循环中增加范围后的Java语言延迟

Question

我有1个数组，像这样的数千个链接图像

let imageList = ["http://img1.jpg", "http://img2.jpg", ...];

我想遍历imageList，并在增加索引20次（n次）后延迟，例如

for(let i = 0; i <= imageList.length; i+=20){
  // with i from 0 -> 20
  // do download image from server
  downloadImage(0,20) // [start, end]
  // delay 5s to prevent server timeout because request many times

  // with i from 20 -> 40
  // do download image from server
  downloadImage(20,40)

  // continue delay 5s

  // .... try to finish
}

Answer 1

设置一些偏移

let offset = 0

for (let i = offset; i <= imageList.length; i += 20) {
  downloadImage(offset, offset + 20) 
  offset += 20
}

Answer 2

您可以使用modulus operator。

let imageList = [“ http://img1.jpg”，“ http://img2.jpg”，...];

for(let i = 0; i <= imageList.length; i++){
  if (i % n == 0) //n is number of images to start delay
  START_YOUR_DELAY_HERE
  downloadImage(20); //20 is number of images you want to download
}