ios - Spritekit 子类节点显示为 nil

Question

大家好，尝试在 SpriteKit 中创建子类节点时遇到一个奇怪的问题。我在编译时没有遇到任何错误，应用程序一直运行，直到我前进到需要将节点添加为场景的子节点的位置，然后失败并显示 reason: 'Attemped to add nil node to parent:我不确定我错过了什么，感谢任何帮助!这是我的节点标题:

#import <SpriteKit/SpriteKit.h>

@interface Ships : SKSpriteNode

-(Ships *)initWithImageNamed: (NSString *)imageName;

@end

下面是实现:

#import "Ships.h"

@implementation Ships

-(Ships *)initWithImageNamed: (NSString *)imageName
{
self = [Ships spriteNodeWithImageNamed:imageName];

// Adds more accurate physics body for ship collisions
CGFloat offsetX = (self.frame.size.width * 1.2) * self.anchorPoint.x;
CGFloat offsetY = (self.frame.size.height * 1.2) * self.anchorPoint.y;

CGMutablePathRef path = CGPathCreateMutable();

CGPathMoveToPoint(path, NULL, 8 - offsetX, 30 - offsetY);
CGPathAddLineToPoint(path, NULL, 7 - offsetX, 22 - offsetY);
CGPathAddLineToPoint(path, NULL, 50 - offsetX, 2 - offsetY);
CGPathAddLineToPoint(path, NULL, 65 - offsetX, 7 - offsetY);
CGPathAddLineToPoint(path, NULL, 70 - offsetX, 8 - offsetY);
CGPathAddLineToPoint(path, NULL, 27 - offsetX, 31 - offsetY);

CGPathCloseSubpath(path);

self.physicsBody = [SKPhysicsBody bodyWithPolygonFromPath:path];
self.physicsBody.dynamic = NO;
self.physicsBody.restitution = 0.0f;
self.physicsBody.friction = 0.0f;
self.physicsBody.linearDamping = 1.0f;
self.physicsBody.allowsRotation = NO;
self.physicsBody.usesPreciseCollisionDetection = YES;

// Keeps player ship on top of all other objects(unless other objects are assigned greater z position
self.zPosition = 100.0f;

return self;
}

@end

然后在我的场景中，我在 interface 中声明了 playerNode : Ships *playerNode; 这是尝试实现节点的方法:

-(void) createPlayerNode
{
playerNode = [playerNode initWithImageNamed:@"Nova-L1"];
playerNode.position = CGPointMake(self.frame.size.width/5, self.frame.size.height/2);
playerNode.physicsBody.categoryBitMask = CollisionCategoryPlayer;
playerNode.physicsBody.collisionBitMask = 0;
playerNode.physicsBody.contactTestBitMask = CollisionCategoryBottom | CollisionCategoryObject | CollisionCategoryScore | CollisionCategoryPup;

[self addChild:playerNode];
}

然后我在应用程序的其他地方调用了 [self createPlayerNode];，我一调用...崩溃。任何帮助是极大的赞赏!另外，我在我的 iPhone 5 上运行

Answer 1

Ships 的初始化器是实例方法而不是类方法，因此您的 alloc/init 语句应该是

playerNode = [[Ships alloc] initWithImageNamed:@"Nova-L1"]];

并在 Ships.m 中替换

self = [Ships spriteNodeWithImageNamed:imageName];

有了这个

self = [super initWithImageNamed:imageName];

另外，创建物理体后要释放路径...

    ship.physicsBody = [SKPhysicsBody bodyWithPolygonFromPath:path];

    CGPathRelease(path);

或者，您可以在 Ships.m 中声明一个方便的方法，以在单个步骤中分配/初始化。

编辑:

在 Ships.m 中声明类方法

+ (Ships *)shipNodeWithImageNamed:(NSString *)imageName
{
    return [[Ships alloc] initWithImageNamed:imageName];
}

将方法原型(prototype)添加到 Ships.h

+ (Ships *)shipNodeWithImageNamed:(NSString *)imageName;

并创建一个新的船节点

playerNode = [Ships shipNodeWithImageNamed:@"Nova-L1"];