Movement not working - iphone

Question

I am making a plat form game, but I am having an issue where only one of the movement buttons work. Can someone please take some time to review my code and see what is wrong with it?
I do not get my errors, my guess is that the there is a problem down where I change the sod variable. When I run the app and click and hold the "left button, it moves a little but then slows to a stop. It is as if the script where I changed the variable was only run one time, even though I hold it down. Interestingly enough, before when I ran it it was just fine. Unfortunately, I do not remember what I changed.
Thanks, James
class GameScene: SKScene {
var alien = SKSpriteNode()
var left = SKSpriteNode()
var right = SKSpriteNode()
var jump = SKSpriteNode()
var level = SKSpriteNode()
var background = SKSpriteNode()
var myLabel = SKLabelNode(fontNamed:"Chalkduster")
var playerLight = SKLightNode()
var xspd :Double = 0
var touching :Bool = false
var alienFrame :String = "stand"
var textureFrames :Double = 0
var buttonTouching :Bool = true
var buttonCheck :Int = 0
var ninety :Double = 0
override func didMoveToView(view: SKView) {
self.physicsWorld.gravity = CGVectorMake(0, -9.8)
alien = SKSpriteNode(imageNamed: "alien_stand")
alien.physicsBody = SKPhysicsBody(circleOfRadius: alien.frame.height / 2)
alien.position = CGPoint(x: self.frame.width / 6, y: self.frame.height / 2)
alien.xScale = 0.7
alien.yScale = 0.7
alien.physicsBody?.affectedByGravity = true
alien.physicsBody?.dynamic = true
alien.physicsBody?.allowsRotation = false
alien.zPosition = 1
alien.zRotation = 0
self.addChild(alien)
left = SKSpriteNode(imageNamed: "left")
left.position = CGPoint(x: self.frame.width / 8, y: self.frame.height / 3.5)
left.physicsBody?.pinned = true
left.xScale = 2
left.yScale = 2
left.zPosition = 3
left.alpha = 0.4
self.addChild(left)
right = SKSpriteNode(imageNamed: "right")
right.position = CGPoint(x: self.frame.width / 3, y: self.frame.height / 3.5)
right.physicsBody?.pinned = true
right.xScale = 2
right.yScale = 2
right.zPosition = 4
right.alpha = 0.4
self.addChild(right)
jump = SKSpriteNode(imageNamed: "up")
jump.position = CGPoint(x: (self.frame.width / 8) * 7, y: self.frame.height / 3.5)
jump.physicsBody?.pinned = true
jump.xScale = 2
jump.yScale = 2
jump.zPosition = 5
jump.alpha = 0.4
self.addChild(jump)
myLabel.text = "Hello, World!";
myLabel.fontSize = 45;
myLabel.position = CGPoint(x:CGRectGetMidX(self.frame), y:CGRectGetMidY(self.frame));
self.addChild(myLabel)
}
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
touching = true
if let touch = touches.first {
if xspd > -40 && xspd < 40 {
buttonCheck = 0
if jump.containsPoint(touch.locationInNode(self)) {
alien.physicsBody?.applyImpulse(CGVectorMake(0, 250))
jump.alpha = 0.1
alien.texture = SKTexture(imageNamed: "alien_jump")
buttonCheck += 1
}
if left.containsPoint(touch.locationInNode(self)) {
xspd -= 6
left.alpha = 0.1
alien.xScale = -0.7
buttonCheck += 1
}
if right.containsPoint(touch.locationInNode(self)) {
xspd += 6
right.alpha = 0.1
alien.xScale = 0.7
buttonCheck += 1
}
if buttonCheck > 0 {
buttonTouching = true
}
else {
buttonTouching = false
}
}
}
}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
touching = false
}
override func update(currentTime: CFTimeInterval) {
updatePositions()
playerLight.position = CGPoint(x: alien.position.x, y: alien.position.y)
textureFrames += 1
}
func updatePositions() {
myLabel.text = String(round(xspd))
alien.physicsBody?.applyImpulse(CGVector(dx: CGFloat(xspd), dy: 0))
if touching == true && buttonTouching == true && xspd > 0 {
if xspd > 0 {
ninety = 900
}
else {
ninety = -900
}
if alienFrame == "stand" {
alien.texture = SKTexture(imageNamed: "alien_walk1")
alienFrame = "walk1"
}
else {
if alienFrame == "walk1" {
if textureFrames > 9.9 / xspd {
alien.texture = SKTexture(imageNamed: "alien_walk2")
alienFrame = "walk2"
textureFrames = 0
}
}
else {
if alienFrame == "walk2" {
if textureFrames > 9.9 / xspd {
alien.texture = SKTexture(imageNamed: "alien_walk1")
alienFrame = "walk1"
textureFrames = 0
}
}
}
}
}
else {
if xspd < 0.6 && xspd > -0.6 {
alien.texture = SKTexture(imageNamed: "alien_stand")
}
else {
if xspd != 0 {
xspd = xspd * 0.85
}
}
right.alpha = 0.4
left.alpha = 0.4
jump.alpha = 0.4
}
}
}

Answer 1

When you start the game, the xspd variable starts off with a value of zero. When tapping the left node, you subtract 6 from the xspd giving you the result of -6 on the xspd. Further you have the updatePositions() function, which is called every frame I suppose and within that function you apply an impulse using a vector based on the xspd value. The if-condition after that is never fulfilled when tapping the left node first since you get a negative xspd value that breaks the condition (&& xspd > 0), hence you never get any animations with an initial velocity with a negative x.
To fix the animation, you could encapsulate the xspd in an abs() which will always return a positive number.
&& abs(xspd) > 0
The next issue is that your player stops moving because if you tap and hold on the left node, you won´t be able to maintain the movement speed without having to tap the left node repeatedly.
A suggestion from me, you could try the following:
if xspd < 0.6 && xspd > -0.6 {
alien.texture = SKTexture(imageNamed: "alien_stand")
} else if touching == false && xspd != 0 { // Never attempt to decrease movement speed if the player is in fact touching a movement button
xspd = xspd * 0.85
}
I hope I've understood your problem correctly and that this is helpful