Iphone xcode CGPoint arc4random不工作

我有22张照片。。。11个是（右墙1、右墙2、右墙3等）其他11个是（左墙1、左墙2、左墙3等）

我通过将它们的y值设置为前一面墙的y值加上墙的高度（所有墙的高度相同），将它们放置在另一面墙的顶部

这个很好用

现在，我试着用arc4random设置x值，这样他们就可以在一定范围内跳到所有地方

右边的墙工作得很好，但左边的墙，其中一些可以工作，但大部分都不会显示在屏幕上

我手动将x值设置为-15，它显示在屏幕上，低于arc4random允许的值

我能想到的唯一问题是我把左边的墙减去了错误的数

这是设置墙位置的代码，我在整个项目中还没有其他代码

-(void)awakeFromNib {

    rightWall1.center = CGPointMake( ((arc4random()%75)+330), (460-((rightWall1.frame.size.height)/2)) );//460 = bottom of screen
    rightWall2.center = CGPointMake( ((arc4random()%75)+330), ((rightWall1.center.y)-(rightWall2.frame.size.height)) );
    rightWall3.center = CGPointMake( ((arc4random()%75)+330), ((rightWall2.center.y)-(rightWall3.frame.size.height)) );
    rightWall4.center = CGPointMake( ((arc4random()%75)+330), ((rightWall3.center.y)-(rightWall4.frame.size.height)) );
    rightWall5.center = CGPointMake( ((arc4random()%75)+330), ((rightWall4.center.y)-(rightWall5.frame.size.height)) );
    rightWall6.center = CGPointMake( ((arc4random()%75)+330), ((rightWall5.center.y)-(rightWall6.frame.size.height)) );
    rightWall7.center = CGPointMake( ((arc4random()%75)+330), ((rightWall6.center.y)-(rightWall7.frame.size.height)) );
    rightWall8.center = CGPointMake( ((arc4random()%75)+330), ((rightWall7.center.y)-(rightWall8.frame.size.height)) );
    rightWall9.center = CGPointMake( ((arc4random()%75)+330), ((rightWall8.center.y)-(rightWall9.frame.size.height)) );
    rightWall10.center = CGPointMake( ((arc4random()%75)+330), ((rightWall9.center.y)-(rightWall10.frame.size.height)) );
    rightWall11.center = CGPointMake( ((arc4random()%75)+330), ((rightWall10.center.y)-(rightWall11.frame.size.height)) );


    leftWall1.center = CGPointMake( ((arc4random()%75)-60), (460-((leftWall1.frame.size.height)/2)) );
    leftWall2.center = CGPointMake( ((arc4random()%75)-60), ((leftWall1.center.y)-(leftWall2.frame.size.height)) );
    leftWall3.center = CGPointMake( ((arc4random()%75)-60), ((leftWall2.center.y)-(leftWall3.frame.size.height)) );
    leftWall4.center = CGPointMake( ((arc4random()%75)-60), ((leftWall3.center.y)-(leftWall4.frame.size.height)) );
    leftWall5.center = CGPointMake( ((arc4random()%75)-60), ((leftWall4.center.y)-(leftWall5.frame.size.height)) );
    leftWall6.center = CGPointMake( ((arc4random()%75)-60), ((leftWall5.center.y)-(leftWall6.frame.size.height)) );
    leftWall7.center = CGPointMake( ((arc4random()%75)-60), ((leftWall6.center.y)-(leftWall7.frame.size.height)) );
    leftWall8.center = CGPointMake( ((arc4random()%75)-60), ((leftWall7.center.y)-(leftWall8.frame.size.height)) );
    leftWall9.center = CGPointMake( ((arc4random()%75)-60), ((leftWall8.center.y)-(leftWall9.frame.size.height)) );
    leftWall10.center = CGPointMake( ((arc4random()%75)-60), ((leftWall9.center.y)-(leftWall10.frame.size.height)) );
    leftWall11.center = CGPointMake( ((arc4random()%75)-60), ((leftWall10.center.y)-(leftWall11.frame.size.height)) );

}

我手动将x值设置为-15，它显示在屏幕上，低于arc4random允许的值

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（（arc4random（）%75）-60）

返回介于-60和14之间的数字，因为

（arc4random（）%75）

返回介于0和74之间的数字。

ohhhhhhhhh！哈哈哈哈哈还是不行，问题是当处理负ARC4随机值时，你不能使用整数，你必须使用浮点数。。如果减法不能只是减法，则必须将arc4random乘以负1浮点值。这是因为arc4random使用我假设的模…arc4random返回无符号值。使用%限制范围。您不需要浮点数，只需要%之后的有符号整数。