通过USB连接到Android平板电脑的设备将断开连接，重新连接时会赢得恢复通信

Question

我正在处理一个问题，即一种称为聚合器板的设备（简称Aggboard）与Android平板电脑断开，并且在重新连接后，它不会在端点之间恢复通信。

一些背景：我一直在尝试重构这个Android应用程序的USB系统。最初，为了在端点之间传输数据，他们使用了usbdeviceconnection.bulktransfer（）方法。我对使用USBREQUEST.Initialize（），USBREQUEST.QUEUE（）和USBDeviceConnection.RequestWait（）方法进行了重构。当在平板电脑上启动Android程序时，我的新方法工作正常（甚至更好），但是当Aggboard有USB中断/断开连接时，一旦重新连接，它就不会在其上停止的地方接收。但是，它们的旧方法usbdeviceconnection.bulktransfer（）确实在重新连接时会进行通信。

旧的bulktransfer（）方法始终删除数据包，这一过程刺激了整个过程，我们认为使用USBREQUEST类可能是一个改进。似乎情况似乎是这种情况，但是看到该产品必须倾向于使其Aggoble被断开/中断，因此，新方法必须允许Aggboard在重新连接后继续提供信息。

这是我重构的代码，以及原始方法：

原始方法[bulktransfer（）] -

import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbEndpoint;
import android.hardware.usb.UsbInterface;
import android.hardware.usb.UsbRequest;
import android.os.AsyncTask;
import android.util.Log;

import java.io.IOException;
import java.nio.ByteBuffer;

public class PayloadTask extends AsyncTask<Payload, Void, Payload> {

    private UsbInterface usbInterface;
    private UsbDeviceConnection usbConnection;
    private UsbEndpoint usbToAggBoard;
    private UsbEndpoint usbFromAggBoard;
    private AggBoard owner;

    PayloadTask(AggBoard owner, UsbInterface intf, UsbDeviceConnection connection) {
        usbConnection = connection;
        usbInterface = intf;
        /*synchronized (intf)*/ {
            usbToAggBoard = intf.getEndpoint(1);
            usbFromAggBoard = intf.getEndpoint(0);
        }
        this.owner = owner;
    }

    @Override
    protected Payload doInBackground(Payload... payloads) {

        if (payloads != null) {
            if (payloads.length > 1) {
                Log.d("PayloadTask", "There was more than one payload. Going to have to iterate.");
                int i = 0;
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                for (Payload payload : payloads) {
                    byte[] buffer = payload.getBytes();

                    while (AndroidUnityPlayerActivity.aggBoard == null)
                    {
                        try {
                            Log.d("PayloadTask", "Waiting for AndroidUnityPlayerActivity.aggboard to not be null");
                            Thread.sleep(50);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                   
                 int sent = usbConnection.bulkTransfer(usbToAggBoard, buffer, buffer.length, 1500);

                    busyWaitMicros(20);

                    if (++i % 1024 == 0) {
                        Log.e(AndroidUnityPlayerActivity.TAG, new Integer(i / 1024 * 8).toString() + "KB sent");
                    }
                    AggBoard.percentInstalled = i * 100 / payloads.length;
                   // Log.w(AndroidUnityPlayerActivity.TAG, new Float((float)i /payloads.length).toString());

                }
                Log.d("PayloadTask", "Finished iterating over the payloads.");
                // rk3188 doesn't seem to see the success/fail message.. so let's fake one :/
                if (AggBoard.encryptedBytes != null) {
                    Log.d("PayloadTask", "Aggboard.encryptedBytes was null. Creating some kind of success response payload??");
                    byte[] response = new byte [] { (byte)Payload.BOOTLOAD_STATUS,
                                                    (byte)BootloadStatusPayload.AGGREGATOR,
                                                    (byte)BootloadStatusPayload.SUCCESS,
                                                    0, 0, 0, 0,
                                                    (byte)Payload.AGGREGATOR_TAIL };
                    if (AggBoard.percentInstalled < 100) {
                        response[2] = (byte)BootloadStatusPayload.ERROR ;
                    }
                    Log.d("PayloadTask", "Creating bootload status SUCCESS task");
                    return Payload.CreatePayload(response);
                }
            } else if (payloads.length == 1 && payloads[0] != null) {
                Log.d("PayloadTask", "There was only one payload. Running it");
                byte[] buffer = payloads[0].getBytes();
                if (AndroidUnityPlayerActivity.aggBoard != null) {
                    Log.d("PayloadTask", "Only one payload, beginning bulk transfer");
                    
                    usbConnection.bulkTransfer(usbToAggBoard, buffer, buffer.length, 100);
                   
                    /*if (Payload.START_SENDING_DATA == buffer[0]) {
                        AndroidUnityPlayerActivity.hasAggBoard = true;
                    }*/
                }
                else{
                    Log.d("PayloadTask", "AndroidUnityPlayerActivity's aggboard was null. Can't perform bulk transfer of payload.");
                }
            }
        } else {
            try {
                Thread.sleep(5);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        byte[] response = new byte[64];
        int result = 0;
        int tries = 0;

        while (result < 1){
            if (tries > 5) {
                Log.d("PayloadTask", "PayloadTask Timed Out.");
                return null;
            } else if (isCancelled()) {
                Log.w("PayloadTask", "PayloadTask Cancelled!");
                return null;
            }

            /*synchronized (usbConnection)*/
           
               result = usbConnection.bulkTransfer(usbFromAggBoard, response, response.length, 25);
               
            tries += 1;

        }
        Log.i("PayloadTask", new Integer(response.length).toString() + " bytes received: ");
        Log.d("PayloadTask", "doInBackground returning some payload from the aggboard.");
        return Payload.CreatePayload(response);
    }

    @Override
    protected void onPostExecute(Payload payload) {
        owner.handlePayload(payload);
    }

    @Override
    protected void onCancelled() {
        Log.d("PayloadTask", "thread canceled");
        super.onCancelled();
    }

    @Override
    protected void onPreExecute() {
        Log.d("PayloadTask", "started thread");
        if (!usbConnection.claimInterface(usbInterface, true)) {
                Log.w("PayloadTask", "Failed to claim interface!");
            }
        else{
            Log.w("PayloadTask", "Claimed interface!");
        }
    }

    public static void busyWaitMicros(long micros){
        long waitUntil = System.nanoTime() + (micros * 1000);
        while(waitUntil > System.nanoTime()){
            ;
        }
    }
}

重构代码[usbrequest/requestWait（）] -

import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbEndpoint;
import android.hardware.usb.UsbInterface;
import android.hardware.usb.UsbRequest;
import android.os.AsyncTask;
import android.util.Log;

import java.io.IOException;
import java.nio.ByteBuffer;

public class PayloadTask extends AsyncTask<Payload, Void, Payload> {

    private UsbInterface usbInterface;
    private UsbDeviceConnection usbConnection;
    private UsbEndpoint usbToAggBoard;
    private UsbEndpoint usbFromAggBoard;
    private AggBoard owner;

    PayloadTask(AggBoard owner, UsbInterface intf, UsbDeviceConnection connection) {
        usbConnection = connection;
        usbInterface = intf;
        /*synchronized (intf)*/ {
            usbToAggBoard = intf.getEndpoint(1);
            usbFromAggBoard = intf.getEndpoint(0);
        }
        this.owner = owner;
    }

    @Override
    protected Payload doInBackground(Payload... payloads) {

        if (payloads != null) {
            if (payloads.length > 1) {
                Log.d("PayloadTask", "There was more than one payload. Going to have to iterate.");
                int i = 0;
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                for (Payload payload : payloads) {
                    byte[] buffer = payload.getBytes();

                    while (AndroidUnityPlayerActivity.aggBoard == null)
                    {
                        try {
                            Log.d("PayloadTask", "Waiting for AndroidUnityPlayerActivity.aggboard to not be null");
                            Thread.sleep(50);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }

                    UsbRequest request = new UsbRequest();

                    ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
                    byteBuffer.rewind();
                    try {
                        request.initialize(usbConnection, usbToAggBoard);
                      
                        if (!request.queue(byteBuffer, buffer.length)) {
                            throw new IOException("Error queueing USB request.");
                        }
                        usbConnection.requestWait();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        if(usbConnection != null) {
                            int sent = request.hashCode();
                            request.close();
                        }
                        else{
                            Log.d("PayloadTask", "Request not received by usbConnection");
                        }
                    }

                    busyWaitMicros(20);

                    if (++i % 1024 == 0) {
                        Log.e(AndroidUnityPlayerActivity.TAG, new Integer(i / 1024 * 8).toString() + "KB sent");
                    }
                    AggBoard.percentInstalled = i * 100 / payloads.length;
                   // Log.w(AndroidUnityPlayerActivity.TAG, new Float((float)i /payloads.length).toString());

                }
                Log.d("PayloadTask", "Finished iterating over the payloads.");
                // rk3188 doesn't seem to see the success/fail message.. so let's fake one :/
                if (AggBoard.encryptedBytes != null) {
                    Log.d("PayloadTask", "Aggboard.encryptedBytes was null. Creating some kind of success response payload??");
                    byte[] response = new byte [] { (byte)Payload.BOOTLOAD_STATUS,
                                                    (byte)BootloadStatusPayload.AGGREGATOR,
                                                    (byte)BootloadStatusPayload.SUCCESS,
                                                    0, 0, 0, 0,
                                                    (byte)Payload.AGGREGATOR_TAIL };
                    if (AggBoard.percentInstalled < 100) {
                        response[2] = (byte)BootloadStatusPayload.ERROR ;
                    }
                    Log.d("PayloadTask", "Creating bootload status SUCCESS task");
                    return Payload.CreatePayload(response);
                }
            } else if (payloads.length == 1 && payloads[0] != null) {
                Log.d("PayloadTask", "There was only one payload. Running it");
                byte[] buffer = payloads[0].getBytes();
                if (AndroidUnityPlayerActivity.aggBoard != null) {
                    Log.d("PayloadTask", "Only one payload, beginning bulk transfer");

                    UsbRequest request = new UsbRequest();
                    ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
                    byteBuffer.rewind();
                    try {
                        request.initialize(usbConnection, usbToAggBoard);

                        if (!request.queue(byteBuffer, buffer.length)) {
                            throw new IOException("Error queueing USB request.");
                        }
                        usbConnection.requestWait();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        if(usbConnection != null) {
                            request.close();
                        }
                        else{
                            Log.d("PayloadTask", "Request not received by usbConnection");
                        }
                    }
                    
                    /*if (Payload.START_SENDING_DATA == buffer[0]) {
                        AndroidUnityPlayerActivity.hasAggBoard = true;
                    }*/
                }
                else{
                    Log.d("PayloadTask", "AndroidUnityPlayerActivity's aggboard was null. Can't perform bulk transfer of payload.");
                }
            }
        } else {
            try {
                Thread.sleep(5);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        byte[] response = new byte[64];
        int result = 0;
        int tries = 0;

        while (result < 1){
            if (tries > 5) {
                Log.d("PayloadTask", "PayloadTask Timed Out.");
                return null;
            } else if (isCancelled()) {
                Log.w("PayloadTask", "PayloadTask Cancelled!");
                return null;
            }

            /*synchronized (usbConnection)*/
            if (usbConnection != null) {
                UsbRequest request = new UsbRequest();
               
                ByteBuffer byteBuffer = ByteBuffer.wrap(response);
                byteBuffer.rewind();
                try {
                    request.initialize(usbConnection, usbFromAggBoard);
                    
                    if (!request.queue(byteBuffer, response.length)) {
                        throw new IOException("Error queueing USB request.");
                    }
                    usbConnection.requestWait();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    if(usbConnection != null) {
                        result = request.hashCode();
                        request.close();
                  
                    }
                    else{
                        Log.d("PayloadTask", "Request not received by usbConnection");
                    }
                }
            }
            tries += 1;

        }
        Log.i("PayloadTask", new Integer(response.length).toString() + " bytes received: ");
        Log.d("PayloadTask", "doInBackground returning some payload from the aggboard.");
        return Payload.CreatePayload(response);
    }

    @Override
    protected void onPostExecute(Payload payload) {
        owner.handlePayload(payload);
    }

    @Override
    protected void onCancelled() {
        Log.d("PayloadTask", "thread canceled");
        super.onCancelled();
    }

    @Override
    protected void onPreExecute() {
        Log.d("PayloadTask", "started thread");
        if (!usbConnection.claimInterface(usbInterface, true)) {
                Log.w("PayloadTask", "Failed to claim interface!");
            }
        else{
            Log.w("PayloadTask", "Claimed interface!");
        }
    }

    public static void busyWaitMicros(long micros){
        long waitUntil = System.nanoTime() + (micros * 1000);
        while(waitUntil > System.nanoTime()){
            ;
        }
    }
}