在IOS中交换图像

Question

我必须在一个屏幕上交换四个图像。只能在左/右/上/下方向交换图像，而不能对角交换。例如，第一个图像可以与它右边和下面的图像交换，第二个图像只能与它左边和下面的一个图像交换，依此类推。有谁能帮我做这件事吗。感谢

Answer 1

要添加拖放功能，假设这就是您的意思，您需要查看UIPanGestureRecognizer

Answer 2

添加滑动手势识别器。当用户滑动时，确定哪个方向并处理图像交换。

[编辑]-想象一个正方形被分成四个相等的部分。左上角部分的索引为零，右上角为一，左下角为2，最后右下角为3。下面的代码检查当前索引，并据此确定是否可以进行图像交换，如果不能，则不执行任何操作。

这段代码是我的想法，所以可能有语法错误，但逻辑是合理的（我希望：D）。

- (void) viewDidLoad {
// turn on user interaction on the image view as its off by default.
[self.imageView setUserInteractionEnabled:TRUE];
UISwipeGestureRecognizer *recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipe:)];
[recognizer setDirection:(UISwipeGestureRecognizerDirectionRight | UISwipeGestureRecognizerDirectionDown | UISwipeGestureRecognizerDirectionLeft | UISwipeGestureRecognizerDirectionUp)];
[self.imageView addGestureRecognizer:recognizer];
self.currentImageIndex = 0;
self.images = [NSArray arrayWithObjects:[UIImage imageNamed:@"top-left"],[UIImage imageNamed:@"top-right"],[UIImage imageNamed:@"bottom-left"],[UIImage imageNamed:@"top-right"],nil];
}

-(void)handleSwipeFrom:(UISwipeGestureRecognizer *)recognizer {
if (recognizer.direction == UISwipeGestureRecognizerDirectionRight) {
if (self.currentImageIndex == 0 || self.currentImageIndex == 2) self.currentImageIndex++; // change to image to the right
else return; // do nothing
}
else if (recognizer.direction == UISwipeGestureRecognizerDirectionLeft) {
if (self.currentImageIndex == 1 || self.currentImageIndex == 3) self.currentImageIndex--; // change to the image to the left
else return; // do nothing
}
else if (recognizer.direction == UISwipeGestureRecognizerDirectionUp) {
if (self.currentImageIndex == 2 || self.currentImageIndex == 3) self.currentImageIndex -= 2; // change to the above image 
else return; // do nothing
}
else if (recognizer.direction == UISwipeGestureRecognizerDirectionDown) {
if (self.currentImageIndex == 0 || self.currentImageIndex == 1) self.currentImageIndex += 2; // change to the above image 
else return; // do nothing
}
[UIView animationWithDuration:0.5 animations:^{
    [self.imageView setAlpha:0];
} completion^(BOOL finished){
    if (finished) {
         [UIView animationWithDuration:0.5 animations:^{
             [self.imageView setImage[self.images objectAtIndex:self.currentImageIndex]];
             [self.imageView setAlpha:1];
         }];
    }
}];
}