MultiDex解析
作者：互联网
1：dex如何分包：
在build.gradle里面设置：
defaultConfig {
multiDexEnabled true
}
自定义的application继承MultiDexApplication。
public class MyApplication extends MultiDexApplication {
..............
}
2:MultiDexApplicatioin代码如何分包：
public class MultiDexApplication extends Application {
public MultiDexApplication() {
}
protected void attachBaseContext(Context base) {
super.attachBaseContext(base);
MultiDex.install(this);
}
}
1:MultiDex.install(this);
public static void install(Context context) {
Log.i("MultiDex", "Installing application");
if (IS_VM_MULTIDEX_CAPABLE) {
Log.i("MultiDex", "VM has multidex support, MultiDex support library is disabled.");
} else if (VERSION.SDK_INT < 4) {
throw new RuntimeException("MultiDex installation failed. SDK " + VERSION.SDK_INT + " is unsupported. Min SDK version is " + 4 + ".");
} else {
try {
ApplicationInfo applicationInfo = getApplicationInfo(context);
if (applicationInfo == null) {
Log.i("MultiDex", "No ApplicationInfo available, i.e. running on a test Context: MultiDex support library is disabled.");
return;
}
// applicationInfo.sourceDir：获取应用存放数据目录 /data/app/package-2/base.apk
// applicationInfo.dataDir： 存放数据的路径 应用数据目录 /data/data/com.example.admin.frameworkdemo
doInstallation(context, new File(applicationInfo.sourceDir), new File(applicationInfo.dataDir), "secondary-dexes", "", true);
} catch (Exception var2) {
Log.e("MultiDex", "MultiDex installation failure", var2);
throw new RuntimeException("MultiDex installation failed (" + var2.getMessage() + ").");
}
Log.i("MultiDex", "install done");
}
}
2:doInstallation：
private static void doInstallation(Context mainContext, File sourceApk, File dataDir, String secondaryFolderName, String prefsKeyPrefix, boolean reinstallOnPatchRecoverableException) throws IOException, IllegalArgumentException, IllegalAccessException, NoSuchFieldException, InvocationTargetException, NoSuchMethodException, SecurityException, ClassNotFoundException, InstantiationException {
synchronized(installedApk) {
// 检查是否已经install过了，避免重复install
if (!installedApk.contains(sourceApk)) {
installedApk.add(sourceApk);
if (VERSION.SDK_INT > 20) {
Log.w("MultiDex", "MultiDex is not guaranteed to work in SDK version " + VERSION.SDK_INT + ": SDK version higher than " + 20 + " should be backed by " + "runtime with built-in multidex capabilty but it's not the " + "case here: java.vm.version=\"" + System.getProperty("java.vm.version") + "\"");
}
ClassLoader loader;
try {
// 获取到的是一个PathClassloader
loader = mainContext.getClassLoader();
} catch (RuntimeException var25) {
Log.w("MultiDex", "Failure while trying to obtain Context class loader. Must be running in test mode. Skip patching.", var25);
return;
}
if (loader == null) {
Log.e("MultiDex", "Context class loader is null. Must be running in test mode. Skip patching.");
} else {
try {
clearOldDexDir(mainContext);
} catch (Throwable var24) {
Log.w("MultiDex", "Something went wrong when trying to clear old MultiDex extraction, continuing without cleaning.", var24);
}
// 构造存放classes.dex的目录/data/data/package/code_cache/secondary-dexesapk中的classes.dex提取并存放为data/data/package/code_cache/secondary-dexes/package--1.apk.classN.zip，以便后续加载到内存中。
try {
List files = extractor.load(mainContext, prefsKeyPrefix, false);
try {
// 加载
installSecondaryDexes(loader, dexDir, files);
} catch (IOException var26) {
if (!reinstallOnPatchRecoverableException) {
throw var26;
}
Log.w("MultiDex", "Failed to install extracted secondary dex files, retrying with forced extraction", var26);
files = extractor.load(mainContext, prefsKeyPrefix, true);
installSecondaryDexes(loader, dexDir, files);
}
} finally {
try {
extractor.close();
} catch (IOException var23) {
closeException = var23;
}
}
if (closeException != null) {
throw closeException;
}
}
}
}
}
3:getDexDir：
// 构造存放classes.dex的目录/data/data/package/code_cache/secondary-dexes
其中dataDir为： /data/data/packagesecondaryFolderName为前面传进来的"secondary-dexes"
private static File getDexDir(Context context, File dataDir, String secondaryFolderName) throws IOException { File cache = new File(dataDir, "code_cache"); try { mkdirChecked(cache); } catch (IOException var5) { cache = new File(context.getFilesDir(), "code_cache"); mkdirChecked(cache); }
///data/data/package/code_cache/secondary-dexesFile dexDir = new File(cache, secondaryFolderName); mkdirChecked(dexDir); return dexDir; }
4:extractor.load:
// 将apk中的classes.dex提取并存放为data/data/package/code_cache/secondary-dexes/package--1.apk.classN.zip，以便后续加载到内存中。
List<? extends File> load(Context context, String prefsKeyPrefix, boolean forceReload) throws IOException {
Log.i("MultiDex", "MultiDexExtractor.load(" + this.sourceApk.getPath() + ", " + forceReload + ", " + prefsKeyPrefix + ")");
if (!this.cacheLock.isValid()) {
throw new IllegalStateException("MultiDexExtractor was closed");
} else {
List files;
if (!forceReload && !isModified(context, this.sourceApk, this.sourceCrc, prefsKeyPrefix)) {
try {
files = this.loadExistingExtractions(context, prefsKeyPrefix);
} catch (IOException var6) {
Log.w("MultiDex", "Failed to reload existing extracted secondary dex files, falling back to fresh extraction", var6);
files = this.performExtractions();
putStoredApkInfo(context, prefsKeyPrefix, getTimeStamp(this.sourceApk), this.sourceCrc, files);
}
} else {
if (forceReload) {
Log.i("MultiDex", "Forced extraction must be performed.");
} else {
Log.i("MultiDex", "Detected that extraction must be performed.");
}
files = this.performExtractions();
putStoredApkInfo(context, prefsKeyPrefix, getTimeStamp(this.sourceApk), this.sourceCrc, files);
}
Log.i("MultiDex", "load found " + files.size() + " secondary dex files");
return files;
}
}
5:解析performExtractions
private List<MultiDexExtractor.ExtractedDex> performExtractions() throws IOException {
// extractedFilePrefix = package-2.apk.classes
String extractedFilePrefix = this.sourceApk.getName() + ".classes";
this.clearDexDir();
List<MultiDexExtractor.ExtractedDex> files = new ArrayList();
// 获取apk的zip对象 ZipFile apk = new ZipFile(this.sourceApk); try { int secondaryNumber = 2; for(ZipEntry dexFile = apk.getEntry("classes" + secondaryNumber + ".dex"); dexFile != null; dexFile = apk.getEntry("classes" + secondaryNumber + ".dex")) {
// fileName = package-2.apk.classes2.zip
String fileName = extractedFilePrefix + secondaryNumber + ".zip";
// dexDir:/data/data/package/code_cache/secondary-dexesMultiDexExtractor.ExtractedDex extractedFile = new MultiDexExtractor.ExtractedDex(this.dexDir, fileName);
// extractedFile:/data/data/package/code_cache/secondary-dexes/package-2.apk.classes2.zip files.add(extractedFile); Log.i("MultiDex", "Extraction is needed for file " + extractedFile); int numAttempts = 0; boolean isExtractionSuccessful = false; while(numAttempts < 3 && !isExtractionSuccessful) { ++numAttempts; extract(apk, dexFile, extractedFile, extractedFilePrefix); try { extractedFile.crc = getZipCrc(extractedFile); isExtractionSuccessful = true; } catch (IOException var18) { isExtractionSuccessful = false; Log.w("MultiDex", "Failed to read crc from " + extractedFile.getAbsolutePath(), var18); } Log.i("MultiDex", "Extraction " + (isExtractionSuccessful ? "succeeded" : "failed") + " '" + extractedFile.getAbsolutePath() + "': length " + extractedFile.length() + " - crc: " + extractedFile.crc); if (!isExtractionSuccessful) { extractedFile.delete(); if (extractedFile.exists()) { Log.w("MultiDex", "Failed to delete corrupted secondary dex '" + extractedFile.getPath() + "'"); } } } if (!isExtractionSuccessful) { throw new IOException("Could not create zip file " + extractedFile.getAbsolutePath() + " for secondary dex (" + secondaryNumber + ")"); } ++secondaryNumber; } } finally { try { apk.close(); } catch (IOException var17) { Log.w("MultiDex", "Failed to close resource", var17); } } return files; }
6：接上面的第2步骤里面的installSecondaryDexes
private static void installSecondaryDexes(ClassLoader loader, File dexDir, List<? extends File> files) throws IllegalArgumentException, IllegalAccessException, NoSuchFieldException, InvocationTargetException, NoSuchMethodException, IOException, SecurityException, ClassNotFoundException, InstantiationException {
if (!files.isEmpty()) {
if (VERSION.SDK_INT >= 19) {
MultiDex.V19.install(loader, files, dexDir);
} else if (VERSION.SDK_INT >= 14) {
MultiDex.V14.install(loader, files);
} else {
MultiDex.V4.install(loader, files);
}
}
}
install：将每一个.zip转化为DexPathList.Element，添加到DexPathList的elements字段中
static void install(ClassLoader loader, List<? extends File> additionalClassPathEntries, File optimizedDirectory) throws IllegalArgumentException, IllegalAccessException, NoSuchFieldException, InvocationTargetException, NoSuchMethodException, IOException {
Field pathListField = MultiDex.findField(loader, "pathList");
Object dexPathList = pathListField.get(loader);
ArrayList<IOException> suppressedExceptions = new ArrayList();
MultiDex.expandFieldArray(dexPathList, "dexElements", makeDexElements(dexPathList, new ArrayList(additionalClassPathEntries), optimizedDirectory, suppressedExceptions));
if (suppressedExceptions.size() > 0) {
Iterator var6 = suppressedExceptions.iterator();
while(var6.hasNext()) {
IOException e = (IOException)var6.next();
Log.w("MultiDex", "Exception in makeDexElement", e);
}
Field suppressedExceptionsField = MultiDex.findField(dexPathList, "dexElementsSuppressedExceptions");
IOException[] dexElementsSuppressedExceptions = (IOException[])((IOException[])suppressedExceptionsField.get(dexPathList));
if (dexElementsSuppressedExceptions == null) {
dexElementsSuppressedExceptions = (IOException[])suppressedExceptions.toArray(new IOException[suppressedExceptions.size()]);
} else {
IOException[] combined = new IOException[suppressedExceptions.size() + dexElementsSuppressedExceptions.length];
suppressedExceptions.toArray(combined);
System.arraycopy(dexElementsSuppressedExceptions, 0, combined, suppressedExceptions.size(), dexElementsSuppressedExceptions.length);
dexElementsSuppressedExceptions = combined;
}
suppressedExceptionsField.set(dexPathList, dexElementsSuppressedExceptions);
IOException exception = new IOException("I/O exception during makeDexElement");
exception.initCause((Throwable)suppressedExceptions.get(0));
throw exception;
}
}
标签：files,Log,MultiDex,IOException,new,解析,data 来源： https://www.cnblogs.com/wnpp/p/14190479.html