android DexClassLoader动态加载技术详解

package com.demo.dex;

/**
 * 对外接口
 * 
 * @author edsheng
 * 
 */
public interface Iinterface {
	public void call();

	public String getData();
}

package com.demo.dex;

import android.content.Context;
import android.widget.Toast;

public class IClass implements Iinterface {

	private Context context;

	public IClass(Context context) {
		super();
		this.context = context;
	}

	@Override
	public void call() {
		Toast.makeText(context, "call method", 0).show();
	}

	@Override
	public String getData() {
		return "hello,i am from IClass";
	}

}

dx --dex --output=testdex.jar test.jar

新建一个andorid工程（我比较懒，刚才已经就是使用的andorid工程），然后把testdex.jar复制到assets目录下面，来看看我的工程目录吧。
然后贴出FileUtil.java的代码

package com.demo.utile;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

import android.content.Context;
import android.os.Environment;

public class FileUtile {
	public static void CopyAssertJarToFile(Context context, String filename,
			String des) {
		try {

			File file = new File(Environment.getExternalStorageDirectory()
					.toString() + File.separator + des);
			if (file.exists()) {
				return;
			}

			InputStream inputStream = context.getAssets().open(filename);
			file.createNewFile();
			FileOutputStream fileOutputStream = new FileOutputStream(file);
			byte buffer[] = new byte[1024];
			int len = 0;
			while ((len = inputStream.read(buffer)) != 0) {
				fileOutputStream.write(buffer, 0, len);
			}
			fileOutputStream.close();
			fileOutputStream.close();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

package com.demo.activity;

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

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.os.Environment;

import com.demo.utile.FileUtile;

import dalvik.system.DexClassLoader;

public class MainActivity extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		FileUtile.CopyAssertJarToFile(this, "testdex.jar", "testdex.jar");

		File file = new File(Environment.getExternalStorageDirectory()
				.toString() + File.separator + "testdex.jar");
		final File optimizedDexOutputPath = getDir("temp", Context.MODE_PRIVATE);
		DexClassLoader classLoader = new DexClassLoader(file.getAbsolutePath(),
				optimizedDexOutputPath.getAbsolutePath(), null,
				getClassLoader());
		try {
			Class<?> iclass = classLoader.loadClass("com.demo.dex.IClass");
			Constructor<?> istructor = iclass.getConstructor(Context.class);
			//利用反射原理去调用
			Method method = iclass.getMethod("call", null);
			String data = (String) method.invoke(istructor.newInstance(this), null);
			System.out.println(data);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

Class<?> iclass = classLoader.loadClass("com.demo.dex.IClass");
			Constructor<?> istructor = iclass.getConstructor(Context.class);
			Iinterface iinterface = (Iinterface) istructor.newInstance(this);
			 String data = iinterface.getData();
			 iinterface.call();
			 Toast.makeText(this, data, 0).show();