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

Question

我想放大和缩小 ImageView ，但我不想为此使用 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;

这对于放大和缩小效果很好。但问题是我想像在 UIScrollView 中一样以特定比例放大和缩小，我们可以设置 maxZoom 和 minZoom。我找不到任何解决方案，关于 UIPinchGestureRecognizer 的每个教程都只描述相同的代码。

Answer 1

在处理手势的类的接口(interface)中声明 2 个 ivars CGFloat __scale 和 CGFloat __previousScale。通过覆盖 init 函数之一将 __scale 设置为 1.0(确保在此处调用 super 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);
    }
}