iOS8.0 之後UIAlertView和UIActionSheet的創建方式的新變化

最近已經換了Xcode 6.1，開始適配iOS 8.0以上版本了，在iOS 8以前，我們創建一個警告視圖（UIAlertView）,通常是這樣的

UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Title" message:@"Message" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"確定", nil];
    [alertView show];

運行後，如圖所示：

通過UIAlertViewDelegate 中的 

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex;

來響應按鈕事件

創建一個選擇按鈕項( UIActionSheet)，通常是這樣的:

UIActionSheet *actioSheet = [[UIActionSheet alloc] initWithTitle:@"Title" delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:@"Destructive" otherButtonTitles:@"otherButton", nil];
    [actioSheet showInView:self.view];

運行後如圖所示：

通過UIActionSheetDelegate中的

- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex;

響應按鈕事件

但是在Xcode 6.1 iOS 8.0 的環境下，創建這兩個控件會出現這樣的提示

( 重要：UIAlerView 在iOS8中已棄用，同時UIAlertViewDeleagte也過時。在iOS8以後用UIAlertController的preferredStyle類型中的UIAlertControllerStyleAlert來創建和管理警告)

雖然蘋果申明UIAlertView已經被被棄用，但是我們創建UIAlertView在iOS 8下運行並沒有給出任何警告……

那我們就一起來看一下這個UIAlertController 是怎麼用的，下面就是UIAlertController.h的全部內容

#import <UIKit/UIViewController.h>

typedef NS_ENUM(NSInteger, UIAlertActionStyle) {
    UIAlertActionStyleDefault = 0,
    UIAlertActionStyleCancel,
    UIAlertActionStyleDestructive
} NS_ENUM_AVAILABLE_IOS(8_0);

typedef NS_ENUM(NSInteger, UIAlertControllerStyle) {
    UIAlertControllerStyleActionSheet = 0,
    UIAlertControllerStyleAlert
} NS_ENUM_AVAILABLE_IOS(8_0);

NS_CLASS_AVAILABLE_IOS(8_0) @interface UIAlertAction : NSObject <NSCopying>

+ (instancetype)actionWithTitle:(NSString *)title style:(UIAlertActionStyle)style handler:(void (^)(UIAlertAction *action))handler;

@property (nonatomic, readonly) NSString *title;
@property (nonatomic, readonly) UIAlertActionStyle style;
@property (nonatomic, getter=isEnabled) BOOL enabled;

@end

NS_CLASS_AVAILABLE_IOS(8_0) @interface UIAlertController : UIViewController

+ (instancetype)alertControllerWithTitle:(NSString *)title message:(NSString *)message preferredStyle:(UIAlertControllerStyle)preferredStyle;

- (void)addAction:(UIAlertAction *)action;
@property (nonatomic, readonly) NSArray *actions;
- (void)addTextFieldWithConfigurationHandler:(void (^)(UITextField *textField))configurationHandler;
@property (nonatomic, readonly) NSArray *textFields;

@property (nonatomic, copy) NSString *title;
@property (nonatomic, copy) NSString *message;

@property (nonatomic, readonly) UIAlertControllerStyle preferredStyle;

@end

使用 + 方法來創建一個UIAlertController

+ (instancetype)alertControllerWithTitle:(NSString *)title message:(NSString *)message preferredStyle:(UIAlertControllerStyle)preferredStyle;

UIAlertControllerStyle枚舉內容：

typedef NS_ENUM(NSInteger, UIAlertControllerStyle) {
    UIAlertControllerStyleActionSheet = 0,
    UIAlertControllerStyleAlert
}

顯然可以通過這個方法同時來創建一個Alert 或者ActionSheet

沒有了按鈕標題參數，取而代之的是一個UIAction類來管理按鈕選項，同樣通過一個+方法來創建

+ (instancetype)actionWithTitle:(NSString *)title style:(UIAlertActionStyle)style handler:(void (^)(UIAlertAction *action))handler;

通過一個Block回調來處理按鈕響應事件，這果然很棒！！

所以呢，在iOS 8後，創建一個AlertView,已經變成這樣了(官方源代碼)：

NSString *title = NSLocalizedString(@"A Short Title Is Best", nil);
    NSString *message = NSLocalizedString(@"A message should be a short, complete sentence.", nil);
    NSString *cancelButtonTitle = NSLocalizedString(@"Cancel", nil);
    NSString *otherButtonTitle = NSLocalizedString(@"OK", nil);

    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:title message:message preferredStyle:UIAlertControllerStyleAlert];
    
    // Create the actions.
    UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:cancelButtonTitle style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
        NSLog(@"The \"Okay/Cancel\" alert's cancel action occured.");
    }];
    
    UIAlertAction *otherAction = [UIAlertAction actionWithTitle:otherButtonTitle style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
        NSLog(@"The \"Okay/Cancel\" alert's other action occured.");
    }];
    
    // Add the actions.
    [alertController addAction:cancelAction];
    [alertController addAction:otherAction];
    
    [self presentViewController:alertController animated:YES completion:nil];

運行後如圖所示：

創建一個ActionSheet方法類似：

NSString *cancelButtonTitle = NSLocalizedString(@"Cancel", nil);
    NSString *destructiveButtonTitle = NSLocalizedString(@"OK", nil);
    
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet];
    
    // Create the actions.
    UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:cancelButtonTitle style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
        NSLog(@"The \"Okay/Cancel\" alert action sheet's cancel action occured.");
    }];
    
    UIAlertAction *destructiveAction = [UIAlertAction actionWithTitle:destructiveButtonTitle style:UIAlertActionStyleDestructive handler:^(UIAlertAction *action) {
        NSLog(@"The \"Okay/Cancel\" alert action sheet's destructive action occured.");
    }];
    
    // Add the actions.
    [alertController addAction:cancelAction];
    [alertController addAction:destructiveAction];
[self presentViewController:alertController animated:YES completion:nil];

運行後如圖所示：