两台android设备间通过OTG-USB连接，实现通信（android设备间的通信）

首先是一个简单的布局activity_chat.xml,就是后面进行通信的交互界面

因为android设备之间的连接涉及到主从设备的问题，所以在这边有一个区分，device包下有BaseChatActivity，ChatAtivity,ConnectActivity

public class ConnectActivity extends AppCompatActivity {

    public static final String DEVICE_EXTRA_KEY = "device";
    private UsbManager mUsbManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chat);

        mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
    }

    @Override
    protected void onResume() {
        super.onResume();

        final HashMap<String, UsbDevice> deviceList = mUsbManager.getDeviceList();

        if (deviceList == null || deviceList.size() == 0) {
            final Intent intent=new Intent(this, InfoActivity.class);
            startActivity(intent);

            finish();
            return;
        }

        if (searchForUsbAccessory(deviceList)) {
            return;
        }

        for (UsbDevice device:deviceList.values()) {
            initAccessory(device);
        }

        finish();
    }

    private boolean searchForUsbAccessory(final HashMap<String, UsbDevice> deviceList) {
        for (UsbDevice device:deviceList.values()) {
            if (isUsbAccessory(device)) {

                final Intent intent=new Intent(this,ChatActivity.class);
                intent.putExtra(DEVICE_EXTRA_KEY, device);
                startActivity(intent);

                finish();
                return true;
            }
        }

        return false;
    }

    private boolean isUsbAccessory(final UsbDevice device) {
        return (device.getProductId() == 0x2d00) || (device.getProductId() == 0x2d01);
    }

    private boolean initAccessory(final UsbDevice device) {

        final UsbDeviceConnection connection = mUsbManager.openDevice(device);

        if (connection == null) {
            return false;
        }

        initStringControlTransfer(connection, 0, "quandoo"); // MANUFACTURER
        initStringControlTransfer(connection, 1, "Android2AndroidAccessory"); // MODEL
        initStringControlTransfer(connection, 2, "showcasing android2android USB communication"); // DESCRIPTION
        initStringControlTransfer(connection, 3, "0.1"); // VERSION
        initStringControlTransfer(connection, 4, "http://quandoo.de"); // URI
        initStringControlTransfer(connection, 5, "42"); // SERIAL

        connection.controlTransfer(0x40, 53, 0, 0, new byte[]{}, 0, Constants.USB_TIMEOUT_IN_MS);

        connection.close();

        return true;
    }

    private void initStringControlTransfer(final UsbDeviceConnection deviceConnection,
                                           final int index,
                                           final String string) {
        deviceConnection.controlTransfer(0x40, 52, 0, index, string.getBytes(), string.length(), Constants.USB_TIMEOUT_IN_MS);
    }

}

然后

public class ChatActivity extends BaseChatActivity {

    private final AtomicBoolean keepThreadAlive = new AtomicBoolean(true);
    private final List<String> sendBuffer = new ArrayList<>();

    @Override
    public void sendString(final String string) {
        sendBuffer.add(string);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        new Thread(new CommunicationRunnable()).start();
    }

    private class CommunicationRunnable implements Runnable {

        @Override
        public void run() {
            final UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);

            final UsbDevice device=getIntent().getParcelableExtra(ConnectActivity.DEVICE_EXTRA_KEY);

            UsbEndpoint endpointIn = null;
            UsbEndpoint endpointOut = null;

            final UsbInterface usbInterface = device.getInterface(0);

            for (int i = 0; i < device.getInterface(0).getEndpointCount(); i++) {

                final UsbEndpoint endpoint = device.getInterface(0).getEndpoint(i);
                if (endpoint.getDirection() == UsbConstants.USB_DIR_IN) {
                    endpointIn = endpoint;
                }
                if (endpoint.getDirection() == UsbConstants.USB_DIR_OUT) {
                    endpointOut = endpoint;
                }

            }

            if (endpointIn == null) {
                printLineToUI("Input Endpoint not found");
                return;
            }

            if (endpointOut == null) {
                printLineToUI("Output Endpoint not found");
                return;
            }

            final UsbDeviceConnection connection = usbManager.openDevice(device);

            if (connection == null) {
                printLineToUI("Could not open device");
                return;
            }

            final boolean claimResult = connection.claimInterface(usbInterface, true);

            if (!claimResult) {
                printLineToUI("Could not claim device");
            } else {
                final byte buff[] = new byte[Constants.BUFFER_SIZE_IN_BYTES];
                printLineToUI("Claimed interface - ready to communicate");

                while (keepThreadAlive.get()) {
                    final int bytesTransferred = connection.bulkTransfer(endpointIn, buff, buff.length, Constants.USB_TIMEOUT_IN_MS);
                    if (bytesTransferred > 0) {
                        printLineToUI("host> "+new String(buff, 0, bytesTransferred));
                    }

                    synchronized (sendBuffer) {
                        if (sendBuffer.size()>0) {
                            final byte[] sendBuff=sendBuffer.get(0).toString().getBytes();
                            connection.bulkTransfer(endpointOut, sendBuff, sendBuff.length, Constants.USB_TIMEOUT_IN_MS);
                            sendBuffer.remove(0);
                        }
                    }
                }
            }

            connection.releaseInterface(usbInterface);
            connection.close();
        }
    }

    @Override
    protected void onStop() {
        super.onStop();
        keepThreadAlive.set(false);
    }
}

接着是

public abstract class BaseChatActivity extends AppCompatActivity {

    TextView contentTextView;
    EditText inputMessage;
    Button input;
    public abstract void sendString(final String string);

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chat);

        contentTextView= (TextView) findViewById(R.id.content_text);
        inputMessage= (EditText) findViewById(R.id.input_edittext);
        input= (Button)findViewById(R.id.send_button);

        //监听发送消息事件
        input.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                final String inputString = inputMessage.getText().toString();
                if (inputString.length() == 0) {
                    return;
                }
                sendString(inputString);
                printLineToUI(getString(R.string.local_prompt2) + inputString);
                inputMessage.setText("");

            }
        });

    }

    public void printLineToUI(final String line) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                contentTextView.setText(contentTextView.getText() + "\n" + line);
            }
        });
    }

}

在host包下同样有BaseChatActivity，ChatAtivity,ConnectActivity三个类，方法和上面一样，就不重复写了

在main包下有

public abstract class AccessoryCommunicator {

    private UsbManager usbManager;
    private Context context;
    private Handler sendHandler;
    private ParcelFileDescriptor fileDescriptor;
    private FileInputStream inStream;
    private FileOutputStream outStream;
    private boolean running;

    public AccessoryCommunicator(final Context context) {
        this.context = context;

        usbManager = (UsbManager) this.context.getSystemService(Context.USB_SERVICE);

        final UsbAccessory[] accessoryList = usbManager.getAccessoryList();

        if (accessoryList == null || accessoryList.length == 0) {
            onError("no accessory found");
        } else {
            openAccessory(accessoryList[0]);
        }
    }

    public void send(byte[] payload) {
        if (sendHandler != null) {
            Message msg = sendHandler.obtainMessage();
            msg.obj = payload;
            sendHandler.sendMessage(msg);
        }
    }

    private void receive(final byte[] payload, final int length) {
        onReceive(payload, length);
    }

    public abstract void onReceive(final byte[] payload, final int length);

    public abstract void onError(String msg);

    public abstract void onConnected();

    public abstract void onDisconnected();

    private class CommunicationThread extends Thread {
        @Override
        public void run() {
            running = true;

            while (running) {
                byte[] msg = new byte[Constants.BUFFER_SIZE_IN_BYTES];
                try {
                    //Handle incoming messages
                    int len = inStream.read(msg);
                    while (inStream != null && len > 0 && running) {
                        receive(msg, len);
                        Thread.sleep(10);
                        len = inStream.read(msg);
                    }
                } catch (final Exception e) {
                    onError("USB Receive Failed " + e.toString() + "\n");
                    closeAccessory();
                }
            }
        }
    }

    private void openAccessory(UsbAccessory accessory) {
        fileDescriptor = usbManager.openAccessory(accessory);
        if (fileDescriptor != null) {

            FileDescriptor fd = fileDescriptor.getFileDescriptor();
            inStream = new FileInputStream(fd);
            outStream = new FileOutputStream(fd);

            new CommunicationThread().start();

            sendHandler = new Handler() {
                public void handleMessage(Message msg) {
                    try {
                        outStream.write((byte[]) msg.obj);
                    } catch (final Exception e) {
                        onError("USB Send Failed " + e.toString() + "\n");
                    }
                }
            };

            onConnected();
        } else {
            onError("could not connect");
        }
    }

    public void closeAccessory() {
        running = false;

        try {
            if (fileDescriptor != null) {
                fileDescriptor.close();
            }
        } catch (IOException e) {
        } finally {
            fileDescriptor = null;
        }

        onDisconnected();
    }

}

然后是

public class Constants {
public static final int USB_TIMEOUT_IN_MS = 100;
public static final int BUFFER_SIZE_IN_BYTES = 256;
}

接着是InfoActivity ，InfoActivity 是整个整个程序的入口，对应的布局文件就一个textView，用于提示连接两台android设备。

public class InfoActivity extends AppCompatActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_info);

    }

}

最后就是在里配置一下就好了

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity android:name="InfoActivity">

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity android:name=".ChatActivity"
            android:screenOrientation="landscape">

            <intent-filter>
                <action android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED" />
            </intent-filter>

            <meta-data
                android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED"
                android:resource="@xml/accessory_filter" />
        </activity>

        <activity android:name=".ConnectActivity"
            android:screenOrientation="landscape">

        </activity>

        <activity android:name=".device.ChatActivity"
            android:screenOrientation="landscape">

            <intent-filter>
                <action android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED" />
            </intent-filter>

            <meta-data
                android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED"
                android:resource="@xml/accessory_filter" />
        </activity>
        <activity android:name=".device.ConnectActivity"
            android:screenOrientation="landscape">

            <intent-filter>
                <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
            </intent-filter>

            <meta-data
                android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
                android:resource="@xml/device_filter" />
        </activity>

    </application>
记录一下亲测好用

两台android设备间通过OTG-USB连接，实现通信（android设备间的通信）

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