限制超视图边界内子视图的移动

我有一个UIView，这是我的VC视图（self.view），我在其中添加了另一个UIView作为子视图，看起来像一个正方形。 我想限制superview里面的子视图的移动。 基本上，子视图不应超出superview范围。
我确实实施了

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { // i check if point of touch is inside my superview i set the center ie UITouch *touch = [[UITouch allObjects] firstObject]; if (CGRectContainsPoint(subview.frame, [touch locationInView:self.view])) { // set the center here... ie subview.center = [touch locationInView:self.view]; } 

这工作和子视图正在移动，但它也移动到超视图之外; 我怎样才能限制超视图中的移动？

我甚至尝试了类似的东西。

 if (CGRectContainsRect(self.view.bounds, subview.frame)) { // this condition works but i don't know why my subview sticks to the sides of superview if i try to drag it through the bounds of superview } 

我在touchesBegan，touchesCancelled中没有做任何事情，也没有任何与touchesEnd相关的东西。

Answer 1

您需要检查要移动的视图的“新框架”，并将其边缘与其超视图的边界进行比较：

 @implementation DraggableView - (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { // restrict to superview bounds CGRect parentFrame = [self.superview bounds]; UITouch *aTouch = [touches anyObject]; CGPoint location = [aTouch locationInView:self]; CGPoint previousLocation = [aTouch previousLocationInView:self]; // new frame for this "draggable" subview, based on touch offset when moving CGRect newFrame = CGRectOffset(self.frame, (location.x - previousLocation.x), (location.y - previousLocation.y)); if (newFrame.origin.x < 0) { // if the new left edge would be outside the superview (dragging left), // set the new origin.x to Zero newFrame.origin.x = 0; } else if (newFrame.origin.x + newFrame.size.width > parentFrame.size.width) { // if the right edge would be outside the superview (dragging right), // set the new origin.x to the width of the superview - the width of this view newFrame.origin.x = parentFrame.size.width - self.frame.size.width; } if (newFrame.origin.y < 0) { // if the new top edge would be outside the superview (dragging up), // set the new origin.y to Zero newFrame.origin.y = 0; } else if (newFrame.origin.y + newFrame.size.height > parentFrame.size.height) { // if the new bottom edge would be outside the superview (dragging down), // set the new origin.y to the height of the superview - the height of this view newFrame.origin.y = parentFrame.size.height - self.frame.size.height; } // update this view's frame self.frame = newFrame; } @end 

这也使用触摸的偏移，而不是在触摸上居中视图（因此当您开始拖动时它不会“跳到您的手指”）。

编辑说明：在此图像中，蓝色视图类是DraggableView …它不能拖动到其superView（红色视图）之外。