usb - Android USB Accessory 无法接收数据，InputStream.read 永远不会返回

Question

我有两部安卓手机，都是安卓6.0。我希望他们通过 USB 相互通信。我有一根 OTG USB 数据线，可以将一部手机插入另一部手机。一个是usb主机，另一个是配件。

我的代码基于以下教程：

• http://developer.android.com/guide/topics/connectivity/usb/host.html
• http://developer.android.com/guide/topics/connectivity/usb/accessory.html

现在

1. 主机和附件可以连接
   根据这个项目：https
   ://github.com/quandoo/android2android-accessory 主机发送控制消息：
   private void initStringControlTransfer(final UsbDeviceConnection deviceConnection, final int index, final String string) { deviceConnection.controlTransfer(0x40, 52, 0, index, string.getBytes(), string.length(), USB_TIMEOUT_IN_MS); } initStringControlTransfer(connection, 0, "UsbTest Example"); // MANUFACTURER initStringControlTransfer(connection, 1, "UsbTest"); // MODEL initStringControlTransfer(connection, 2, "Test Usb Host and Accessory"); // DESCRIPTION initStringControlTransfer(connection, 3, "0.1"); // VERSION initStringControlTransfer(connection, 4, ""); // URI initStringControlTransfer(connection, 5, "42"); // SERIAL connection.controlTransfer(0x40, 53, 0, 0, new byte[]{}, 0, USB_TIMEOUT_IN_MS);
2. 主机可以使用 UsbRequest 从附件接收数据
   主机代码：
   UsbRequest request = new UsbRequest(); request.initialize(mConnection, mEndIn); boolean ret = request.queue(buffer, BUFFER_SIZE_IN_BYTES); if (ret) { if (mConnection.requestWait() == request) { // Succeed } }
   附件代码：
   try { mOutStream.write(sendBuff); mOutStream.flush(); } catch (IOException e) { }
3. 配件无法接收数据
   主机代码
   int len = mInStream.read(msg); // block here, read never return if (len > 0) { // succeed }
   配件代码：
   UsbRequest request = new UsbRequest(); request.initialize(mConnection, mEndOut); ByteBuffer buffer = ByteBuffer.wrap(text.getBytes()); boolean ret = request.queue(buffer, text.getBytes().length); if (ret) { // request.queue succeed } // if I use bulkTransfer, it always return a negative value //int len = mConnection.bulkTransfer(mEndOut, text.getBytes(), text.getBytes().length, USB_TIMEOUT_IN_MS); //if (len < 0) { // // always run here //} else { //
//}

有人知道吗？