How do i move the sprite while the finger is touching?

Question

I'm working on a small game to learn more xcode and objective-C.

I want to move my sprite along one axis while i am touching. I know how to use SKAction with moveBy, but the sprite stops moving when it reaches the stated distance.

I want the sprite to move untill the touch ends. Currently i'm only moving it along the x axis.

Answer 1

There are several ways you could do this.

Here's a simple one: in your touchesBegan:withEvent: , set a flag to YES in your scene indicating that the finger is down. In touchesEnded:withEvent: , set the flag to NO . In your scene's update: method, if the flag is YES , modify the sprite's position.

@implementation MyScene {
    BOOL shouldMoveSprite;
    SKNode *movableSprite;
    NSTimeInterval lastMoveTime;
}

 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    lastMoveTime = HUGE_VAL;
    shouldMoveSprite = YES;
}

 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    shouldMoveSprite = NO;
}

 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    shouldMoveSprite = NO;
}

static CGFloat kSpriteVelocity = 100;

- (void)update:(NSTimeInterval)currentTime {
    NSTImeInterval elapsed = currentTime - lastMoveTime;
    lastMoveTime = currentTime;
    if (elapsed > 0) {
        CGFloat offset = kSpriteVelocity * elapsed;
        CGPoint position = movableSprite.position;
        position.x += offset;
        movableSprite.position = position;
    }
}

Another approach would be, when the touch begins, to attach a custom action (using +[SKAction customActionWithDuration:block:] ) to the sprite that moves it a little bit, and to remove the action when the touch ends.

Another approach would be to use the physics engine. When the touch begins, set the sprite's physicsBody.velocity to a non-zero vector (or apply an impulse). When the touch ends, set the velocity back to CGVectorMake(0,0) .

Answer 2

Here's what I did -- not sure if it's the most efficient method, but it works the way I want it to!

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    if (self.isFingerOnBowl)
    {
        UITouch *touch = [touches anyObject];
        CGPoint touchLocation = [touch locationInNode:self];
        moveBowlToPoint = [SKAction moveToX:(touchLocation.x) duration:0.01];
        [_bowl runAction:moveBowlToPoint];
    }
}