在一个循环中一个接一个地完成多个任务

Question

我有对象数组， 我想为这个数组的每个对象创建一个 pdf。为此，我使用了一个循环，但问题是它为我创建了最后一个的 PDF 文件。

我想我知道为什么，因为任务没有时间完成它继续下一个。

我想在创建 pdf 文件之前停止循环，然后继续下一次迭代...

每次迭代我都想停止循环以腾出时间来创建 pdf 文件

这是我的代码：

for (i in 0 until multipleInvoice!!.size) {

            receiveUser = MainActivity.users.find { it.codeZ == multipleInvoice!![i].customerCodeZ }
            products = multipleInvoice!![i].retrieveInvoice(this)
            receiveInvoice = multipleInvoice!![i]

            doAsync {
                // Long background task
                progressBar.setVisible()
                htmlContent = renderHTML()

                uiThread {
                    //webViewInitializer(htmlContent)
                    doAsync {
                        htmlToPDF(htmlContent) //Is function create PDF file on the phone!!!
                        //Here I want to stop the loop until the file is created 
                        // (by the function of the line above). As soon as the file is created, we take the loop 
                    }
                    progressBar.setGone()
                }
            }
        }

Answer 1

你不能使用任何循环来实现你想要的。有一种方法可以使用递归执行您想要的操作。当您有多个发票时，调用第 0 个位置的此函数以呈现 PDF。

if(multipleInvoice?:0 >0)    
  renderInvoice(0)


fun renderInvoice(i:Int) {

        receiveUser = MainActivity.users.find { it.codeZ == multipleInvoice!![i].customerCodeZ }
        products = multipleInvoice!![i].retrieveInvoice(this)
        receiveInvoice = multipleInvoice!![i]

        doAsync {
            // Long background task
            progressBar.setVisible()
            htmlContent = renderHTML()

            uiThread {
                //webViewInitializer(htmlContent)
                doAsync {
                    htmlToPDF(htmlContent) //Is function create PDF file on the phone!!!
                    //Here I want to stop the loop until the file is created 
                    // (by the function of the line above). As soon as the file is created, we take the loop 
                   if(i< multipleInvoice!!.size)
                     renderInvoice(++i)
                }
                progressBar.setGone()
            }
        }
    }