Question

我将PDF文件存储在某个路径中。如果我下载了该文件，则再次点击下载链接如何发出警报＆＃34;你已经下载了这个文件。您想重新下载＆＃34;？

function downloadFile(){

window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, 
    function onFileSystemSuccess(fileSystem) {
        fileSystem.root.getFile(
        "dummy.html", {create: true, exclusive: false}, 
        function gotFileEntry(fileEntry) {
            var sPath = fileEntry.fullPath.replace("dummy.html","");
            var fileTransfer = new FileTransfer();
            fileEntry.remove();

            fileTransfer.download(
                "http://www.w3.org/2011/web-apps-ws/papers/Nitobi.pdf",
                sPath + "theFile.pdf",
                function(theFile) {
                    console.log("download complete: " + theFile.toURI());
                    showLink(theFile.toURI());
                },
                function(error) {
                    console.log("download error source " + error.source);
                    console.log("download error target " + error.target);
                    console.log("upload error code: " + error.code);
                }
            );
        }, fail);
    }, fail);
};
}

Answer 1

这是一个非常好的问题，所以我在这种情况下简要解释一下我们要检查2条件杉木

在该文件路径上文件名不存在的IS文件然后我们必须下载文件

如果该文件中存在文件名，那么你必须检查该文件的MD5 ，因为同名的另一个文件也可能存在，所以在此条件我们必须使用文件MD5

检查文件内容

private File longF ;
private MessageDigest md;
longF = "your file path which u want to check weather it is present or not ";
String digest ="";
md = MessageDigest.getInstance("MD5");

        if(longF.exists())
                          {
                     digest = Constant.getDigest(new FileInputStream(longF), md, 2048);
                          }
                else
                    {
                            System.out.println("not already exit according to file path condition " );

                          } 

             if(digest.equals(selectMD5))
        {
            System.out.println("Open That file=========");
                }

如何检查存储中存在的下载文件

1 个答案: