现问题.

if (isSystemOTA) {    parallelOTAResult = true;    parallelOTAThrowable = null;    Log.w(TAG, "systemOTA, try parallel oat dexes!!!!!");    ParallelDexOptimizer.optimizeAll(            legalFiles, optimizeDir,            new ParallelDexOptimizer.ResultCallback() {                @Override                public void onSuccess(File dexFile, File optimizedDir) {                    // Do nothing.                }                @Override                public void onFailed(File dexFile, File optimizedDir, Throwable thr) {                    parallelOTAResult = false;                    parallelOTAThrowable = thr;                }            }    );    if (!parallelOTAResult) {        Log.e(TAG, "parallel oat dexes failed");        intentResult.putExtra(IntentUtil.INTENT_PATCH_EXCEPTION, parallelOTAThrowable);        IntentUtil.setIntentReturnCode(intentResult, Constants.ERROR_LOAD_PATCH_VERSION_PARALLEL_DEX_OPT_EXCEPTION);        return false;    }}

dex补丁的重置是在线程池中执行,并且利用CountDownLatch挂起主线程,直到线程池中的task都执行完毕再恢复主线程.在很极端的情况下可能会造成ANR.

private static boolean optimizeAllLocked(Collection<File> dexFiles, File optimizedDir, AtomicInteger successCount, ResultCallback cb) {    final CountDownLatch lauch = new CountDownLatch(dexFiles.size());    final ExecutorService threadPool = Executors.newCachedThreadPool();    long startTick = System.nanoTime();    for (File dexFile : dexFiles) {        OptimizeWorker worker = new OptimizeWorker(dexFile, optimizedDir, successCount, lauch, cb);        threadPool.submit(worker);    }    try {        lauch.await();        long timeCost = (System.nanoTime() - startTick) / 1000000;        if (successCount.get() == dexFiles.size()) {            Log.i(TAG, "All dexes are optimized successfully, cost: " + timeCost + " ms.");            return true;        } else {            Log.e(TAG, "Dexes optimizing failed, some dexes are not optimized.");            return false;        }    } catch (InterruptedException e) {        Log.w(TAG, "Dex optimizing was interrupted.", e);        return false;    } finally {        threadPool.shutdown();    }}

加载Dex

经过一系列的校验,终于到真正加载dex补丁的步骤了.Tinker加载dex补丁按照系统版本不同分成了四条分支.同样加载失败之后记录失败信息到intentResult中.

1. V4 Android SDK版本小于14
2. V14 Android SDK版本小于19
3. V19 Android SDK版本小于 23
4. V23 Android SDK版本大于等于23
   
   • Android N 改造ClassLoader

try {    SystemClassLoaderAdder.installDexes(application, classLoader, optimizeDir, legalFiles);} catch (Throwable e) {    Log.e(TAG, "install dexes failed");    intentResult.putExtra(IntentUtil.INTENT_PATCH_EXCEPTION, e);    IntentUtil.setIntentReturnCode(intentResult, Constants.ERROR_LOAD_PATCH_VERSION_DEX_LOAD_EXCEPTION);    return false;}Log.i(TAG, "after loaded classloader: " + application.getClassLoader().toString());

• V4 Android SDK版本小于14

  在Android SDK4到14之间PathClassLoader.java的实现是直接继承自ClassLoader,findClass时是根据mFiles数组来遍历mDexs数组(类似于dexElements).从mDexs数组中的dex根据类名来加载Class,规则也是按照遍历的顺序加载,只要有加载出来的Class就直接return掉.

  Android 2.3.6版本源码

  public class PathClassLoader extends ClassLoader {private final String path;private final String[] mPaths;private final File[] mFiles;private final ZipFile[] mZips;private final DexFile[] mDexs;@Overrideprotected Class<?> findClass(String name) throws ClassNotFoundException{    //System.out.println("PathClassLoader " + this + ": findClass '" + name + "'");    byte[] data = null;    int length = mPaths.length;    for (int i = 0; i < length; i++) {        //System.out.println("My path is: " + mPaths[i]);        if (mDexs[i] != null) {            Class clazz = mDexs[i].loadClassBinaryName(name, this);            if (clazz != null)                return clazz;        } else if (mZips[i] != null) {            String fileName = name.replace('.', '/') + ".class";            data = loadFromArchive(mZips[i], fileName);        } else {            File pathFile = mFiles[i];            if (pathFile.isDirectory()) {                String fileName =                    mPaths[i] + "/" + name.replace('.', '/') + ".class";                data = loadFromDirectory(fileName);            } else {                //System.out.println("PathClassLoader: can't find '"                //    + mPaths[i] + "'");            }        }    }    throw new ClassNotFoundException(name + " in loader " + this);}

  在DexClassLoader.java的构造方法中可以看到path,mPaths,mFiles, mZips和mDexs五个关键属性之间是互相联系的,所以在做热修复时要同时对这五个属性同步操作,来确保数据的一致性.

  this.path = path;this.libPath = libPath;mPaths = path.split(":");int length = mPaths.length;//System.out.println("PathClassLoader: " + mPaths);mFiles = new File[length];mZips = new ZipFile[length];mDexs = new DexFile[length];.../* open all Zip and DEX files up front */for (int i = 0; i < length; i++) {    //System.out.println("My path is: " + mPaths[i]);    File pathFile = new File(mPaths[i]);    mFiles[i] = pathFile;    if (pathFile.isFile()) {        try {            mZips[i] = new ZipFile(pathFile);        }        catch (IOException ioex) {        }        if (wantDex) {            /* we need both DEX and Zip, because dex has no resources */            try {                mDexs[i] = new DexFile(pathFile);            }            catch (IOException ioex) {}        }    }}

  所以在Tinker中,要加载这类系统的补丁包最核心的地方就是path,mPaths,mFiles, mZips和mDexs五个属性的的操作.根据补丁文件的个数建立四个关键属性对应的数组,再通过遍历补丁文件,对四个数组和一个字符串进行填充.再利用反射将新的数组插入到原数组头部,完成补丁加载的过程.

  private static void install(ClassLoader loader, List<File> additionalClassPathEntries, File optimizedDirectory)        throws IllegalArgumentException, IllegalAccessException,        NoSuchFieldException, IOException {    int extraSize = additionalClassPathEntries.size();    Field pathField = ReflectUtil.findField(loader, "path");    StringBuilder path = new StringBuilder((String) pathField.get(loader));    String[] extraPaths = new String[extraSize];    File[] extraFiles = new File[extraSize];    ZipFile[] extraZips = new ZipFile[extraSize];    DexFile[] extraDexs = new DexFile[extraSize];    for (ListIterator<File> iterator = additionalClassPathEntries.listIterator();         iterator.hasNext();) {        File additionalEntry = iterator.next();        String entryPath = additionalEntry.getAbsolutePath();        path.append(':').append(entryPath);        int index = iterator.previousIndex();        extraPaths[index] = entryPath;        extraFiles[index] = additionalEntry;        extraZips[index] = new ZipFile(additionalEntry);        //edit by zhangshaowen        String outputPathName = PatchFileUtil.optimizedPathFor(additionalEntry, optimizedDirectory);        //for below 4.0, we must input jar or zip        extraDexs[index] = DexFile.loadDex(entryPath, outputPathName, 0);    }    pathField.set(loader, path.toString());    ReflectUtil.expandFieldArray(loader, "mPaths", extraPaths);    ReflectUtil.expandFieldArray(loader, "mFiles", extraFiles);    ReflectUtil.expandFieldArray(loader, "mZips", extraZips);    try {        ReflectUtil.expandFieldArray(loader, "mDexs", extraDexs);    } catch (Exception e) {    }}

  对原数组的操作是利用反射,先拿到原数组的对象original, 再根据original的类型长度以及补丁数组的长度重新创建出一个新数组combined.接下来使用arraycopy将补丁数组和原数组copy到combined中,最后将该数组赋值给filedName对应的属性.

  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);}

• V14 Android SDK版本小于19

  在这个Android版本的区间内不再像老版本的那样要维护四个数组,源码从中抽离出了一个类DexPathList.java,加载dex的关键数组也变成了dexElements,并且dexElements是根据makeDexElements方法生成的.对比过源码其实就可以发现dexElements其实就是老版本中mFiles, mZips和mDexs的封装,makeDexElements方法就是老版本DexClassLoader.java构造方法中对数组初始化的动作.

  Android 4.2.2版本源码

  final class DexPathList {    /** list of dex/resource (class path) elements */    private final Element[] dexElements;    public Class findClass(String name) {        for (Element element : dexElements) {            DexFile dex = element.dexFile;            if (dex != null) {                Class clazz = dex.loadClassBinaryName(name, definingContext);                if (clazz != null) {                    return clazz;                }            }        }        return null;    }    /**     * Makes an array of dex/resource path elements, one per element of     * the given array.     */    private static Element[] makeDexElements(ArrayList<File> files,            File optimizedDirectory) {        ArrayList<Element> elements = new ArrayList<Element>();        /*         * Open all files and load the (direct or contained) dex files         * up front.         */        for (File file : files) {            File zip = null;            DexFile dex = null;            String name = file.getName();            if (name.endsWith(DEX_SUFFIX)) {                // Raw dex file (not inside a zip/jar).                try {                    dex = loadDexFile(file, optimizedDirectory);                } catch (IOException ex) {                    System.logE("Unable to load dex file: " + file, ex);                }            } else if (name.endsWith(APK_SUFFIX) || name.endsWith(JAR_SUFFIX)                    || name.endsWith(ZIP_SUFFIX)) {                zip = file;                try {                    dex = loadDexFile(file, optimizedDirectory);                } catch (IOException ignored) {                    /*                     * IOException might get thrown "legitimately" by                     * the DexFile constructor if the zip file turns                     * out to be resource-only (that is, no                     * classes.dex file in it). Safe to just ignore                     * the exception here, and let dex == null.                     */                }            } else {                System.logW("Unknown file type for: " + file);            }            if ((zip != null) || (dex != null)) {                elements.add(new Element(file, zip, dex));            }        }        return elements.toArray(new Element[elements.size()]);    }}

  系统既然自己做了封装,那么我们反射调用起来也会更方便.首先反射拿到反射得到PathClassLoader中的pathList对象,再将补丁文件通过反射调用makeDexElements得到补丁文件的Element[],再将补丁包的Element数组插入到dexElements中,方法如V4.完成补丁加载.

  private static void install(ClassLoader loader, List<File> additionalClassPathEntries,                            File optimizedDirectory)        throws IllegalArgumentException, IllegalAccessException,        NoSuchFieldException, InvocationTargetException, NoSuchMethodException {    /* The patched class loader is expected to be a descendant of     * dalvik.system.BaseDexClassLoader. We modify its     * dalvik.system.DexPathList pathList field to append additional DEX     * file entries.     */    Field pathListField = ReflectUtil.findField(loader, "pathList");    Object dexPathList = pathListField.get(loader);    //通过反射调用makeDexElements方法生成补丁包的dex数组,再将其插入到dexElements的头部    ReflectUtil.expandFieldArray(dexPathList, "dexElements", makeDexElements(dexPathList,            new ArrayList<File>(additionalClassPathEntries), optimizedDirectory));}/** * A wrapper around * {@code private static final dalvik.system.DexPathList#makeDexElements}. */private static Object[] makeDexElements(        Object dexPathList, ArrayList<File> files, File optimizedDirectory)        throws IllegalAccessException, InvocationTargetException,        NoSuchMethodException {    Method makeDexElements =            ReflectUtil.findMethod(dexPathList, "makeDexElements", ArrayList.class, File.class);    //反射调用makeDexElements方法根据files得到新dexElements数组    return (Object[]) makeDexElements.invoke(dexPathList, files, optimizedDirectory);}

• V19 Android SDK版本小于 23

  在该版本系统区间中,加载补丁涉及到的修改只是增加了一个exElementsSuppressedExceptions异常数组的维护.所以在加载补丁的时候就跟V14差不多了.既然只是多了一个异常的管理,为什么Tinker源码在利用反射找makeDexElements(ArrayList,File,ArrayList),如果找不到就接着找makeDexElements(List,File,List)？为了在Android源码中找到答案我去查找了4.4, 5.0,5.1版本的DexPathList源码,发现方法的参数都是ArrayList,根本没有List.百思不得姐之后就问了一下Tinker的作者,他们说在线上发现有机子的rom中这个方法的参数就是List.

  private static Object[] makeDexElements(        Object dexPathList, ArrayList<File> files, File optimizedDirectory,        ArrayList<IOException> suppressedExceptions)        throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {    Method makeDexElements = null;    try {        makeDexElements = ReflectUtil.findMethod(dexPathList, "makeDexElements", ArrayList.class, File.class,                ArrayList.class);    } catch (NoSuchMethodException e) {        Log.e(TAG, "NoSuchMethodException: makeDexElements(ArrayList,File,ArrayList) failure");        try {            makeDexElements = ReflectUtil.findMethod(dexPathList, "makeDexElements", List.class, File.class, List.class);        } catch (NoSuchMethodException e1) {            Log.e(TAG, "NoSuchMethodException: makeDexElements(List,File,List) failure");            throw e1;        }    }    return (Object[]) makeDexElements.invoke(dexPathList, files, optimizedDirectory, suppressedExceptions);}

• V23 Android SDK版本大于等于23

  因为V23中包含有Android 7.0的系统版本,由于Android N混合编译与对热补丁影响解析,这会造成要修复的class被缓存在App image中,App image中的class会插入PathClassLoader中,而PathClassLoader 加载补丁的时候不会替换缓存的class,最终会导致在全量更新的情况下有可能部分类是从base.apk中加载,部分类是从patch.dex中加载,抛出IllegalAccessError.Tinker的解决方案是在运行时改写PathClassLoader来加载类,让App image中的缓存失效.

  所以要解决N里面混编的问题,核心着手点就是要替换PathClassLoader使他在加载dex的时候不加载做过优化的dex文件,重新加载原始的dex文件.这个点要从哪里切入呢? 在Android 7.0的源码中定位到了在makePathElements方法中调用的loadDexFile方法.从代码上来看是要在调用的时候有传递有效的optimizedDirectory参数,就会去opt过的路径下加载dex文件.所以我们在调用的时候不传optimizedDirectory参数就可以达到重新加载原始dex文件从而去除混编优化的目的.

  private static DexFile loadDexFile(File file, File optimizedDirectory, ClassLoader loader,                                   Element[] elements)        throws IOException {    if (optimizedDirectory == null) {        return new DexFile(file, loader, elements);    } else {        String optimizedPath = optimizedPathFor(file, optimizedDirectory);        return DexFile.loadDex(file.getPath(), optimizedPath, 0, loader, elements);    }}

  知道了解决方案和切入点,接下来分析一下Tinker做法.在加载补丁之前利用反射替换原PathClassLoader以及与它相关的所有引用.首先根据原PathClassLoader的parent 构建出AndroidNClassLoader;再反射拿到original的pathList;接着反射拿到pathList对象的definingContext属性,因为该属性是original的引用,需要拿到之后替换成新loader的引用;继续反射拿到androidNClassLoader的pathList对象,并且替换成original的;再反射拿到original的pathList的dexElements,并且遍历出dexElements中真实的dex文件名之后存储起来;接下来反射拿到original的pathList的makePathElements方法并调用注意方法第二个参数optDir要设置为null,重新生成dexElements数组,并替换原来的数组.最终完成AndroidNClassLoader的创建,以及子类引用的替换.

  private static AndroidNClassLoader createAndroidNClassLoader(PathClassLoader original) throws Exception {    //let all element ""    AndroidNClassLoader androidNClassLoader = new AndroidNClassLoader("",  original);    Field originPathList = ShareReflectUtil.findField(original, "pathList");    Object originPathListObject = originPathList.get(original);    //should reflect definingContext also    Field originClassloader = ShareReflectUtil.findField(originPathListObject, "definingContext");    originClassloader.set(originPathListObject, androidNClassLoader);    //copy pathList    Field pathListField = ShareReflectUtil.findField(androidNClassLoader, "pathList");    //just use PathClassloader's pathList    pathListField.set(androidNClassLoader, originPathListObject);    //we must recreate dexFile due to dexCache    List<File> additionalClassPathEntries = new ArrayList<>();    Field dexElement = ShareReflectUtil.findField(originPathListObject, "dexElements");    Object[] originDexElements = (Object[]) dexElement.get(originPathListObject);    for (Object element : originDexElements) {        DexFile dexFile = (DexFile) ShareReflectUtil.findField(element, "dexFile").get(element);        additionalClassPathEntries.add(new File(dexFile.getName()));        //protect for java.lang.AssertionError: Failed to close dex file in finalizer.        oldDexFiles.add(dexFile);    }    Method makePathElements = ShareReflectUtil.findMethod(originPathListObject, "makePathElements", List.class, File.class,        List.class);    ArrayList<IOException> suppressedExceptions = new ArrayList<>();    Object[] newDexElements = (Object[]) makePathElements.invoke(originPathListObject, additionalClassPathEntries, null, suppressedExceptions);    dexElement.set(originPathListObject, newDexElements);    return androidNClassLoader;}

  做完新AndroidNClassLoader的创建之后就是替换真正的ClassLoader的引用了.在全局Context中持有的LoadedApk的对象mPackageInfo的属性中,有一个ClassLoader类的对象mClassLoader.层层反射将mClassLoader的引用替换为上面创建出来的AndroidNClassLoader对象.同时将Thread中持有的ClassLoader也同步替换为AndroidNClassLoader.至此PathClassLoader的修改和替换都已经完成了,接下来就可以正常得加载补丁dex了.

  String defBase = "mBase";String defPackageInfo = "mPackageInfo";String defClassLoader = "mClassLoader";Context baseContext = (Context) ReflectUtil.findField(application, defBase).get(application);Object basePackageInfo = ReflectUtil.findField(baseContext, defPackageInfo).get(baseContext);Field classLoaderField = ReflectUtil.findField(basePackageInfo, defClassLoader);Thread.currentThread().setContextClassLoader(reflectClassLoader);classLoaderField.set(basePackageInfo, reflectClassLoader);

  在Android系统在该版本区间之内时,DexPathList类中的findclass方法跟V19相比是没有变化的.但是生成dexElements数组用的方法名发生了变化.所以在这个版本中反射生成补丁包的Element[]就需要兼容这些变化.

  Android 6.0.0版本源码, 相比老版本makeDexElements(ArrayList,File,ArrayList)方法变成了makePathElements(List,File,List).

   /** * Makes an array of dex/resource path elements, one per element of * the given array. */private static Element[] makePathElements(List<File> files, File optimizedDirectory,                                          List<IOException> suppressedExceptions) {    ···}

  Android 7.0.0版本源码,该方法名又发生了变化.根据职能做了一些区分和重载.

   /** * Makes an array of dex/resource path elements, one per element of * the given array. */private static Element[] makeDexElements(List<File> files, File optimizedDirectory,                                         List<IOException> suppressedExceptions,                                         ClassLoader loader) {    return makeElements(files, optimizedDirectory, suppressedExceptions, false, loader);}/** * Makes an array of directory/zip path elements, one per element of the given array. */private static Element[] makePathElements(List<File> files,                                          List<IOException> suppressedExceptions,                                          ClassLoader loader) {    return makeElements(files, null, suppressedExceptions, true, loader);}private static Element[] makePathElements(List<File> files, File optimizedDirectory,                                          List<IOException> suppressedExceptions) {    return makeElements(files, optimizedDirectory, suppressedExceptions, false, null);}private static Element[] makeElements(List<File> files, File optimizedDirectory,                                      List<IOException> suppressedExceptions,                                      boolean ignoreDexFiles,                                      ClassLoader loader) {    ···}

  结合上面两个系统版本的分析,在反射findMethod时做多种情况的处理,同时也避免V19中描述的rom问题.

  private static Object[] makePathElements(        Object dexPathList, ArrayList<File> files, File optimizedDirectory,        ArrayList<IOException> suppressedExceptions)        throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {    Method makePathElements;    try {        makePathElements = ReflectUtil.findMethod(dexPathList, "makePathElements", List.class, File.class,                List.class);    } catch (NoSuchMethodException e) {        Log.e(TAG, "NoSuchMethodException: makePathElements(List,File,List) failure");        try {            makePathElements = ReflectUtil.findMethod(dexPathList, "makePathElements", ArrayList.class, File.class, ArrayList.class);        } catch (NoSuchMethodException e1) {            Log.e(TAG, "NoSuchMethodException: makeDexElements(ArrayList,File,ArrayList) failure");            try {                Log.e(TAG, "NoSuchMethodException: try use v19 instead");                return V19.makeDexElements(dexPathList, files, optimizedDirectory, suppressedExceptions);            } catch (NoSuchMethodException e2) {                Log.e(TAG, "NoSuchMethodException: makeDexElements(List,File,List) failure");                throw e2;            }        }    }    return (Object[]) makePathElements.invoke(dexPathList, files, optimizedDirectory, suppressedExceptions);}

卸载 Dex补丁

校验和加载Dex补丁的流程都已经分析完了.接下来就是验证补丁是否加载成功,这里是通过反射拿到TinkerTestDexLoad.isPatch静态属性来判断.在没有补丁加载的情况下都是返回false的,在补丁中修改isPatch属性为true.所以只要反射拿到isPatch的属性为true就说明补丁已经成功加载进来了.如果返回false则卸载Dex补丁恢复到加载之前的数据状态.

private static boolean checkDexInstall(ClassLoader classLoader) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {    Class<?> clazz = Class.forName(CHECK_DEX_CLASS, true, classLoader);    Field filed = ShareReflectUtil.findField(clazz, CHECK_DEX_FIELD);    boolean isPatch = (boolean) filed.get(null);    Log.w(TAG, "checkDexInstall result:" + isPatch);    return isPatch;}

补丁的卸载就不需要跟加载一样要区分那么多版本,因为Android 4.0开始就都是在操作DexPathList类中的dexElements数组,Android 4.0之前是在V4补丁加载中提到过的那四个数组.卸载就根据补丁的数量把数组头部的数据都移除掉.其中reduceFieldArray的作用跟加载补丁V4中提到的expandFieldArray完全相反.

public static void uninstallPatchDex(ClassLoader classLoader) throws Throwable {    if (sPatchDexCount <= 0) {        return;    }    if (Build.VERSION.SDK_INT >= 14) {        Field pathListField = ShareReflectUtil.findField(classLoader, "pathList");        Object dexPathList = pathListField.get(classLoader);        ShareReflectUtil.reduceFieldArray(dexPathList, "dexElements", sPatchDexCount);    } else {        ShareReflectUtil.reduceFieldArray(classLoader, "mPaths", sPatchDexCount);        ShareReflectUtil.reduceFieldArray(classLoader, "mFiles", sPatchDexCount);        ShareReflectUtil.reduceFieldArray(classLoader, "mZips", sPatchDexCount);        try {            ShareReflectUtil.reduceFieldArray(classLoader, "mDexs", sPatchDexCount);        } catch (Exception e) {        }    }}

到这里Dex补丁的加载流程就完全分析完了,下面会继续分析SO和资源的操作流程.

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