Cocos2D检查精灵是否在屏幕外？

Question

Im using this code to fire upwards:

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

//Spawn the bullet
CCSprite * projectile = [CCSprite spriteWithFile:@"Projectile.png" rect:CGRectMake(0, 0,    17.5, 10)];
projectile.position = ccp(donk.position.x , 50);
[self addChild:projectile];

//Actualy Fire
[projectile runAction: [CCMoveTo actionWithDuration:.2 position: ccp (donk.position.x , 350)]];


}

It works like I want but how can i use an if statement to check if the projectile it is off the top off the screen so I can remove it?

I tried using this:

    if (projectile.position.y >= 330) {
    CCLOG(@"Removed");
    [self removeChild:projectile cleanup:YES];
}

but I forgot that touches ended is only called once.

Answer 1

Think about when you should be checking whether the bullet is offscreen. Not at the same instant it was fired, right?

There are many ways to do this.

• You have a moveTo action already. CCActions can have callbacks that tell you when they're completed; see the header.

• You can define an update: method and enable it with scheduleUpdates to be able to test the position every frame.

• If you use a physics engine, you can make a "wall" for the edge of the screen and remove the bullet in response to collision detection.

There are probably other ways, too. Look into what the framework provides.

Answer 2

What about this:

[projectile runAction:[CCSequence actions:
                       [CCMoveTo actionWithDuration:.2 position:ccp(donk.position.x,350)], 
                       [CCCallBlock actionWithBlock:^{
        [projectile removeFromParentAndCleanup:YES];
    }], 
                        nil]];

(not tested)