iphone - UIWebView 内的滑动手势识别

Question

我已经阅读了很多关于此的问题，但似乎没有一个能够实现我正在寻找的东西......所以可以说我UIWebView在UIViewController. 有UIViewController一个SwipeGestureRecognizer工作正常。UIWebView只要没有滚动条，它甚至可以在-- 中工作。（在我加载页面之前，或者即使我加载的页面可以适当地适合我的UIWebView. 但是，如果我加载需要向左或向右水平滚动的网页，那么在UIWebView我的视图部分内，我无法识别任何滑动手势。每次单击/拖动/滑动都会触发滚动动作。有没有办法区分“滑动”和仅用手指滚动（不是抬起它，而是拖动滚动）。

Answer 1

是的，你可以告诉 UIWebView 的 UIScrollView 它的 UIPanGestureRecognizer 应该只在你自己的 UISwipeGestureRecognizer 失败时触发。

这就是你的做法：

UISwipeGestureRecognizer *rightSwipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeGesture:)];
UISwipeGestureRecognizer *leftSwipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeGesture:)];
rightSwipeGesture.direction = UISwipeGestureRecognizerDirectionRight;
leftSwipeGesture.direction = UISwipeGestureRecognizerDirectionLeft;
[self.view addGestureRecognizer:rightSwipeGesture];
[self.view addGestureRecognizer:leftSwipeGesture];

[_webView.scrollView.panGestureRecognizer requireGestureRecognizerToFail:rightSwipeGesture];
[_webView.scrollView.panGestureRecognizer requireGestureRecognizerToFail:leftSwipeGesture];

那应该对你有用。

Answer 2

您必须继承 UIWebView 并覆盖手势识别器调用。

编辑 - 看看这篇文章处理 UIWebview 内部的触摸和这个链接http://mithin.in/2009/08/26/detecting-taps-and-events-on-uiwebview-the-right-way/

Answer 3

Johannes Fahrenkrug 的回答成功地有条件地阻止了 webView 的内置平移手势。但是，我发现这仅在 webView 的平移手势非常慢时才有效……如果我以任何合理的速度平移 webView，就会触发滑动手势。我只想要快速滑动来触发滑动手势，而中等或慢速平移来使用默认的 webView 滚动功能。

UISwipeGestureRecognizer 没有用于自定义滑动速度的属性，而 UIPanGestureRecognizer 具有速度属性但无法设置所需的速度，因此我根据本教程设置了自定义手势识别器：

FastSwipeGestureRecognizer.h

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

#define REQUIRED_TOUCHES 5
#define REQUIRED_STRAIGHTNESS 3
#define REQUIRED_TIME .1

typedef enum {
    DirectionUp = 0,
    DirectionRight,
    DirectionDown,
    DirectionLeft
} Direction;

@interface FastSwipeGestureRecognizer : UIGestureRecognizer {
    CGPoint firstTouchLocation;
    NSTimeInterval firstTouchTime;
    int touchesCount;

    Direction direction;
}

@property (nonatomic) CGPoint firstTouchLocation;
@property (nonatomic) NSTimeInterval firstTouchTime;
@property (nonatomic) int touchesCount;

@property (nonatomic) Direction direction;

@end

FastSwipeGestureRecognizer.m

#import "FastSwipeGestureRecognizer.h"

@implementation FastSwipeGestureRecognizer

@synthesize firstTouchLocation;
@synthesize firstTouchTime;
@synthesize touchesCount;

-(void)reset {
    [super reset];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesBegan:touches withEvent:event];
    self.firstTouchLocation = [[touches anyObject] locationInView:self.view];
    self.firstTouchTime = [NSDate timeIntervalSinceReferenceDate];
    self.touchesCount = 1;
    self.state = UIGestureRecognizerStatePossible;
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesMoved:touches withEvent:event];
    self.touchesCount++;
    if (self.touchesCount > REQUIRED_TOUCHES) { // wait until we have a few touches before we evaluate the gesture
        CGPoint thisTouchLocation = [[touches anyObject] locationInView:self.view];
        float horizontalRatio = (ABS(thisTouchLocation.x - self.firstTouchLocation.x) / ABS(thisTouchLocation.y - self.firstTouchLocation.y));
        float verticalRatio = 1 / horizontalRatio;
        NSTimeInterval elapsedTime = [NSDate timeIntervalSinceReferenceDate] - self.firstTouchTime;
        NSLog(@"swipe? %f, %f, %f", verticalRatio, horizontalRatio, elapsedTime);

        // if we're moving straight enough and fast enough, complete the gesture
        if (((horizontalRatio > REQUIRED_STRAIGHTNESS)||(verticalRatio > REQUIRED_STRAIGHTNESS))&&(elapsedTime < REQUIRED_TIME)) {
            if (horizontalRatio > REQUIRED_STRAIGHTNESS) {
                self.direction = (thisTouchLocation.x > self.firstTouchLocation.x) ? DirectionRight : DirectionLeft ;
            } else if (verticalRatio > REQUIRED_STRAIGHTNESS) {
                self.direction = (thisTouchLocation.y > self.firstTouchLocation.y) ? DirectionDown : DirectionUp ;
            }
            self.state = UIGestureRecognizerStateRecognized;
        } else {
            self.state = UIGestureRecognizerStateFailed;
        }
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesEnded:touches withEvent:event];
    if (self.touchesCount < REQUIRED_TOUCHES) {
        self.state = UIGestureRecognizerStateFailed;
    }
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesCancelled:touches withEvent:event];
    self.state = UIGestureRecognizerStateFailed;
}

@end

设置你的手势

FastSwipeGestureRecognizer *swipeGesture = [[FastSwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeGesture:)];
[self.view addGestureRecognizer:swipeGesture];
[self.webView.scrollView.panGestureRecognizer requireGestureRecognizerToFail:swipeGesture];

然后检测接收到的手势的方向

- (void)handleSwipeGesture:(FastSwipeGestureRecognizer *)gesture {
    if (gesture.state == UIGestureRecognizerStateEnded) {
        if (gesture.direction == DirectionRight) {
            // do something
        } else if (gesture.direction == DirectionLeft) {
            // do something
        } else if (gesture.direction == DirectionUp) {
            // do something
        } else if (gesture.direction == DirectionDown) {
            // do something
        }
    }
}

请注意，这只需要一个手势来处理所有四个滑动方向，而不是每个方向一个 UISwipeGestureRecognizer。