28

我想以基类不支持的方式缩放和取消缩放。

例如，在收到双击时。

4

5 回答 5

14

在玩弄东西并让它工作之后，我正在回答我自己的问题。

Apple 在其关于如何处理双击的文档中提供了一个非常简单的示例。

进行程序化缩放的基本方法是自己做，然后告诉 UIScrollView 你做了。

  • 调整内部视图的框架和边界。
  • 将内部视图标记为需要显示。
  • 告诉 UIScrollView 新的内容大小。
  • 计算缩放后应显示的内部视图部分，并将 UIScrollView 平移到该位置。

另一个关键：一旦你告诉 UIScrollView 你的新内容大小，它似乎会重置其当前缩放级别的概念。您现在处于新的 1.0 缩放系数。因此，您几乎肯定会想要重置最小和最大缩放系数。

于 2008-10-07T14:27:17.217 回答
13

停止重新发明轮子！看看苹果是怎么做到的！

ScrollViewSuite -> Apple 文档页面

ScrollViewSuite 直接链接 -> XcodeProject

这正是您正在寻找的。

干杯!

于 2010-10-07T14:32:05.043 回答
13

注意：这是非常过时的。它大约从 iOS 2.x 时代开始，实际上已经在 iOS 3.x 左右得到修复。

仅出于历史目的将其保留在这里。

我想我找到了一个干净的解决方案，我制作了一个 UIScrollView 子类来封装它。

说明编程缩放（+双击处理）和照片库样式的分页+缩放+滚动以及 ZoomScrollView 类的示例代码可在github.com/andreyvit/ScrollingMadness 获得。

简而言之，我的解决方案是从 中返回一个新的虚拟视图viewForZoomingInScrollView:，暂时将您的内容视图（UIImageView 等）作为其子视图。在scrollViewDidEndZooming:我们相反的情况下，处理虚拟视图并将您的内容视图移回滚动视图。

为什么有帮助？这是一种击败我们无法以编程方式更改的持久视图比例的方法。UIScrollView 本身不保留当前视图比例。相反，每个 UIView 都能够保持其当前视图比例（在 _gestureInfo 字段指向的 UIGestureInfo 对象内）。通过为每个缩放操作提供一个新的 UIView，我们总是从缩放比例 1.00 开始。

这有什么帮助？我们自己存储当前缩放比例，并手动将其应用于我们的内容视图，例如contentView.transform = CGAffineTransformMakeScale(zoomScale, zoomScale). 然而，这与 UIScrollView 希望在用户捏住视图时重置转换相冲突。通过给 UIScrollView 另一个带有标识变换的视图来缩放，我们不再为变换同一个视图而战。UIScrollView 可以愉快地相信它每次都以缩放 1.00 开始，并以标识变换开始缩放视图，并且它的内部视图应用了与我们当前实际缩放比例相对应的变换。

现在，ZoomScrollView 封装了所有这些东西。为了完整起见，这里是它的代码，但是我真的建议从 GitHub 下载示例项目（你不需要使用 Git，那里有一个下载按钮）。如果你想收到有关示例代码更新的通知（你应该——我计划维护和更新这个类！），要么关注 GitHub 上的项目，要么给我发电子邮件至 andreyvit@gmail.com。

界面：

/*
 ZoomScrollView makes UIScrollView easier to use:

 - ZoomScrollView is a drop-in replacement subclass of UIScrollView

 - ZoomScrollView adds programmatic zooming
   (see `setZoomScale:centeredAt:animated:`)

 - ZoomScrollView allows you to get the current zoom scale
   (see `zoomScale` property)

 - ZoomScrollView handles double-tap zooming for you
   (see `zoomInOnDoubleTap`, `zoomOutOnDoubleTap`)

 - ZoomScrollView forwards touch events to its delegate, allowing to handle
   custom gestures easily (triple-tap? two-finger scrolling?)

 Drop-in replacement:

 You can replace `[UIScrollView alloc]` with `[ZoomScrollView alloc]` or change
 class in Interface Builder, and everything should continue to work. The only
 catch is that you should not *read* the 'delegate' property; to get your delegate,
 please use zoomScrollViewDelegate property instead. (You can set the delegate
 via either of these properties, but reading 'delegate' does not work.)

 Zoom scale:

 Reading zoomScale property returns the scale of the last scaling operation.
 If your viewForZoomingInScrollView can return different views over time,
 please keep in mind that any view you return is instantly scaled to zoomScale.

 Delegate:

 The delegate accepted by ZoomScrollView is a regular UIScrollViewDelegate,
 however additional methods from `NSObject(ZoomScrollViewDelegateMethods)` category
 will be called on your delegate if defined.

 Method `scrollViewDidEndZooming:withView:atScale:` is called after any 'bounce'
 animations really finish. UIScrollView often calls it earlier, violating
 the documented contract of UIScrollViewDelegate.

 Instead of reading 'delegate' property (which currently returns the scroll
 view itself), you should read 'zoomScrollViewDelegate' property which
 correctly returns your delegate. Setting works with either of them (so you
 can still set your delegate in the Interface Builder).

 */

@interface ZoomScrollView : UIScrollView {
@private
    BOOL _zoomInOnDoubleTap;
    BOOL _zoomOutOnDoubleTap;
    BOOL _zoomingDidEnd;
    BOOL _ignoreSubsequentTouches;                                // after one of delegate touch methods returns YES, subsequent touch events are not forwarded to UIScrollView
    float _zoomScale;
    float _realMinimumZoomScale, _realMaximumZoomScale;           // as set by the user (UIScrollView's min/maxZoomScale == our min/maxZoomScale divided by _zoomScale)
    id _realDelegate;                       // as set by the user (UIScrollView's delegate is set to self)
    UIView *_realZoomView;                      // the view for zooming returned by the delegate
    UIView *_zoomWrapperView;               // the disposable wrapper view actually used for zooming
}

// if both are enabled, zoom-in takes precedence unless the view is at maximum zoom scale
@property(nonatomic, assign) BOOL zoomInOnDoubleTap;
@property(nonatomic, assign) BOOL zoomOutOnDoubleTap;

@property(nonatomic, assign) id<UIScrollViewDelegate> zoomScrollViewDelegate;

@end

@interface ZoomScrollView (Zooming)

@property(nonatomic, assign) float zoomScale;                     // from minimumZoomScale to maximumZoomScale

- (void)setZoomScale:(float)zoomScale animated:(BOOL)animated;    // centerPoint == center of the scroll view
- (void)setZoomScale:(float)zoomScale centeredAt:(CGPoint)centerPoint animated:(BOOL)animated;

@end

@interface NSObject (ZoomScrollViewDelegateMethods)

// return YES to stop processing, NO to pass the event to UIScrollView (mnemonic: default is to pass, and default return value in Obj-C is NO)
- (BOOL)zoomScrollView:(ZoomScrollView *)zoomScrollView touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
- (BOOL)zoomScrollView:(ZoomScrollView *)zoomScrollView touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
- (BOOL)zoomScrollView:(ZoomScrollView *)zoomScrollView touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
- (BOOL)zoomScrollView:(ZoomScrollView *)zoomScrollView touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;

@end

执行：

@interface ZoomScrollView (DelegateMethods) <UIScrollViewDelegate>
@end

@interface ZoomScrollView (ZoomingPrivate)
- (void)_setZoomScaleAndUpdateVirtualScales:(float)zoomScale;           // set UIScrollView's minimumZoomScale/maximumZoomScale
- (BOOL)_handleDoubleTapWith:(UITouch *)touch;
- (UIView *)_createWrapperViewForZoomingInsteadOfView:(UIView *)view;   // create a disposable wrapper view for zooming
- (void)_zoomDidEndBouncing;
- (void)_programmaticZoomAnimationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(UIView *)context;
- (void)_setTransformOn:(UIView *)view;
@end


@implementation ZoomScrollView

@synthesize zoomInOnDoubleTap=_zoomInOnDoubleTap, zoomOutOnDoubleTap=_zoomOutOnDoubleTap;
@synthesize zoomScrollViewDelegate=_realDelegate;

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        _zoomScale = 1.0f;
        _realMinimumZoomScale = super.minimumZoomScale;
        _realMaximumZoomScale = super.maximumZoomScale;
        super.delegate = self;
    }
    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super initWithCoder:aDecoder]) {
        _zoomScale = 1.0f;
        _realMinimumZoomScale = super.minimumZoomScale;
        _realMaximumZoomScale = super.maximumZoomScale;
        super.delegate = self;
    }
    return self;
}

- (id<UIScrollViewDelegate>)realDelegate {
    return _realDelegate;
}
- (void)setDelegate:(id<UIScrollViewDelegate>)delegate {
    _realDelegate = delegate;
}

- (float)minimumZoomScale {
    return _realMinimumZoomScale;
}
- (void)setMinimumZoomScale:(float)value {
    _realMinimumZoomScale = value;
    [self _setZoomScaleAndUpdateVirtualScales:_zoomScale];
}

- (float)maximumZoomScale {
    return _realMaximumZoomScale;
}
- (void)setMaximumZoomScale:(float)value {
    _realMaximumZoomScale = value;
    [self _setZoomScaleAndUpdateVirtualScales:_zoomScale];
}

@end


@implementation ZoomScrollView (Zooming)

- (void)_setZoomScaleAndUpdateVirtualScales:(float)zoomScale {
    _zoomScale = zoomScale;
    // prevent accumulation of error, and prevent a common bug in the user's code (comparing floats with '==')
    if (ABS(_zoomScale - _realMinimumZoomScale) < 1e-5)
        _zoomScale = _realMinimumZoomScale;
    else if (ABS(_zoomScale - _realMaximumZoomScale) < 1e-5)
        _zoomScale = _realMaximumZoomScale;
    super.minimumZoomScale = _realMinimumZoomScale / _zoomScale;
    super.maximumZoomScale = _realMaximumZoomScale / _zoomScale;
}

- (void)_setTransformOn:(UIView *)view {
    if (ABS(_zoomScale - 1.0f) < 1e-5)
        view.transform = CGAffineTransformIdentity;
    else
        view.transform = CGAffineTransformMakeScale(_zoomScale, _zoomScale);
}

- (float)zoomScale {
    return _zoomScale;
}

- (void)setZoomScale:(float)zoomScale {
    [self setZoomScale:zoomScale animated:NO];
}

- (void)setZoomScale:(float)zoomScale animated:(BOOL)animated {
    [self setZoomScale:zoomScale centeredAt:CGPointMake(self.frame.size.width / 2, self.frame.size.height / 2) animated:animated];
}

- (void)setZoomScale:(float)zoomScale centeredAt:(CGPoint)centerPoint animated:(BOOL)animated {
    if (![_realDelegate respondsToSelector:@selector(viewForZoomingInScrollView:)]) {
        NSLog(@"setZoomScale called on ZoomScrollView, however delegate does not implement viewForZoomingInScrollView");
        return;
    }

    // viewForZoomingInScrollView may change contentOffset, and centerPoint is relative to the current one
    CGPoint origin = self.contentOffset;
    centerPoint = CGPointMake(centerPoint.x - origin.x, centerPoint.y - origin.y);

    UIView *viewForZooming = [_realDelegate viewForZoomingInScrollView:self];
    if (viewForZooming == nil)
        return;

    if (animated) {
        [UIView beginAnimations:nil context:viewForZooming];
        [UIView setAnimationDuration: 0.2];
        [UIView setAnimationDelegate: self];
        [UIView setAnimationDidStopSelector: @selector(_programmaticZoomAnimationDidStop:finished:context:)];
    }

    [self _setZoomScaleAndUpdateVirtualScales:zoomScale];
    [self _setTransformOn:viewForZooming];

    CGSize zoomViewSize   = viewForZooming.frame.size;
    CGSize scrollViewSize = self.frame.size;
    viewForZooming.frame = CGRectMake(0, 0, zoomViewSize.width, zoomViewSize.height);
    self.contentSize = zoomViewSize;
    self.contentOffset = CGPointMake(MAX(MIN(zoomViewSize.width*centerPoint.x/scrollViewSize.width - scrollViewSize.width/2, zoomViewSize.width - scrollViewSize.width), 0),
                                     MAX(MIN(zoomViewSize.height*centerPoint.y/scrollViewSize.height - scrollViewSize.height/2, zoomViewSize.height - scrollViewSize.height), 0));

    if (animated) {
        [UIView commitAnimations];
    } else {
        [self _programmaticZoomAnimationDidStop:nil finished:nil context:viewForZooming];
    }
}

- (void)_programmaticZoomAnimationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(UIView *)context {
    if ([_realDelegate respondsToSelector:@selector(scrollViewDidEndZooming:withView:atScale:)])
        [_realDelegate scrollViewDidEndZooming:self withView:context atScale:_zoomScale];
}

- (BOOL)_handleDoubleTapWith:(UITouch *)touch {
    if (!_zoomInOnDoubleTap && !_zoomOutOnDoubleTap)
        return NO;
    if (_zoomInOnDoubleTap && ABS(_zoomScale - _realMaximumZoomScale) > 1e-5)
        [self setZoomScale:_realMaximumZoomScale centeredAt:[touch locationInView:self] animated:YES];
    else if (_zoomOutOnDoubleTap && ABS(_zoomScale - _realMinimumZoomScale) > 1e-5)
        [self setZoomScale:_realMinimumZoomScale animated:YES];
    return YES;
}

// the heart of the zooming technique: zooming starts here
- (UIView *)_createWrapperViewForZoomingInsteadOfView:(UIView *)view {
    if (_zoomWrapperView != nil) // not sure this is really possible
        [self _zoomDidEndBouncing]; // ...but just in case cleanup the previous zoom op

    _realZoomView = [view retain];
    [view removeFromSuperview];
    [self _setTransformOn:_realZoomView]; // should be already set, except if this is a different view
    _realZoomView.frame = CGRectMake(0, 0, _realZoomView.frame.size.width, _realZoomView.frame.size.height);
    _zoomWrapperView = [[UIView alloc] initWithFrame:view.frame];
    [_zoomWrapperView addSubview:view];
    [self addSubview:_zoomWrapperView];

    return _zoomWrapperView;
}

// the heart of the zooming technique: zooming ends here
- (void)_zoomDidEndBouncing {
    _zoomingDidEnd = NO;
    [_realZoomView removeFromSuperview];
    [self _setTransformOn:_realZoomView];
    _realZoomView.frame = _zoomWrapperView.frame;
    [self addSubview:_realZoomView];

    [_zoomWrapperView release];
    _zoomWrapperView = nil;

    if ([_realDelegate respondsToSelector:@selector(scrollViewDidEndZooming:withView:atScale:)])
        [_realDelegate scrollViewDidEndZooming:self withView:_realZoomView atScale:_zoomScale];
    [_realZoomView release];
    _realZoomView = nil;
}

@end


@implementation ZoomScrollView (DelegateMethods)

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    if ([_realDelegate respondsToSelector:@selector(scrollViewWillBeginDragging:)])
        [_realDelegate scrollViewWillBeginDragging:self];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    if ([_realDelegate respondsToSelector:@selector(scrollViewDidEndDragging:willDecelerate:)])
        [_realDelegate scrollViewDidEndDragging:self willDecelerate:decelerate];
}

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView {
    if ([_realDelegate respondsToSelector:@selector(scrollViewWillBeginDecelerating:)])
        [_realDelegate scrollViewWillBeginDecelerating:self];
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    if ([_realDelegate respondsToSelector:@selector(scrollViewDidEndDecelerating:)])
        [_realDelegate scrollViewDidEndDecelerating:self];
}

- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
    if ([_realDelegate respondsToSelector:@selector(scrollViewDidEndScrollingAnimation:)])
        [_realDelegate scrollViewDidEndScrollingAnimation:self];
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    UIView *viewForZooming = nil;
    if ([_realDelegate respondsToSelector:@selector(viewForZoomingInScrollView:)])
        viewForZooming = [_realDelegate viewForZoomingInScrollView:self];
    if (viewForZooming != nil)
        viewForZooming = [self _createWrapperViewForZoomingInsteadOfView:viewForZooming];
    return viewForZooming;
}

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
    [self _setZoomScaleAndUpdateVirtualScales:_zoomScale * scale];

    // often UIScrollView continues bouncing even after the call to this method, so we have to use delays
    _zoomingDidEnd = YES; // signal scrollViewDidScroll to schedule _zoomDidEndBouncing call
    [self performSelector:@selector(_zoomDidEndBouncing) withObject:nil afterDelay:0.1];
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if (_zoomWrapperView != nil && _zoomingDidEnd) {
        [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(_zoomDidEndBouncing) object:nil];
        [self performSelector:@selector(_zoomDidEndBouncing) withObject:nil afterDelay:0.1];
    }

    if ([_realDelegate respondsToSelector:@selector(scrollViewDidScroll:)])
        [_realDelegate scrollViewDidScroll:self];
}

- (BOOL)scrollViewShouldScrollToTop:(UIScrollView *)scrollView {
    if ([_realDelegate respondsToSelector:@selector(scrollViewShouldScrollToTop:)])
        return [_realDelegate scrollViewShouldScrollToTop:self];
    else
        return YES;
}

- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView {
    if ([_realDelegate respondsToSelector:@selector(scrollViewDidScrollToTop:)])
        [_realDelegate scrollViewDidScrollToTop:self];  
}

@end


@implementation ZoomScrollView (EventForwarding)

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    id delegate = self.delegate;
    if ([delegate respondsToSelector:@selector(zoomScrollView:touchesBegan:withEvent:)])
        _ignoreSubsequentTouches = [delegate zoomScrollView:self touchesBegan:touches withEvent:event];
    if (_ignoreSubsequentTouches)
        return;
    if ([touches count] == 1 && [[touches anyObject] tapCount] == 2)
        if ([self _handleDoubleTapWith:[touches anyObject]])
            return;
    [super touchesBegan:touches withEvent:event];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    id delegate = self.delegate;
    if ([delegate respondsToSelector:@selector(zoomScrollView:touchesMoved:withEvent:)])
        if ([delegate zoomScrollView:self touchesMoved:touches withEvent:event]) {
            _ignoreSubsequentTouches = YES;
            [super touchesCancelled:touches withEvent:event];
        }
    if (_ignoreSubsequentTouches)
        return;
    [super touchesMoved:touches withEvent:event];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    id delegate = self.delegate;
    if ([delegate respondsToSelector:@selector(zoomScrollView:touchesEnded:withEvent:)])
        if ([delegate zoomScrollView:self touchesEnded:touches withEvent:event]) {
            _ignoreSubsequentTouches = YES;
            [super touchesCancelled:touches withEvent:event];
        }
    if (_ignoreSubsequentTouches)
        return;
    [super touchesEnded:touches withEvent:event];
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    id delegate = self.delegate;
    if ([delegate respondsToSelector:@selector(zoomScrollView:touchesCancelled:withEvent:)])
        if ([delegate zoomScrollView:self touchesCancelled:touches withEvent:event])
            _ignoreSubsequentTouches = YES;
    [super touchesCancelled:touches withEvent:event];
}

@end
于 2009-05-07T21:16:01.057 回答
4

我想我知道 Darron 指的是什么文档。在文档“iPhone OS 编程指南”中有一节“处理多点触控事件”。其中包含清单 7-1：

- (void) touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event {
 UIScrollView  *scrollView = (UIScrollView*)[self superview];
 UITouch       *touch = [touches anyObject];
 CGSize        size;
 CGPoint       point;

 if([touch tapCount] == 2) {
    if(![_viewController _isZoomed]) {
        point = [touch locationInView:self];
        size = [self bounds].size;
        point.x /= size.width;
        point.y /= size.height;

        [_viewController _setZoomed:YES];

        size = [scrollView contentSize];
        point.x *= size.width;
        point.y *= size.height;
        size = [scrollView bounds].size;
        point.x -= size.width / 2;
        point.y -= size.height / 2;
        [scrollView setContentOffset:point animated:NO];
    }
        else
        [_viewController _setZoomed:NO];
    }
 }

}
于 2009-03-20T21:58:22.743 回答
0

达伦，你能提供一个苹果例子的链接吗？或者标题以便我可以找到它？我看到http://developer.apple.com/iphone/library/samplecode/Touches/index.html，但这不包括缩放。

我在程序化缩放后看到的问题是手势缩放将缩放捕捉回程序化缩放发生之前的状态。似乎 UIScrollView 在内部保持有关缩放因子/级别的状态，但我没有确凿的证据。

谢谢，-安德鲁

编辑：我刚刚意识到，您正在解决这样一个事实，即您通过调整大小和更改缩放因子 1.0 的含义几乎无法控制 UIScrollView 的内部缩放因子。有点骇人听闻，但似乎所有苹果都留给我们了。也许自定义类可以封装这个技巧......

于 2008-10-18T17:57:30.360 回答