android.applicationVariants.all { variant ->task "fix${variant.name.capitalize()}MainDexClassList" << {logger.info "Fixing main dex keep file for $variant.name"File keepFile = new File("$buildDir/intermediates/multi-dex/$variant.buildType.name/maindexlist.txt")keepFile.withWriterAppend { w ->// Get a reader for the input filew.append('\n')new File("${projectDir}/multidex.keep").withReader { r ->// And write data from the input into the outputw << r << '\n'}logger.info "Updated main dex keep file for ${keepFile.getAbsolutePath()}\n$keepFile.text"}}
}
tasks.whenTaskAdded { task ->android.applicationVariants.all { variant ->if (task.name == "create${variant.name.capitalize()}MainDexClassList") {task.finalizedBy "fix${variant.name.capitalize()}MainDexClassList"}}
}

public class MultiDexUtils {private static final String EXTRACTED_NAME_EXT = ".classes";private static final String EXTRACTED_SUFFIX = ".zip";private static final String SECONDARY_FOLDER_NAME = "code_cache" + File.separator +"secondary-dexes";private static final String PREFS_FILE = "multidex.version";private static final String KEY_DEX_NUMBER = "dex.number";private SharedPreferences getMultiDexPreferences(Context context) {return context.getSharedPreferences(PREFS_FILE,Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB? Context.MODE_PRIVATE: Context.MODE_PRIVATE | Context.MODE_MULTI_PROCESS);}/*** get all the dex path** @param context the application context* @return all the dex path* @throws PackageManager.NameNotFoundException* @throws IOException*/public List<String> getSourcePaths(Context context) throws PackageManager.NameNotFoundException, IOException {final ApplicationInfo applicationInfo = context.getPackageManager().getApplicationInfo(context.getPackageName(), 0);final File sourceApk = new File(applicationInfo.sourceDir);final File dexDir = new File(applicationInfo.dataDir, SECONDARY_FOLDER_NAME);final List<String> sourcePaths = new ArrayList<>();sourcePaths.add(applicationInfo.sourceDir); //add the default apk path//the prefix of extracted file, ie: test.classesfinal String extractedFilePrefix = sourceApk.getName() + EXTRACTED_NAME_EXT;//the total dex numbersfinal int totalDexNumber = getMultiDexPreferences(context).getInt(KEY_DEX_NUMBER, 1);for (int secondaryNumber = 2; secondaryNumber <= totalDexNumber; secondaryNumber++) {//for each dex file, ie: test.classes2.zip, test.classes3.zip...final String fileName = extractedFilePrefix + secondaryNumber + EXTRACTED_SUFFIX;final File extractedFile = new File(dexDir, fileName);if (extractedFile.isFile()) {sourcePaths.add(extractedFile.getAbsolutePath());//we ignore the verify zip part} else {throw new IOException("Missing extracted secondary dex file '" +extractedFile.getPath() + "'");}}return sourcePaths;}/*** get all the external classes name in "classes2.dex", "classes3.dex" ....** @param context the application context* @return all the classes name in the external dex* @throws PackageManager.NameNotFoundException* @throws IOException*/public List<String> getExternalDexClasses(Context context) throws PackageManager.NameNotFoundException, IOException {final List<String> paths = getSourcePaths(context);if(paths.size() <= 1) {// no external dexreturn null;}// the first element is the main dex, remove it.paths.remove(0);final List<String> classNames = new ArrayList<>();for (String path : paths) {try {DexFile dexfile = null;if (path.endsWith(EXTRACTED_SUFFIX)) {//NOT use new DexFile(path), because it will throw "permission error in /data/dalvik-cache"dexfile = DexFile.loadDex(path, path + ".tmp", 0);} else {dexfile = new DexFile(path);}final Enumeration<String> dexEntries = dexfile.entries();while (dexEntries.hasMoreElements()) {classNames.add(dexEntries.nextElement());}} catch (IOException e) {throw new IOException("Error at loading dex file '" +path + "'");}}return classNames;}/*** Get all loaded external classes name in "classes2.dex", "classes3.dex" ....* @param context* @return get all loaded external classes*/public List<String> getLoadedExternalDexClasses(Context context) {try {final List<String> externalDexClasses = getExternalDexClasses(context);if (externalDexClasses != null && !externalDexClasses.isEmpty()) {final ArrayList<String> classList = new ArrayList<>();final java.lang.reflect.Method m = ClassLoader.class.getDeclaredMethod("findLoadedClass", new Class[]{String.class});m.setAccessible(true);final ClassLoader cl = context.getClassLoader();for (String clazz : externalDexClasses) {if (m.invoke(cl, clazz) != null) {classList.add(clazz.replaceAll("\\.", "/").replaceAll("$", ".class"));}}return classList;}} catch (Exception e) {e.printStackTrace();}return null;}
}