我有更多页面将显示 UIAlertController。

所以我需要在一页的方法和类中编写警报代码。

我想使用类并调用方法可以在任何 Viewcontroller 上显示警报。

如何在类中编写presentviewcontroller。

我的头文件如下:

 #import <Foundation/Foundation.h>
 #import "VisionAPI.h"

 @interface VisionAPI : NSObject

 +(void) showMessageAlert:(NSString *) title andMessage:(NSString*) msg andDoneMsg:(NSString*) done;

 @end

我的实现文件如下:

 #import "VisionAPI.h"
 #import <UIKit/UIKit.h>
 @implementation VisionAPI

 +(void) showMessageAlert:(NSString *) title andMessage:(NSString*) msg andDoneMsg:(NSString*) done{

     UIAlertController *showMsgAlertController = [UIAlertController alertControllerWithTitle: title message: msg preferredStyle: UIAlertControllerStyleAlert];
UIAlertAction *showMsgAlertControllerOkAction = [UIAlertAction actionWithTitle:done  style:UIAlertActionStyleDefault
                                                       handler:nil];
       [showMsgAlertController addAction:showMsgAlertControllerOkAction];
dispatch_async(dispatch_get_main_queue(), ^{

       [self presentViewController:showMsgAlertController animated:YES completion:nil];
     });
 }
 @end

但是上面的代码会在这一行显示错误:

 [self presentViewController:showMsgAlertController animated:YES completion:nil];

如何在 NSObject 中呈现 ViewController，或者如何解决问题。

最佳答案

Add view controller as a parameter argument in your function and pass the 'self' (instance/object of view controller) from which view controller, you want to present your alert controller.

+(void) showMessageAlert:(NSString *) title andMessage:(NSString*) msg andDoneMsg:(NSString*) done fromViewController: (UIViewController)viewController{

     UIAlertController *showMsgAlertController = [UIAlertController alertControllerWithTitle: title message: msg preferredStyle: UIAlertControllerStyleAlert];
UIAlertAction *showMsgAlertControllerOkAction = [UIAlertAction actionWithTitle:done  style:UIAlertActionStyleDefault
                                                       handler:nil];
       [showMsgAlertController addAction:showMsgAlertControllerOkAction];
dispatch_async(dispatch_get_main_queue(), ^{

       [viewController presentViewController:showMsgAlertController animated:YES completion:nil];
     });
 }
 @end

如果您不想每次都将 View Controller 作为此函数的参数参数传递，您也可以使用应用程序的 Root View Controller 。如下:

+(void) showMessageAlert:(NSString *) title andMessage:(NSString*) msg andDoneMsg:(NSString*) done{

         UIAlertController *showMsgAlertController = [UIAlertController alertControllerWithTitle: title message: msg preferredStyle: UIAlertControllerStyleAlert];
    UIAlertAction *showMsgAlertControllerOkAction = [UIAlertAction actionWithTitle:done  style:UIAlertActionStyleDefault
                                                           handler:nil];
           [showMsgAlertController addAction:showMsgAlertControllerOkAction];
    dispatch_async(dispatch_get_main_queue(), ^{

RootViewController *rootController = (RootViewController*)[[(AppDelegate*)
                                   [[UIApplication sharedApplication]delegate] window] rootViewController];

           [rootController presentViewController:showMsgAlertController animated:YES completion:nil];
         });
     }
@end

关于iOS 显示警报 Controller 对象，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/43999660/