iOS 8 中用于绘图应用的 SpriteKit 渲染问题

Question

我有一个绘图模拟 SKScene，它在 iOS 7 中运行良好，但在 iOS 8 中无法运行。这既适用于模拟器，也适用于设备。

场景应该在手指触摸屏幕的地方显示黑线，并且在您完成“绘制”一条线后它们应该持续存在。这是它在 iOS 7 中的屏幕截图：

虽然没有崩溃，但在 iOS 8 中根本不会渲染线条。我只是得到一个空白画布。 NSLogging 表明它确实正确注册了 touchesBegan/Moved/Ended 函数。

我已经完整地制作了整个课程：

@implementation CSDraw

-(id)initWithSize:(CGSize)size type:(NSString *)CSType stresslevel:(NSInteger)stress_indicator { //designated initializer
    if (self = [super initWithSize:size type: CSType stresslevel:stress_indicator]) {
        NSLog(@"Creating new scene from CSDraw within the init");
    }
    return self;
}


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

    self.swiped = NO;
    UITouch *touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];

    self.pathToDraw = CGPathCreateMutable();

    CGPathMoveToPoint(self.pathToDraw, NULL, positionInScene.x, positionInScene.y);

    self.lineNode = [SKShapeNode node];
    self.lineNode.path = self.pathToDraw;
    self.lineNode.strokeColor = [SKColor blackColor];
    self.lineNode.lineWidth = 10;
    self.lineNode.zPosition = 50;

    [self addChild:self.lineNode];

}


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

    CGPathAddLineToPoint(self.pathToDraw, NULL, positionInScene.x, positionInScene.y);
    self.lineNode.path = self.pathToDraw;

}

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

    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];

    if(!self.swiped) { //user just tapped once, draw a single point
        SKSpriteNode *dot = [SKSpriteNode spriteNodeWithColor:[SKColor blackColor] size:CGSizeMake(10, 10)];
        dot.position = positionInScene;
        [self addChild: dot];

    } else { //calls touchesMoved
    }

    //[self.lineNode removeFromParent]; //comment out this line if you want line to remain on screen
    CGPathRelease(self.pathToDraw);
}
@end

这个类是根据我在this StackOverFlow answer 中找到的代码编写的。

Answer 1

我在使用 Sprite Kit iOS8 游戏时遇到了类似的问题，并通过以下方式对其进行了修复：尝试在 touchesMoved 函数中的 CGPathAddLineToPoint 调用之前立即添加一个 CGPathMoveToPoint 调用。

根据 CGPathAddLineToPoint 的类引用，调用 CGPathAddLineToPoint 会自动“将当前点更新到指定位置 (x,y) [新端点]”。但是，直到我在每次 CGPathAddLineToPoint 调用之前通过调用 CGPathMoveToPoint 手动执行此操作，我的线条才在 iOS8 中正确呈现。不知道为什么会这样。可能是 iOS8 中 Sprite Kit 的一个错误。

请在下面找到修改后的代码，其中的更改标有/* new */ 注释。该代码假定您有一个名为 lastPointTouched 的 CGPoint 属性。

 @implementation CSDraw

-(id)initWithSize:(CGSize)size type:(NSString *)CSType stresslevel:(NSInteger)stress_indicator { //designated initializer
    if (self = [super initWithSize:size type: CSType stresslevel:stress_indicator]) {
        NSLog(@"Creating new scene from CSDraw within the init");
    }
    return self;
}

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

    self.swiped = NO;
    UITouch *touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];

    self.pathToDraw = CGPathCreateMutable();

    CGPathMoveToPoint(self.pathToDraw, NULL, positionInScene.x, positionInScene.y);
    /* new */ self.lastPointTouched = positionInScene; 

    self.lineNode = [SKShapeNode node];
    self.lineNode.path = self.pathToDraw;
    self.lineNode.strokeColor = [SKColor blackColor];
    self.lineNode.lineWidth = 10;
    self.lineNode.zPosition = 50;

    [self addChild:self.lineNode];

}

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

    /* new */ CGPathMoveToPoint(self.pathToDraw, NULL, self.lastPointTouched.x, self.lastPointTouched.y);
    CGPathAddLineToPoint(self.pathToDraw, NULL, positionInScene.x, positionInScene.y);
    /* new */ self.lastPointTouched = positionInScene;
    self.lineNode.path = self.pathToDraw;

}

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

    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];

    if(!self.swiped) { //user just tapped once, draw a single point
        SKSpriteNode *dot = [SKSpriteNode spriteNodeWithColor:[SKColor blackColor] size:CGSizeMake(10, 10)];
        dot.position = positionInScene;
        [self addChild: dot];

    } else { //calls touchesMoved
    }

    //[self.lineNode removeFromParent]; //comment out this line if you want line to remain on screen
    CGPathRelease(self.pathToDraw);
}
@end