iOS8开发之iOS8的UIAlertController

在iOS8之前用UIActionSheet和UIAlertView来提供按钮选择和提示性信息，比如UIActionSheet可以这样写：

 UIActionSheet *actionSheet = [[UIActionSheet alloc]
                                  initWithTitle:@"title,nil时不显示"
                                  delegate:self
                                  cancelButtonTitle:@"取消"
                                  destructiveButtonTitle:@"确定"
                                  otherButtonTitles:@"第一项", @"第二项",nil];
    actionSheet.actionSheetStyle = UIActionSheetStyleBlackOpaque;
    [actionSheet showInView:self.view];

然后在协议中实现代理:

 (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
 {
     if (buttonIndex == 0) {
         NSLog(@"确定");
     }else if (buttonIndex == 1) {
         NSLog(@"第一项");
     }else if(buttonIndex == 2) {
         NSLog(@"第二项");
     }else if(buttonIndex == actionSheet.cancleButtonIndex) {
         NSLog(@"取消");
     }

 }
 - (void)actionSheetCancel:(UIActionSheet *)actionSheet{

 }
 -(void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex{

 }
 -(void)actionSheet:(UIActionSheet *)actionSheet willDismissWithButtonIndex:(NSInteger)buttonIndex{

 }

如果需要修改按钮字体、颜色等可以实现以下代理：

 - (void)willPresentActionSheet:(UIActionSheet *)actionSheet {
     for (UIView *subViwe in actionSheet.subviews) {
         if ([subViwe isKindOfClass:[UILabel class]]) {
             UILabel *label = (UILabel *)subViwe;
             label.font = [UIFont systemFontOfSize:16];
             label.frame = CGRectMake(CGRectGetMinX(label.frame), CGRectGetMinY(label.frame), CGRectGetWidth(label.frame), CGRectGetHeight(label.frame)+20);
         }
         if ([subViwe isKindOfClass:[UIButton class]]) {
             UIButton *button = (UIButton*)subViwe;
             if ([button.titleLabel.text isEqualToString:@"确定"]) {
                 [button setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
             } else {
                 [button setTitleColor:[WTDevice getGreenColor] forState:UIControlStateNormal];
             }
             button.titleLabel.font = [UIFont systemFontOfSize:18];
         }
     }
 }

以上代码（代理部分），在ios7及以下版本中是有效的，但是在iOS8中却不起作用，因为iOS8抛弃了UIActionSheet和UIAlertView，取而代之的是UIAlertController，其使用方法如下(代替UIAlertView)：

 #ifdef __IPHONE_8_0
         if (TARGET_IS_IOS8) {
             UIAlertController *actionSheetController = [UIAlertController alertControllerWithTitle:@"提示"
                                                                                            message:@"需要设置允许访问相机，操作方法见“设置”->“帮助中心”"
                                                                                     preferredStyle:UIAlertControllerStyleAlert];
             UIAlertAction *actionCancel = [UIAlertAction actionWithTitle:@"确定"
                                                                    style:UIAlertActionStyleDestructive
                                                                  handler:^(UIAlertAction * action) {}];

             [actionSheetController addAction:actionCancel];
             [actionSheetController.view setTintColor:[WTDevice getGreenColor]];
             [self presentViewController:actionSheetController animated:YES completion:nil];
         }
 #endif
         if (TARGET_NOT_IOS8) {
             UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"需要设置允许访问相机，操作方法见“设置”->“帮助中心”" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:nil];
             [alert show];
         }

代替UIActionSheet：

 #ifdef __IPHONE_8_0
     if (TARGET_IS_IOS8) {
         UIAlertController *actionSheetController = [UIAlertController alertControllerWithTitle:@"action选项"
                                                                                        message:nil
                                                                                 preferredStyle:UIAlertControllerStyleActionSheet];
         UIAlertAction *action0 = [UIAlertAction actionWithTitle:@"选项一"
                                                          style:UIAlertActionStyleDefault
                                                        handler:^(UIAlertAction * action) {
                                                            [self customMethod1];
                                                        }];
         [actionSheetController addAction:action0];

         UIAlertAction *action = [UIAlertAction actionWithTitle:@"选项二"
                                                          style:UIAlertActionStyleDefault
                                                        handler:^(UIAlertAction * action) {
                                                            [self <span style="font-family: Arial, Helvetica, sans-serif;">customMethod2</span>];
                                                        }];
         UIAlertAction *action1 = [UIAlertAction actionWithTitle:@"选项三"
                                                           style:UIAlertActionStyleDefault
                                                         handler:^(UIAlertAction * action) {
                                                             [self customMethod3];
                                                         }];
         UIAlertAction *actionCancel = [UIAlertAction actionWithTitle:@"取消"
                                                                style:UIAlertActionStyleCancel
                                                              handler:^(UIAlertAction * action) {}];

         [actionSheetController addAction:action];
         [actionSheetController addAction:action1];
         [actionSheetController addAction:actionCancel];
         [actionSheetController.view setTintColor:[UIColor greenColor]];
         [self presentViewController:actionSheetController animated:YES completion:nil];
     }
 #endif
     if (TARGET_NOT_IOS8) {
         UIActionSheet *as = [[UIActionSheet alloc] initWithTitle:@"action选项" delegate:self cancelButtonTitle:@"取消" destructiveButtonTitle:nil otherButtonTitles:@"选项一",@"选项二",@"选项三", nil nil];
         [as showInView:self.view];
     }

至于两者的区别，可以看到，iOS8之前是在controller的view上边又覆盖了一层view，iOS8之后则是present了一个controller并且将代理换成了block，代码显得更加紧凑。