UIPinchGestureRecognizer定位两个手指之间的压缩视图 [英] UIPinchGestureRecognizer position the pinched view between the two fingers

问题描述

我成功实现了捏缩放视图。但是，这种观点并没有将自己定位在我希望的位置。对于带有iPad的stackoverflowers，我希望我的视图能够像iPad Photos.app一样居中：当您捏合和放大相册时，照片会出现在正在扩展的视图中。该视图大致位于第一个手指的右上角和另一个手指的左下角。我用pan识别器混合它，但这样用户总是需要捏，然后平移以进行调整。

I successfully implemented a pinch a zoom of a view. However, the view doesn't position itself where I wished it to be. For the stackoverflowers with an iPad, I would like my view to be centered like on the iPad Photos.app : when you pinch&zoom on an album, the photos present themselves in a view that is expanding. This view is approximately centered with the top right hand corner on the first finger and the bottom left hand finger on the other finger. I mixed it with a pan recognizer, but this way the user always has to pinch, and then pan to adjust.

这是图解说明，我可以发布一个视频我的应用程序，如果这不清楚（没有秘密，我正在尝试重现iPad的Photos.app ...）

Here are so graphic explanation, I could post a video of my app if that's unclear (no secret, i'm trying to reproduce the Photos.app of the iPad...)

所以对于手指的初始位置，开始缩放：

So for an initial position of the fingers, begining zooming :

这是现在的实际缩放框架。方块较大，但位置低于手指

This is the actual "zoomed" frame for now. The square is bigger, but the position is below the fingers

这是我想要的：相同的大小，但不同的origin.x和y：

Here is what I would like to have : same size, but different origin.x and y :

（抱歉我糟糕的Photoshop技能^^）

(sorry about my poor photoshop skills ^^)

推荐答案

你可以得到 CGPoint handlingPinchGesture 中的以下代码，两个手指之间的中点code>。

You can get the CGPoint of the midpoint between two fingers via the following code in the method handlingPinchGesture.

CGPoint point = [sender locationInView:self];

我的整个 handlePinchGesture 方法如下。

/*
instance variables

CGFloat lastScale;
CGPoint lastPoint;
*/

- (void)handlePinchGesture:(UIPinchGestureRecognizer *)sender {
    if ([sender numberOfTouches] < 2)
        return;

    if (sender.state == UIGestureRecognizerStateBegan) {
        lastScale = 1.0;
        lastPoint = [sender locationInView:self];
    }

    // Scale
    CGFloat scale = 1.0 - (lastScale - sender.scale);
    [self.layer setAffineTransform:
        CGAffineTransformScale([self.layer affineTransform], 
                               scale, 
                               scale)];
    lastScale = sender.scale;

    // Translate
    CGPoint point = [sender locationInView:self];
    [self.layer setAffineTransform:
        CGAffineTransformTranslate([self.layer affineTransform], 
                                   point.x - lastPoint.x, 
                                   point.y - lastPoint.y)];
    lastPoint = [sender locationInView:self];
}

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