我有 22 张图片... 11 张是（rightwall1、rightwall2、rightwall3 等），另外 11 张是（leftwall1、leftwall2、leftwall3 等）
我通过将它们的 y 值设置为之前的墙壁 y 值加上墙壁的高度（所有墙壁的高度相同），将它们放在另一个之上。
这很好用！
现在，我试图使用 arc4random 设置 x 值，这样它们就会在一定范围内跳跃整个地方......
右边的墙完美地工作，但左边的墙，其中一些工作，但大部分没有出现在屏幕上。
我手动将 x 值 1 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为左墙减去错误？
这是设置墙壁位置的代码，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)) );
}