Eclipse版本android 65535解决方案(原理等同android studio现在的分包方式)

　　由于工作的需要看了下Eclipse下android65535的解决方案，查了好多文档，真心的发自内心的说一句请不要再拷贝别人的博客了，害人，真害人。

　　

　　接下来我说下我的实现方式，首先说下65535的最可能的触发原因(三方jar用的太多了)

　　首先：合并jar.

　　这里合并到jar使用的事ant的脚本，如何你电脑安装了ant，那ok，如果没有安装这里也不啰嗦告诉你怎么安装了，百度一下吧，安装总的来说没啥技术含量。安装ant之后配置如下脚本文件。

　　

<?xml version="1.0" encoding="utf-8"?>  
<project name="b" basedir="E:\libs\all" default="makeSuperJar">  
<target name="makeSuperJar"  description="description">  
    <jar destfile="all.jar">  
    	<zipfileset src="Android_Location_V1.1.2.jar"/>   
        <zipfileset src="Android_Map_2.1.4.jar"/>          
        <zipfileset src="Android_Services_2.1.4.jar"/>
        <zipfileset src="commons-net-3.3.jar"/>
        <zipfileset src="gson-2.2.1.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。 

　　然后将合并的jar转换成dex文件，怎么找到dx工具，见图

 

　　直接在当前路径下执行cmd命令，然后输入dx --dex --output=E:\libs\classes.dex E:\libs\all.jar，这里我写的是我自己的路径。输出文件为classes.dex,由于apk默认会将项目中的class文件编译成classes.dex，所以这里你需要更改下你的输出文件名，这里这个名字要有规范，严格的命名classes2.dex,classes3.dex.....,至于为什么，这是MultiDex的自己要求的，这里是仿Android sutudio的分包方式，请严格执行。

之后将classes.dex文件放置到项目的src目录下即可。

　　现在执行你还差最后一步导入MutiDex类库，你可以在网上去下载，或者直接copy我下边的代码，这里最主要想说的是如何使用

　　在你的项目的Application类中配置如下代码：

public class MyApplication extends Application{
    
    @Override
    protected void attachBaseContext(Context base) {
        // TODO Auto-generated method stub
        super.attachBaseContext(base);
        MultiDex.install(this);
        
    }
}

　　 到这里基本上配置算是完成了，this all over.

　　一下是类库MultiDex的类库Code，有需要的直接拷贝即可，这里不作为关键点来分析

　　MultiDex类：

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.support.multidex;

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;

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;

/**
 * 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

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.support.multidex;

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

/**
 * Minimal MultiDex capable application. To use the legacy multidex library there is 3 possibility:
 * <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>
 *   <ul>
 */
public class MultiDexApplication extends Application {
  @Override
  protected void attachBaseContext(Context base) {
    super.attachBaseContext(base);
    MultiDex.install(this);
  }
}

MultiDexExtractor类

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.support.multidex;

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

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;

/**
 * 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

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/* Apache Harmony HEADER because the code in this class comes mostly from ZipFile, ZipEntry and
 * ZipConstants from android libcore.
 */

package android.support.multidex;

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();
    }
}