今天在xcode8.1的AppDelegate.m中要添加一个提示框，发现添加不上，试了试UIAlertView可以正常添加，但是在xcode8.0之后UIAlertView就被UIAlertController取代了，所以嘛，咱们也要与时俱进嘛！

 一、UIAlertController的简单使用：

//创建UIAlertController    //UIAlertControllerStyle 这是提示框显示的两种形式    //UIAlertControllerStyleAlert 在屏幕中央显示    //UIAlertControllerStyleActionSheet 从屏幕底部弹出    UIAlertController *alertCtl = [UIAlertController alertControllerWithTitle:@"提示" message:@"提示框" preferredStyle:UIAlertControllerStyleAlert];    //提示框的响应动作  UIAlertAction    UIAlertAction *actionOne = [UIAlertAction actionWithTitle:@"actionOne" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {        //点击事件可以在这里添加        NSLog(@"点击了ActionOne");    }];    UIAlertAction *actionTwo = [UIAlertAction actionWithTitle:@"actionTwo" style:UIAlertActionStyleCancel handler:nil];    UIAlertAction *actionThree = [UIAlertAction actionWithTitle:@"actionThree" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {        NSLog(@"点击了actionThree");    }]; //添加动作至UIAlertController控制器上    [alertCtl addAction:actionOne];    [alertCtl addAction:actionTwo];    [alertCtl addAction:actionThree];      [self presentViewController:alertCtl animated:YES completion:nil];

二、在AppDelegate中的使用：

//初始化UIAlertController    UIAlertController *alertCtl = [UIAlertController alertControllerWithTitle:@"提示" message:@"AppDelegate中" preferredStyle:UIAlertControllerStyleAlert];    UIAlertAction *alertAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleDefault handler:nil];    [alertCtl addAction:alertAction];    //初始化UIWindows    UIWindow *aW = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];    aW.rootViewController = [[UIViewController alloc]init];    aW.windowLevel = UIWindowLevelAlert + 1;    [aW makeKeyAndVisible];    [aW.rootViewController presentViewController:alertCtl animated:YES completion:nil];