Objective-C SpriteKit Create dotted line to certain points

问题

I have a certain point at the bottom of the screen . . . when I touch the screen somewhere, I'd like a dotted line to appear between the point, and the point my finger is at. The length and rotation of the line will change based on where my finger is, or moves to.

I'm assuming I'd make the dotted line with a repetition of a small line image, but I guess that's why I need your help!

回答1:

Note that all this can be organized better, and I personally don't like SKShapeNode in any shape :) or form, but this is the one way to do it:

#import "GameScene.h"



@implementation GameScene{
    SKShapeNode *line;
}

-(void)didMoveToView:(SKView *)view {
    /* Setup your scene here */

    line = [SKShapeNode node];
    [self addChild:line];
    [line setStrokeColor:[UIColor redColor]];

}

-(void)drawLine:(CGPoint)endingPoint{

    CGMutablePathRef pathToDraw = CGPathCreateMutable();
    CGPathMoveToPoint(pathToDraw, NULL, CGRectGetMidX(self.frame),CGRectGetMidY(self.frame));
    CGPathAddLineToPoint(pathToDraw, NULL, endingPoint.x,endingPoint.y);

    CGFloat pattern[2];
    pattern[0] = 20.0;
    pattern[1] = 20.0;
    CGPathRef dashed =
    CGPathCreateCopyByDashingPath(pathToDraw,NULL,0,pattern,2);

    line.path = dashed;

    CGPathRelease(dashed);
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    /* Called when a touch begins */

    for (UITouch *touch in touches) {
        CGPoint location = [touch locationInNode:self];

        [self drawLine:location];

    }
}

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

        [self drawLine:location];

    }
}

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

    line.path = nil;

}

The result is:

Also I don't know how much performant this is, but you can test it, tweak it and improve it. Or even use SKSpriteNode like you said. Happy coding!

EDIT:

I just noticed that you said dotted (not dashed) :)

You have to change pattern to something like:

 pattern[0] = 3.0;
 pattern[1] = 3.0;

来源：https://stackoverflow.com/questions/29356901/objective-c-spritekit-create-dotted-line-to-certain-points