使用 Touch iOS Sprite Kit 画线

Question

我正在使用以下代码在我的精灵套件场景中绘制线条，但没有显示任何内容。但是节点数增加了。任何人都可以看到可能是什么问题。我一直在与这段代码作斗争

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];

    pathToDraw = CGPathCreateMutable();
    CGPathMoveToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);

    lineNode = [SKShapeNode node];
    lineNode.path = pathToDraw;
    lineNode.strokeColor = [SKColor redColor];
    //lineNode.lineWidth = 2;
    [self addChild:lineNode];
}

- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    CGPathAddLineToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
    lineNode.path = pathToDraw;

}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{

  //  lineNode.physicsBody = [SKPhysicsBody bodyWithPolygonFromPath:pathToDraw];
  //  lineNode.physicsBody.dynamic = NO;
  //  lineNode.physicsBody.categoryBitMask = lines;
  //  lineNode.physicsBody.contactTestBitMask = 0;
  //  lineNode.physicsBody.collisionBitMask = blueParticles | redParticles| yellowParticles;

    CGPathRelease(pathToDraw);
}

编辑------ 删除后台节点后代码可以工作。如何设置后台节点以便可以在上面运行？谢谢

SKSpriteNode *background;

        if(screenHeight == 480){
            background = [SKSpriteNode spriteNodeWithImageNamed:@"iPhone4BG.png"];
        }
        if(screenHeight == 568){
            background = [SKSpriteNode spriteNodeWithImageNamed:@"iPhone5BG.png"];
        }
        if(screenHeight == 667){
            background = [SKSpriteNode spriteNodeWithImageNamed:@"iPhone6BG.png"];
        }
        if(screenHeight == 736){
            background = [SKSpriteNode spriteNodeWithImageNamed:@"iPhone6PlusBG.png"];
        }

        background.position = CGPointMake(screenWidth/2, screenHeight/2);
        background.size = CGSizeMake(screenWidth, screenHeight);

       // [self addChild:background];

Answer 1

注意 核心问题是模拟器未呈现未关闭的路径。在设备上，问题不存在。还涉及到原始海报未提及且未在代码中表示的背景元素。这个答案将解决模拟器上的问题。

要解决您的问题，请按如下方式修改您的代码：

- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    CGPathAddLineToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
    // add this line to fix your issue
    CGPathMoveToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
    lineNode.path = pathToDraw;

}

核心问题是当它去渲染路径时，它没有完整的路径。您当前的方法是不断修改每个 touchMove 的路径。

关闭子路径的方式是：

CGPathCloseSubpath(pathToDraw);

但是，每次您在路径中添加一个段时，我都选择只使用CGPathMoveToPoint。

来自CGPathMoveToPoint 的 CGPath 参考：

这个函数结束已经在进行的子路径（如果有的话）并开始一个新的子路径，在一个可选的变换之后将起点和当前点初始化到指定的位置（x,y）。

我在渲染之前关闭当前子路径，并设置下一段的起始位置。

但是，如果您要绘制一条长线或多条线，您将遇到 cmets 中链接中定义的主要性能问题。画一条很长的线，你就会明白我的意思。通过最少的线条绘制，您可能会摆脱当前的方法。

遗憾的是，使用SKShapeNode 绘制的这种性质并没有得到应有的优化。

Answer 2

我认为这就是您想要实现的。它会在您移动手指时绘制一条临时线（白色），并在您抬起手指时绘制一条最终线（红色）。您将需要声明一个名为startingPoint 的CGPoint 实例变量并删除名为pathToDraw 的CGMutablePathRef ivar。也可以修改代码以绘制多个连接的线段。

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];

    startingPoint = positionInScene;
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];

    // Remove temporary line if it exist
    [lineNode removeFromParent];

    CGMutablePathRef pathToDraw = CGPathCreateMutable();
    CGPathMoveToPoint(pathToDraw, NULL, startingPoint.x, startingPoint.y);
    CGPathAddLineToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);

    lineNode = [SKShapeNode node];
    lineNode.path = pathToDraw;
    //CGPathRelease(pathToDraw);
    lineNode.strokeColor = [SKColor whiteColor];
    lineNode.lineWidth = 1;
    [self addChild:lineNode];
}

- (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];

    // Remove temporary line
    [lineNode removeFromParent];

    CGMutablePathRef pathToDraw = CGPathCreateMutable();
    CGPathMoveToPoint(pathToDraw, NULL, startingPoint.x, startingPoint.y);
    CGPathAddLineToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);

    SKShapeNode *finalLineNode = [SKShapeNode node];
    finalLineNode.path = pathToDraw;
    //CGPathRelease(pathToDraw);
    finalLineNode.strokeColor = [SKColor redColor];
    finalLineNode.lineWidth = 1;
    [self addChild:finalLineNode];
}