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，但我认为它会产生一些副作用，因为它们会降低用户体验质量。
当您放下两根手指然后移动其中一根时，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，创建自定义手势识别器是解决此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。是否有这样的UIGestureRecognizer？
答案 0 :(得分：8)
很抱歉，这是我用于其中一个演示应用程序的代码，它可以在不使用scrollview的情况下同时进行缩放和平移。
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;
}
以下是完整的源代码：
#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
答案 1 :(得分：4)
所以我创建了自定义手势识别器，因为没有人给我一个更好的解决方案，达到了预期的效果。下面是关键代码片段，允许自定义识别器指示视图应重新定位的位置以及新的比例应该是什么，以质心作为平移和缩放效果的中心，以便手指下方的像素保持在手指下方时间，除非手指看起来旋转，这是不受支持的，我无法做任何事情来阻止他们这样的手势。该手势识别器用两个手指同时平移和缩放。我需要稍后为一个手指平移添加支持，即使两个手指中的一个被抬起。
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
// We can only process if we have two fingers down...
if ( FirstFinger == nil || SecondFinger == nil )
return;
// We do not attempt to determine if the first finger, second finger, or
// both fingers are the reason for this method call. For this reason, we
// do not know if either is stale or updated, and thus we cannot rely
// upon the UITouch's previousLocationInView method. Therefore, we need to
// cache the latest UITouch's locationInView information each pass.
// Break down the previous finger coordinates...
float A0x = PreviousFirstFinger.x;
float A0y = PreviousFirstFinger.y;
float A1x = PreviousSecondFinger.x;
float A1y = PreviousSecondFinger.y;
// Update our cache with the current fingers for next pass through here...
PreviousFirstFinger = [FirstFinger locationInView:nil];
PreviousSecondFinger = [SecondFinger locationInView:nil];
// Break down the current finger coordinates...
float B0x = PreviousFirstFinger.x;
float B0y = PreviousFirstFinger.y;
float B1x = PreviousSecondFinger.x;
float B1y = PreviousSecondFinger.y;
// Calculate the zoom resulting from the two fingers moving toward or away from each other...
float OldScale = Scale;
Scale *= sqrt((B0x-B1x)*(B0x-B1x) + (B0y-B1y)*(B0y-B1y))/sqrt((A0x-A1x)*(A0x-A1x) + (A0y-A1y)*(A0y-A1y));
// Calculate the old and new centroids so that we can compare the centroid's movement...
CGPoint OldCentroid = { (A0x + A1x)/2, (A0y + A1y)/2 };
CGPoint NewCentroid = { (B0x + B1x)/2, (B0y + B1y)/2 };
// Calculate the pan values to apply to the view so that the combination of zoom and pan
// appear to apply to the centroid rather than the center of the view...
Center.x = NewCentroid.x + (Scale/OldScale)*(self.view.center.x - OldCentroid.x);
Center.y = NewCentroid.y + (Scale/OldScale)*(self.view.center.y - OldCentroid.y);
}
视图控制器通过将新比例和中心分配给相关视图来处理事件。我注意到其他手势识别器倾向于允许控制器进行一些数学运算，但我试图在识别器中进行所有数学运算。
-(void)handlePixelTrack:(PixelTrackGestureRecognizer*)sender
{
sender.view.center= sender.Center;
sender.view.transform = CGAffineTransformMakeScale(sender.Scale, sender.Scale);
}
答案 2 :(得分：1)
更简单的解决方案是将视图放在滚动视图中。然后你可以免费获得捏和平底锅。否则，您可以将pan和pinch手势委托设置为self，并为shouldRecognizeSimultaneously返回YES。至于缩放到用户手指的中心，我从来没有正确地解决过这个问题，但它涉及在改变其比例之前操纵视图的anchorPoint（我认为）。 / p>