在Android 5.0上动态加载DEX文件 [英] Load DEX file dynamically on Android 5.0

问题描述

在Android 5.0之前，我能够使用DexClassLoader动态加载DEX文件并调用 loadClass（）方法，但是在最新的Android版本中，我得到了 ClassNotFoundException 。

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.

这是我在做什么：

1. 生成DEX文件。

1. Generate DEX file.

../android-sdk/android-sdk-linux_86/build-tools/21.1.1/dx --dex --output=bin/output.dex  bin/output.jar

创建一个DexClassLoader。

Create a DexClassLoader.

DexClassLoader cl = new DexClassLoader(
dexFile.getAbsolutePath(),
odexFile.getAbsolutePath(),
null,
mContext.getClassLoader());

调用 cl.loadClass（ myMethod）;

我知道ART使用dex2oat生成由ART加载的ELF文件但在第2步中，我正在生成ODEX文件，因此我不需要在ART中完成在运行时加载DEX文件的操作，有人可以帮助我吗？

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 ?

推荐答案

更新

这对Dalvik和ART均有效： new DexClassLoader（jarredDex.getAbsolutePath（），上下文。 getDir（ outdex，Context.MODE_PRIVATE）.getAbsolutePath（），null，context.getClassLoader（））; 其中， jarredDex 是一个jar- classes.dex 的文件。可以通过运行 dx --dex --output = filename.jar your / classes / dir 来获得Jar。

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.

我已经从本文。但是ART使用 PathClassLoader 代替了Dalvik的 DexClassLoader 。这段代码已经在Android 6的模拟器上以及在Android 5.1的小米上进行了测试，并且可以正常工作：

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);
}

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