随机CGPoint x值不起作用

问题描述

| 我有22个图像... 11个是（rightwall1，rightwall2，rightwall3等），其他11个是（leftwall1，leftwall2，leftwall3等） 我将每个y的y值设置为先前的墙y值加上墙的高度（所有墙的高度相同），从而将每个墙放置在另一个的顶部。 这样很好！ 现在，我试图使用arc4random设置x值，以使它们在一定范围内在整个位置上跳跃（对于左壁：（-35至15）和对于右壁：（330至405））。 。 右侧墙可以正常工作，但是左侧墙可以正常工作，但是大多数都不会显示在屏幕上。 我手动将x的值设置为-45，它显示在屏幕上，并且低于arc4random允许的值。 我能想到的唯一问题是我要减去左墙的错误？ 这是设置墙壁位置的代码，在整个项目中我还没有其他代码。

-(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( (15-(arc4random()%50)),(460-((leftWall1.frame.size.height)/2)) );
        leftWall2.center = CGPointMake( (15-(arc4random()%50)),((leftWall1.center.y)-(leftWall2.frame.size.height)) );
        leftWall3.center = CGPointMake( (15-(arc4random()%50)),((leftWall2.center.y)-(leftWall3.frame.size.height)) );
        leftWall4.center = CGPointMake( (15-(arc4random()%50)),((leftWall3.center.y)-(leftWall4.frame.size.height)) );
        leftWall5.center = CGPointMake( (15-(arc4random()%50)),((leftWall4.center.y)-(leftWall5.frame.size.height)) );
        leftWall6.center = CGPointMake( (15-(arc4random()%50)),((leftWall5.center.y)-(leftWall6.frame.size.height)) );
        leftWall7.center = CGPointMake( (15-(arc4random()%50)),((leftWall6.center.y)-(leftWall7.frame.size.height)) );
        leftWall8.center = CGPointMake( (15-(arc4random()%50)),((leftWall7.center.y)-(leftWall8.frame.size.height)) );
        leftWall9.center = CGPointMake( (15-(arc4random()%50)),((leftWall8.center.y)-(leftWall9.frame.size.height)) );
        leftWall10.center = CGPointMake( (15-(arc4random()%50)),((leftWall9.center.y)-(leftWall10.frame.size.height)) );
        leftWall11.center = CGPointMake( (15-(arc4random()%50)),((leftWall10.center.y)-(leftWall11.frame.size.height)) );

}

    

解决方法

        事实证明，使用arc4random无法获得负整数值（可以理解，因为arc4random使用模数。...整数... ??哈哈）所以我使用了float ... 不能说：

(-1)*(arc4random() ....

你不得不说：

float num1;
num1 = -1;
(num1)*(arc4random() ....

奇怪...减法也一样...您必须将负的浮点数乘以arc4random ..