綁定在UIPanGestureRecognizer中添加的視圖的移動，在其超級視圖中

我想知道在使用GestureRecognizer時，是否有方法來限制UIView在其超級視圖中的移動。綁定在UIPanGestureRecognizer中添加的視圖的移動，在其超級視圖中

例如。我有一個UIImageview我加入UIPanGestureRecognizer與動作panPiece。我按照以下方式調整其中心，以避免其移出超級視角。但它不能正常工作。

-(CGPoint) centerWithBounds:(CGPoint)center andViewFrame:(CGRect)viewFrame andBoundingFrame:(CGRect)boundingFrame{ 

CGFloat lowerXBound = boundingFrame.origin.x + (viewFrame.size.width/2); 
CGFloat higherXBound = boundingFrame.origin.x + boundingFrame.size.width - (viewFrame.size.width/2); 

CGFloat lowerYBound = boundingFrame.origin.y + (viewFrame.size.height/2); 
CGFloat higherYBound = boundingFrame.origin.y + boundingFrame.size.height - (viewFrame.size.height/2); 

if (center.x < lowerXBound) { 
    center.x = lowerXBound; 
} 
if (center.x > higherXBound){ 
    center.x = higherXBound; 
} 
if (center.y < lowerYBound) { 
    center.y = lowerYBound; 
} 
if (center.y > higherYBound){ 
    center.y = higherYBound; 
} 

return center; 
} 

- (void)panPiece:(UIPanGestureRecognizer *)gestureRecognizer 
{ 
    UIView *piece = [gestureRecognizer view]; 

    [self adjustAnchorPointForGestureRecognizer:gestureRecognizer]; 

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged) { 
     CGPoint translation = [gestureRecognizer translationInView:[piece superview]]; 
     CGPoint translatedCenter = CGPointMake([piece center].x + translation.x, [piece center].y + translation.y); 
    CGPoint center = [self centerWithBounds:translatedCenter andViewFrame:[piece frame] andBoundingFrame:[[piece superview] frame]]; 
     [piece setCenter:center]; 
     [gestureRecognizer setTranslation:CGPointZero inView:[piece superview]]; 
    } 
}

代碼幫助表示讚賞。

來源

2010-11-08 rkb