iOS presentViewController代表返回黑色屏幕

Question

我在我的项目中创建了两个视图。我希望能够点击我的主视图上的按钮，另一个视图（ChooseCar）会弹出，允许用户选择一些东西，然后它将重新打开输入信息的旧视图（ViewController）。我已经完成了它的代码，但由于某种原因，当我点击按钮时，屏幕变黑并且什么也没有发生，我很确定这是非常简单的事情，我只是无法理解它。

我会附上下面的意见代码，谢谢。

ViewController.h

// 
// ViewController.h 
// 
// Created by Curtis Boylan on 24/11/2016. 
// Copyright © 2016. All rights reserved. 
// 

#import <UIKit/UIKit.h> 
#import "ChooseCar.h" 

@interface ViewController : UIViewController <ChooseCarDelegate> 
- (IBAction)chooselocation; 
@property (strong, nonatomic) IBOutlet UILabel *wherelocation; 

@end 

ViewController.m

// 
// ViewController.m 
// 
// Created by Curtis Boylan on 24/11/2016. 
// Copyright © 2016. All rights reserved. 
// 

#import "ViewController.h" 

@interface ViewController() 
@end 

@implementation ViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
} 
- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 
-(UIStatusBarStyle)preferredStatusBarStyle{ 
    return UIStatusBarStyleLightContent; 
} 
- (IBAction)chooselocation { 
    ChooseCar *acController = [[ChooseCar alloc] init]; 
    // acController.delegate = self; 
    [self presentViewController:acController animated:YES completion:nil];} 

- (void)addItemViewController:(ChooseCar *)controller didFinishEnteringItem:(NSString *)item 
{ 
    NSLog(@"This was returned from ChooseCar %@",item); 
} 

@end 

ChooseCar.h

// 
// ChooseCar.h 
// 
// Created by Curtis Boylan on 24/11/2016. 
// Copyright © 2016. All rights reserved. 
// 

#import <UIKit/UIKit.h> 
@class ChooseCar; 

@protocol ChooseCarDelegate <NSObject> 
- (void)addItemViewController:(ChooseCar *)controller didFinishEnteringItem:(NSString *)item; 
@end 

@interface ChooseCar : UIViewController 

@end 

ChooseCar.m

// 
// ChooseCar.m 
// 
// Created by Curtis Boylan on 24/11/2016. 
// Copyright © 2016. All rights reserved. 
// 

#import "ChooseCar.h" 

@interface ChooseCar() 
@property (nonatomic, weak) id <ChooseCarDelegate> delegate; 
@end 

@implementation ChooseCar 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 

    NSString *itemToPassBack = @"Pass this value back to ViewControllerA"; 
    [self.delegate addItemViewController:self didFinishEnteringItem:itemToPassBack]; 

} 

- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 

/* 
#pragma mark - Navigation 

// In a storyboard-based application, you will often want to do a little preparation before navigation 
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { 
    // Get the new view controller using [segue destinationViewController]. 
    // Pass the selected object to the new view controller. 
} 
*/ 

@end 

Answer 1

它很容易做到：

1）我相信你的ChooseCar VC在storyboard创建。 如果是，你应该设置Storyboard ID这样的：

2）在你的ViewController.m，更新chooselocation方法是：

- (IBAction)chooselocation { 
//ChooseCar *acController = [[ChooseCar alloc] init]; 

UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil]; 


ChooseCar *acController = [sb instantiateViewControllerWithIdentifier:@"ChooseCar"]; 

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

} 

编辑

如果您想通过代表传递价值：

在我给的基础上。

1）削减该代码@property (nonatomic, weak) id <ChooseCarDelegate> delegate;从ChooseCar.m到ChooseCar.h，确保ChooseCar.h这样的：

#import <UIKit/UIKit.h> 

@class ChooseCar; 

@protocol ChooseCarDelegate <NSObject> 


- (void)addItemViewController:(ChooseCar *)controller didFinishEnteringItem:(NSString *)item; 

@end 


@interface ChooseCar : UIViewController 

@property (nonatomic, weak) id <ChooseCarDelegate> delegate; 

@end 

2）在ViewController.m，你应该遵守protocal，并设置caController的代表。

#import "ChooseCar.h" 
#import "ViewController.h" 

@interface ViewController() <ChooseCarDelegate> 

@end 

@implementation ViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
} 
- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 
-(UIStatusBarStyle)preferredStatusBarStyle{ 
    return UIStatusBarStyleLightContent; 
} 
- (IBAction)chooselocation { 
    //ChooseCar *acController = [[ChooseCar alloc] init]; 

    UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil]; 


    ChooseCar *acController = [sb instantiateViewControllerWithIdentifier:@"ChooseCar"]; 

    acController.delegate = self; 

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

} 

- (void)addItemViewController:(ChooseCar *)controller didFinishEnteringItem:(NSString *)item 
{ 
    NSLog(@"This was returned from ChooseCar %@",item); 
} 

@end 

3）如果你想传递的价值，你应该把这个代码到你的动作：

NSString *itemToPassBack = @"Pass this value back to ViewControllerA"; 
[self.delegate addItemViewController:self didFinishEnteringItem:itemToPassBack]; 

Answer 2

改为如下代码：

视图控制器。^ h

#import <UIKit/UIKit.h> 
#import "ChooseCar.h" 

@interface ViewController : UIViewController <ChooseCarDelegate> 
- (IBAction)chooselocation; 
@property (strong, nonatomic) IBOutlet UILabel *wherelocation; 

@end 

ViewController.m

#import "ViewController.h" 

@interface ViewController() 
{ 
    ChooseCar *acController; 
} 
@end 

@implementation ViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
} 
- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 
-(UIStatusBarStyle)preferredStatusBarStyle{ 
    return UIStatusBarStyleLightContent; 
} 
- (IBAction)chooselocation { 

    acController = [self.storyboard instantiateViewControllerWithIdentifier:@"ChooseCar"]; 
    acController.delegate = self; 
    [self presentViewController:acController animated:YES completion:nil]; 

} 

- (void)addItemViewController:(ChooseCar *)controller didFinishEnteringItem:(NSString *)item 
{ 
    [acController dismissViewControllerAnimated:true completion:nil]; 
    NSLog(@"This was returned from ChooseCar %@",item); 
} 

@end 

而且设置故事板故事板ID。更多详情请参阅随附的屏幕截图：

ChooseCar.h

#import <UIKit/UIKit.h> 
@class ChooseCar; 

@protocol ChooseCarDelegate <NSObject> 
- (void)addItemViewController:(ChooseCar *)controller didFinishEnteringItem:(NSString *)item; 
@end 

@interface ChooseCar : UIViewController 
@property (nonatomic, weak) id <ChooseCarDelegate> delegate; 
@end 

ChooseCar.m

#import "ChooseCar.h" 

@interface ChooseCar() 
@end 

@implementation ChooseCar 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 

// NSString *itemToPassBack = @"Pass this value back to ViewControllerA"; 
// [self.delegate addItemViewController:self didFinishEnteringItem:itemToPassBack]; 

} 

- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 
- (IBAction)backButtonClicked:(id)sender { 
    NSString *itemToPassBack = @"Pass this value back to ViewControllerA"; 
    [self.delegate addItemViewController:self didFinishEnteringItem:itemToPassBack]; 
} 

/* 
#pragma mark - Navigation 

// In a storyboard-based application, you will often want to do a little preparation before navigation 
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { 
// Get the new view controller using [segue destinationViewController]. 
// Pass the selected object to the new view controller. 
} 
*/ 

@end