如果检测到超出范围，则禁用平移手势

Posted 2023-03-16

【中文标题】如果检测到超出范围，则禁用平移手势

【英文标题】：Disabling Pan Gesture if out of bounds detected

【发布时间】：2012-12-14 14:53:41

【问题描述】：

我有一个 UIView 我正在尝试在屏幕上上下移动，但是我只想让它平移，这样当它处于正常位置 (0, 0) 时你不能向下拖动视图

我试图检测识别器的中心何时不是视图高度的一半，但是视图是不可移动的，并且中心始终是高度的一半（在本例中为 230）。

有什么想法吗？

- (IBAction)panDetected:(UIPanGestureRecognizer *)recognizer 
    CGPoint translation = [recognizer translationInView:self.view];
    NSLog(@"\ncenter.y: %f\ntranslation.y: %f\n", recognizer.view.center.y, translation.y);
    if (recognizer.view.center.y > ([[UIScreen mainScreen] bounds].size.height - 20)/2) 
            return;
    
    recognizer.view.center = CGPointMake(recognizer.view.center.x,
                                         recognizer.view.center.y + translation.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];

【问题讨论】：

recognizer.view.center = CGPointMake(recognizer.view.center.x, MAX(recognizer.view.center.y + translation.y, 230));

【参考方案1】：

不要手动计算点是否在视图的范围内，而是使用CGRectContainsPoint(rect, point)。这对我有用，我喜欢它，因为它更短且更具可读性：

func handlePan(pan: UIPanGestureRecognizer) 
    switch pan.state 
    case .Began:
        if CGRectContainsPoint(self.pannableView.frame, pan.locationInView(self.pannableView)) 
            // Gesture started inside the pannable view. Do your thing.
        

【参考方案2】：

CGPoint translation = [recognizer translationInView:self.view];
CGPoint finalpoint = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y+ translation.y);

//limit the boundary    
if ((recognizer.view.frame.origin.x>0 && translation.x > 0) || (recognizer.view.frame.origin.x + recognizer.view.frame.size.width<=320 && translation.x < 0))
    finalpoint.x = recognizer.view.center.x;

if ((recognizer.view.frame.origin.y>0 && translation.y > 0) || (recognizer.view.frame.origin.y + recognizer.view.frame.size.height<=self.view.frame.size.height && translation.y < 0))
    finalpoint.y = recognizer.view.center.y;

//set final position
recognizer.view.center = finalpoint;
[recognizer setTranslation:CGPointZero inView:self.view];

【参考方案3】：

试试

CGPoint translation = [recognizer translationInView:self.view];  
if (translation.x+recognizer.view.frame.origin.x<0||translation.y+recognizer.view.frame.origin.y<0)
    
        return;
    

 recognizer.view.center = CGPointMake(recognizer.view.center.x,
                                     recognizer.view.center.y + translation.y);
[recognizer setTranslation:CGPointMake(0, 0) inView:self.view];

【参考方案4】：

recognizer.view.center = CGPointMake(recognizer.view.center.x, MAX(recognizer.view.center.y + translation.y, ([[UIScreen mainScreen] bounds].size.height - 20)/2));