如果檢測到越界，則禁用Pan Gesture

Question

我有一個UIView我試圖在屏幕上上下移動，但是我只希望它能夠平移，這樣當它處於正常位置時（0,0）你就無法將視圖向下拖動

我試圖檢測識別器的中心何時不是視圖高度的一半，然而視圖是不可移動的，並且中心總是高度的一半（在這種情況下為230）。

有任何想法嗎？

- (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];
}

Answer 1

不使用手動計算點是否在視圖的邊界內， CGRectContainsPoint(rect, point)使用CGRectContainsPoint(rect, point) 。 這對我有用，我喜歡它，因為它更短，更易讀：

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.
        }
}

Answer 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];

Answer 3

嘗試

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];

Answer 4

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