解决android eclipse方法超出65535的问题

    开发了一个项目，不断加功能，终于遇到了个问题，就是方法数量超过65536个了。这就尴尬了，这个功能有必须要，其他的该删的都删了。从网上找了很多方法，试了感觉不完整，不知道是个人理解不够还是别的原因，反正这次记录一下，以便下次需要，又忘记了。

1、首先得装好ant，这个ant配置安装网上一大把，就过了；

2、然后弄个xml文件，格式如下：

<?xml version="1.0" encoding="utf-8"?>  

<project name="libs" basedir="D:\all" default="makeSuperJar">  

<target name="makeSuperJar"  description="description">  

    <jar destfile="libs.jar">  

    <zipfileset src="alipaySdk-20160803.jar"/>   

        <zipfileset src="BaiduLBS_Android.jar"/>          

        <zipfileset src="gson-2.2.2.jar"/>

        <zipfileset src="httpmime-4.1.2.jar"/>

        <zipfileset src="javacv.jar"/>

        <zipfileset src="javacpp.jar"/>

        <zipfileset src="jg_filter_sdk_1.1.jar"/>
<zipfileset src="libammsdk.jar"/>

        <zipfileset src="MobCommons-2016.1107.1809.jar"/>

        <zipfileset src="MobTools-2016.1107.1809.jar"/>

        <zipfileset src="Msc.jar"/>

        <zipfileset src="ormlite-android-4.48.jar"/>

        <zipfileset src="ormlite-core-4.48.jar"/>

        <zipfileset src="ormlite-jdbc-4.48.jar"/>

        <zipfileset src="ShareSDK-Core-2.7.10.jar"/>

        <zipfileset src="ShareSDK-QQ-2.7.10.jar"/>

        <zipfileset src="ShareSDK-QZone-2.7.10.jar"/>

        <zipfileset src="ShareSDK-ShortMessage-2.7.10.jar"/>

        <zipfileset src="ShareSDK-SinaWeibo-2.7.10.jar"/>

        <zipfileset src="ShareSDK-Wechat-2.7.10.jar"/>

        <zipfileset src="ShareSDK-Wechat-Core-2.7.10.jar"/>

        <zipfileset src="ShareSDK-Wechat-Moments-2.7.10.jar"/>

        <zipfileset src="Xg_sdk_v2.43_20160308_1031.jar"/>

        <zipfileset src="zxing.jar"/>

    </jar>  

</target>  

</project>

这里你只需要改下你的basedir目录地址,destfile输出文件的名字和zipfileset你需要合并的jar即可

。这里一定要注意上面的配置文件和要合并的包在同一个目录下，不然会报无法找到project all的错

3、准备条件做好了以后，打开dos，输入ant -buildfile D:libs\b.xml 这时如果成功了就会D盘all目录下就会出现libs.jar包

4、将打好jar包 项目--右键--Build Path --Configure Build Path --- Libraries ---AddExternal JARs导入，删除以前libs下面的包，前提是这些包都在2中xml里有，

5、生成dex文件,先用dos进入到sdk\build-tools\21.0.0目录下，后面的21.0.0是可以不同的，然后输入dx --dex --output=D:\classes.dex D:\all\libs.jar
，这里libs.jar 是3生成的jar包，成功了就会生成classes.dex文件在D盘根目录下，将文件重命名为classes2.dex直接复制到项目src目录即可。

6、OK，这里到执行还差重要的一步了就是导入MutiDex类库，这个网上一大把，这个文章中有这个类库代码，也是我参照的文章http://www.mamicode.com/info-detail-1578920.html。我这里就多此一举了：

MultiDex类

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.ListIterator;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.zip.ZipFile;

import android.app.Application;
import android.content.Context;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.os.Build;
import android.util.Log;
import dalvik.system.DexFile;

/**
* Monkey patches {@link Context#getClassLoader() the application context class
* loader} in order to load classes from more than one dex file. The primary
* {@code classes.dex} must contain the classes necessary for calling this
* class methods. Secondary dex files named classes2.dex, classes3.dex... found
* in the application apk will be added to the classloader after first call to
* {@link #install(Context)}.
*
* <p/>
* This library provides compatibility for platforms with API level 4 through 20. This library does
* nothing on newer versions of the platform which provide built-in support for secondary dex files.
*/
public final class MultiDex {

static final String TAG = "MultiDex";

private static final String OLD_SECONDARY_FOLDER_NAME = "secondary-dexes";

private static final String SECONDARY_FOLDER_NAME = "code_cache" + File.separator +
"secondary-dexes";

private static final int MAX_SUPPORTED_SDK_VERSION = 20;

private static final int MIN_SDK_VERSION = 4;

private static final int VM_WITH_MULTIDEX_VERSION_MAJOR = 2;

private static final int VM_WITH_MULTIDEX_VERSION_MINOR = 1;

private static final Set<String> installedApk = new HashSet<String>();

private static final boolean IS_VM_MULTIDEX_CAPABLE =
isVMMultidexCapable(System.getProperty("java.vm.version"));

private MultiDex() {}

/**
* Patches the application context class loader by appending extra dex files
* loaded from the application apk. This method should be called in the
* attachBaseContext of your {@link Application}, see
* {@link MultiDexApplication} for more explanation and an example.
*
* @param context application context.
* @throws RuntimeException if an error occurred preventing the classloader
* extension.
*/
public static void install(Context context) {
Log.i(TAG, "install");
if (IS_VM_MULTIDEX_CAPABLE) {
Log.i(TAG, "VM has multidex support, MultiDex support library is disabled.");
return;
}

if (Build.VERSION.SDK_INT < MIN_SDK_VERSION) {
throw new RuntimeException("Multi dex installation failed. SDK " + Build.VERSION.SDK_INT
+ " is unsupported. Min SDK version is " + MIN_SDK_VERSION + ".");
}

try {
ApplicationInfo applicationInfo = getApplicationInfo(context);
if (applicationInfo == null) {
// Looks like running on a test Context, so just return without patching.
return;
}

synchronized (installedApk) {
String apkPath = applicationInfo.sourceDir;
if (installedApk.contains(apkPath)) {
return;
}
installedApk.add(apkPath);

if (Build.VERSION.SDK_INT > MAX_SUPPORTED_SDK_VERSION) {
Log.w(TAG, "MultiDex is not guaranteed to work in SDK version "
+ Build.VERSION.SDK_INT + ": SDK version higher than "
+ MAX_SUPPORTED_SDK_VERSION + " 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") + "\"");
}

/* 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.
*/
ClassLoader loader;
try {
loader = context.getClassLoader();
} catch (RuntimeException e) {
/* Ignore those exceptions so that we don‘t break tests relying on Context like
* a android.test.mock.MockContext or a android.content.ContextWrapper with a
* null base Context.
*/
Log.w(TAG, "Failure while trying to obtain Context class loader. " +
"Must be running in test mode. Skip patching.", e);
return;
}
if (loader == null) {
// Note, the context class loader is null when running Robolectric tests.
Log.e(TAG,
"Context class loader is null. Must be running in test mode. "
+ "Skip patching.");
return;
}

try {
clearOldDexDir(context);
} catch (Throwable t) {
Log.w(TAG, "Something went wrong when trying to clear old MultiDex extraction, "
+ "continuing without cleaning.", t);
}

File dexDir = new File(applicationInfo.dataDir, SECONDARY_FOLDER_NAME);
List<File> files = MultiDexExtractor.load(context, applicationInfo, dexDir, false);
if (checkValidZipFiles(files)) {
installSecondaryDexes(loader, dexDir, files);
} else {
Log.w(TAG, "Files were not valid zip files. Forcing a reload.");
// Try again, but this time force a reload of the zip file.
files = MultiDexExtractor.load(context, applicationInfo, dexDir, true);

if (checkValidZipFiles(files)) {
installSecondaryDexes(loader, dexDir, files);
} else {
// Second time didn‘t work, give up
throw new RuntimeException("Zip files were not valid.");
}
}
}

} catch (Exception e) {
Log.e(TAG, "Multidex installation failure", e);
throw new RuntimeException("Multi dex installation failed (" + e.getMessage() + ").");
}
Log.i(TAG, "install done");
}

private static ApplicationInfo getApplicationInfo(Context context)
throws NameNotFoundException {
PackageManager pm;
String packageName;
try {
pm = context.getPackageManager();
packageName = context.getPackageName();
} catch (RuntimeException e) {
/* Ignore those exceptions so that we don‘t break tests relying on Context like
* a android.test.mock.MockContext or a android.content.ContextWrapper with a null
* base Context.
*/
Log.w(TAG, "Failure while trying to obtain ApplicationInfo from Context. " +
"Must be running in test mode. Skip patching.", e);
return null;
}
if (pm == null || packageName == null) {
// This is most likely a mock context, so just return without patching.
return null;
}
ApplicationInfo applicationInfo =
pm.getApplicationInfo(packageName, PackageManager.GET_META_DATA);
return applicationInfo;
}

/**
* Identifies if the current VM has a native support for multidex, meaning there is no need for
* additional installation by this library.
* @return true if the VM handles multidex
*/
/* package visible for test */
static boolean isVMMultidexCapable(String versionString) {
boolean isMultidexCapable = false;
if (versionString != null) {
Matcher matcher = Pattern.compile("(\\d+)\\.(\\d+)(\\.\\d+)?").matcher(versionString);
if (matcher.matches()) {
try {
int major = Integer.parseInt(matcher.group(1));
int minor = Integer.parseInt(matcher.group(2));
isMultidexCapable = (major > VM_WITH_MULTIDEX_VERSION_MAJOR)
|| ((major == VM_WITH_MULTIDEX_VERSION_MAJOR)
&& (minor >= VM_WITH_MULTIDEX_VERSION_MINOR));
} catch (NumberFormatException e) {
// let isMultidexCapable be false
}
}
}
Log.i(TAG, "VM with version " + versionString +
(isMultidexCapable ?
" has multidex support" :
" does not have multidex support"));
return isMultidexCapable;
}

private static void installSecondaryDexes(ClassLoader loader, File dexDir, List<File> files)
throws IllegalArgumentException, IllegalAccessException, NoSuchFieldException,
InvocationTargetException, NoSuchMethodException, IOException {
if (!files.isEmpty()) {
if (Build.VERSION.SDK_INT >= 19) {
V19.install(loader, files, dexDir);
} else if (Build.VERSION.SDK_INT >= 14) {
V14.install(loader, files, dexDir);
} else {
V4.install(loader, files);
}
}
}

/**
* Returns whether all files in the list are valid zip files. If {@code files} is empty, then
* returns true.
*/
private static boolean checkValidZipFiles(List<File> files) {
for (File file : files) {
if (!MultiDexExtractor.verifyZipFile(file)) {
return false;
}
}
return true;
}

/**
* 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
*/
private 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());
}

/**
* Locates a given method anywhere in the class inheritance hierarchy.
*
* @param instance an object to search the method into.
* @param name method name
* @param parameterTypes method parameter types
* @return a method object
* @throws NoSuchMethodException if the method cannot be located
*/
private static Method findMethod(Object instance, String name, Class<?>... parameterTypes)
throws NoSuchMethodException {
for (Class<?> clazz = instance.getClass(); clazz != null; clazz = clazz.getSuperclass()) {
try {
Method method = clazz.getDeclaredMethod(name, parameterTypes);

if (!method.isAccessible()) {
method.setAccessible(true);
}

return method;
} catch (NoSuchMethodException e) {
// ignore and search next
}
}

throw new NoSuchMethodException("Method " + name + " with parameters " +
Arrays.asList(parameterTypes) + " not found in " + instance.getClass());
}

/**
* 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.
*/
private 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);
System.arraycopy(original, 0, combined, 0, original.length);
System.arraycopy(extraElements, 0, combined, original.length, extraElements.length);
jlrField.set(instance, combined);
}

private static void clearOldDexDir(Context context) throws Exception {
File dexDir = new File(context.getFilesDir(), OLD_SECONDARY_FOLDER_NAME);
if (dexDir.isDirectory()) {
Log.i(TAG, "Clearing old secondary dex dir (" + dexDir.getPath() + ").");
File[] files = dexDir.listFiles();
if (files == null) {
Log.w(TAG, "Failed to list secondary dex dir content (" + dexDir.getPath() + ").");
return;
}
for (File oldFile : files) {
Log.i(TAG, "Trying to delete old file " + oldFile.getPath() + " of size "
+ oldFile.length());
if (!oldFile.delete()) {
Log.w(TAG, "Failed to delete old file " + oldFile.getPath());
} else {
Log.i(TAG, "Deleted old file " + oldFile.getPath());
}
}
if (!dexDir.delete()) {
Log.w(TAG, "Failed to delete secondary dex dir " + dexDir.getPath());
} else {
Log.i(TAG, "Deleted old secondary dex dir " + dexDir.getPath());
}
}
}

/**
* Installer for platform versions 19.
*/
private static final class V19 {

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 = findField(loader, "pathList");
Object dexPathList = pathListField.get(loader);
ArrayList<IOException> suppressedExceptions = new ArrayList<IOException>();
expandFieldArray(dexPathList, "dexElements", makeDexElements(dexPathList,
new ArrayList<File>(additionalClassPathEntries), optimizedDirectory,
suppressedExceptions));
if (suppressedExceptions.size() > 0) {
for (IOException e : suppressedExceptions) {
Log.w(TAG, "Exception in makeDexElement", e);
}
Field suppressedExceptionsField =
findField(loader, "dexElementsSuppressedExceptions");
IOException[] dexElementsSuppressedExceptions =
(IOException[]) suppressedExceptionsField.get(loader);

if (dexElementsSuppressedExceptions == null) {
dexElementsSuppressedExceptions =
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(loader, dexElementsSuppressedExceptions);
}
}

/**
* A wrapper around
* {@code private static final dalvik.system.DexPathList#makeDexElements}.
*/
private static Object[] makeDexElements(
Object dexPathList, ArrayList<File> files, File optimizedDirectory,
ArrayList<IOException> suppressedExceptions)
throws IllegalAccessException, InvocationTargetException,
NoSuchMethodException {
Method makeDexElements =
findMethod(dexPathList, "makeDexElements", ArrayList.class, File.class,
ArrayList.class);

return (Object[]) makeDexElements.invoke(dexPathList, files, optimizedDirectory,
suppressedExceptions);
}
}

/**
* Installer for platform versions 14, 15, 16, 17 and 18.
*/
private static final class V14 {

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 = findField(loader, "pathList");
Object dexPathList = pathListField.get(loader);
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 =
findMethod(dexPathList, "makeDexElements", ArrayList.class, File.class);

return (Object[]) makeDexElements.invoke(dexPathList, files, optimizedDirectory);
}
}

/**
* Installer for platform versions 4 to 13.
*/
private static final class V4 {
private static void install(ClassLoader loader, List<File> additionalClassPathEntries)
throws IllegalArgumentException, IllegalAccessException,
NoSuchFieldException, IOException {
/* The patched class loader is expected to be a descendant of
* dalvik.system.DexClassLoader. We modify its
* fields mPaths, mFiles, mZips and mDexs to append additional DEX
* file entries.
*/
int extraSize = additionalClassPathEntries.size();

Field pathField = 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);
extraDexs[index] = DexFile.loadDex(entryPath, entryPath + ".dex", 0);
}

pathField.set(loader, path.toString());
expandFieldArray(loader, "mPaths", extraPaths);
expandFieldArray(loader, "mFiles", extraFiles);
expandFieldArray(loader, "mZips", extraZips);
expandFieldArray(loader, "mDexs", extraDexs);
}
}

}MultiDexApplication类

import android.app.Application;
import android.content.Context;

/**
* * Minimal MultiDex capable application. To use the legacy multidex library
* there is 3 possibility: 24 *
* <ul>
* *
* <li>Declare this class as the application in your AndroidManifest.xml.</li>
* *
* <li>Have your {@link Application} extends this class.</li>
* *
* <li>Have your {@link Application} override attachBaseContext starting with<br>
* * <code>
protected void attachBaseContext(Context base) {<br>
super.attachBaseContext(base);<br>
MultiDex.install(this);
</code></li> 3 *
* <ul>
*/
public class MultiDexApplication extends Application {
@Override
protected void attachBaseContext(Context base) {
super.attachBaseContext(base);
MultiDex.install(this);
}
}

MultiDexExtractor类

import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.File;
import java.io.FileFilter;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipException;
import java.util.zip.ZipFile;
import java.util.zip.ZipOutputStream;

import android.content.Context;
import android.content.SharedPreferences;
import android.content.pm.ApplicationInfo;
import android.os.Build;
import android.util.Log;

/**
* Exposes application secondary dex files as files in the application data
* directory.
*/
final class MultiDexExtractor {

private static final String TAG = MultiDex.TAG;

/**
* We look for additional dex files named {@code classes2.dex},
* {@code classes3.dex}, etc.
*/
private static final String DEX_PREFIX = "classes";
private static final String DEX_SUFFIX = ".dex";

private static final String EXTRACTED_NAME_EXT = ".classes";
private static final String EXTRACTED_SUFFIX = ".zip";
private static final int MAX_EXTRACT_ATTEMPTS = 3;

private static final String PREFS_FILE = "multidex.version";
private static final String KEY_TIME_STAMP = "timestamp";
private static final String KEY_CRC = "crc";
private static final String KEY_DEX_NUMBER = "dex.number";

/**
* Size of reading buffers.
*/
private static final int BUFFER_SIZE = 0x4000;
/* Keep value away from 0 because it is a too probable time stamp value */
private static final long NO_VALUE = -1L;

/**
* Extracts application secondary dexes into files in the application data
* directory.
*
* @return a list of files that were created. The list may be empty if there
*         are no secondary dex files.
* @throws IOException
*             if encounters a problem while reading or writing secondary
*             dex files
*/
static List<File> load(Context context, ApplicationInfo applicationInfo,
File dexDir, boolean forceReload) throws IOException {
Log.i(TAG, "MultiDexExtractor.load(" + applicationInfo.sourceDir + ", "
+ forceReload + ")");
final File sourceApk = new File(applicationInfo.sourceDir);
long currentCrc = getZipCrc(sourceApk);

List<File> files;
if (!forceReload && !isModified(context, sourceApk, currentCrc)) {
try {
files = loadExistingExtractions(context, sourceApk, dexDir);
} catch (IOException ioe) {
Log.w(TAG,
"Failed to reload existing extracted secondary dex files,"
+ " falling back to fresh extraction", ioe);
files = performExtractions(sourceApk, dexDir);
putStoredApkInfo(context, getTimeStamp(sourceApk), currentCrc,
files.size() + 1);

}
} else {
Log.i(TAG, "Detected that extraction must be performed.");
files = performExtractions(sourceApk, dexDir);
putStoredApkInfo(context, getTimeStamp(sourceApk), currentCrc,
files.size() + 1);
}

Log.i(TAG, "load found " + files.size() + " secondary dex files");
return files;
}

private static List<File> loadExistingExtractions(Context context,
File sourceApk, File dexDir) throws IOException {
Log.i(TAG, "loading existing secondary dex files");

final String extractedFilePrefix = sourceApk.getName()
+ EXTRACTED_NAME_EXT;
int totalDexNumber = getMultiDexPreferences(context).getInt(
KEY_DEX_NUMBER, 1);
final List<File> files = new ArrayList<File>(totalDexNumber);

for (int secondaryNumber = 2; secondaryNumber <= totalDexNumber; secondaryNumber++) {
String fileName = extractedFilePrefix + secondaryNumber
+ EXTRACTED_SUFFIX;
File extractedFile = new File(dexDir, fileName);
if (extractedFile.isFile()) {
files.add(extractedFile);
if (!verifyZipFile(extractedFile)) {
Log.i(TAG, "Invalid zip file: " + extractedFile);
throw new IOException("Invalid ZIP file.");
}
} else {
throw new IOException("Missing extracted secondary dex file ‘"
+ extractedFile.getPath() + "‘");
}
}

return files;
}

private static boolean isModified(Context context, File archive,
long currentCrc) {
SharedPreferences prefs = getMultiDexPreferences(context);
return (prefs.getLong(KEY_TIME_STAMP, NO_VALUE) != getTimeStamp(archive))
|| (prefs.getLong(KEY_CRC, NO_VALUE) != currentCrc);
}

private static long getTimeStamp(File archive) {
long timeStamp = archive.lastModified();
if (timeStamp == NO_VALUE) {
// never return NO_VALUE
timeStamp--;
}
return timeStamp;
}

private static long getZipCrc(File archive) throws IOException {
long computedValue = ZipUtil.getZipCrc(archive);
if (computedValue == NO_VALUE) {
// never return NO_VALUE
computedValue--;
}
return computedValue;
}

private static List<File> performExtractions(File sourceApk, File dexDir)
throws IOException {

final String extractedFilePrefix = sourceApk.getName()
+ EXTRACTED_NAME_EXT;

// Ensure that whatever deletions happen in prepareDexDir only happen if
// the zip that
// contains a secondary dex file in there is not consistent with the
// latest apk. Otherwise,
// multi-process race conditions can cause a crash loop where one
// process deletes the zip
// while another had created it.
prepareDexDir(dexDir, extractedFilePrefix);

List<File> files = new ArrayList<File>();

final ZipFile apk = new ZipFile(sourceApk);
try {

int secondaryNumber = 2;

ZipEntry dexFile = apk.getEntry(DEX_PREFIX + secondaryNumber
+ DEX_SUFFIX);
while (dexFile != null) {
String fileName = extractedFilePrefix + secondaryNumber
+ EXTRACTED_SUFFIX;
File extractedFile = new File(dexDir, fileName);
files.add(extractedFile);

Log.i(TAG, "Extraction is needed for file " + extractedFile);
int numAttempts = 0;
boolean isExtractionSuccessful = false;
while (numAttempts < MAX_EXTRACT_ATTEMPTS
&& !isExtractionSuccessful) {
numAttempts++;

// Create a zip file (extractedFile) containing only the
// secondary dex file
// (dexFile) from the apk.
extract(apk, dexFile, extractedFile, extractedFilePrefix);

// Verify that the extracted file is indeed a zip file.
isExtractionSuccessful = verifyZipFile(extractedFile);

// Log the sha1 of the extracted zip file
Log.i(TAG, "Extraction "
+ (isExtractionSuccessful ? "success" : "failed")
+ " - length " + extractedFile.getAbsolutePath()
+ ": " + extractedFile.length());
if (!isExtractionSuccessful) {
// Delete the extracted file
extractedFile.delete();
if (extractedFile.exists()) {
Log.w(TAG,
"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++;
dexFile = apk.getEntry(DEX_PREFIX + secondaryNumber
+ DEX_SUFFIX);
}
} finally {
try {
apk.close();
} catch (IOException e) {
Log.w(TAG, "Failed to close resource", e);
}
}

return files;
}

private static void putStoredApkInfo(Context context, long timeStamp,
long crc, int totalDexNumber) {
SharedPreferences prefs = getMultiDexPreferences(context);
SharedPreferences.Editor edit = prefs.edit();
edit.putLong(KEY_TIME_STAMP, timeStamp);
edit.putLong(KEY_CRC, crc);
/*
* SharedPreferences.Editor doc says that apply() and commit()
* "atomically performs the requested modifications" it should be OK to
* rely on saving the dex files number (getting old number value would
* go along with old crc and time stamp).
*/
edit.putInt(KEY_DEX_NUMBER, totalDexNumber);
apply(edit);
}

private static 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);
}

/**
* This removes any files that do not have the correct prefix.
*/
private static void prepareDexDir(File dexDir,
final String extractedFilePrefix) throws IOException {
dexDir.mkdirs();
if (!dexDir.isDirectory()) {
throw new IOException("Failed to create dex directory "
+ dexDir.getPath());
}

// Clean possible old files
FileFilter filter = new FileFilter() {

@Override
public boolean accept(File pathname) {
return !pathname.getName().startsWith(extractedFilePrefix);
}
};
File[] files = dexDir.listFiles(filter);
if (files == null) {
Log.w(TAG,
"Failed to list secondary dex dir content ("
+ dexDir.getPath() + ").");
return;
}
for (File oldFile : files) {
Log.i(TAG, "Trying to delete old file " + oldFile.getPath()
+ " of size " + oldFile.length());
if (!oldFile.delete()) {
Log.w(TAG, "Failed to delete old file " + oldFile.getPath());
} else {
Log.i(TAG, "Deleted old file " + oldFile.getPath());
}
}
}

private static void extract(ZipFile apk, ZipEntry dexFile, File extractTo,
String extractedFilePrefix) throws IOException,
FileNotFoundException {

InputStream in = apk.getInputStream(dexFile);
ZipOutputStream out = null;
File tmp = File.createTempFile(extractedFilePrefix, EXTRACTED_SUFFIX,
extractTo.getParentFile());
Log.i(TAG, "Extracting " + tmp.getPath());
try {
out = new ZipOutputStream(new BufferedOutputStream(
new FileOutputStream(tmp)));
try {
ZipEntry classesDex = new ZipEntry("classes.dex");
// keep zip entry time since it is the criteria used by Dalvik
classesDex.setTime(dexFile.getTime());
out.putNextEntry(classesDex);

byte[] buffer = new byte[BUFFER_SIZE];
int length = in.read(buffer);
while (length != -1) {
out.write(buffer, 0, length);
length = in.read(buffer);
}
out.closeEntry();
} finally {
out.close();
}
Log.i(TAG, "Renaming to " + extractTo.getPath());
if (!tmp.renameTo(extractTo)) {
throw new IOException("Failed to rename \""
+ tmp.getAbsolutePath() + "\" to \""
+ extractTo.getAbsolutePath() + "\"");
}
} finally {
closeQuietly(in);
tmp.delete(); // return status ignored
}
}

/**
* Returns whether the file is a valid zip file.
*/
static boolean verifyZipFile(File file) {
try {
ZipFile zipFile = new ZipFile(file);
try {
zipFile.close();
return true;
} catch (IOException e) {
Log.w(TAG,
"Failed to close zip file: " + file.getAbsolutePath());
}
} catch (ZipException ex) {
Log.w(TAG, "File " + file.getAbsolutePath()
+ " is not a valid zip file.", ex);
} catch (IOException ex) {
Log.w(TAG,
"Got an IOException trying to open zip file: "
+ file.getAbsolutePath(), ex);
}
return false;
}

/**
* Closes the given {@code Closeable}. Suppresses any IO exceptions.
*/
private static void closeQuietly(Closeable closeable) {
try {
closeable.close();
} catch (IOException e) {
Log.w(TAG, "Failed to close resource", e);
}
}

// The following is taken from SharedPreferencesCompat to avoid having a
// dependency of the
// multidex support library on another support library.
private static Method sApplyMethod; // final
static {
try {
Class<?> cls = SharedPreferences.Editor.class;
sApplyMethod = cls.getMethod("apply");
} catch (NoSuchMethodException unused) {
sApplyMethod = null;
}
}

private static void apply(SharedPreferences.Editor editor) {
if (sApplyMethod != null) {
try {
sApplyMethod.invoke(editor);
return;
} catch (InvocationTargetException unused) {
// fall through
} catch (IllegalAccessException unused) {
// fall through
}
}
editor.commit();
}
}

ZipUtil类

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.zip.CRC32;
import java.util.zip.ZipException;

/**
* Tools to build a quick partial crc of zip files.
*/
final class ZipUtil {
static class CentralDirectory {
long offset;
long size;
}

/* redefine those constant here because of bug 13721174 preventing to compile using the
* constants defined in ZipFile */
private static final int ENDHDR = 22;
private static final int ENDSIG = 0x6054b50;

/**
* Size of reading buffers.
*/
private static final int BUFFER_SIZE = 0x4000;

/**
* Compute crc32 of the central directory of an apk. The central directory contains
* the crc32 of each entries in the zip so the computed result is considered valid for the whole
* zip file. Does not support zip64 nor multidisk but it should be OK for now since ZipFile does
* not either.
*/
static long getZipCrc(File apk) throws IOException {
RandomAccessFile raf = new RandomAccessFile(apk, "r");
try {
CentralDirectory dir = findCentralDirectory(raf);

return computeCrcOfCentralDir(raf, dir);
} finally {
raf.close();
}
}

/* Package visible for testing */
static CentralDirectory findCentralDirectory(RandomAccessFile raf) throws IOException,
ZipException {
long scanOffset = raf.length() - ENDHDR;
if (scanOffset < 0) {
throw new ZipException("File too short to be a zip file: " + raf.length());
}

long stopOffset = scanOffset - 0x10000 /* ".ZIP file comment"‘s max length */;
if (stopOffset < 0) {
stopOffset = 0;
}

int endSig = Integer.reverseBytes(ENDSIG);
while (true) {
raf.seek(scanOffset);
if (raf.readInt() == endSig) {
break;
}

scanOffset--;
if (scanOffset < stopOffset) {
throw new ZipException("End Of Central Directory signature not found");
}
}
// Read the End Of Central Directory. ENDHDR includes the signature
// bytes,
// which we‘ve already read.

// Pull out the information we need.
raf.skipBytes(2); // diskNumber
raf.skipBytes(2); // diskWithCentralDir
raf.skipBytes(2); // numEntries
raf.skipBytes(2); // totalNumEntries
CentralDirectory dir = new CentralDirectory();
dir.size = Integer.reverseBytes(raf.readInt()) & 0xFFFFFFFFL;
dir.offset = Integer.reverseBytes(raf.readInt()) & 0xFFFFFFFFL;
return dir;
}

/* Package visible for testing */
static long computeCrcOfCentralDir(RandomAccessFile raf, CentralDirectory dir)
throws IOException {
CRC32 crc = new CRC32();
long stillToRead = dir.size;
raf.seek(dir.offset);
int length = (int) Math.min(BUFFER_SIZE, stillToRead);
byte[] buffer = new byte[BUFFER_SIZE];
length = raf.read(buffer, 0, length);
while (length != -1) {
crc.update(buffer, 0, length);
stillToRead -= length;
if (stillToRead == 0) {
break;
}
length = (int) Math.min(BUFFER_SIZE, stillToRead);
length = raf.read(buffer, 0, length);
}
return crc.getValue();
}
}

最后还是感谢这http://www.mamicode.com/info-detail-1578920.html、http://blog.csdn.net/lxlyhm/article/details/52608190这两篇文章博主