使用 Sprite Kit 移动背景

Question

我已经开始使用 Sprite Kit。我正在开发一款具有移动背景的游戏。现在我想知道如果我触摸屏幕如何使背景移动得更快，以及当我松开手指时如何正常移动背景。

我现在正在像这样移动我的背景。

代码开头是这样的：

-(id)initWithSize:(CGSize)size {    
     if (self = [super initWithSize:size]) {

     [self addBackground]


};
return self;
}

 -(void)addBackground{


SKTexture* background = [SKTexture textureWithImageNamed:@"backgroundImage"];

SKAction* moveBackground = [SKAction moveByX:-1704*2 y:0 duration:0.004 * background.size.width*2];
SKAction* putOnStart = [SKAction moveByX:1704*2 y:0 duration:0];
SKAction* moveForever = [SKAction repeatActionForever:[SKAction sequence:@[moveBackground, putOnStart]]];

 for( int i = 0; i < 2 + self.frame.size.width / ( background.size.width * 2 ); ++i )      {
    SKSpriteNode* sprite = [SKSpriteNode spriteNodeWithTexture:background size:CGSizeMake(1704 ,320)];
         sprite.position = CGPointMake(i * sprite.size.width, sprite.size.height / 2);
    [background runAction:moveForever];
    [self addChild:sprite];
}
 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    touching = YES;
}

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

我在视图出现时初始化它。现在问题是我想更新SKAction moveBackround 的持续时间。

Answer 1

抱歉之前的回答。我完全误读了你的问题，喝了太多咖啡:)

看看这段用于移动背景的代码。正如您所问的，它能够以 2 种速度移动，具体取决于是否记录了触摸。

#import "MyScene.h"

// this a from a project I did for an iPhone 5s
// the background image I used is 2048 wide by 640 high and is a @2x.png

 static const float CONSTANT_MOVE_POINTS_PER_SEC = 300.0;

 static inline CGPoint CGPointMultiplyScalar(const CGPoint a,
                                             const CGFloat b)
{
    return CGPointMake(a.x * b, a.y * b);
}

 static inline CGPoint CGPointAdd(const CGPoint a,
                                  const CGPoint b)
{
    return CGPointMake(a.x + b.x, a.y + b.y);
}

@implementation MyScene {
    SKNode *_bgLayer;
    int _gameSpeedPlus;
    NSTimeInterval _dt;
    NSTimeInterval _lastUpdateTime;
}

-(id)initWithSize:(CGSize)size {    
    if (self = [super initWithSize:size])
    {
        _bgLayer = [SKNode node];
        [self addChild:_bgLayer];
        _gameSpeedPlus = 0;

        for (int i = 0; i < 2; i++) {
            SKSpriteNode * bg = [SKSpriteNode spriteNodeWithImageNamed:@"background"];
            bg.anchorPoint = CGPointZero;
            bg.position = CGPointMake(i * bg.size.width, 0);
            bg.name = @"bg";
            [_bgLayer addChild:bg];
        }
    }
    return self;
}

- (void)moveBg {
    CGPoint bgVelocity = CGPointMake(-(CONSTANT_MOVE_POINTS_PER_SEC + _gameSpeedPlus), 0);
    CGPoint amtToMove = CGPointMultiplyScalar(bgVelocity, _dt);
    _bgLayer.position = CGPointAdd(_bgLayer.position, amtToMove);

    [_bgLayer enumerateChildNodesWithName:@"bg"
                               usingBlock:^(SKNode *node, BOOL *stop){
                                   SKSpriteNode * bg = (SKSpriteNode *) node;
                                   CGPoint bgScreenPos = [_bgLayer convertPoint:bg.position
                                                                     toNode:self];
                                   if (bgScreenPos.x <= -bg.size.width) {
                                       bg.position = CGPointMake(bg.position.x+bg.size.width*2,
                                                             bg.position.y);
                               }
                           }];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    _gameSpeedPlus = 200; // change value to increase or decrease speed
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    _gameSpeedPlus = 0;
}

-(void)update:(CFTimeInterval)currentTime {
    if (_lastUpdateTime) {
        _dt = currentTime - _lastUpdateTime;
    } else {
        _dt = 0;
    }
    _lastUpdateTime = currentTime;
        [self moveBg];
    }


@end