Question

我正在尝试通过USB串口使用Mike Wakerly的usb-serial-for-android库与Arduino Mega克隆进行通信（谢谢！）我已经挖掘了权限错误，但现在我得到了以下问题：

09-02 15:08:03.628  18694-18792/org.drivebuv.buvmonitor W/SerialInputOutputManager﹕ Run ending due to exception: Error queueing request.
java.io.IOException: Error queueing request.
        at org.drivebuv.buvmonitor.CdcAcmSerialDriver$CdcAcmSerialPort.read(CdcAcmSerialDriver.java:168)
        at org.drivebuv.buvmonitor.SerialInputOutputManager.step(SerialInputOutputManager.java:158)
        at org.drivebuv.buvmonitor.SerialInputOutputManager.run(SerialInputOutputManager.java:140)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
        at java.util.concurrent.FutureTask.run(FutureTask.java:237)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
        at java.lang.Thread.run(Thread.java:818)

方法如下。抛出错误的行是!request.queue(buf, dest.length)

的if循环

public int read(byte[] dest, int timeoutMillis) throws IOException {
        if (mEnableAsyncReads) {
          final UsbRequest request = new UsbRequest();
          try {
            request.initialize(mConnection, mReadEndpoint);
            final ByteBuffer buf = ByteBuffer.wrap(dest);
            if (!request.queue(buf, dest.length)) {
              throw new IOException("Error queueing request.");
            }

            final UsbRequest response = mConnection.requestWait();
            if (response == null) {
              throw new IOException("Null response");
            }

            final int nread = buf.position();
            if (nread > 0) {
              Log.d(TAG, HexDump.dumpHexString(dest, 0, Math.min(32, dest.length)));
              return nread;
            } else {
              return 0;
            }
          } finally {
            request.close();
          }
        }

        final int numBytesRead;
        synchronized (mReadBufferLock) {
            int readAmt = Math.min(dest.length, mReadBuffer.length);
            numBytesRead = mConnection.bulkTransfer(mReadEndpoint, mReadBuffer, readAmt,
                    timeoutMillis);
            if (numBytesRead < 0) {
                // This sucks: we get -1 on timeout, not 0 as preferred.
                // We *should* use UsbRequest, except it has a bug/api oversight
                // where there is no way to determine the number of bytes read
                // in response :\ -- http://b.android.com/28023
                if (timeoutMillis == Integer.MAX_VALUE) {
                    // Hack: Special case "~infinite timeout" as an error.
                    return -1;
                }
                return 0;
            }
            System.arraycopy(mReadBuffer, 0, dest, 0, numBytesRead);
        }
        return numBytesRead;
    }

以前，他在第319行的CdcAcmSerialDriver.java中似乎有一个错误： mDataInterface = mDevice.getInterface(1);

所以我将1更改为0，根据How to fix java.lang.ArrayIndexOutOfBoundsException: length=1; index=1修复了索引越界错误。结束将所有.java文件移动到我的包中以便编辑它们。甚至不确定这是否相关。

目前，我的应用程序在该异常后挂起。一句话：我在这里用低级代码游泳并且没有使用kludges。请你指点我的土地:)？

什么原因导致UsbRequest从队列方法中抛出IO Exception？

0 个答案: