DownloadManager怎么设置通知栏图标

DownloadManager怎么设置通知栏图标，我的是一个默认的Android机器人的图标，有没有大神知道怎么修改

https://zhidao.baidu.com/question/745796807727624332.html

private final NotificationManager mNotifManager;
mNotifManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

final Notification.Builder builder = new Notification.Builder(mContext);
builder.setSmallIcon(R.drawable.stat_sys_download);//这里设置图标
...
final Notification notif = builder.build();
mNotifManager.notifyAsUser(tagName, 0, notif, UserHandle.CURRENT);