相机预览层上的uibutton在拖动后跳回其初始位置（UIPanGestureRecognizer手势）答案

【问题标题】：uibutton on camera preview layer jumps back to its initial location after dragged (UIPanGestureRecognizer gesture)相机预览层上的uibutton在拖动后跳回其初始位置（UIPanGestureRecognizer手势）
【发布时间】：2016-03-08 07:15:19
【问题描述】：

我尝试了很多方法，但无法解决这个问题。我在 AVCaptureVideoPreviewLayer 顶部有按钮定义如下：

AVCaptureVideoPreviewLayer *previewLayer = (AVCaptureVideoPreviewLayer *)self.previewView.layer;

对于按钮，我定义了一个用于拖动的手势识别器：

UIPanGestureRecognizer *focPanRecognizer;
focPanRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(wasDragged:)];
[focPanRecognizer setMinimumNumberOfTouches:1];
[focPanRecognizer setMaximumNumberOfTouches:1];
focPanRecognizer.cancelsTouchesInView = YES;
[self.focusButton addGestureRecognizer:focPanRecognizer];
[self.focusButton setUserInteractionEnabled:YES];

拖动通过以下方法处理：

- (void)wasDragged:(UIPanGestureRecognizer *)recognizer
{
    if (recognizer.state == UIGestureRecognizerStateChanged ||
        recognizer.state == UIGestureRecognizerStateEnded) {
        UIButton *draggedButton = (UIButton *) recognizer.view;
        CGPoint translation = [recognizer translationInView:self.previewView];       
        CGRect newButtonFrame = draggedButton.frame;
        newButtonFrame.origin.x += translation.x;
        newButtonFrame.origin.y += translation.y;
        draggedButton.frame = newButtonFrame;
        [recognizer setTranslation:CGPointZero inView:self.previewView];
    }
}

当我拖动按钮时，如果我关闭相机镜头，它会正确拖动。如果相机镜头打开，按钮会立即跳回原来的位置。

可能是什么问题？非常感谢您的帮助。

【问题讨论】：

标签： ios camera uibutton drag pan

【解决方案1】：

问题在于布局中使用的约束。正如 jkanter 在iOS >> Dragged View is Jumping Back to Original Position >> Auto Layout Combined with UIPanGestureRecognizer Issue 的回答中所解释的那样，更新约束有所帮助

【讨论】：