向固定点旋转箭头（类似时钟的动画）

Question

我想旋转这个箭头穿过时钟中的一个固定点。下面的代码没有做我打算做的事情，它将整个箭头旋转到圆心。我还尝试在圆形路径上设置动画，但它没有给我想要的效果...... 我想让这个箭头绕一个圆圈旋转，同时箭头指向这个圆圈的中心

-(void) addArrow2:(CGSize)size{
    _Arrow2 = [SKSpriteNode spriteNodeWithImageNamed:@"arrow2"];
    _Arrow2.position = CGPointMake(self.frame.size.width/2 , self.frame.size.height/2 +30);
    SKAction *rotate = [SKAction rotateByAngle:M_2_PI duration:1];
    SKAction *forever = [SKAction repeatActionForever:rotate];

    _Arrow2.yScale = 0.45;
    _Arrow2.xScale = 0.45;

    [self addChild:_Arrow2];

    [_Arrow2 runAction:forever];
}

Answer 1

我想你有这种箭头→。将 anchorPoint 更改为 (1.0, 0.5) 并使箭头沿着圆形路径移动。进行一些更改以满足您的需要。

- (void)addArrow2
{
    _Arrow2 = [SKSpriteNode spriteNodeWithImageNamed:@"arrow2"];
    _Arrow2.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2+30);
    _Arrow2.anchorPoint = CGPointMake(1.0, 0.5);
    _Arrow2.yScale = 0.45;
    _Arrow2.xScale = 0.45;

    // Make a circle path
    CGMutablePathRef circle = CGPathCreateMutable();
    CGFloat centerX = self.frame.size.width/2;
    CGFloat centerY = self.frame.size.height/2;
    CGFloat radius = 25.0;
    CGFloat startAngle = 0.0;
    CGFloat endAngle = 2*M_PI;
    CGPathAddArc(circle, NULL, centerX, centerY, radius, startAngle, endAngle, true);
    CGPathCloseSubpath(circle);
    SKAction *followPath = [SKAction followPath:circle asOffset:NO orientToPath:YES duration:2.0];

    // Infinite rotation
    SKAction *forever = [SKAction repeatActionForever:followPath];
    [_Arrow2 runAction:forever];

    [self addChild:_Arrow2];
}

动画预览：

向固定点旋转箭头（类似时钟的动画）

Rotating an arrow towards a fixed point (clock like animation)

animation

objective-c

game-engine

ios

sprite-kit