3

我正在实施的视图有问题。

这是一个在 CATiledLayer 中显示 pdf 页面的视图。该平铺视图位于 UISCrollView 内。

我将视图控制为“ZoomingPDFView”苹果示例。我做了一些修改，以便在未启用滚动时识别滑动手势，并在此站点上的各种线程和问题中提供建议。那时，手势被称为一次。但是由于我需要解耦视图并委托滑动以缓存页面并执行通用视图，因此我创建了一个视图控制器来处理滑动手势，并且页面加载方法提高了 pdf 视图的性能。

现在我有一侧的视图和另一侧的控制器，滑动手势被检测到两次，我什至无法得到问题的线索。

这是控制台输出

2010-11-19 11:45:08.370 ZoomingPDFViewerForIPad[20327:207] initWithFrame and page
2010-11-19 11:45:08.530 ZoomingPDFViewerForIPad[20327:207] drawPage
2010-11-19 11:45:08.531 ZoomingPDFViewerForIPad[20327:207] scale: 1.000000
2010-11-19 11:45:08.531 ZoomingPDFViewerForIPad[20327:207] pdf scale: 1.290062
2010-11-19 11:45:08.532 ZoomingPDFViewerForIPad[20327:207] pdf initial scale: 1.290062
2010-11-19 11:45:15.488 ZoomingPDFViewerForIPad[20327:207] left
2010-11-19 11:45:15.489 ZoomingPDFViewerForIPad[20327:207] left
2010-11-19 11:45:15.490 ZoomingPDFViewerForIPad[20327:207] initWithFrame and page
2010-11-19 11:45:15.538 ZoomingPDFViewerForIPad[20327:207] drawPage
2010-11-19 11:45:15.538 ZoomingPDFViewerForIPad[20327:207] scale: 1.000000
2010-11-19 11:45:15.539 ZoomingPDFViewerForIPad[20327:207] pdf scale: 1.290062
2010-11-19 11:45:15.539 ZoomingPDFViewerForIPad[20327:207] pdf initial scale: 1.290062
2010-11-19 11:45:15.540 ZoomingPDFViewerForIPad[20327:1a07] initWithFrame and page
2010-11-19 11:45:15.541 ZoomingPDFViewerForIPad[20327:5f07] initWithFrame and page
2010-11-19 11:45:15.593 ZoomingPDFViewerForIPad[20327:1a07] drawPage
2010-11-19 11:45:15.594 ZoomingPDFViewerForIPad[20327:1a07] scale: 1.000000
2010-11-19 11:45:15.594 ZoomingPDFViewerForIPad[20327:1a07] pdf scale: 1.290062
2010-11-19 11:45:15.595 ZoomingPDFViewerForIPad[20327:1a07] pdf initial scale: 1.290062
2010-11-19 11:45:15.695 ZoomingPDFViewerForIPad[20327:5f07] drawPage
2010-11-19 11:45:15.704 ZoomingPDFViewerForIPad[20327:5f07] scale: 1.000000
2010-11-19 11:45:15.707 ZoomingPDFViewerForIPad[20327:5f07] pdf scale: 1.290062
2010-11-19 11:45:15.713 ZoomingPDFViewerForIPad[20327:5f07] pdf initial scale: 1.290062

这是代码：

#import <UIKit/UIKit.h>

@class TiledPDFView;
@protocol PDFScrollViewDelegate;

@interface PDFScrollView : UIScrollView <UIScrollViewDelegate> {
 // The TiledPDFView that is currently front most
 TiledPDFView *pdfView;
 // The old TiledPDFView that we draw on top of when the zooming stops
 TiledPDFView *oldPDFView;


 // A low res image of the PDF page that is displayed until the TiledPDFView
 // renders its content.
 UIImageView *backgroundImageView;


 id<PDFScrollViewDelegate,NSObject> pdfViewDelegate;

 // current pdf zoom scale
 CGFloat pdfScale;

 CGPDFPageRef page;
 CGPDFDocumentRef pdf;
 CGFloat initialScale;
 TiledPDFView *initialTiledView;
 int currentPage;
 int pageCount;

 UITapGestureRecognizer *doubleTap,*twoFingerDoubleTap;
 UISwipeGestureRecognizer *rightSwipe, *leftSwipe;



}

@property (nonatomic,retain) id<PDFScrollViewDelegate> pdfViewDelegate;
-(id)initWithFrame:(CGRect)rect;
-(id)initWithFrame:(CGRect)frame andPDFPage:(CGPDFPageRef)aPage;
-(void)enableGestures;
-(void)drawPage;
@end

@implementation PDFScrollView
@synthesize pdfViewDelegate;

….

-(void)enableGestures{
 leftSwipe = [[UISwipeGestureRecognizer alloc ]initWithTarget:self action:@selector(handleRightSwipe:)];

 leftSwipe.direction = UISwipeGestureRecognizerDirectionRight;

 [self addGestureRecognizer:leftSwipe];

 //add right swipe
 rightSwipe = [[UISwipeGestureRecognizer alloc ]initWithTarget:self action:@selector(handleLeftSwipe:)];
 rightSwipe.direction = UISwipeGestureRecognizerDirectionLeft;
 [self addGestureRecognizer:rightSwipe];



 doubleTap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(handleDoubleTap:)];
 doubleTap.numberOfTapsRequired =2;
 doubleTap.numberOfTouchesRequired =1;
 [self addGestureRecognizer:doubleTap];


 twoFingerDoubleTap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(handleTwoFingerDoubleTap:)];
 twoFingerDoubleTap.numberOfTapsRequired =2;
 twoFingerDoubleTap.numberOfTouchesRequired =2;
 [self addGestureRecognizer:twoFingerDoubleTap];


}

// some more code
@end

#import <UIKit/UIKit.h>
#import "PDFScrollViewDelegate.h"
@class TiledPDFView;


@interface ZoomingPDFViewerForIPadViewController : UIViewController <UIScrollViewDelegate,PDFScrollViewDelegate>  {

 CGPDFPageRef page;



 CGPDFDocumentRef pdf;

 NSInteger currentPage;



 NSInteger pageCount;

 PDFScrollView *myScrollView;

 PDFScrollView *previousPage;
 PDFScrollView *nextPage;

}

-(id)initWithResourcePath:(NSString*)path ;
-(void)loadNextPage;
-(void)loadPreviousPage;
@end


@implementation ZoomingPDFViewerForIPadViewController

// some more code
#pragma mark -
#pragma mark PDFScrollViewDelegate methods
/* 
 called when user swipes right on the view
 */

-(void)viewDetectedRightSwipe:(PDFScrollView*)pdfScrollView withGesture:(UISwipeGestureRecognizer*)recognizer {
  NSLog(@"right");
 if (currentPage>1){
  //decreate page counter
  currentPage--;


  // release old next page

  if(nextPage){
   [nextPage release];
  }
  // set the actual page as the next one
  nextPage = [myScrollView retain];

  // remove the view from the actual view
  [myScrollView removeFromSuperview];

  // check if the previous page is loaded
  if(!previousPage)
   [self loadPreviousPage];

  // set the previouse page as the actual page
  myScrollView = previousPage;

  myScrollView.pdfViewDelegate = self;
  //[myScrollView drawPage];
  // load a new previous page
  //[NSThread detachNewThreadSelector:@selector(loadNextPage) toTarget:self withObject:nil];
  //[self loadNextPage];


 }
}
/*
 called when user swipes left on the view
 */
-(void)viewDetectedLeftSwipe:(PDFScrollView*)pdfScrollView withGesture:(UISwipeGestureRecognizer*)recognizer{
 NSLog(@"left");
 // if the end of the document isn't reached 
 if (currentPage<pageCount){
  //increment current page
  currentPage++;
  // if a previous page has been loaded release it
  if (previousPage) {
   [previousPage release];
  }
  // assing the actual view to as a previous page  and retain it before it gets release by superview
  previousPage = [myScrollView retain];
  // remove the view from the super view 
  [myScrollView removeFromSuperview];

  // if a next page hasn't beeen loaded yet, load it on this thread
  if (!nextPage)
   [self loadNextPage];

  // assign the next page as the current page
  myScrollView = nextPage;

  // put the current page the delegate
  myScrollView.pdfViewDelegate = self;

  // add the current page to the super view
  [[self view] addSubview:myScrollView];

  // load a next page.
  [NSThread detachNewThreadSelector:@selector(loadNextPage) toTarget:self withObject:nil];
 //[self loadNextPage];


 }  

}

/*
 called when the user taps the screen
 */
-(void)viewDetectedTapping:(PDFScrollView*)pdfScrollView withGesture:(UITapGestureRecognizer*)recognizer {
 NSLog(@"tapped");
 [myScrollView setZoomScale:1.0f animated:YES];


}


-(void)loadNextPage {
 NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 CGPDFPageRef aPage =  CGPDFDocumentGetPage(pdf, currentPage+1);
 nextPage = [[PDFScrollView alloc] initWithFrame:myScrollView.frame andPDFPage:aPage ];
 [pool release];
}



-(void)loadPreviousPage {

 NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; 
 CGPDFPageRef aPage =  CGPDFDocumentGetPage(pdf, currentPage-1);
 previousPage = [[PDFScrollView alloc] initWithFrame:myScrollView.frame andPDFPage:aPage];
 [pool release];
}
@end

这是手势触发的代码。

-(void)handleRightSwipe:(UIGestureRecognizer*)gesture {


    if ([pdfViewDelegate respondsToSelector:@selector(viewDetectedRightSwipe:withGesture:)]) {
        UISwipeGestureRecognizer *swipe = (UISwipeGestureRecognizer*)gesture;
        [pdfViewDelegate viewDetectedRightSwipe:self withGesture:swipe];

    }




}
-(void)handleLeftSwipe :(UIGestureRecognizer*)gesture{


    if ([pdfViewDelegate respondsToSelector:@selector(viewDetectedLeftSwipe:withGesture:)]) {
        UISwipeGestureRecognizer *swipe= (UISwipeGestureRecognizer*)gesture;
        [pdfViewDelegate viewDetectedLeftSwipe:self withGesture:swipe];

    }

}

在此先感谢您的时间

4

8 回答 8

7

我遇到了完全相同的问题，我的猜测是执行此行时触发了第二个操作：

[myScrollView removeFromSuperview];

出于某种原因， UISwipeGestureRecognizer 在它附加到的视图被删除时触发。似乎没有其他 UIGestureRecognizer 可以这样做。

我的解决方案是在调用 removeFromSuperview 之前禁用所有手势识别器：

for (UIGestureRecognizer *g in myScrollView.gestureRecognizers) {
    g.enabled = NO;
    g.delegate = nil;
}
[myScrollView removeFromSuperview];

这并不理想，但它成功了。

于 2010-12-04T04:04:53.293 回答
5

@帕库，

不要使用计时器！

您需要查看手势状态。UIGestureRecognizer 向您发送有关您正在获取手势的哪一部分的信息。手势不是一个单一的事件。想想捏合手势……它不会只发生一次，它会开始、改变位置，并且可以取消、失败或结束。每次发生其中一件事情时，您的回调就会运行。

只是忽略紧密发生的事件通常会起作用，但是例如滑动手势可能会比您的时间窗口持续更长的时间。

switch (sender.state) {
    case UIGestureRecognizerStateBegan:
        self.dragging = [self objectToRotateOrPinch:sender];
        break;
    case UIGestureRecognizerStateEnded:
        self.dragging = nil;
        break;
    case UIGestureRecognizerStateCancelled:
        self.dragging = nil;
        break;
    case UIGestureRecognizerStateFailed:
        self.dragging = nil;
        break;
    case UIGestureRecognizerStateChanged:
        // rotate or pinch
        break;
    default:
        break;
}

如果您只关心滑动发生的时间，那么您只想在状态 == UIGestureRecognizerStateEnded 时做出反应。

于 2010-12-02T00:06:05.870 回答
2

在 iOS 4.xx 上存在一个错误，如果您在回调中 removeFromSuperview，则会导致回调被调用两次。

您可以在 removeFromSuperview 中将 enabled 属性设置为 NO：

- (void)removeFromSuperview
{
    for(UIGestureRecognizer* gestureRecognizer in self.gestureRecognizers) {
        gestureRecognizer.enabled = NO;
    }
    [super removeFromSuperview];
}

- (void)willMoveToSuperview:(UIView *)newSuperview
{
    for(UIGestureRecognizer* gestureRecognizer in self.gestureRecognizers) {
        gestureRecognizer.enabled = YES;
    }
    [super willMoveToSuperview:newSuperview];
}

但是，回调仍然会触发，即使它被禁用。所以你应该在回调中检查启用的属性：

- (void)didSwipeRight:(UISwipeGestureRecognizer *)gestureRecognizer
{
    if (gestureRecognizer.enabled) {
            //do something useful...
    }
}
于 2012-06-29T13:05:05.510 回答
1

在将手势传递给委托之前尝试检查手势的状态属性：

-(void)handleRightSwipe:(UIGestureRecognizer*)gesture {
    if (gesture.state != UIGestureRecognizerStateEnded)
        return; //gesture not finished yet

    if ([pdfViewDelegate respondsToSelector:@selector(viewDetectedRightSwipe:withGesture:)]) {
        UISwipeGestureRecognizer *swipe = (UISwipeGestureRecognizer*)gesture;
        [pdfViewDelegate viewDetectedRightSwipe:self withGesture:swipe];
    }
}

如果可行，请对左滑动执行相同操作。

于 2010-11-20T19:47:41.833 回答
1

以下代码是一个简单的解决方法，我认为它不太可能产生任何不需要的副作用。

- (void) leftSwipe: (UISwipeGestureRecognizer *) recognizer;
{
    if (![recognizer isEnabled]) return;    
    [recognizer setEnabled:NO];
    [recognizer performSelector:@selector(setEnabled:) withObject: [NSNumber numberWithBool:YES] afterDelay:0.1];
       // your gesture handling code here....

当我从使用通知接收手势切换到直接接收手势时，我遇到了这个问题，但我没有进一步研究这个问题。state 属性对我绝对没有帮助 - 日志显示第一次和第二次调用提供了相同状态的识别器。

于 2011-01-11T17:57:56.230 回答
1

我遇到了同样的问题，似乎是当您尝试删除视图（Gesture Fires）时出现问题，所以，重写 removeFromSuperview ......这个片段对我有用......

- (void)removeFromSuperview
{
    for(UIGestureRecognizer* gesture in [self gestureRecognizers])
        [self removeGestureRecognizer:gesture];
    [super removeFromSuperview];
}
于 2011-09-04T01:42:05.903 回答
1

我遇到了完全相同的问题，您也可以向removeGestureRecognizer:UIView 类发送消息。

-(void)handleLeftSwipe:(UIGestureRecognizer *)gesture
{
    UIView *vw = [gesture view];
    [view removeGestureRecognizer:gesture];
    [view removeFromSuperview];
}

但是，我仍然不知道为什么从超级视图中删除视图时会“触发”手势。

干杯，

于 2011-12-30T19:12:30.220 回答
-1

当手势被用户“完成”时检测到，aBitObvious 的答案很好，但它确实是开始深入研究问题的好地方。这里的问题是手势本身被检测到一次，但与之相关的动作被触发两次。我做了一个计时器来跟踪这些调用之间的毫秒数，以忽略对操作的虚假调用。

于 2010-12-01T23:54:07.683 回答