使用按钮点击在 NSArray 对象上循环

Question

我有一个 NSStrings 数组，我想将其用作 UIImageView 图像名称的来源。

当用户点击一个按钮时，我将新图像（数组中的下一个对象）加载到同一图像视图中，这将是最终目标。实际上我有一个有效但愚蠢的解决方案，但这不是我想要的。我想将数组中的字符串名称加载到 UIImage，因为这个 if 语句可以随着 30-40 个对象变得非常大，而且不太可靠。我不太擅长 for 循环，所以如果有人能告诉我如何用 loop 或任何其他方式获得相同的结果，我将不胜感激。

- (IBAction)changeImage:(id)sender {

    if (!self.userImageView.image) {


        UIImage *image = [UIImage imageNamed:@"img1.png"];
        self.userImageView.image = image;
        self.currentDisplayedImageString = @"img1.png";
     // self.currentDisplayedImageString is an ivar, type of NSString
    }
    else {

        if ([self.currentDisplayedImageString isEqualToString:@"img1.png"]) {

            UIImage *image = [UIImage imageNamed:@"img2.png"];
            self.userImageView.image = image;
            self.currentDisplayedImageString = @"img2.png";

        }
        if ([self.currentDisplayedImageString isEqualToString:@"img2.png"]) {

            UIImage *image = [UIImage imageNamed:@"img3.png"];
            self.userImageView.image = image;
            self.currentDisplayedImageString = @"img3.png";

        }
        // AND SO ON...

    }
}

Answer 1

类似于：

@interface ViewController ()

@property (strong, nonatomic) UIImageView *imageView;
@property (strong, nonatomic) NSArray *imageNames;
@property (assign, nonatomic) int currentImageIndex;

@end

@implementation ViewController

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

    self.imageNames = @[@"img1", @"img2", @"img3", @"img4"];
    self.currentImageIndex = -1;
}

- (void)changeImage {
    if (++self.currentImageIndex == self.imageNames.count) {
        self.currentImageIndex = 0;
    }
    self.imageView.image = [UIImage imageNamed:self.imageNames[self.currentImageIndex]];
}

@end

希望对您有所帮助！

Answer 2

如果您的图像名称实际上是 "img1," "img2," "img3," 等，您实际上不需要数组来存储它们，因为名称本质上是索引自身。相反，我建议您这样做：

- (IBAction)changeImage:(id)sender {

    if (!self.userImageView.image || 
        [self.currentDisplayedImageString isEqualToString:@"img40.png"]) {
        self.currentDisplayedImageString = @"img1.png";
    }
    else {
        // Get the filename's numerical index by parsing out the numerical component
        NSString *index = [[self.currentDisplayedImageString componentsSeparatedByCharactersInSet:
                            [[NSCharacterSet decimalDigitCharacterSet] invertedSet]]
                           componentsJoinedByString:@""];
        // "Increment" the currentDisplayedImageString
        self.currentDisplayedImageString = [NSString stringWithFormat:@"img%@.png", index];
    }

    // Then update the image
    UIImage *image = [UIImage imageNamed:currentDisplayedImageString];
    self.userImageView.image = image;

}

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