使用UIPanGestureRecognizer

Question

我有一个小的imageView，使用UIPanGestureRecognizer在屏幕上移动，但是当它从超级视图的边缘出来时没有得到更多的触摸，因此不能再回头。我怎样才能防止图像从超级视图的边缘出来？ 这是代码：

- (void)pan:(UIPanGestureRecognizer *)gestureRecognizer 
{ 
if (inLongPress) { 
    UIView *hitView = [gestureRecognizer view]; 

    [self adjustAnchorPointForGestureRecognizer:gestureRecognizer]; 

    if (!(CGRectContainsRect(self.imageView.frame, hitView.frame))) { 

     [UIView beginAnimations:@"" context:NULL]; 
     [hitView setCenter:CGPointMake(_prevCenter.x, _prevCenter.y)]; 
     [UIView commitAnimations]; 

    } 
    _prevCenter=hitView.center; 

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged) { 
     CGPoint translation = [gestureRecognizer translationInView:[hitView superview]]; 

     [hitView setCenter:CGPointMake([hitView center].x + translation.x, [hitView center].y + translation.y)]; 

     [gestureRecognizer setTranslation:CGPointZero inView:[hitView superview]]; 
    } 

    if ([gestureRecognizer state] == UIGestureRecognizerStateEnded){ 
     inLongPress=NO; 
     hitView.alpha=1.0; 
    } 
} 

}

Answer 1

只是用了几个if，限制了CGPoint到所允许的范围。

像这样可以确保您不能移动对象的视图之外：

CGFloat proposedX = location.x; 
CGFloat proposedY = location.y; 

CGRect objectFrame = hitView.frame; 
CGFloat allowedXMin = 0 + objectFrame.size.width/2.0f; 
CGFloat allowedXMax = self.view.bounds.size.width - objectFrame.size.width/2.0f; 
CGFloat allowedYMin = 0 + objectFrame.size.height/2.0f; 
CGFloat allowedYMax = self.view.bounds.size.height - objectFrame.size.height/2.0f; 

if (proposedX < allowedXMin) { 
    proposedX = allowedXMin; 
} 
else if (proposedX > allowedXMax) { 
    proposedX = allowedXMax; 
} 

if (proposedY < allowedYMin) { 
    proposedY = allowedYMin; 
} 
else if (proposedY > allowedYMax) { 
    proposedY = allowedYMax; 
} 
location = CGPointMake(proposedX, proposedY); 

hitView.center = location; 

Answer 2

在视图控制器的你的viewDidLoad方法，只需设置clipsToBounds您的上海华的属性YES。

[superview setClipsToBounds:YES];