類的載入機制

需要注意的地方

• 1.每次生成之後一定要測試；
• 2.儘量的不要分包，不要分多個dex
• 3.混淆的時候，設計到NDK AndFix.java 不要混淆
• 4.生成包之後一般會加固什麼的，這個時候生成的差分包，一定要在之前去生成。
• 5.既然是去修復方法，第一個不能增加成員變數，不能增加方法

原始碼

public class FixDexManager {
    private Context mContext;
    private File mDexFile;
    private static final String TAG = FixDexManager.class.getSimpleName();
    private
 
 Object applicationDexElements;

    public FixDexManager(Context context) {
        this.mContext = context;
        //可以訪問的dex目錄
        mDexFile = context.getDir("odex", Context.MODE_PRIVATE);
    }

    /**
     * 修復dex包
     */
    public void fixDex(String fixDexPath) throws Exception {

        //2.獲取下載好的補丁 dexElement
 

        //2.1移動到系統能夠訪問的 dex目錄下
        File srcFile = new File(fixDexPath);
        if (!srcFile.exists()) {
            throw new FileNotFoundException(fixDexPath);
        }
        File destFile = new File(mDexFile, srcFile.getName());
        if (destFile.exists()) {
            Log.d(TAG, "patch ["
 
 + fixDexPath + "] has be loaded.");
            return;
        }
        copyFile(srcFile, destFile);
        //2.2ClassLoader讀取fileDex路徑
        List<File> fixDexFiles = new ArrayList<>();
        fixDexFiles.add(destFile);


    }

    /**
     * 把dexElement注入到classLoader
     */
    private void injectDexElement(ClassLoader classLoader, Object dexElements) throws Exception {
        //1.先獲取pathList
        Field pathListField = BaseDexClassLoader.class.getDeclaredField("pathList");
        //所有屬性都可以獲得
        pathListField.setAccessible(true);
        Object pathList = pathListField.get(classLoader);
        //2.獲得pathList中的dexElements
        Field dexElementsFiled = pathList.getClass().getDeclaredField("dexElements");
        dexElementsFiled.setAccessible(true);
        //注入
        dexElementsFiled.set(dexElementsFiled.get(pathList), dexElements);
    }

    /**
     * 合併陣列
     */
    private static Object combineArray(Object arrayLhs, Object arrayRhs) {
        Class<?> localClass = arrayLhs.getClass().getComponentType();//獲得陣列物件
        int i = Array.getLength(arrayLhs);
        int j = Array.getLength(arrayRhs);
        Object result = Array.newInstance(localClass, j);
        for (int k = 0; k < j; ++k) {
            if (k < i) {
                Array.set(result, k, Array.get(arrayLhs, k));
            } else {
                Array.set(result, k, Array.get(arrayLhs, k - 1));
            }
        }
        return result;
    }

    /**
     * 將路徑複製到目標檔案下
     */
    public static void copyFile(File src, File dest) throws IOException {
        FileChannel inChannel = null;
        FileChannel outChannel = null;
        try {
            if (!dest.exists()) {
                dest.createNewFile();
            }
            inChannel = new FileInputStream(src).getChannel();
            outChannel = new FileOutputStream(dest).getChannel();
            inChannel.transferTo(0, inChannel.size(), outChannel);
        } finally {
            if (inChannel != null) {
                inChannel.close();
            }
            if (outChannel != null) {
                outChannel.close();
            }
        }
    }

    /**
     * 從classLoader中獲取
     *
     * @param classLoader
     */
    private Object getDexElementsByClassLoader(ClassLoader classLoader) throws Exception {
        //1.先獲取pathList
        Field pathListField = BaseDexClassLoader.class.getDeclaredField("pathList");
        //所有屬性都可以獲得
        pathListField.setAccessible(true);
        Object pathList = pathListField.get(classLoader);
        //2.獲得pathList中的dexElements
        Field dexElementsFiled = pathList.getClass().getDeclaredField("dexElements");
        dexElementsFiled.setAccessible(true);
        return dexElementsFiled.get(pathList);
    }

    /**
     * 載入全部的修復包
     */
    public void loadFixDex() throws Exception {
        File[] dexFiles = mDexFile.listFiles();
        List<File> fixDexFiles = new ArrayList<>();
        for (File dexFile : dexFiles) {
            if (dexFile.getName().endsWith(".dex")) {
                fixDexFiles.add(dexFile);
            }
        }
        fixDexFiles(fixDexFiles);
    }

    /**
     * 修復dex
     */
    private void fixDexFiles(List<File> fixDexFiles) throws Exception {
        //1.先獲取已執行的dexElement
        ClassLoader applicationClassLoader = mContext.getClassLoader();
        Object dexElements = getDexElementsByClassLoader(applicationClassLoader);
        File optimizedDirectory = new File(mDexFile, "odex");
        if (!optimizedDirectory.exists()) {
            optimizedDirectory.mkdir();
        }
        //修復
        for (File fixDexFile : fixDexFiles) {

            ClassLoader fixDexClassLoader = new BaseDexClassLoader(
                    fixDexFile.getAbsolutePath(),//dex路徑 必須要在應用目錄下的dex檔案中
                    optimizedDirectory,//解壓路徑
                    null,//.so檔案的位置
                    applicationClassLoader//父classloader
            );
            Object fixDexElement = getDexElementsByClassLoader(fixDexClassLoader);

            //3.把補丁的dexElement插到已經執行好的dexElements的最前面
            //合併陣列
            applicationDexElements = combineArray(dexElements, fixDexElement);

        }
        //注入到原來的類中applicationClassLoader
        injectDexElement(applicationClassLoader, applicationDexElements);
    }
}