Strange behavior of sprite Kit - ios

Question

I am setting background color in this code:
- (void)randomBackground {
int random = arc4random() % 3;
NSLog(#"%d", random);
switch (random) {
case 0:
self.background = [SKSpriteNode spriteNodeWithImageNamed:#"image1"];
break;
case 1:
self.background = [SKSpriteNode spriteNodeWithImageNamed:#"image2"];
break;
case 2:
self.background = [SKSpriteNode spriteNodeWithImageNamed:#"image3"];
break;
}
self.background.position = CGPointMake(self.size.width / 2.0, self.size.height / 2.0);
}
-(id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
NSLog(#"Size: %#", NSStringFromCGSize(size));
}
self.physicsWorld.gravity = CGVectorMake(0, 0);
self.physicsWorld.contactDelegate = self;
return self;
}
-(void)didMoveToView:(nonnull SKView *)view {
self.backgroundColor = [SKColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0];
[self randomBackground];
self.player = [SKSpriteNode spriteNodeWithImageNamed:#"ninja"];
self.player.position = CGPointMake(self.player.size.width / 2.0, self.player.size.height / 2.0);
[self removeAllChildren];
[self addChild:self.background];
[self addChild:self.player];
}
After my player looses, I present another scene, and than present this scene again:
SKAction *loseAction = [SKAction runBlock:^{
SKTransition *reveal = [SKTransition flipHorizontalWithDuration:0.5];
GameOverScene *gameOverScene = [[GameOverScene alloc] initWithSize:self.size won:NO];
[self.view presentScene:gameOverScene transition:reveal];
}];
[hero runAction:[SKAction sequence:#[move, loseAction, moveDone]]];
Here is how I present main scene again:
[self runAction:
[SKAction sequence:#[[SKAction waitForDuration:0.5],
[SKAction runBlock:^{
[self.parentScene removeAllChildren];
SKTransition *reveal = [SKTransition flipHorizontalWithDuration:0.5];
GameScene *myScene = [GameScene sceneWithSize:self.size];
[self.view presentScene:myScene transition:reveal];
}]
]]];
The problem is that sometimes, when a specific background is loaded, the whole content seems to be covered by it, however, when I nslog the children of scene, the background is on the first place of an array.
As the result, I can see only background. Strangely enough, this happens only on certain backgrounds, while on other backgrounds it is OK and the content is displayed properly.
Any ideas how to fix it?

Answer 1

The order of initialization is actually very interesting, but its a completely different topic. To fix your issue, you need to specify each node's position on the z-axis, through the property zPosition. For example, if you write:
background.zPosition = -1;
myNode.zPosition = 1;
myNode will always present itself on top of background.