iphone - 如何设置最小和最大y值？

Question

我正在我的应用程序中实现一个可拖动的 UIView。我的代码工作得很好，但我想设置 UIView 可以移动的限制区域。

我的代码:

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event allTouches] anyObject];

    if( [touch view] == camview)
    {
        CGPoint location = [touch locationInView:self.view;
        startX = camview.center.x;
        startY= location.y - camview.center.y;        
    }
}


- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch = [[event allTouches] anyObject];

    if( [touch view] == camview)
    {
        CGPoint location = [touch locationInView:self.view];
        location.y =location.y - startY;
        location.x = startX;
        camview.center = location;
    }
}

那么如何设置UIView可以拖动的最小和最大y值呢？

谢谢!

Answer 1

如果您有兴趣确保 View 框架不会超过或低于某个 y 值，您可以执行以下操作，

- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{

    CGFloat minY, maxY; //The position in your self.view you are interested in

    UITouch *touch = [[event allTouches] anyObject];

    if( [touch view] == camview)
    {
        CGPoint location = [touch locationInView:self.view];
        location.y = location.y - startY;
        location.y = MIN(location.y,maxY);   //Always <= maxY
        location.y = MAX(location.y,minY);   //Always >= minY
        location.x = startX;
        camview.center = location;
    }
}