iOS7 SKScene如何让精灵从屏幕边缘反弹？

Question

我正在建造一个带有球在iPad屏幕内弹跳的游戏.类似于Pong游戏.我看到SKScene的SKPhysicsWorld具有重力属性,还可以控制物体相互碰撞的方式.

有没有什么方法可以自动检测精灵的边缘是否与屏幕边缘相撞,所以它可以反弹掉？或者我是否需要编写自己的碰撞代码？

Answer 1

您不需要编写太多代码就可以使球从屏幕边缘反弹.物理环境可以处理上述所有内容,您只需要以正确的方式实例化sprite.

首先,您必须设置场景的physicsBody:

self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];

在场景的.h文件中创建两个位掩码类别:

static const uint8_t ballCategory = 1;
static const uint8_t wallCategory = 2;

并给场景的物理主体一个类别:

self.physicsBody.categoryBitMask = wallCategory;

然后创建你的精灵:

SKSpriteNode *spriteNode = [SKSpriteNode spriteNodeWithImageNamed:@"ball.png"]; 

spriteNode.name = @"ball";

spriteNode.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:25];
spriteNode.position = CGPointMake(10.0,10.0); //or anything you want
spriteNode.physicsBody.dynamic = YES;
spriteNode.physicsBody.affectedByGravity = NO;

spriteNode.physicsBody.categoryBitMask = ballCategory;
spriteNode.physicsBody.collisionBitMask = wallCategory;

spriteNode.physicsBody.restitution = 1.0;
spriteNode.physicsBody.friction = 0.0;
spriteNode.physicsBody.linearDamping = 0.0;
spriteNode.physicsBody.angularDamping = 0.0;

[self addChild:spriteNode];

而不是给spriteNode一个[SKAction moveTo: duration:],给它的物理体施加一个冲动.

CGVector impulse = CGVectorMake(1.0,1.0);
[spriteNode.physicsBody applyImpulse:impulse];

瞧!球将从墙上弹起,没有任何阻止它.

这就是.h文件应该是这样的:

#import <SpriteKit/SpriteKit.h>

static const uint8_t ballCategory = 1;
static const uint8_t wallCategory = 2;

@interface BallBounce : SKScene

@end

这就是.m文件的样子:

#import "BallBounce.h"

@implementation BallBounce

-(instancetype)initWithSize:(CGSize)size
{
    if (self = [super initWithSize:size])
    {
        self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
        self.physicsBody.categoryBitMask = wallCategory;

        SKSpriteNode *spriteNode = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(50, 50)];

        spriteNode.name = @"ball";

        spriteNode.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:25];
        spriteNode.position = CGPointMake(10.0,10.0); //or anything you want
        spriteNode.physicsBody.dynamic = YES;
        spriteNode.physicsBody.affectedByGravity = NO;

        spriteNode.physicsBody.categoryBitMask = ballCategory;
        spriteNode.physicsBody.collisionBitMask = wallCategory;

        spriteNode.physicsBody.restitution = 1.0;
        spriteNode.physicsBody.friction = 0.0;
        spriteNode.physicsBody.linearDamping = 0.0;
        spriteNode.physicsBody.angularDamping = 0.0;

        [self addChild:spriteNode];

        CGVector impulse = CGVectorMake(100.0,100.0);
        [spriteNode.physicsBody applyImpulse:impulse];

    }

    return self;
}

@end

Answer 2

您是否尝试过设置SKScene的物理主体

[self setPhysicsBody:[SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame]];  //Physics body of Scene

这应该保持你的节点在框架内.

w ^