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：

[objc] view
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1. UIActionSheet *actionSheet = [[UIActionSheet alloc]    
2.                                  initWithTitle:@"title,nil时不显示"    
3.                                  delegate:self    
4.                                  cancelButtonTitle:@"取消"    
5.                                  destructiveButtonTitle:@"确定"    
6.                                  otherButtonTitles:@"第一项", @"第二项",nil];    
7.    actionSheet.actionSheetStyle = UIActionSheetStyleBlackOpaque;    
8.    [actionSheet showInView:self.view];  

然后在协议中实现代理:

[objc] view
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1. (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex    
2. {    
3.     if (buttonIndex == 0) {    
4.         NSLog(@"确定");    
5.     }else if (buttonIndex == 1) {    
6.         NSLog(@"第一项");    
7.     }else if(buttonIndex == 2) {    
8.         NSLog(@"第二项");    
9.     }else if(buttonIndex == actionSheet.cancleButtonIndex) {    
10.         NSLog(@"取消");    
11.     }     
12.     
13. }    
14. - (void)actionSheetCancel:(UIActionSheet *)actionSheet{      
15.     
16. }      
17. -(void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex{      
18.     
19. }      
20. -(void)actionSheet:(UIActionSheet *)actionSheet willDismissWithButtonIndex:(NSInteger)buttonIndex{      
21.     
22. }    

如果需要修改按钮字体、颜色等可以实现以下代理：

[objc] view
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1. - (void)willPresentActionSheet:(UIActionSheet *)actionSheet {  
2.     for (UIView *subViwe in actionSheet.subviews) {  
3.         if ([subViwe isKindOfClass:[UILabel class]]) {  
4.             UILabel *label = (UILabel *)subViwe;  
5.             label.font = [UIFont systemFontOfSize:16];  
6.             label.frame = CGRectMake(CGRectGetMinX(label.frame), CGRectGetMinY(label.frame), CGRectGetWidth(label.frame), CGRectGetHeight(label.frame)+20);  
7.         }  
8.         if ([subViwe isKindOfClass:[UIButton class]]) {  
9.             UIButton *button = (UIButton*)subViwe;  
10.             if ([button.titleLabel.text isEqualToString:@"确定"]) {  
11.                 [button setTitleColor:[UIColor redColor] forState:UIControlStateNormal];  
12.             } else {  
13.                 [button setTitleColor:[WTDevice getGreenColor] forState:UIControlStateNormal];  
14.             }  
15.             button.titleLabel.font = [UIFont systemFontOfSize:18];  
16.         }  
17.     }  
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)：

[objc] view
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1. #ifdef __IPHONE_8_0  
2.         if (TARGET_IS_IOS8) {  
3.             UIAlertController *actionSheetController = [UIAlertController alertControllerWithTitle:@"提示"  
4.                                                                                            message:@"需要设置允许访问相机，操作方法见“设置”->“帮助中心”"  
5.                                                                                     preferredStyle:UIAlertControllerStyleAlert];  
6.             UIAlertAction *actionCancel = [UIAlertAction actionWithTitle:@"确定"  
7.                                                                    style:UIAlertActionStyleDestructive  
8.                                                                  handler:^(UIAlertAction * action) {}];  
9.               
10.             [actionSheetController addAction:actionCancel];  
11.             [actionSheetController.view setTintColor:[WTDevice getGreenColor]];  
12.             [self presentViewController:actionSheetController animated:YES completion:nil];  
13.         }  
14. #endif  
15.         if (TARGET_NOT_IOS8) {  
16.             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];  
17.             [alert show];  
18.         }  

代替UIActionSheet：

[objc] view
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1. #ifdef __IPHONE_8_0  
2.     if (TARGET_IS_IOS8) {  
3.         UIAlertController *actionSheetController = [UIAlertController alertControllerWithTitle:@"action选项"  
4.                                                                                        message:nil  
5.                                                                                 preferredStyle:UIAlertControllerStyleActionSheet];  
6.         UIAlertAction *action0 = [UIAlertAction actionWithTitle:@"选项一"  
7.                                                          style:UIAlertActionStyleDefault  
8.                                                        handler:^(UIAlertAction * action) {  
9.                                                            [self customMethod1];  
10.                                                        }];  
11.         [actionSheetController addAction:action0];  
12.           
13.         UIAlertAction *action = [UIAlertAction actionWithTitle:@"选项二"  
14.                                                          style:UIAlertActionStyleDefault  
15.                                                        handler:^(UIAlertAction * action) {  
16.                                                            [self <span style="font-family: Arial, Helvetica, sans-serif;">customMethod2</span>];  
17.                                                        }];  
18.         UIAlertAction *action1 = [UIAlertAction actionWithTitle:@"选项三"  
19.                                                           style:UIAlertActionStyleDefault  
20.                                                         handler:^(UIAlertAction * action) {  
21.                                                             [self customMethod3];  
22.                                                         }];  
23.         UIAlertAction *actionCancel = [UIAlertAction actionWithTitle:@"取消"  
24.                                                                style:UIAlertActionStyleCancel  
25.                                                              handler:^(UIAlertAction * action) {}];  
26.           
27.         [actionSheetController addAction:action];  
28.         [actionSheetController addAction:action1];  
29.         [actionSheetController addAction:actionCancel];  
30.         [actionSheetController.view setTintColor:[UIColor greenColor]];  
31.         [self presentViewController:actionSheetController animated:YES completion:nil];  
32.     }  
33. #endif  
34.     if (TARGET_NOT_IOS8) {  
35.         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];  
36.         [as showInView:self.view];  
37.     }  

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。