spritekit碰撞检测不起作用

Question

无论我做什么，我似乎无法让我的代码记下一次碰撞。没有任何Nslogs输出任何东西所以我知道代码甚至从未注意到碰撞。我尝试了很多尺寸的图像，甚至尝试多次更改节点类型类别，但仍然没有。我在这里做错了什么？

      #import "JKGPlayer.h"
#import "JKGMyScene.h"
static const uint32_t firstNodeTypeCategory     =  0x1 << 1;
static const uint32_t secondNodeTypeCategory        =  0x1 << 2;

// 1
@interface JKGMyScene () <SKPhysicsContactDelegate>
@property (nonatomic) JKGPlayer * player;
@property (nonatomic) SKSpriteNode * plat2;
@property (nonatomic) SKSpriteNode * a1;
@property (nonatomic) SKSpriteNode * a2;
@end 
@implementation JKGMyScene

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

    // 2
    NSLog(@"Size: %@", NSStringFromCGSize(size));

    // 3
    self.backgroundColor = [SKColor colorWithRed:1.0 green:.50 blue:1.0 alpha:1.0];

    // 4
    _plat2 = [SKSpriteNode spriteNodeWithImageNamed:@"twa1.png"];
    _plat2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:_plat2.size];
    _plat2.position = CGPointMake(500, 500);
    _plat2.zPosition = 15;
    _plat2.physicsBody.dynamic = NO;
    _plat2.physicsBody.usesPreciseCollisionDetection = YES;
    _plat2.physicsBody.friction = 0;
    _plat2.name = @"plat2";
    _plat2.physicsBody.categoryBitMask = secondNodeTypeCategory;
    _plat2.physicsBody.contactTestBitMask = firstNodeTypeCategory;
    _plat2.physicsBody.collisionBitMask = secondNodeTypeCategory;
    [self addChild:_plat2];

    _a1 = [SKSpriteNode spriteNodeWithImageNamed:@"sun.png"];
    _a1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:_a1.size];
    _a1.position = CGPointMake(500, 450);
    _a1.zPosition = 15;
    _a1.physicsBody.dynamic = NO;
    _a1.physicsBody.usesPreciseCollisionDetection = YES;
    _a1.physicsBody.friction = 0;
    _a1.name = @"plat2";
    _a1.physicsBody.categoryBitMask = firstNodeTypeCategory;
    _a1.physicsBody.contactTestBitMask = secondNodeTypeCategory;
    _a1.physicsBody.collisionBitMask = firstNodeTypeCategory;
    [self addChild:_a1];

    _a2 = [SKSpriteNode spriteNodeWithImageNamed:@"sun.png"];
    _a2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:_a2.size];
    _a2.position = CGPointMake(500, 500);
    _a2.zPosition = 15;
    _a2.physicsBody.dynamic = NO;
    _a2.physicsBody.usesPreciseCollisionDetection = YES;
    _a2.physicsBody.friction = 0;
    _a2.name = @"plat2";
    _a2.physicsBody.categoryBitMask = secondNodeTypeCategory;
    _a2.physicsBody.contactTestBitMask = firstNodeTypeCategory;
    _a2.physicsBody.collisionBitMask = secondNodeTypeCategory;
    [self addChild:_a2];

    self.player = [[JKGPlayer alloc] initWithImageNamed:@"walkright1"];
    self.player.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:self.player.size];
    self.player.position = CGPointMake(500, 550);
    self.player.zPosition = 15;
    self.player.physicsBody.dynamic = NO;
    self.player.physicsBody.usesPreciseCollisionDetection = YES;
    self.player.physicsBody.friction = 0;
    self.player.name = @"player";
    self.player.physicsBody.categoryBitMask = firstNodeTypeCategory;
    self.player.physicsBody.contactTestBitMask = secondNodeTypeCategory;
    self.player.physicsBody.collisionBitMask = firstNodeTypeCategory;

    [self  addChild:self.player];
    self.userInteractionEnabled = YES;
    self.physicsWorld.gravity = CGVectorMake(0,0);
    self.physicsWorld.contactDelegate = self;

}
return self;
 }

 - (void)updateWithTimeSinceLastUpdate:(CFTimeInterval)timeSinceLast {

 }

 - (void)update:(NSTimeInterval)currentTime {
      self.player.desiredPosition = CGPointMake(self.player.position.x, self.player.position.y-1);
      self.player.position = self.player.desiredPosition;
     self.player.onGround = NO;
  }

 -(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

int x = self.player.position.x-5;
int y = self.player.position.y-5;
CGPoint A = CGPointMake(x, y);
self.player.position = A;
// 1 - Choose one of the touches to work with
UITouch * touch = [touches anyObject];
CGPoint location = [touch locationInNode:self];
 }

 - (void)projectile:(SKSpriteNode *)projectile didCollideWithMonster:(SKSpriteNode *)monster {
      NSLog(@"Hit");
 }

 - (void)didBeginContact:(SKPhysicsContact *)contact{
     NSLog(@"AAAAAA");
     // 1
     SKPhysicsBody *firstBody, *secondBody;

if (contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask){
    firstBody = contact.bodyA;
    secondBody = contact.bodyB;
}
else
{
    firstBody = contact.bodyB;
    secondBody = contact.bodyA;
}

// 2
if ((firstBody.categoryBitMask & firstNodeTypeCategory) != 0 &&
    (secondBody.categoryBitMask & secondNodeTypeCategory) != 0)
{
    [self projectile:(SKSpriteNode *) firstBody.node didCollideWithMonster:(SKSpriteNode *) secondBody.node];
}


}