動態加載其他已經安裝的apk的dex文件， 并通過反射執行

    private void useDexClassLoader(){

                //創建一個意圖，用來找到指定的apk

                Intent intent = new Intent("com.suchangli.android.plugin", null);

                //獲得包管理器

                PackageManager pm = getPackageManager();

                List<ResolveInfo> resolveinfoes =  pm.queryIntentActivities(intent, 0);

                //獲得指定的activity的信息

                ActivityInfo actInfo = resolveinfoes.get(0).activityInfo;


            //獲得包名  
            String pacageName = actInfo.packageName;  
            //獲得apk的目錄或者jar的目錄  
            String apkPath = actInfo.applicationInfo.sourceDir;  
            //dex解壓后的目錄,注意，這個用宿主程序的目錄，android中只允許程序讀取寫自己  
            //目錄下的文件  
            String dexOutputDir = getApplicationInfo().dataDir;  

            //native代碼的目錄  
            String libPath = actInfo.applicationInfo.nativeLibraryDir;  
            //創建類加載器，把dex加載到虛擬機中  
            DexClassLoader calssLoader = new DexClassLoader(apkPath, dexOutputDir, libPath,  
                            this.getClass().getClassLoader());  

            //利用反射調用插件包內的類的方法  

            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();  
                }  
    }  </pre>