Ios 在两点之间来回滑动按钮

我尝试使用UIPangestureRecognitor在两点之间滑动按钮，就像音量滑块一样。下面的代码允许我来回滑动按钮，但按钮并不是每次都停在同一点上，也就是说，当我向右滑动按钮时，它有时停在应该停的地方，有时停在应该停的地方+/-10像素。我做错了什么

- (void)handlePan:(UIPanGestureRecognizer *)recognizer {

    CGPoint location = [recognizer locationInView:self];


    // 1
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        // if the gesture just started, record current center location
        _originalCenter = self.sliderButton.center;
    }

    // 2
    if (recognizer.state == UIGestureRecognizerStateChanged) {
        // move the checkmarks and main label based on touch
        //CGPoint translation = [recognizer translationInView:self];

        // move slider button
        if (location.x < 70 + 178 && location.x > 70) {
            self.sliderButton.center = CGPointMake(location.x,  _originalCenter.y);
        } 

        // determine whether the item has been dragged far enough to initiate a removal
        if (location.x > 170 + 70) {
            _draggedToEnd = YES;
        } else {
            _draggedToEnd = NO;
        }
    }

    // 3
    if (recognizer.state == UIGestureRecognizerStateEnded) {

        if (_draggedToEnd) {
            // notify the delegate that this item should be deleted
            [self buttonDraggedToEnd];
        }

    }
}

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当位置在点之外时，将其放置在最近的点上如何？因此，如果汤姆·欧文建议的方法是这样做的话！我看不到在手势完成后修复视图位置的代码部分。它是buttonDraggedToEnd的一部分吗？如果是这样，请发布相关代码。汤姆，谢谢！将其添加为答案，我将接受：