ios - 可拖动图像 ios 的边界

Question

我正在尝试创建一个可拖动的图像，但我试图将其拖动限制在一个小方 block 内而不是整个屏幕内。有人可以告诉我哪里出错了吗？我已将到目前为止的代码放在下面:

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch = [[event allTouches] anyObject];
    if([touch view] == dot) {
        CGPoint location = [touch locationInView:self.view];
        dot.center = location;
        if (location.x >10) {
            location.x =10;
        } else if (location.x <10) {
            location.x = 10;
        }
        if (location.y >20) {
            location.y =20;
        } else if (location.y < 20) {
            location.y = 20;
        }      
    }
}

Answer 1

您在对其进行更改之前分配位置。

首先将限制应用于 location，然后将其分配给 dot。

此外，您显示的限制会将您的头寸锁定在 10,20，因为您不允许它超过 10 或小于 10。与 20 一样。

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch = [[event allTouches] anyObject];
    if([touch view] == dot) {
        CGPoint location = [touch locationInView:self.view];
        location.x = MIN(MAX(location.x, 0),10);
        location.y = MIN(MAX(location.y, 0),20);
        dot.center = location;     
    }
}