accessing to classes of app from dex file by classloader

Question

I have a app that recieve a dex file from server then save it on sdcard and load it for

doing some functions.I am loading a my app\'s class from my dex file as followi

Answer 1

See if you're following these steps.

1. Do you have the library file as an APK or a JAR containing (Classes.dex) file on the SD Card?
2. Copy the APK file into a temporary folder into your application director /data/data/your.app.name/tmp. This is important as for security reasons Android doesn't let you load something off the SD card.
3. Use DexClassLoader as described here -> How to load a Java class dynamically on android/dalvik?
4. Use this classloader instance for loading any dynamic class files.

If you have more than 1 JAR files then merge them into a single DEX file/APK.

To convert your Java JAR file or classes into DEX you need to use the Android SDK's dx.bat. Here's a sample ANT script to do. This can also be done via Command line too with similar arguments.

<exec executable="dx.bat">
    <arg value="--dex" />
    <arg value="--output=${target.directory.fullpath}/${apk.name}" />
    <arg value="--positions=lines" />
    <arg path="${classes.directory.full.path}" />
</exec>

Answer 2

@zohreh Replace the below line

final DexClassLoader classloader = new DexClassLoader(libPath, tmpDir.getAbsolutePath(), null, this.getClass().getClassLoader());

to

final DexClassLoader classloader = new DexClassLoader(libPath, tmpDir.getAbsolutePath(), null, ClassLoader.getSystemClassLoader());

Answer 3

I found my answer I need change

final Class<Object> classToLoad = (Class<Object>)classloader.loadClass("com.example.myapp.M");

to

final Class<Object> classToLoad = (Class<Object>)Class.forName("com.example.myapp.M");

in my dex file