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我制作了一个读取 pdf 文件的应用程序，我想从平板电脑打印文档。所以当我将打印机的 USB 连接到端口时，它应该首先检测 USB 是否已连接，然后如果打印机已连接，则打印文档。如果有人对此概念有想法，请在此处分享。任何帮助，将不胜感激