Question

我正试图通过单击按钮向后循环一个数组。

我当前的代码很接近，但效果不好。

- (void)viewDidLoad {
self.imageNames = [NSArray arrayWithObjects:@"MyFirstImage", @"AnotherImage", nil];
currentImageIndex = 0;
[super viewDidLoad];
}

......什么有效：

- (IBAction)change {
UIImage* imageToShow = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[imageNames objectAtIndex:currentImageIndex] ofType:@"png"];
currentImageIndex++;
if (currentImageIndex >= imageNames.count) {
    currentImageIndex = 0;
}
}

......以及什么不起作用：

- (IBAction)changeBack {
UIImage* imageToShow = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[imageNames objectAtIndex:currentImageIndex] ofType:@"png"];
currentImageIndex--;
if (currentImageIndex >= imageNames.count) {
    currentImageIndex = 0;
}
}

非常感谢任何帮助！

谢谢！

Answer 1

您需要先更改索引，然后获取图像。当向后移动时，您需要在消极时将索引重置为最大值（count-1）：

- (IBAction)changeBack {
    currentImageIndex--;
    if (currentImageIndex < 0) {    // was first image
        currentImageIndex = imageNames.count-1;  // last image 
    }

    UIImage* imageToShow = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[imageNames objectAtIndex:currentImageIndex] ofType:@"png"];
}

要前进到下一张图片：

- (IBAction)change {
    currentImageIndex++;
    if (currentImageIndex >= imageNames.count) {    // was last image
        currentImageIndex = 0;  // back to first image 
    }

    UIImage* imageToShow = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[imageNames objectAtIndex:currentImageIndex] ofType:@"png"];
}

Answer 2

也许在changeBack方法中，您应该更改此行代码以显示以下内容：

if (currentImageIndex <= 0) { currentImageIndex = imageNames.count; }

（假设当用户超过第一张图片时，他们会回到最后一张图片）

通过NSArray向后循环

2 个答案: