objective-c - UISwipeGestureRecognizer 调用了两次

Question

我在实现一个 View 时遇到问题。

这是一个在 CATiledLayer 中显示 pdf 页面的 View 。该平铺 View 位于 UISCrollView 内。

我将 View 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，并在本网站的各种主题和问题中提供建议。当时，手势被称为一次。但由于我需要解耦 View 并委托(delegate)滑动来缓存页面并实现多功能 View ，我创建了一个 View Controller 来处理滑动手势，页面加载方法提高了 pdf View 的性能。

现在我的 View 在一侧， Controller 在另一侧，滑动手势被检测到两次，我什至无法获得问题的线索。

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

代码如下:

#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];

    }

}

提前感谢您的宝贵时间

Answer 1

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 在它所附加的 View 被移除时触发。似乎没有其他 UIGestureRecognizer 可以做到这一点。

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];

它并不理想，但它确实起到了作用。