我想一个一个下载多个文件（文件下载，我们开始下载下一个文件）。使用这种方法，我可以跟踪文件的下载。问题是，我使用的是下面的$ C $下执行任务：

 文件fil​​e = NULL;
                的for（int i = 0; I＆LT; videos.length;我++）{
                     文件=新的文件（root.getPath（）+视频[I]）;
                     布尔存在= file.exists（）;
                     如果（存在）{
                         //tv.append("\n\n"+fileNames[i]+已经存在）;
                         继续;
                     }
                     其他 {
                         currentFile =视频[I]
                         新DownloadFileAsync（）执行（videoURL +视频[I]，视频[I]）。

                     }
                     文件= NULL;
                }
 

正如你所看到的，我称之为新DownloadFileAsync（）执行（videoURL +视频[I]，视频[I]）。在循环中这显然开始对每个文件的任务，并同时下载它们。

我的问题是，：如何运行任务执行特定文件，检查它是否已经downloaded-如果是的话，通过执行为它的任务继续进行下一个文件？

如果我理解正确的话，你不想一（连续）来下载同恬E（同时）中的所有文件，但之一。 为了做到这一点建立与URL的字符串数组下载，并调用执行（）与该阵列。

例：假设你的 DownloadFileAsync 预计字符串作为   参数，它的 doInBackground方法，你会打电话来：

 新DownloadFileAsync（）执行（URL1，URL2，URL3，url4，VIDEO1，VIDEO2，VIDEO3，VIDEO4）。
 

I'm trying to download multiple files one by one (file is downloaded, we start downloading the next file). Using this method I can keep track of the files being downloaded. The problem is that I'm using the following code for executing a Task:

                File file = null;                
                for(int i=0; i< videos.length; i++) {
                     file = new File(root.getPath() + videos[i]);
                     boolean exists = file.exists();
                     if(exists){
                         //tv.append("\n\n"+fileNames[i]+" already exists");
                         continue;
                     }
                     else {
                         currentFile = videos[i];
                         new DownloadFileAsync().execute(videoURL+videos[i],videos[i]);            

                     }
                     file = null;
                }

As you can see, I call new DownloadFileAsync().execute(videoURL+videos[i],videos[i]); in a loop which obviously start a task for each of the files and downloads them simultaneously.

My question is: How can I run execute the task for a specific file, check if it has been downloaded- if yes, proceed with next file by executing a task for it?

If I understand correctly, you do not want to download all the files at the same tim e(simultaneously) but one by one (serially). In order to do so build a String array with the URLs to download, and call execute() with that array.

Example: Assuming that your DownloadFileAsync expects String as a parameter to it's doInBackground method, you would call to:

new DownloadFileAsync().execute(url1, url2, url3, url4, video1, video2, video3, video4);