SKShapeNode检测两行相交

Question

I am working on a application and i am drawing line based on user touch of user finger. Once the touch end event received the line is converted to last path. A new line is draw with name "Current path" node when a new touch began event received. I added a physics body for both the line with opposite contact bit mask but i am not able to receive collision event. Following is my code:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    currentPath = CGPathCreateMutable();
    currentPathNode = [self newLineNodeWithFillColor :  CURRENT_LINE_COLOR];
    CGPathMoveToPoint(currentPath, NULL, positionInScene.x, positionInScene.y);
    currentPathNode.path = currentPath;
    [self addChild:currentPathNode];
    uint32_t contactBitMask = circleCategory | lastPathCategory;
    [self addPhysicsBodyForLine:currentPathNode withCategoryBitMask:drawPathCategory withContactBitMask:contactBitMask];
}
- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    CGPathAddLineToPoint(currentPath, NULL, positionInScene.x, positionInScene.y);
    currentPathNode.path = currentPath;
    uint32_t contactBitMask = lastPathCategory;
    [self addPhysicsBodyForLine:currentPathNode withCategoryBitMask:drawPathCategory withContactBitMask:contactBitMask];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    if(lastPath == nil){
        lastPath = CGPathCreateMutable();
    }
    CGPathAddPath(lastPath, nil, currentPath);
    [lastPathNode removeFromParent];
    if(currentPathNode != nil){
        [currentPathNode removeFromParent];
        currentPathNode = nil;
    }
    lastPathNode = [self newLineNodeWithFillColor : LAST_LINE_COLOR];
    lastPathNode.path = lastPath;
    [self addChild:lastPathNode];
    [self addPhysicsBodyForLine:lastPathNode withCategoryBitMask:lastPathCategory withContactBitMask:drawPathCategory];
    CGPathRelease(currentPath);
}  
- (void) addPhysicsBodyForLine:(SKShapeNode*)node withCategoryBitMask:(uint32_t)category withContactBitMask:(uint32_t)contactBitMask{
    node.physicsBody =  [SKPhysicsBody bodyWithEdgeChainFromPath:node.path];
    node.physicsBody.categoryBitMask    = category;
    node.physicsBody.contactTestBitMask = contactBitMask;
    node.physicsBody.collisionBitMask = contactBitMask;
    node.physicsBody.dynamic          = YES;
    node.physicsBody.usesPreciseCollisionDetection = YES;
}

But collision is not Detected? Any Solution.

Answer 1

Collisions do not work that way. You will only register a collision if you use physics to move a node's position. Creating a new physics body over (or across) an already existing physics body will not register a collision.

You can use -(BOOL)intersectsNode:(SKNode *)node every time a new path is drawn to check if the new node intersects any other node.