Question

如果有人遇到适用于iOS的Google地图应用，可以用一根手指放大/缩小：在uiscrollview上双击，然后立即向上或向下滑动手指以放大/缩小。有谁知道这是如何实现的？谷歌发布了任何片段吗？

Answer 1

我将此功能添加到my UIScrollView category 实际的点击识别很容易，计算“正确”（无论感觉“正确”）zoomScale是问题......如果您认为该类别处理不够好，请不要犹豫告诉我和在github页面上打开一个新问题。

Answer 2

此示例使用UIScrollView的常规缩放功能，其中包含UIImageView作为子视图。例如，您可以在MWPhotoBrowser库中找到此类缩放的实现。 _imageView，_doubleTapBeganPoint，_longPressBeganPoint，_minScale是您的类（UIScrollView子类）iVars。所以从初始化开始：

UILongPressGestureRecognizer* lpgs = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(imageLongPressed:)];
lpgs.minimumPressDuration = .2;
[self addGestureRecognizer:lpgs];

标准缩放处理程序：

- (UIView*)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    return _imageView;
}

使用touchesBegan捕捉双击（UITapGestureRecognizer不希望因某种原因使用UILongPressGestureRecognizer）：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    UITouch *touch = [touches anyObject];
    NSUInteger tapCount = touch.tapCount;
    switch (tapCount) {
        case 2:
            [self handleDoubleTapBegan:[touch locationInView:self.superview]];
            break;
        default:
            break;
    }
    [[self nextResponder] touchesEnded:touches withEvent:event];
}

- (void)handleDoubleTapBegan:(CGPoint)touchPoint {

    _doubleTapBeganPoint = touchPoint;

    NSLog(@"image double tap began at location: %@", NSStringFromCGPoint(touchPoint));
}

处理长按并使用Y坐标中的差异来计算缩放比例。 _minScale存储您的初始zoomScale，以便我们可以恢复它。

- (void) imageLongPressed:(UIGestureRecognizer*)gesture {

    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        self.maximumZoomScale = _maxScale * 2;
        self.minimumZoomScale = _minScale / 3;

        _longPressBeganPoint = [gesture locationInView:self.superview];

        [self setZoomScale:_minScale animated:YES];
        NSLog(@"image long press began at location: %@", NSStringFromCGPoint(_longPressBeganPoint));
    }
    else if (gesture.state == UIGestureRecognizerStateChanged)
    {
        CGPoint p = [gesture locationInView:self.superview];

        //NSLog(@"image long press changed at location: %@", NSStringFromCGPoint(p));

        if (CGPointEqualToPoint(_longPressBeganPoint, _doubleTapBeganPoint))
        {
            _zoom = _minScale + (p.y - _longPressBeganPoint.y) / 100.0;

            NSLog(@"zoom scale: %f", _zoom);

            [self setZoomScale:_zoom animated:NO];
        }
    }
    else if (gesture.state == UIGestureRecognizerStateEnded)
    {
        NSLog(@"image long press ended at location: %@", NSStringFromCGPoint([gesture locationInView:gesture.view]));

        if (self.zoomScale < _minScale)
        {
            [self setZoomScale:_minScale animated:YES];
            NSLog(@"min zoom scale: %f", _minScale);
        }
    }
}

Answer 3

使用UIPanGestureRecognizer跟踪上/下拖动。要确保仅在双击时触发，请为其指定执行以下操作的委托：

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {
    if gestureRecognizer == yourZoomRecognizer {
        return touch.tapCount == 2
    } else {
        return true
    }
}

现在处理来自手势识别器的消息。您可以像这样导出缩放比例：

let zoomFactor: CGFloat = 1.01        //Each point of pan zooms in or out by this much
var zoomScale: CGFloat = 1            //Dummy variable for example purposes.

@IBAction func handleZoomGesture(sender: UIPanGestureRecognizer) {
    if sender.state == .began {
        //Set initial translation to reflect the current zoomScale
        let logZoom = log(zoomScale) / log(zoomFactor)
        sender.setTranslation(CGPoint(x: 0, y: logZoom), in: sender.view)
    } else if sender.state == .changed {
        let logZoom = sender.translation(in: sender.view).y
        zoomScale = pow(zoomFactor, logZoom)
    }
}

这并没有显示在scrollview上实际设置zoomScale，这是一堆额外的代码 - 你需要获得平移手势的位置并围绕它放大缩放。您还需要钳制zoomScale，也可以处理缩放结束。

双击和滑动/拖动手指可放大/缩小

3 个答案: