Question

我必须在第一个视图控制器上随时随地隐藏它，当应用程序启动时，你有两个按钮白色和黑色。当用户按下任一按钮并向后按以查看1时，它会显示白色方块和黑色方块，具体取决于用户选择的位置。

以下代码：

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidAppear:(BOOL)animated {
    NSUserDefaults *SetBlack = [NSUserDefaults standardUserDefaults];
    blacksquare.hidden = [SetBlack boolForKey:@"black"];

    NSUserDefaults *SetWhite = [NSUserDefaults standardUserDefaults];
    whitesquare.hidden = [SetWhite boolForKey:@"white"];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

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

@end

和

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (IBAction)black:(id)sender{
    NSUserDefaults *SetBlack = [NSUserDefaults standardUserDefaults];
    [SetBlack setBool:NO forKey:@"black"];
}

- (IBAction)white:(id)sender{
    NSUserDefaults *SetWhite = [NSUserDefaults standardUserDefaults];
    [SetWhite setBool:NO forKey:@"black"];
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

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

- (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

- (IBAction)black:(id)sender{
NSUserDefaults *SetBlack = [NSUserDefaults standardUserDefaults];
[SetBlack setBool:NO forKey:@"black"];
}

- (IBAction)white:(id)sender{
NSUserDefaults *SetWhite = [NSUserDefaults standardUserDefaults];
[SetWhite setBool:NO forKey:@"black"];
}

上面的代码应该是这样的

 - (IBAction)black:(id)sender{
NSUserDefaults *SetBlack = [NSUserDefaults standardUserDefaults];
[SetBlack setBool:NO forKey:@"black"];
[SetBlack synchronize]; // added synchronize method
}

- (IBAction)white:(id)sender{
NSUserDefaults *SetWhite = [NSUserDefaults standardUserDefaults];
[SetWhite setBool:NO forKey:@"black"];
[SetWhite synchronize]; // added synchronize method
}

来自NSUserDefaults synchronize

的文档

因为此方法是定期自动调用的，所以只有在您不能等待自动同步时（例如，如果您的应用程序即将退出）或者您希望将用户默认值更新为打开时，才使用此方法即使您没有进行任何更改，也可以使用磁盘。

Answer 2

您必须使用[[NSUserDefaults standardDefaults] synchronize];在NSUserDefaults中设置值以保存。

如何使用nsuserdefaults和.hidden保存和加载要在另一个视图控制器上查看的图片

2 个答案: