如何设置最小和最大y值？

Question

我在我的应用程序中实现了一个可拖动的UIView。代码我工作得很好，但我想设置一个限制区UIView可以移动。

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; 
    } 
} 

所以，我怎么可以设置最小和最大y值UIView的可拖动？

谢谢！

Answer 1

如果你有兴趣在确保视图框不走超过或低于一定的y值，你可以做到以下几点，

- (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; 
    } 
}