Question

我不是在谈论缩放如何在这里工作。

有人注意到Instagram的缩放吗？它可以作为默认的工作，但是当你开始放大它时，imageView会扩展到设备的整个屏幕，它们如何顺利？有人知道可以指出吗？

Answer 1

我创建了一个简单的Github项目，完全符合您的要求。看看这里： https://github.com/twomedia/TMImageZoom

我通过创建一个处理手势状态变化的类来实现这一目标。然后，我在窗口上创建一个UIImageView，并将其定位/调整到原始图像视图，从而创建用户缩放imageView的效果。这是以上链接中的一小段代码：

-(void) gestureStateChanged:(id)gesture withZoomImageView:(UIImageView*)imageView {

// Insure user is passing correct UIPinchGestureRecognizer class.
if (![gesture isKindOfClass:[UIPinchGestureRecognizer class]]) {
    NSLog(@"(TMImageZoom): Must be using a UIPinchGestureRecognizer, currently you're using a: %@",[gesture class]);
    return;
}

UIPinchGestureRecognizer *theGesture = gesture;

// Prevent animation issues if currently animating reset.
if (isAnimatingReset) {
    return;
}

// Reset zoom if state = UIGestureRecognizerStateEnded
if (theGesture.state == UIGestureRecognizerStateEnded || theGesture.state == UIGestureRecognizerStateCancelled || theGesture.state == UIGestureRecognizerStateFailed) {
    [self resetImageZoom];
}

// Ignore other views trying to start zoom if already zooming with another view
if (isHandlingGesture && hostImageView != imageView) {
    NSLog(@"(TMImageZoom): 'gestureStateChanged:' ignored since this imageView isnt being tracked");
    return;
}

// Start handling gestures if state = UIGestureRecognizerStateBegan and not already handling gestures.
if (!isHandlingGesture && theGesture.state == UIGestureRecognizerStateBegan) {
    isHandlingGesture = YES;

    // Set Host ImageView
    hostImageView = imageView;
    imageView.hidden = YES;

    // Convert local point to window coordinates
    CGPoint point = [imageView convertPoint:imageView.frame.origin toView:nil];
    startingRect = CGRectMake(point.x, point.y, imageView.frame.size.width, imageView.frame.size.height);

    // Post Notification
    [[NSNotificationCenter defaultCenter] postNotificationName:TMImageZoom_Started_Zoom_Notification object:nil];

    // Get current window and set starting vars
    UIWindow *currentWindow = [UIApplication sharedApplication].keyWindow;
    firstCenterPoint = [theGesture locationInView:currentWindow];

    // Init zoom ImageView
    currentImageView = [[UIImageView alloc] initWithImage:imageView.image];
    currentImageView.contentMode = UIViewContentModeScaleAspectFill;
    [currentImageView setFrame:startingRect];
    [currentWindow addSubview:currentImageView];
}

// Reset if user removes a finger (Since center calculation would cause image to jump to finger as center. Maybe this could be improved later)
if (theGesture.numberOfTouches < 2) {
    [self resetImageZoom];
    return;
}

// Update scale & center
if (theGesture.state == UIGestureRecognizerStateChanged) {
    NSLog(@"gesture.scale = %f", theGesture.scale);

    // Calculate new image scale.
    CGFloat currentScale = currentImageView.frame.size.width / startingRect.size.width;
    CGFloat newScale = currentScale * theGesture.scale;
    [currentImageView setFrame:CGRectMake(currentImageView.frame.origin.x, currentImageView.frame.origin.y, startingRect.size.width*newScale, startingRect.size.height*newScale)];

    // Calculate new center
    UIWindow *currentWindow = [UIApplication sharedApplication].keyWindow;
    int centerXDif = firstCenterPoint.x-[theGesture locationInView:currentWindow].x;
    int centerYDif = firstCenterPoint.y-[theGesture locationInView:currentWindow].y;
    currentImageView.center = CGPointMake((startingRect.origin.x+(startingRect.size.width/2))-centerXDif, (startingRect.origin.y+(startingRect.size.height/2))-centerYDif);

    // Reset gesture scale
    theGesture.scale = 1;
}
}

Answer 2

复制此行为的一种方法可能是向UIPinchGestureRecognizer添加UIImageView。然后使用scale的{{1}}属性并相应地缩放UIPinchGestureRecognizer的框架。 example

Answer 3

我建议使用第三方库。它们总是很容易集成和使用

尝试检查这些：

https://github.com/NYTimes/NYTPhotoViewer
这个不是鼓舞人心的信心https://github.com/StuartMorris0/SPMZoomableUIImageView

Official apple Guide

Rey Wenderlish guides are pretty nice too

无论如何，只需谷歌吧！，祝你好运！

Instagram的缩放是如何工作的？

3 个答案: