随机 CGPoint x 值不起作用

Question

我有 22 个图像... 11 个是（rightwall1、rightwall2、rightwall3 等），其他 11 个是（leftwall1、leftwall2、leftwall3 等）

我通过将它们的 y 值设置为前一堵墙 y 将每个图像放置在另一个图像的上面值加上墙的高度（所有墙的高度相同）。

这很好用！

现在，我尝试使用 arc4random 设置 x 值，以便它们会在一定范围内跳跃（对于左墙：（-35 到 15）＆对于右墙：（330 到 405））。 ..

右墙工作正常，但左墙，其中一些可以工作，但大多数不会显示在屏幕上。

我手动将 x 值 1 设置为 -45，它显示在屏幕上，并且低于 arc4random 允许它运行的值。

我能想到的唯一问题是我减去左墙的错误？

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( (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)) );

}

Answer 1

事实证明，你无法使用 arc4random 获得负整数值（这是有道理的，因为 arc4random 使用模数......整数......？哈哈）所以我使用浮点数......

不能说：

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

你必须说：

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

奇怪...同样适用于减法...你必须添加负 1 浮点数乘以 arc4random ..