Question

我的观点中添加了UIPanGestureRecognizer 问题是，当触摸被识别为平移手势时，它必须移动几个点，并且我无法在UIGestureRecognizerStateBegan状态下提取原始触摸位置。在此状态下，translationInView:为（0,0），任何后续移动都是从此点开始计算的，而不是从原始位置计算出来的。

有没有办法从手势识别器本身提取原始位置，还是需要覆盖touchesBegan:方法？

Answer 1

您应该能够为手势识别器设置delegate并实施

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch

获得初步接触。

Answer 2

您可以通过实施自定义PanGestureRecognizer来解决此问题，该自定义保存原始触摸点并使其可供调用者使用。

我走了这条路，因为我也想控制移动的距离以触发平移手势。

这对你的情况来说可能有点过头了，但是效果很好而且听起来不那么困难。

要获得接触点坐标，只需拨打：

[sender touchPointInView:yourView]

而不是：

[sender locationInView:yourView]

以下是PanGestureRecognizer.m的代码：

#import "PanGestureRecognizer.h"
#import <UIKit/UIGestureRecognizerSubclass.h>

@implementation PanGestureRecognizer

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesBegan:touches withEvent:event];
    UITouch *touch = [touches anyObject];

    // touchPoint is defined as: @property (assign,nonatomic) CGPoint touchPoint;

    self.touchPoint = [touch locationInView:nil];   
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesMoved:touches withEvent:event];
    UITouch *touch = [touches anyObject];
    CGPoint p = [touch locationInView:nil];

    // customize the pan distance threshold

    CGFloat dx = fabs(p.x-self.touchPoint.x);
    CGFloat dy = fabs(p.y-self.touchPoint.y);

    if ( dx > 2 || dy > 2)  {
        if (self.state == UIGestureRecognizerStatePossible) {
            [self setState:UIGestureRecognizerStateBegan];
        }
        else {
            [self setState:UIGestureRecognizerStateChanged];
        }
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesEnded:touches withEvent:event];

    if (self.state == UIGestureRecognizerStateChanged) {
        [self setState:UIGestureRecognizerStateEnded];
    }
    else {
        [self setState:UIGestureRecognizerStateCancelled];
    }
}

- (void) reset
{
}

// this returns the original touch point

- (CGPoint) touchPointInView:(UIView *)view
{
    CGPoint p = [view convertPoint:self.touchPoint fromView:nil];

    return p;
}

@end

Answer 3

如果您使用locationInView:而不是translationInView:，您将获得绝对坐标而不是相对坐标。但是你必须启动平移以获得输入...要解决此问题，您的视图可以是UIButton，您可以触发与- (IBAction)buttonWasTouched:(UIButton *)button forEvent:(UIEvent *)event连接的"touch down"，如下所示：

-(IBAction)shakeIntensityPanGesturebuttonWasTouched:(UIButton *)button forEvent:(UIEvent *)event
{
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint location = [touch locationInView:touch.view]; //touch location local cordinates
}

Answer 4

您可以使用UIGestureRecognizerState

- (void) onPanGesture:(UIPanGestureRecognizer *)sender {
    if(sender.state == UIGestureRecognizerStateBegan) {
        origin = [sender locationInView];
    } else {
        current = [sender locationInView];
        // Initial touch stored in origin
    }
}

斯威夫特（ish）：

var state = recognizer.state
if state == UIGestureRecognizerState.Began {
    println(recognizer.locationInView(viewForGesture))
    //this will be the point of first touch
}

从UIPanGestureRecognizer获取原始触摸位置

4 个答案: