[UIColor colorWithRed:arc4random_uniform(256)/255.0
green:arc4random_uniform(256)/255.0
blue:arc4random_uniform(256)/255.0 alpha:0.3]
隨機(jī)數(shù)函數(shù)arc4random_uniform(x)屹逛,可以用來(lái)產(chǎn)生0~(x-1)范圍內(nèi)的隨機(jī)數(shù)导狡。如果要生成1~x的隨機(jī)數(shù):arc4random_uniform(x)+1