问题
im currently working on an app in which your player which is a small round ball, gets dragged around the screen by your finger. Then every 10 seconds a enemy ball gets added in which automatically tracks your ball and follows it until it runs into it. this is the code I have for this so far. you can drag your ball around the screen, bu the enemy ball which is only showing up as a red x even though its file is in the assets gets spawned every frame and they just move to the position of where your ball was when it was spawned. is there any way I can fix this, any help is appreciated. the contact between the balls I will add later on.
import SpriteKit
import GameplayKit
class GameScene: SKScene {
var me = SKSpriteNode()
let enemy = SKSpriteNode (imageNamed: "ellipse 1")
override func didMove(to view: SKView) {
me = self.childNode(withName: "me") as! SKSpriteNode
let border = SKPhysicsBody (edgeLoopFrom: self.frame)
border.friction = 0
self.physicsBody = border
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches{
let location = touch.location(in: self)
me.run(SKAction.moveTo(x: location.x, duration: 0))
me.run(SKAction.moveTo(y: location.y, duration: 0))
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches{
let location = touch.location(in: self)
me.run(SKAction.moveTo(x: location.x, duration: 0))
me.run(SKAction.moveTo(y: location.y, duration: 0))
}
}
override func update(_ currentTime: TimeInterval) {
let enemy = SKSpriteNode (imageNamed: "ball 2")
enemy.position = CGPoint(x:667, y: -200)
enemy.run(SKAction.moveTo(x: me.position.x, duration: 1.5))
enemy.run(SKAction.moveTo(y: me.position.y, duration: 1.5))
enemy.zPosition = +1
addChild(enemy)
}
}
回答1:
So the problem you're having is that your enemy ball images aren't loading, and you're seeing a red X instead?
If so you need to break your code that creates your sprite into steps. First load the image into a temporary variable, print it, and then use the image to create your sprite:
let enemyImage = imageNamed: "ellipse 1"
print("enemyImage = \(enemyImage)")
let enemy = SKSpriteNode (enemyImage)
If enemyImage is nil, you need to figure out why that is.
回答2:
Here is a modified version of your code that'll spawn an enemy once every 10 seconds and have them follow you. I used the Spaceship graphic provided by Apple's SpriteKit template for the enemy. As for your issue with the enemy graphic not showing up I'd make sure that the image is named "ball 2" in the assets folder.
import SpriteKit
import GameplayKit
class Enemy: SKSpriteNode {
var enemySpeed: CGFloat = 4
}
class GameScene: SKScene {
var me: SKSpriteNode!
var enemies = [Enemy]()
override func didMove(to view: SKView) {
me = self.childNode(withName: "me") as! SKSpriteNode
let border = SKPhysicsBody (edgeLoopFrom: self.frame)
border.friction = 0
self.physicsBody = border
spawnEnemy() // Spawn an enemy to begin with
Timer.scheduledTimer(timeInterval: 10.0, target: self, selector: #selector(spawnEnemy), userInfo: nil, repeats: true) // Spawns an enemy every 10 seconds
}
func spawnEnemy() {
let enemy = Enemy(imageNamed: "Spaceship")
enemy.xScale = 0.25
enemy.yScale = 0.25
enemy.position = CGPoint(x: CGFloat(arc4random() % UInt32(size.width)) - size.width / 2, y: CGFloat(arc4random() % UInt32(size.height)) - size.height / 2)
enemy.zPosition = 1
addChild(enemy)
enemies.append(enemy)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
let location = touch.location(in: self)
me.run(SKAction.move(to: location, duration: 0.05))
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
let location = touch.location(in: self)
me.run(SKAction.move(to: location, duration: 0.05))
}
}
override func update(_ currentTime: TimeInterval) {
for enemy in enemies {
let angle = CGFloat(atan2f(Float(me.position.y - enemy.position.y), Float(me.position.x - enemy.position.x)))
enemy.zRotation = angle - CGFloat.pi / 2
enemy.position = CGPoint(x: enemy.position.x + cos(angle) * enemy.enemySpeed, y: enemy.position.y + sin(angle) * enemy.enemySpeed)
}
}
}
回答3:
import SpriteKit
import GameplayKit
class GameScene: SKScene {
var me = SKSpriteNode()
override func didMove(to view: SKView) {
me = self.childNode(withName: "me") as! SKSpriteNode
let border = SKPhysicsBody (edgeLoopFrom: self.frame)
border.friction = 0
self.physicsBody = border
run(SKAction.repeatForever(SKAction.sequence([SKAction.run(createEnemy), SKAction.wait(forDuration: 10.0)])))
}
func createEnemy () {
let enemy = SKSpriteNode(imageNamed: "ball 1")
enemy.name = "enemy"
enemy.position = CGPoint(x:667, y: -200)
enemy.run(SKAction.moveTo(x: me.position.x, duration: 1.5))
enemy.run(SKAction.moveTo(y: me.position.y, duration: 1.5))
enemy.zPosition = +1
addChild(enemy)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches{
let location = touch.location(in: self)
me.run(SKAction.moveTo(x: location.x, duration: 0))
me.run(SKAction.moveTo(y: location.y, duration: 0))
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches{
let location = touch.location(in: self)
me.run(SKAction.moveTo(x: location.x, duration: 0))
me.run(SKAction.moveTo(y: location.y, duration: 0))
}
}
override func update(_ currentTime: TimeInterval) {
}
}
来源：https://stackoverflow.com/questions/44058895/how-to-have-a-enemy-be-added-in-every-10-seconds-and-have-this-enemy-track-your