Sprite 套件 CGPoint 未按预期工作

Posted 2023-03-14

【中文标题】Sprite 套件 CGPoint 未按预期工作

【英文标题】：Sprite kit CGPoint not working as expected

【发布时间】：2013-12-18 12:20:29

【问题描述】：

我正在用 Sprite Kit 编写游戏，但我遇到了 CGPoint 问题，目前如果手机是纵向的，对象从屏幕右侧进入并移到左侧，我需要它来从屏幕顶部进入并落到底部，如何让它从屏幕顶部生成？此刻它也向右走，我想向下走这里是与“导弹”相关的所有代码..

static inline CGPoint CGPointAdd(const CGPoint a, const CGPoint b)

return CGPointMake(a.x + b.x, a.y + b.y);


static inline CGPoint CGPointMultiplyScalar(const CGPoint a, const CGFloat b)

return CGPointMake(a.x  * b, a.y * b);




-(void)addMissile

//initalizing spaceship node
SKSpriteNode *missile;
missile = [SKSpriteNode spriteNodeWithImageNamed:@"red-missile.png"];
[missile setScale:.01];

//Adding SpriteKit physicsBody for collision detection
missile.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:missile.size];
missile.physicsBody.categoryBitMask = obstacleCategory;
missile.physicsBody.dynamic = YES;
missile.physicsBody.contactTestBitMask = shipCategory;
missile.physicsBody.collisionBitMask = 0;
missile.physicsBody.usesPreciseCollisionDetection = YES;
missile.name = @"missile";

//selecting random y position for missile
//int t = arc4random() % 300;
missile.position = CGPointMake(100, 100);

[self addChild:missile];




- (void)moveObstacle

    NSArray *nodes = self.children;//1

for(SKNode * node in nodes)
    if (![node.name  isEqual: @"bg"] && ![node.name  isEqual: @"ship"]) 
        SKSpriteNode *ob = (SKSpriteNode *) node;
        CGPoint obVelocity = CGPointMake(-OBJECT_VELOCITY, 0);
        CGPoint amtToMove = CGPointMultiplyScalar(obVelocity,_dt);

        ob.position = CGPointAdd(ob.position, amtToMove);
        if(ob.position.y < 100)
        
            [ob removeFromParent];
        
    

【参考方案1】：

导弹动画很简单，所以在这种情况下您不需要 GDPointAdd 和 MultiplyByScalar

如果您需要从上到下移动的导弹，这里是代码

- (void)shootMissile 
     // Sprite Kit knows that we are working with images so we don't need to pass the image’s extension
     SKSpriteNode *missile = [SKSpriteNode spriteNodeWithImageNamed:@"red-missile"];
     // Position the missile outside the top
     missile.position = CGPointMake(self.size.width/2, self.size.height + missile.size.height/2);
     // Add the missile to the scene
     [self addChild:missile];

     // Here is the Magic
     // Run a sequence
     [missile runAction:[SKAction sequence:@[
         // Move the missile and Specify the animation time
         [SKAction moveByX:0 y:-(self.size.height + missile.size.height) duration:3],
         // When the missile is outside the bottom
         // The missile will disappear
         [SKAction removeFromParent]                               ]
     ]];

你只需要在你想发射导弹时调用这个函数

现在您可以将所有物理特性添加到导弹

祝你好运！！

【讨论】：

如何更新？我目前的方法不起作用

如果你从 touchesBegan 调用 shootMissile，每次你触摸屏幕都会出现一个导弹如果你在 update 里面调用它，每秒钟都会出现一个导弹。或者更新它是什么意思？给我更多信息，我会帮你的

【参考方案2】：

试试这个代码：

- (void)moveObstacle

    NSArray *nodes = self.children;//1

    for(SKNode * node in nodes)
        if (![node.name  isEqual: @"bg"] && ![node.name  isEqual: @"ship"]) 
            SKSpriteNode *ob = (SKSpriteNode *) node;
            CGPoint obVelocity = CGPointMake(0, -OBJECT_VELOCITY);
            CGPoint amtToMove = CGPointMultiplyScalar(obVelocity,_dt);

            ob.position = CGPointAdd(ob.position, amtToMove);
            if(ob.position.y < 0)
            
                [ob removeFromParent];
            
        
    

虽然我不知道_dt 代表什么。