Dynamic Library Loader for Android

DynamicLibLoader.java

package com.rdm.neocastapp;

import android.content.ContextWrapper;
import android.util.Log;

import java.io.File;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import dalvik.system.DexClassLoader;

public class DynamicLibLoader {
    protected final File mDexDir;

    public DynamicLibLoader(ContextWrapper contextWrapper) {
        mDexDir = contextWrapper.getDir("dex", 0);
    }

    public DynamicLibLoader(String dexCacheDir) {
        mDexDir = new File(dexCacheDir);
    }

    public static Class<?>[] toParameterTypes(Class<?>... parameterTypes) {
        return parameterTypes;
    }

    public static Object[] toArgs(Object... args) {
        return args;
    }

    // Run method "main(String[])" in fullClassName
    // found in the dexed jar file, libraryFileName,
    // with no command line arguments
    public void runMain(String libraryFileName,
                        String fullClassName,
                        String... args) {
        final Class<?>[] parameterTypes = toParameterTypes(String[].class);
        //final Object[] args = toArgs(new String[0]);
        runMethod(libraryFileName, fullClassName, "main", parameterTypes, args);
    }

    // Find methodName(parameterTypes) in fullClassName inside
    // the dexed jar file, libraryFileName and run it with args
    // - parameterTypes and args can be null
    // - use the toParameterTypes() and toArgs() methods for convenience
    public Object runMethod(String libraryFileName,
                            String fullClassName,
                            String methodName,
                            Class<?>[] parameterTypes,
                            Object[] args) throws IllegalArgumentException {
        try {
            @SuppressWarnings("unchecked")
            final Class<Object> classToLoad = (Class<Object>) getClass(libraryFileName, fullClassName);
            final Object instance = classToLoad.newInstance();
            final Method main = classToLoad.getMethod(methodName, parameterTypes);
            //final String[] args = new String[0];
            //main.invoke(instance, (Object) args);
            return main.invoke(instance, args);
        } catch (InstantiationException | IllegalAccessException |
                 NoSuchMethodException | InvocationTargetException e) {
            throw new IllegalArgumentException(e);
        }
    }

    // Find methodName(parameterTypes) in fullClassName inside
    // the dexed jar file, libraryFileName and run it with args
    // - parameterTypes and args can be null
    // - use the toParameterTypes() and toArgs() methods for convenience
    public Object newInstance(String libraryFileName,
                              String fullClassName) throws IllegalArgumentException {
        try {
            @SuppressWarnings("unchecked")
            final Class<Object> classToLoad = (Class<Object>) getClass(libraryFileName, fullClassName);
            return classToLoad.newInstance();
        } catch (InstantiationException | IllegalAccessException e) {
            throw new IllegalArgumentException(e);
        }
    }

    public final Class<?> getClass(String libraryFileName,
                                   String fullClassName) throws IllegalArgumentException {
        try {
            deleteCachedDexFiles(libraryFileName);
            Log.i("DLL", "exists? " + new File(libraryFileName).exists());
            final DexClassLoader classLoader = new DexClassLoader(
                    libraryFileName, mDexDir.getAbsolutePath(), null,
                    this.getClass().getClassLoader());
            return classLoader.loadClass(fullClassName);
        } catch (ClassNotFoundException e) {
            throw new IllegalArgumentException(e);
        }
    }

    // Note: About re-loading a jar file in the same process' lifetime
    //
    // If we try to load the same jar file by name,
    // but not by content (different file, same name)
    // as previously loaded in this current process,
    // this process will crash with a SIGBUS error.
    // While setIntentRedelivery(true) above *will*
    // cause Android to restart us and re-send the
    // current Intent, this is not very graceful.
    // Instead, it seems that if you clear out the
    // dex cache, all is good.
    //
    // TODO: Only delete the cache file for the library we're loading
     void deleteCachedDexFiles(String libraryFileName) {
         String libName = new File(libraryFileName).getName();
         if (libName.endsWith(".apk") || libName.endsWith(".jar"))
             libName = libName.substring(0, libName.length() - 4);
         Log.i("DynamicLibLoader", "deleteCacheDexFiles(" + libName + ") from " + mDexDir.getAbsolutePath());
         for (File f : mDexDir.listFiles()) {
             Log.i("DLL", "Dex File: " + f.getName());
             // only delete the dex file matching the library file name?
             if (f.isFile() && f.getName()
                     .endsWith(".dex")) {
                 f.delete();
             }
         }
    }
}