利用Java反射机制改变SharedPreferences存储路径

private void savePreToSDcard() {  
        try {  
            Field field;  
            // 获取ContextWrapper对象中的mBase变量。该变量保存了ContextImpl对象  
            field = ContextWrapper.class.getDeclaredField("mBase");  
            field.setAccessible(true);  
            // 获取mBase变量  
            Object obj = field.get(this);  
            // 获取ContextImpl。mPreferencesDir变量，该变量保存了数据文件的保存路径  
            field = obj.getClass().getDeclaredField("mPreferencesDir");  
            field.setAccessible(true);  
            // 创建自定义路径  
            File file = new File("/sdcard");  
            // 修改mPreferencesDir变量的值  
            field.set(obj, file);  
            SharedPreferences mySharedPreferences = getSharedPreferences(  
                    "config", Activity.MODE_PRIVATE);  
            SharedPreferences.Editor editor = mySharedPreferences.edit();  
            editor.putString("name", "20130310");  
            editor.commit();  
        } catch (NoSuchFieldException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        } catch (IllegalArgumentException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        } catch (IllegalAccessException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
    }