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

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

声明2个ivars CGFloat __scale并CGFloat __previousScale在处理手势的类的接口中.设置__scale为1.0覆盖其中一个init函数(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);
    }
}