SKNode 从触摸点开始缩放

问题描述

我已将 UIPinchGestureRecognizer 添加到我的 scene.view 以缩放我的内容.我实际上缩放了所有可见内容所在的父节点.但是我有缩放点的问题.事情是从左下角开始的节点规模.这绝对不是我想要的.我是否必须编写大量代码才能从发生收缩的点开始扩展?你能不能给一些提示，告诉你应该遵循什么方法.

I have added UIPinchGestureRecognizer to my scene.view to scale my content. I actually scale the parent node where all my visible contents reside. But I have problem though with scaling point. The thing is node scale from the lower-left corner. It's definitely not what I want. Do I have to write lots of code to be able to scale from the point where pinching occurs? Could you please give some hints as to what way to follow.

推荐答案

我一直在解决同样的问题，我的解决方案如下所示.不确定这是否是最好的方法，但到目前为止它似乎有效.我正在使用此代码放大和缩小具有多个 SKSpriteNode 子项的 SKNode.孩子们都根据需要使用 SKNode 移动和缩放.缩放的锚点是捏合手势的位置.场景中的父 SKScene 和其他 SKNode 不受影响.所有的工作都发生在recognizer.state == UIGestureRecognizerStateChanged 期间.

I have been working on the same problem and my solution is shown below. Not sure if it is the best way to do it, but so far it seems to work. I'm using this code to zoom in and out of an SKNode that has several SKSpriteNode children. The children all move and scale with the SKNode as desired. The anchor point for the scaling is the location of the pinch gesture. The parent SKScene and other SKNodes in the scene are not affected. All of the work takes place during recognizer.state == UIGestureRecognizerStateChanged.

// instance variables of MyScene.
SKNode *_mySkNode;
UIPinchGestureRecognizer *_pinchGestureRecognizer;

- (void)didMoveToView:(SKView *)view
{
    _pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handleZoomFrom:)];
    [[self view] addGestureRecognizer:_pinchGestureRecognizer];
}

// Method that is called by my UIPinchGestureRecognizer.
- (void)handleZoomFrom:(UIPinchGestureRecognizer *)recognizer
{
     CGPoint anchorPoint = [recognizer locationInView:recognizer.view];
     anchorPoint = [self convertPointFromView:anchorPoint];

     if (recognizer.state == UIGestureRecognizerStateBegan) {

         // No code needed for zooming...

     } else if (recognizer.state == UIGestureRecognizerStateChanged) {

         CGPoint anchorPointInMySkNode = [_mySkNode convertPoint:anchorPoint fromNode:self];

         [_mySkNode setScale:(_mySkNode.xScale * recognizer.scale)];

         CGPoint mySkNodeAnchorPointInScene = [self convertPoint:anchorPointInMySkNode fromNode:_mySkNode];
         CGPoint translationOfAnchorInScene = CGPointSubtract(anchorPoint, mySkNodeAnchorPointInScene);

         _mySkNode.position = CGPointAdd(_mySkNode.position, translationOfAnchorInScene);

         recognizer.scale = 1.0;

     } else if (recognizer.state == UIGestureRecognizerStateEnded) {

         // No code needed here for zooming...

     }
}

以下是上面使用的辅助函数.它们来自 Ray Wenderlich 关于 Sprite Kit 的书.

The following are helper functions that were used above. They are from the Ray Wenderlich book on Sprite Kit.

SKT_INLINE CGPoint CGPointAdd(CGPoint point1, CGPoint point2) {
    return CGPointMake(point1.x + point2.x, point1.y + point2.y);
}

SKT_INLINE CGPoint CGPointSubtract(CGPoint point1, CGPoint point2) {
    return CGPointMake(point1.x - point2.x, point1.y - point2.y);
}

SKT_INLINE GLKVector2 GLKVector2FromCGPoint(CGPoint point) {
    return GLKVector2Make(point.x, point.y);
}

SKT_INLINE CGPoint CGPointFromGLKVector2(GLKVector2 vector) {
    return CGPointMake(vector.x, vector.y);
}

SKT_INLINE CGPoint CGPointMultiplyScalar(CGPoint point, CGFloat value) {
    return CGPointFromGLKVector2(GLKVector2MultiplyScalar(GLKVector2FromCGPoint(point), value));
}

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