是否有一个手势识别器可以同时处理捏和平移？

Question

所以我正在使用iOS 4.2来为我的应用程序添加缩放和平移.我已经实现了UIPinchGestureRecognizer和UIPanGestureRecognizer的实例.在我看来,其中只有一个是一次识别一个手势.特别地,后者仅在一个手指向下时作出反应,而前者在第二手指存在时作出反应.这没关系,但它有一些副作用,我认为这会产生低劣的用户体验质量.

当您放下两根手指然后移动其中一根手指时,图像会像应该的那样展开(放大),但手指下方的像素不再位于手指下方.图像从图像中心缩放,而不是两个手指之间的中点.而这个中心点本身就在发展.我希望中心点的运动能够决定整体图像的平移.

几乎所有iOS应用程序都有相同的行为,图像放大或缩小图像中心周围而不是手指跟踪手指下方的像素？

在我看来,创建一个自定义手势识别器是解决这个问题的正确设计方法,但在我看来,有人会创建这样的识别器,以便商业免费下载和使用.有没有这样的UIGestureRecognizer？

Answer 1

抱歉,这是我用于其中一个演示应用程序的代码,它可以同时捏缩放和平移,而无需使用scrollview.

不要忘记遵守UIGestureRecognizerDelegate协议

如果你无法同时获得捏和平移,也许是因为你错过了这种方法:

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

这是完整的源代码:

#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    isEditing = false;

    photoView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
    [photoView setImage:[UIImage imageNamed:@"photo.png"]];
    photoView.hidden = YES;

    maskView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
    [maskView setImage:[UIImage imageNamed:@"maskguide.png"]];
    maskView.hidden = YES;

    displayImage = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];

    UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)];

    [panGesture setDelegate:self];
    [pinchGesture setDelegate:self];

    [photoView addGestureRecognizer:panGesture];
    [photoView addGestureRecognizer:pinchGesture];
    [photoView setUserInteractionEnabled:YES];

    [panGesture release];
    [pinchGesture release];

    btnEdit = [[UIButton alloc] initWithFrame:CGRectMake(60, 400, 200, 50)];
    [btnEdit setBackgroundColor:[UIColor blackColor]];
    [btnEdit setTitle:@"Start Editing" forState:UIControlStateNormal];
    [btnEdit addTarget:self action:@selector(toggleEditing) forControlEvents:UIControlEventTouchUpInside];

    [[self view] addSubview:displayImage];
    [[self view] addSubview:photoView];
    [[self view] addSubview:maskView];
    [[self view] addSubview:btnEdit];

    [self updateMaskedImage];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

-(void)dealloc
{
    [btnEdit release];

    [super dealloc];
}

#pragma mark -
#pragma mark Update Masked Image Method
#pragma mark -

-(void)updateMaskedImage
{
    maskView.hidden = YES;

    UIImage *finalImage = 
    [self maskImage:[self captureView:self.view]
           withMask:[UIImage imageNamed:@"mask.png"]];


    maskView.hidden = NO;

    //UIImage *finalImage = [self maskImage:photoView.image withMask:[UIImage imageNamed:@"mask.png"]];

    [displayImage setImage:finalImage];
}

- (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage {

    CGImageRef maskRef = maskImage.CGImage; 

    CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
                                        CGImageGetHeight(maskRef),
                                        CGImageGetBitsPerComponent(maskRef),
                                        CGImageGetBitsPerPixel(maskRef),
                                        CGImageGetBytesPerRow(maskRef),
                                        CGImageGetDataProvider(maskRef), NULL, false);

    CGImageRef masked = CGImageCreateWithMask([image CGImage], mask);
    return [UIImage imageWithCGImage:masked];

}

#pragma mark -
#pragma mark Touches Began
#pragma mark -

// adjusts the editing flag to make dragging and drop work
-(void)toggleEditing
{
    if(!isEditing)
    {
        isEditing = true;

        NSLog(@"editing...");

        [btnEdit setTitle:@"Stop Editing" forState:UIControlStateNormal];

        displayImage.hidden = YES;
        photoView.hidden = NO;
        maskView.hidden = NO;
    }
    else
    {
        isEditing = false;

        [self updateMaskedImage];

        NSLog(@"stopped editting");

        [btnEdit setTitle:@"Start Editing" forState:UIControlStateNormal];

        displayImage.hidden = NO;
        photoView.hidden = YES;
        maskView.hidden = YES;
    }
}

/*
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{   
    if(isEditing)
    {
        UITouch *finger = [touches anyObject];
        CGPoint currentPosition = [finger locationInView:self.view];

        //[maskView setCenter:currentPosition];
        //[photoView setCenter:currentPosition];
        if([touches count] == 1)
        {
            [photoView setCenter:currentPosition];
        }
        else if([touches count] == 2)
        {

        }
    }
}
*/

-(void)handlePan:(UIPanGestureRecognizer *)recognizer
{    
    CGPoint translation = [recognizer translationInView:self.view];
    recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, 
                                         recognizer.view.center.y + translation.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
}

-(void)handlePinch:(UIPinchGestureRecognizer *)recognizer
{    
    recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
    recognizer.scale = 1;
}

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

#pragma mark -
#pragma mark Capture Screen Function
#pragma mark -

- (UIImage*)captureView:(UIView *)yourView 
{
    UIGraphicsBeginImageContextWithOptions(yourView.bounds.size, yourView.opaque, 0.0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [yourView.layer renderInContext:context];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

#pragma mark -

@end