Android应用程序读取几个端点AsynTasks coliding

Question

我想构建一个能够连接到USB设备中几个不同接口的应用程序。我试图使用AsyncTasks和Executor来实现这一点，但是当我实例化一个新的AsyncTask时，它给了我错误：“无法执行任务：任务已经在运行。”为什么会这样？我在doInBackground方法上有一个无限循环，但我认为这个过程与那个过程并行。有人能帮助我吗？

代码：

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private void addInterface (UsbInterface intf, UsbEndpoint ep){

    if (selectedDevice != null && intf != null && ep != null) {

        if (mConnection != null && mConnection.claimInterface(intf, true)) {

            listOfSelectedUsbInterface.add(intf);
            listOfSelectedUsbEndpoint.add(ep);

            bufferList.add(ByteBuffer.allocate(ep.getMaxPacketSize())) ;
            requestList.add(new UsbRequest());
            requestList.get(requestList.size()-1).initialize(mConnection, listOfSelectedUsbEndpoint.get(listOfSelectedUsbEndpoint.size() - 1));

            int index= listOfSelectedUsbEndpoint.size()-1;
            AsyncTask taskToAdd = new USB_asyncTask().execute(new Integer(index));
            taskToAdd.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);


            Log.d(TAG, "Number o endpoints: " + listOfSelectedUsbEndpoint.size());
        }
        else {
            Log.d(TAG, "Device open FAIL");
            mConnection = null;
        }
    }
}


private class USB_asyncTask extends AsyncTask <Integer,Void,String> {

    @Override
    protected String doInBackground( Integer... idx) {

        int index = idx[0].intValue();

        while(true) {
            requestList.get(index).queue(bufferList.get(index), listOfSelectedUsbEndpoint.get(index).getMaxPacketSize());

            Log.d(TAG, "Interrupt in " + index );
            // wait for status event
            if (mConnection.requestWait() == requestList.get(index)) {

                String str = "Interface Id (" + listOfSelectedUsbInterface.get(index).getId() + "):  " + String.format("%02X", bufferList.get(index).get(0));
                for (int i = 1; i < listOfSelectedUsbEndpoint.get(index).getMaxPacketSize(); i++) {
                    str += String.format(":%02X", bufferList.get(index).get(i));
                }

                final String stringtodisplay=str;
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            textInfo.setText(stringtodisplay);
                        }
                    });
            }
        }
    }