ios - 将 UIImageView 设置在屏幕右侧

Question

我有一个名为 ufo 的 UIImageView。它在屏幕外向左移动，直到您再也看不到它为止，我希望它在屏幕右侧重生并移入。左侧正在工作，但右侧没有。

if (ufo.center.x < (-ufo.frame.size.width/2)) {
            ufo.center = CGPointMake((backGround.frame.size.width -    (ufo.frame.size.width / 2)), ufo.center.y);
        }

它完全在右侧重生，没有离开屏幕。我知道 CGPointMake 中应该有一个 +，但它在左侧出现故障!

有人可以帮忙吗？

谢谢。

Answer 1

根据您的标准，我会做类似以下的事情:

if (ufo.center.x < (backGround.frame.origin.x - (ufo.bounds.size.width / 2.0))) 
{
    //just guessing, since you haven't shown your animation code, but, add the following line:
    [ufo.layer removeAllAnimations];
    //you haven't shown enough, so here is another shot in the dark:
    [timer invalidate];
    ufo.center = CGPointMake((backGround.frame.size.width + (ufo.bounds.size.width / 2.0)), ufo.center.y);
}

以下内容 用于根据一些猜测(因为您没有提供足够的信息)和您目前提供的信息来模仿您的游戏行为。

根据你的标准，你的 UFO 现在在我的屏幕上从右到左再向右飞:

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self createMyUFOandMyBackground];
}

- (void)createMyUFOandMyBackground
{
    myBackground = [[UIImageView alloc] initWithFrame:self.view.bounds];
    myBackground.image = [UIImage imageNamed:@"background"];
    [self.view addSubview:myBackground];

    myUFO = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"ufo"]];
    myUFO.center = (CGPoint){myBackground.bounds.size.width + (myUFO.bounds.size.width / 2.0f), myBackground.center.y};
    [self.view addSubview:myUFO];

    [self createTimer];
}

- (void)createTimer
{
    myTimer = [NSTimer scheduledTimerWithTimeInterval:0.05f target:self selector:@selector(moveUFOToLeft) userInfo:nil repeats:YES];
}

- (void)moveUFOToLeft
{
    temp = 0;
    if (myUFO.center.x < (myBackground.frame.origin.x - (myUFO.bounds.size.width / 2.0)))
    {
        [myTimer invalidate];
        myTimer = nil;
        myUFO.center = CGPointMake((myBackground.frame.size.width + (myUFO.bounds.size.width / 2.0)), myUFO.center.y);
        [self restartMyTimerAfterSeconds];
    }
    else
    {
        temp = - arc4random_uniform(10);
        myUFO.center = CGPointMake(myUFO.center.x + temp, myUFO.center.y);
    }
}

- (void)restartMyTimerAfterSeconds
{
    //This is specific to your game; I will leave that to you.

    [self createTimer];
}