在UITableView中观察捏合多点触摸手势

我想在UITableView上实现一个捏合/外出,我已经看了几个方法,包括这个:

类似的问题

但是虽然我可以创建一个UIViewTouch对象并将其覆盖到我的UITableView上,滚动事件不会被转发到我的UITableView,我仍然可以选择单元格,并且它们通过触发转换到新的ViewController对象来正确响应.但是,尽管传递了touchesBegan,touchesMoved和touchesEnded事件,但我无法滚动UITableView.

这似乎是一个经典问题.在我的情况下,我想拦截UIWebView上的一些事件,这些事件不能被子类化,等等.

我发现最好的方法是使用UIWindow拦截事件:

EventInterceptWindow.h

@protocol EventInterceptWindowDelegate
- (BOOL)interceptEvent:(UIEvent *)event; // return YES if event handled
@end


@interface EventInterceptWindow : UIWindow {
    // It would appear that using the variable name 'delegate' in any UI Kit
    // subclass is a really bad idea because it can occlude the same name in a
    // superclass and silently break things like autorotation.
    id  eventInterceptDelegate;
}

@property(nonatomic, assign)
    id  eventInterceptDelegate;

@end

EventInterceptWindow.m:

#import "EventInterceptWindow.h"

@implementation EventInterceptWindow

@synthesize eventInterceptDelegate;

- (void)sendEvent:(UIEvent *)event {
    if ([eventInterceptDelegate interceptEvent:event] == NO)
        [super sendEvent:event];
}

@end

创建该类,将MainWindow.xib中的UIWindow类更改为EventInterceptWindow,然后将eventInterceptDelegate设置为要拦截事件的视图控制器.拦截双击的示例:

- (BOOL)interceptEvent:(UIEvent *)event {
    NSSet *touches = [event allTouches];
    UITouch *oneTouch = [touches anyObject];
    UIView *touchView = [oneTouch view];
    //  NSLog(@"tap count = %d", [oneTouch tapCount]);
    // check for taps on the web view which really end up being dispatched to
    // a scroll view
    if (touchView && [touchView isDescendantOfView:webView]
            && touches && oneTouch.phase == UITouchPhaseBegan) {
        if ([oneTouch tapCount] == 2) {
            [self toggleScreenDecorations];
            return YES;
        }
    }   
    return NO;
}

相关信息:http: //iphoneincubator.com/blog/windows-views/360idev-iphone-developers-conference-presentation

尼姆罗德写道:

某处将eventInterceptDelegate设置为您要拦截事件的视图控制器

我没有立即理解这句话.为了让与我有同样问题的其他人的利益,我这样做的方法是将以下代码添加到我必须检测触摸的UIView子类中.

- (void) viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    // Register to receive touch events
    MyApplicationAppDelegate *appDelegate = (MyApplicationAppDelegate *) [[UIApplication sharedApplication] delegate];
    EventInterceptWindow *window = (EventInterceptWindow *) appDelegate.window;
    window.eventInterceptDelegate = self;
}


- (void) viewWillDisappear:(BOOL) animated
{
    // Deregister from receiving touch events
    MyApplicationAppDelegate *appDelegate = (MyApplicationAppDelegate *) [[UIApplication sharedApplication] delegate];
    EventInterceptWindow *window = (EventInterceptWindow *) appDelegate.window;
    window.eventInterceptDelegate = nil;

    [super viewWillDisappear:animated];
}


- (BOOL) interceptEvent:(UIEvent *) event
{
    NSLog(@"interceptEvent is being called...");
    return NO;
}

这个版本interceptEvent:是一个简单的缩放检测实现.NB.一些代码来自Apress的Beginning iPhone 3 Development.

CGFloat initialDistance;

- (BOOL) interceptEvent:(UIEvent *) event
{
    NSSet *touches = [event allTouches];

    // Give up if user wasn't using two fingers
    if([touches count] != 2) return NO;

    UITouchPhase phase = ((UITouch *) [touches anyObject]).phase;
    CGPoint firstPoint = [[[touches allObjects] objectAtIndex:0] locationInView:self.view];
    CGPoint secondPoint = [[[touches allObjects] objectAtIndex:1] locationInView:self.view];

    CGFloat deltaX = secondPoint.x - firstPoint.x;
    CGFloat deltaY = secondPoint.y - firstPoint.y;
    CGFloat distance = sqrt(deltaX*deltaX + deltaY*deltaY);

    if(phase == UITouchPhaseBegan)
    {
        initialDistance = distance;
    }
    else if(phase == UITouchPhaseMoved)
    {
        CGFloat currentDistance = distance;
        if(initialDistance == 0) initialDistance = currentDistance;
        else if(currentDistance - initialDistance > kMinimumPinchDelta) NSLog(@"Zoom in");
        else if(initialDistance - currentDistance > kMinimumPinchDelta) NSLog(@"Zoom out");
    }
    else if(phase == UITouchPhaseEnded)
    {
        initialDistance = 0;
    }

    return YES;
}

编辑:虽然这个代码在iPhone模拟器中工作得很好,但当我在iPhone设备上运行时,我遇到了与表滚动相关的奇怪错误.如果您也遇到这种情况,则强制该interceptEvent:方法在所有情况下都返回NO.这意味着超类也将处理触摸事件,但幸运的是,这并没有破坏我的代码.