Android检查下载的文件是否存在

Question

I try, to check if this file exists after i downloaded it, but its says to me that is doesnt exist

@Override
public void handleResult(Result result)
{

    myResult = result;
    dm = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
    Uri uri = Uri.parse(result.getText());
    DownloadManager.Request request = new DownloadManager.Request(uri);
    request.allowScanningByMediaScanner();
    request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
    String nameOfFile = URLUtil.guessFileName(result.getText(),null, MimeTypeMap.getFileExtensionFromUrl(result.getText()));
    request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, nameOfFile);

    dm.enqueue(request);
    String erg = "";
    File mPath = new File((Environment.DIRECTORY_DOWNLOADS + "/" + nameOfFile));
    if (mPath.getAbsoluteFile().exists()) {
        erg = "existiert";
    }else
    {
        erg = "existiert nicht";
    }
}

Answer 1

The downloading process is happening on background. So after enqueue() your file doesn't exist cause it's not downloaded yet. You just need to register BroadcastReceiver with this ACTION_DOWNLOAD_COMPLETE intent filter. And DownloadManager will broadcast when downloads complete. See documentation here: https://developer.android.com/reference/android/app/DownloadManager.html#ACTION_DOWNLOAD_COMPLETE