由于 Mike Repass 关于传递普通旧上下文的评论，部分问题已得到解决.

Part of the problem was fixed thanks to the comment from Mike Repass about passing a plain old context.

至于对话框没有显示......我只是愚蠢，因为我在执行外部 AsyncTask 之后调用了 .get() 阻塞了 UI 线程.显然，对话框不会以这种方式显示.

As for the dialog not showing up...I was just being stupid because I called a .get() after the execute OUTSIDE the AsyncTask which blocks the UI thread. Obviously the dialog is not going to show up that way.