無法檢查文件是否存在

Question

我正在嘗試下載一個文件，如果它存在，請刪除它並再次下載。
下載有效。 但是 function checkFile永遠找不到文件，我不知道為什么。

private fun startDownloading() {

        checkFile()

        val url = etUrl.text.toString()
        val request = DownloadManager.Request(Uri.parse(url))
        //allow type of networks to download file(s) by default, by default both are allowed
        request.setAllowedNetworkTypes((DownloadManager.Request.NETWORK_MOBILE or DownloadManager.Request.NETWORK_WIFI))
        request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "$folderName/$fileName")

        //get download service, and enqueue file
        val manager = getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
        manager.enqueue(request)
    }


    private fun checkFile(){
        val file = File(Environment.DIRECTORY_DOWNLOADS, "$folderName/$fileName")
        if(file.exists()){
            Toast.makeText(this, "File exists", Toast.LENGTH_LONG).show()
            file.delete()
        }else{
            Toast.makeText(this, file.toString() + " doesn't exist", Toast.LENGTH_LONG).show()
        }
    }

提前致謝。

Answer 1

您使用以下命令在公共外部存儲目錄中創建文件：

     request.setDestinationInExternalPublicDir(
        Environment.DIRECTORY_DOWNLOADS,
        "$folderName/$fileName"
    )

但是您嘗試從相對（從應用程序的當前目錄）路徑中讀取它：

    val file = File(Environment.DIRECTORY_DOWNLOADS, "$folderName/$fileName")

您需要使用相對於公共外部存儲目錄的下載目錄：

    val file = File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "$folderName/$fileName")