iOS开发UI -- UIAlertController(提示框)

两种提示方式

UIAlertControllerStyleActionSheet 提示从下面出来
UIAlertControllerStyleAlert 提示在中间出来

- (IBAction)LoginBt:(UIButton *)sender {    UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:@"提示" message:@"登陆成功" preferredStyle:UIAlertControllerStyleActionSheet];    //判断    if ([_NameTf.text isEqualToString:_uername] && [_PasswordTf.text isEqualToString:_passWord]) {        alertVC.message = @"欢迎回来";    }else    {    alertVC.message = @"用户名或者密码错误";    }    //添加事件    UIAlertAction *action = [UIAlertAction actionWithTitle:@"确定" style:(UIAlertActionStyleDefault) handler:^(UIAlertAction *action) {        NSLog(@"点击确定按钮");    }];    [alertVC addAction:action];    //模态显示    [self presentViewController:alertVC animated:YES completion:nil];}