Как включить Android менеджер загрузки

пожалуйста, отредактируйте мой ответ, если он недействителен

Проверьте, доступен ли менеджер загрузки:

   int state = this.getPackageManager().getApplicationEnabledSetting("com.android.providers.downloads");

if(state==PackageManager.COMPONENT_ENABLED_STATE_DISABLED||
state==PackageManager.COMPONENT_ENABLED_STATE_DISABLED_USER
||state==PackageManager.COMPONENT_ENABLED_STATE_DISABLED_UNTIL_USED){

// Cannot download using download manager
}

            else {
                request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, fileName);
                request.setDescription(fileName);   
                manager.enqueue(request); 
            }

и решение для попытки включить Диспетчер загрузки:

packageName = "com.android.providers.downloads"

try {
    //Open the specific App Info page:
    Intent intent = new Intent(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
    intent.setData(Uri.parse("package:" + packageName));
    startActivity(intent);

} catch ( ActivityNotFoundException e ) {
    //e.printStackTrace();

    //Open the generic Apps page:
    Intent intent = new Intent(android.provider.Settings.ACTION_MANAGE_APPLICATIONS_SETTINGS);
    startActivity(intent);

}

Google Gmail Inbox проверил, отключен ли DownloadManager, если true, то покажите AlertDialog, чтобы сообщить пользователю, чтобы включить DownloadManager в настройках.На скриншоте показано ниже:

Я написал класс DownloadManagerResolver чтобы исправить это, надеюсь, что это может помочь вам.:)

public final class DownloadManagerResolver {

private static final String DOWNLOAD_MANAGER_PACKAGE_NAME = "com.android.providers.downloads";

/**
 * Resolve whether the DownloadManager is enable in current devices.
 *
 * @return true if DownloadManager is enable,false otherwise.
 */
public static boolean resolve(Context context) {
    boolean enable = resolveEnable(context);
    if (!enable) {
        AlertDialog alertDialog = createDialog(context);
        alertDialog.show();
    }
    return enable;
}

/**
 * Resolve whether the DownloadManager is enable in current devices.
 *
 * @param context
 * @return true if DownloadManager is enable,false otherwise.
 */
private static boolean resolveEnable(Context context) {
    int state = context.getPackageManager()
            .getApplicationEnabledSetting(DOWNLOAD_MANAGER_PACKAGE_NAME);

    if (Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN_MR2) {
        return !(state == PackageManager.COMPONENT_ENABLED_STATE_DISABLED ||
                state == PackageManager.COMPONENT_ENABLED_STATE_DISABLED_USER
                || state == PackageManager.COMPONENT_ENABLED_STATE_DISABLED_UNTIL_USED);
    } else {
        return !(state == PackageManager.COMPONENT_ENABLED_STATE_DISABLED ||
                state == PackageManager.COMPONENT_ENABLED_STATE_DISABLED_USER);
    }
}

private static AlertDialog createDialog(final Context context) {
    AppCompatTextView messageTextView = new AppCompatTextView(context);
    messageTextView.setTextSize(16f);
    messageTextView.setText("DownloadManager is disabled. Please enable it.");
    return new AlertDialog.Builder(context)
            .setView(messageTextView, 50, 30, 50, 30)
            .setPositiveButton("ok", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    enableDownloadManager(context);
                }
            })
            .setCancelable(false)
            .create();
}

/**
 * Start activity to Settings to enable DownloadManager.
 */
private static void enableDownloadManager(Context context) {
    try {
        //Open the specific App Info page:
        Intent intent = new Intent(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
        intent.setData(Uri.parse("package:" + DOWNLOAD_MANAGER_PACKAGE_NAME));
        context.startActivity(intent);
    } catch (ActivityNotFoundException e) {
        e.printStackTrace();

        //Open the generic Apps page:
        Intent intent = new Intent(android.provider.Settings.ACTION_MANAGE_APPLICATIONS_SETTINGS);
        context.startActivity(intent);
    }
}
}

может быть это поможет вам.

downloadManager = (DownloadManager)getSystemService(DOWNLOAD_SERVICE);
   DownloadManager.Request request = new DownloadManager.Request(Download_Uri);
   //Restrict the types of networks over which this download may proceed.
   request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI | DownloadManager.Request.NETWORK_MOBILE);
   //Set whether this download may proceed over a roaming connection.
   request.setAllowedOverRoaming(false);
   //Set the title of this download, to be displayed in notifications (if enabled).
   request.setTitle("My Data Download");
   //Set a description of this download, to be displayed in notifications (if enabled)
   request.setDescription("Android Data download using DownloadManager.");
   //Set the local destination for the downloaded file to a path within the application's external files directory
   request.setDestinationInExternalFilesDir(this,Environment.DIRECTORY_DOWNLOADS,"CountryList.json");

   //Enqueue a new download and same the referenceId
   downloadReference = downloadManager.enqueue(request);

http://www.mysamplecode.com/2012/09/android-downloadmanager-example.html