【BUG】修复横屏切换导致MainActivity onDestroy调用，导致程序kill的bug。（重要：如果target > 13，还需要加上ScreenSize）
如果不加android:configChanges="orientation",Activity会自动重新走一遍它的生命周期，即先销毁再重新创建，加上后只会调用onConfigurationChanged。
如果你的target > 13时，还必须得加上“ScreenSize”（If your application targets API level 13 or higher (as declared by the minSdkVersion and targetSdkVersion attributes), then you should also declare the "screenSize"    configuration, because it also changes when a device switches between portrait and landscape orientations.）。