Question

我想放大并缩小图像视图，我不想使用UIScrollView。所以为此我使用了UIPinchGestureRecognizer，这是我的代码 -

[recognizer view].transform = CGAffineTransformScale([[recognizer view] transform], [recognizer scale], [recognizer scale]);
recognizer.scale = 1;

这适用于放大和缩小。但问题是我想放大和缩小特定比例，如在UIScrollView中我们可以设置maxZoom和minZoom。我找不到任何解决方案，每个关于UIPinchGestureRecognizer的教程都只描述相同的代码。

Answer 1

在处理手势的类的界面中声明2个ivars CGFloat __scale和CGFloat __previousScale。通过覆盖其中一个__scale函数将1.0设置为init（确保在此处调用超级构造函数）。

-(void) zoom:(UIPinchGestureRecognizer *)gesture {

    NSLog(@"Scale: %f", [gesture scale]);
    if ([gesture state] == UIGestureRecognizerStateBegan) {
        __previousScale = __scale;
    }

    CGFloat currentScale = MAX(MIN([gesture scale] * __scale, MAX_SCALE), MIN_SCALE);  
    CGFloat scaleStep = currentScale / __previousScale;
    [self.view setTransform: CGAffineTransformScale(self.view.transform, scaleStep, scaleStep)];

    __previousScale = currentScale;

    if ([gesture state] == UIGestureRecognizerStateEnded || 
        [gesture state] == UIGestureRecognizerStateCancelled ||
        [gesture state] == UIGestureRecognizerStateFailed) {
        // Gesture can fail (or cancelled?) when the notification and the object is dragged simultaneously
        __scale = currentScale;
        NSLog(@"Final scale: %f", __scale);
    }
}

Answer 2

 – (void)handlePinchGesture:(UIPinchGestureRecognizer *)gestureRecognizer 
    {
        if([gestureRecognizer state] == UIGestureRecognizerStateBegan) {
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = [gestureRecognizer scale];
        }

        if ([gestureRecognizer state] == UIGestureRecognizerStateBegan ||
        [gestureRecognizer state] == UIGestureRecognizerStateChanged) {

        CGFloat currentScale = [[[gestureRecognizer view].layer valueForKeyPath:@”transform.scale”] floatValue];

        // Constants to adjust the max/min values of zoom
        const CGFloat kMaxScale = 2.0;
        const CGFloat kMinScale = 1.0;

        CGFloat newScale = 1 –  (lastScale – [gestureRecognizer scale]); // new scale is in the range (0-1)
        newScale = MIN(newScale, kMaxScale / currentScale);
        newScale = MAX(newScale, kMinScale / currentScale);
        CGAffineTransform transform = CGAffineTransformScale([[gestureRecognizer view] transform], newScale, newScale);
        [gestureRecognizer view].transform = transform;

        lastScale = [gestureRecognizer scale];  // Store the previous scale factor for the next pinch gesture call
        }

    }

Answer 3

我有类似的情况。我的要求是如果imageView小于最小尺寸或大于某个最大尺寸，imageView将反弹回其最后一次转换。

if ((self.frame.size.width > IMAGE_MIN_SIZE) && (self.frame.size.height > IMAGE_MIN_SIZE) && (self.frame.size.width < IMAGE_MAX_SIZE) && (self.frame.size.height < IMAGE_MAX_SIZE)) {
    lastSizeTransform = self.transform;
}else {
    self.transform = lastSizeTransform;
}

这里的自我是imageView。

Answer 4

如果您在捏合时记录了view.transform，则可以看到放大和缩小的图像协调。所以，这个解决方案并不像我预期的那样有效。我这样做了我的解决方案;

Obj-C版

    - (void)handlePinchGesture:(UIPinchGestureRecognizer *)recognizer {

        [recognizer.view setTransform:CGAffineTransformScale(recognizer.view.transform, 
recognizer.scale, recognizer.scale)];

        if (recognizer.view.transform.a > 1.6) {

            CGAffineTransform fooTransform = recognizer.view.transform;
            fooTransform.a = 1.6; // this is x coordinate
            fooTransform.d = 1.6; // this is y coordinate
            recognizer.view.transform = fooTransform;
        }

        if (recognizer.view.transform.a < 0.95) {

            CGAffineTransform fooTransform = recognizer.view.transform;
            fooTransform.a = 0.95; // this is x coordinate
            fooTransform.d = 0.95; // this is y coordinate
            recognizer.view.transform = fooTransform;
        }
        recognizer.scale = 1.0;
    }

Swift版本

func handlePinchGesture(recognizer: UIPinchGestureRecognizer) {

        if let view = recognizer.view {
            view.transform = CGAffineTransformScale(view.transform,
                recognizer.scale, recognizer.scale)
            if CGFloat(view.transform.a) > 1.6 {
                view.transform.a = 1.6 // this is x coordinate
                view.transform.d = 1.6 // this is x coordinate
            }
            if CGFloat(view.transform.d) < 0.95 {
                view.transform.a = 0.95 // this is x coordinate
                view.transform.d = 0.95 // this is x coordinate
            }
            recognizer.scale = 1
        }
    }

如何使用UIPinchGestureRecognizer设置最小和最大缩放比例

4 个答案:

Obj-C版

Swift版本