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，不能在对角线交换图像。 例如，第一张图像可以与其右侧和下方的图像交换，第二张图像只能与其左侧和下方的图像交换，依此类推。 谁能帮我一下如何做。 谢谢

Answer 1

要添加拖放功能（假设这就是您的意思），您需要研究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]-想象一个分成四个相等部分的正方形。 左上部分的索引为零，右上部分的索引为1，左下部分的索引为2，最后右下部分的索引为3。下面的代码检查当前索引，并从中确定当前是否有图像可以进行交换，如果不进行交换，则不执行任何操作。

这段代码是从我的头上来的，所以可能会有语法错误，但是逻辑是合理的（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];
         }];
    }
}];
}