动态加载其他已经安装的apk的dex文件， 并通过反射执行

    private void useDexClassLoader(){  
                //创建一个意图，用来找到指定的apk  
                Intent intent = new Intent("com.suchangli.android.plugin",null);  
                //获得包管理器  
                PackageManager pm = getPackageManager();  
                List<ResolveInfo> resolveinfoes =  pm.queryIntentActivities(intent,0);  
                //获得指定的activity的信息  
                ActivityInfo actInfo = resolveinfoes.get(0).activityInfo;  
                  
                //获得包名  
                String pacageName = actInfo.packageName;  
                //获得apk的目录或者jar的目录  
                String apkPath = actInfo.applicationInfo.sourceDir;  
                //dex解压后的目录,注意，这个用宿主程序的目录，android中只允许程序读取写自己  
                //目录下的文件  
                String dexOutputDir = getApplicationInfo().dataDir;  
                  
                //native代码的目录  
                String libPath = actInfo.applicationInfo.nativeLibraryDir;  
                //创建类加载器，把dex加载到虚拟机中  
                DexClassLoader calssLoader = new DexClassLoader(apkPath,dexOutputDir,libPath,this.getClass().getClassLoader());  
                  
                //利用反射调用插件包内的类的方法  
                  
                try {  
                            Class<?> clazz = calssLoader.loadClass(pacageName+".Plugin1");  
                              
                            Object obj = clazz.newInstance();  
                            Class[] param = new Class[2];  
                            param[0] = Integer.TYPE;  
                            param[1] = Integer.TYPE;  
                              
                            Method method = clazz.getMethod("function1",param);  
                              
                            Integer ret = (Integer)method.invoke(obj,1,12);  
                              
                            Log.i("Host","return result is " + ret);  
                              
                    } catch (ClassNotFoundException e) {  
                            e.printStackTrace();  
                    } catch (InstantiationException e) {  
                            e.printStackTrace();  
                    } catch (IllegalAccessException e) {  
                            e.printStackTrace();  
                    } catch (NoSuchMethodException e) {  
                            e.printStackTrace();  
                    } catch (IllegalArgumentException e) {  
                            e.printStackTrace();  
                    } catch (InvocationTargetException e) {  
                            e.printStackTrace();  
                    }  
        }