一次由UILongPressGestureRecognizer触发拖动时，如何防止UIView“跳动”？

Question

Intended function:

After long-pressing a button, have the ability to drag it around on the screen.

Jumping Bug:

When I initially start dragging the button, its center "jumps" to the CGPoint that registered my initial click to trigger the long press. Eg, I long-press click a button on its top right, and once I start dragging the cursor while holding it the button jumps to that "top right" location.

After that jump - all dragging is fine.

Code:

- (void)longPress:(UILongPressGestureRecognizer*)receivedGesture
{
   if (receivedGesture.state == UIGestureRecognizerStateChanged)
   {
       CGPoint translation = [receivedGesture locationInView:self.scrollView];
       pannedBadge.center = translation;
   }
} 

Ultimate question:

What's the solution here? How do I make it such that the initial dragging moves the button from its original center?

Thanks!

Answer 1

通常，要使视图可拖动，我要做的是检测触摸的起点，然后获取其移动（触摸）的差异，然后按如下所示设置视图的中心：我没有将其设置为绝对触摸，但我使用刚刚检测到的触摸移动来相对设置它。

Answer 2

The reason is that your translation point is asking the gesture's location in the view, not the center of the view it's over. If you start pannedBadge.center to be the button's center, I that should work. Hope this helps!