Load DEX file dynamically on Android 5.0

android, android-runtime, classloader, dex, dex2oat

Solution

Update

This works both on Dalvik and ART: `new DexClassLoader(jarredDex.getAbsolutePath(), context.getDir("outdex", Context.MODE_PRIVATE).getAbsolutePath(), null, context.getClassLoader());` where `jarredDex` is a jar-file with `classes.dex`. Jar can be obtained by running `dx --dex --output=filename.jar your/classes/dir`.

Original answer

I've took a code sample from this article. But ART uses `PathClassLoader` instead of Dalvik's `DexClassLoader`. This code is tested on emulator with Android 6 and on Xiaomi with Android 5.1 and works fine:

// Before the secondary dex file can be processed by the DexClassLoader,
// it has to be first copied from asset resource to a storage location.
File dexInternalStoragePath = new File(getDir("dex", Context.MODE_PRIVATE), SECONDARY_DEX_NAME);
try (BufferedInputStream bis = new BufferedInputStream(getAssets().open(SECONDARY_DEX_NAME));
     OutputStream dexWriter = new BufferedOutputStream(new FileOutputStream(dexInternalStoragePath))) {

    byte[] buf = new byte[BUF_SIZE];
    int len;
    while((len = bis.read(buf, 0, BUF_SIZE)) > 0) {
        dexWriter.write(buf, 0, len);
    }
} catch (IOException e) {
    throw new RuntimeException(e);
}

try {
    PathClassLoader loader = new PathClassLoader(dexInternalStoragePath.getAbsolutePath(), getClassLoader());
    Class<?> toasterClass = loader.loadClass("my.package.ToasterImpl");
    Toaster toaster = (Toaster) toasterClass.newInstance();
    toaster.show(this, "Success!");
} catch (ReflectiveOperationException e) {
    throw new RuntimeException(e);
}

Problem

Prior to Android 5.0 I was able to load DEX files dynamically using DexClassLoader and calling `loadClass()` method but with the latest Android version I get a `ClassNotFoundException`. Here is what I am doing: Generate DEX file. ``` ../android-sdk/android-sdk-linux_86/build-tools/21.1.1/dx --dex --output=bin/output.dex bin/output.jar ``` Create a DexClassLoader. ``` DexClassLoader cl = new DexClassLoader( dexFile.getAbsolutePath(), odexFile.getAbsolutePath(), null, mContext.getClassLoader()); ``` Call `cl.loadClass("myMethod");` I am aware that ART uses dex2oat to generate an ELF file that is the loaded by ART but in step 2 I am generating an ODEX file so I am not what needs to be done in ART to load a DEX file at runtime, can anyone help me ?

Original source