<?xml version="1.0" encoding="utf-8"?>

<resources>
    <item name="workouttype" type="id" />
    <item name="txthello" type="id"/>
</resources>

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/editTextFirstName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="100dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="First Name"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editTextLastName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="Last Name"
        app:layout_constraintStart_toStartOf="@+id/editTextFirstName"
        app:layout_constraintTop_toBottomOf="@+id/editTextFirstName" />

    <EditText
        android:id="@+id/editTextEmail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="Email"
        app:layout_constraintEnd_toEndOf="@+id/editTextLastName"
        app:layout_constraintStart_toStartOf="@+id/editTextLastName"
        app:layout_constraintTop_toBottomOf="@+id/editTextLastName" />

    <Button
        android:id="@+id/btnRegister"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="100dp"
        android:text="Register"
        app:layout_constraintEnd_toEndOf="@+id/editTextEmail"
        app:layout_constraintStart_toStartOf="@+id/editTextEmail"
        app:layout_constraintTop_toBottomOf="@+id/editTextEmail" />

    <TextView
        android:id="@+id/textViewFirstName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="100dp"
        android:text="First Name"
        app:layout_constraintEnd_toEndOf="@+id/btnRegister"
        app:layout_constraintStart_toStartOf="@+id/btnRegister"
        app:layout_constraintTop_toBottomOf="@+id/btnRegister" />

    <TextView
        android:id="@+id/textViewLastName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:text="Last Name"
        app:layout_constraintEnd_toEndOf="@+id/textViewFirstName"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="@+id/textViewFirstName"
        app:layout_constraintTop_toBottomOf="@+id/textViewFirstName" />

    <TextView
        android:id="@+id/textViewEmail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:text="Email"
        app:layout_constraintEnd_toEndOf="@+id/textViewLastName"
        app:layout_constraintStart_toStartOf="@+id/textViewLastName"
        app:layout_constraintTop_toBottomOf="@+id/textViewLastName" />
</androidx.constraintlayout.widget.ConstraintLayout>

package com.ascenzi.usb_serial_testing;

import android.app.PendingIntent;
import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.hardware.usb.UsbDevice;
import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbManager;
import android.os.Binder;
import android.os.Handler;
import android.os.IBinder;
import android.util.Log;
import android.widget.TextView;

import com.felhr.usbserial.CDCSerialDevice;
import com.felhr.usbserial.UsbSerialDevice;
import com.felhr.usbserial.UsbSerialInterface;

import java.io.Serializable;
import java.io.UnsupportedEncodingException;

import java.util.HashMap;
import java.util.Map;

//import okio.Buffer;

public class UsbService extends Service implements Serializable
{

    public static final String TAG = "UsbService";

    public static final String ACTION_USB_READY = "com.felhr.connectivityservices.USB_READY";
    public static final String ACTION_USB_ATTACHED = "android.hardware.usb.action.USB_DEVICE_ATTACHED";
    public static final String ACTION_USB_DETACHED = "android.hardware.usb.action.USB_DEVICE_DETACHED";
    public static final String ACTION_USB_NOT_SUPPORTED = "com.felhr.usbservice.USB_NOT_SUPPORTED";
    public static final String ACTION_NO_USB = "com.felhr.usbservice.NO_USB";
    public static final String ACTION_USB_PERMISSION_GRANTED = "com.felhr.usbservice.USB_PERMISSION_GRANTED";
    public static final String ACTION_USB_PERMISSION_NOT_GRANTED = "com.felhr.usbservice.USB_PERMISSION_NOT_GRANTED";
    public static final String ACTION_USB_DISCONNECTED = "com.felhr.usbservice.USB_DISCONNECTED";
    public static final String ACTION_CDC_DRIVER_NOT_WORKING = "com.felhr.connectivityservices.ACTION_CDC_DRIVER_NOT_WORKING";
    public static final String ACTION_USB_DEVICE_NOT_WORKING = "com.felhr.connectivityservices.ACTION_USB_DEVICE_NOT_WORKING";
    public static final int MESSAGE_FROM_SERIAL_PORT = 0;
    public static final int CTS_CHANGE = 1;
    public static final int DSR_CHANGE = 2;
    private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
    private static final int BAUD_RATE = 115200; // BaudRate. Change this value if you need
    public static boolean SERVICE_CONNECTED = false;

    private IBinder binder = new UsbBinder();

    private Context context;
    private Handler mHandler;
    private UsbManager usbManager;
    private UsbDevice device;
    private UsbDeviceConnection connection;
    private UsbSerialDevice serialPort;

    private TextView t1;

    //private Buffer buffer = new Buffer();
    private String mode;

    private boolean serialPortConnected;

    /*
     *  Data received from serial port will be received here. Just populate onReceivedData with your code
     *  In this particular example. byte stream is converted to String and send to UI thread to
     *  be treated there.
     */
    private UsbSerialInterface.UsbReadCallback mCallback = new UsbSerialInterface.UsbReadCallback() {
        @Override
        public void onReceivedData(byte[] arg0) {
            try {
                String data = new String(arg0, "UTF-8");
                if (mHandler != null)
                    mHandler.obtainMessage(MESSAGE_FROM_SERIAL_PORT, data).sendToTarget();
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
        }
    };

    /*
     * State changes in the CTS line will be received here
     */
    private UsbSerialInterface.UsbCTSCallback ctsCallback = new UsbSerialInterface.UsbCTSCallback() {
        @Override
        public void onCTSChanged(boolean state) {
            if(mHandler != null)
                mHandler.obtainMessage(CTS_CHANGE).sendToTarget();
        }
    };

    /*
     * State changes in the DSR line will be received here
     */
    private UsbSerialInterface.UsbDSRCallback dsrCallback = new UsbSerialInterface.UsbDSRCallback() {
        @Override
        public void onDSRChanged(boolean state) {
            if(mHandler != null)
                mHandler.obtainMessage(DSR_CHANGE).sendToTarget();
        }
    };
    /*
     * Different notifications from OS will be received here (USB attached, detached, permission responses...)
     * About BroadcastReceiver: http://developer.android.com/reference/android/content/BroadcastReceiver.html
     */
    private final BroadcastReceiver usbReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context arg0, Intent arg1) {
            if (arg1.getAction().equals(ACTION_USB_PERMISSION)) {
                boolean granted = arg1.getExtras().getBoolean(UsbManager.EXTRA_PERMISSION_GRANTED);
                if (granted) // User accepted our USB connection. Try to open the device as a serial port
                {
                    Intent intent = new Intent(ACTION_USB_PERMISSION_GRANTED);
                    arg0.sendBroadcast(intent);
                    connection = usbManager.openDevice(device);
                    new ConnectionThread().start();
                } else // User not accepted our USB connection. Send an Intent to the Main Activity
                {
                    Intent intent = new Intent(ACTION_USB_PERMISSION_NOT_GRANTED);
                    arg0.sendBroadcast(intent);
                }
            } else if (arg1.getAction().equals(ACTION_USB_ATTACHED)) {
                if (!serialPortConnected)
                    findSerialPortDevice(); // A USB device has been attached. Try to open it as a Serial port
            } else if (arg1.getAction().equals(ACTION_USB_DETACHED)) {
                // Usb device was disconnected. send an intent to the Main Activity
                Intent intent = new Intent(ACTION_USB_DISCONNECTED);
                arg0.sendBroadcast(intent);
                if (serialPortConnected) {
                    serialPort.close();
                }
                serialPortConnected = false;
            }
        }
    };

    /*
     * onCreate will be executed when service is started. It configures an IntentFilter to listen for
     * incoming Intents (USB ATTACHED, USB DETACHED...) and it tries to open a serial port.
     */
    @Override
    public void onCreate() {
        this.context = this;
        serialPortConnected = false;
        UsbService.SERVICE_CONNECTED = true;
        setFilter();
        usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
        findSerialPortDevice();
    }

    /* MUST READ about services
     * http://developer.android.com/guide/components/services.html
     * http://developer.android.com/guide/components/bound-services.html
     */
    @Override
    public IBinder onBind(Intent intent) {
        return binder;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return Service.START_NOT_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        serialPort.close();
        unregisterReceiver(usbReceiver);
        UsbService.SERVICE_CONNECTED = false;
    }

    /*
     * This function will be called from MainActivity to write data through Serial Port
     */
    public void write(byte[] data) {
        if (serialPort != null)
        {
            serialPort.write(data);
        }
    }


    public void setHandler(Handler mHandler) {
        this.mHandler = mHandler;
    }

    private void findSerialPortDevice() {
        // This snippet will try to open the first encountered usb device connected, excluding usb root hubs
        HashMap<String, UsbDevice> usbDevices = usbManager.getDeviceList();
        if (!usbDevices.isEmpty()) {

            // first, dump the hashmap for diagnostic purposes
            for (Map.Entry<String, UsbDevice> entry : usbDevices.entrySet()) {
                device = entry.getValue();
                Log.d(TAG, String.format("USBDevice.HashMap (vid:pid) (%X:%X)-%b class:%X:%X name:%s",
                                         device.getVendorId(), device.getProductId(),
                                         UsbSerialDevice.isSupported(device),
                                         device.getDeviceClass(), device.getDeviceSubclass(),
                                         device.getDeviceName()));
            }

            for (Map.Entry<String, UsbDevice> entry : usbDevices.entrySet()) {
                device = entry.getValue();
                int deviceVID = device.getVendorId();
                int devicePID = device.getProductId();

//                if (deviceVID != 0x1d6b && (devicePID != 0x0001 && devicePID != 0x0002 && devicePID != 0x0003) && deviceVID != 0x5c6 && devicePID != 0x904c) {
                if (UsbSerialDevice.isSupported(device)) {
                    // There is a supported device connected - request permission to access it.
                    requestUserPermission();
                    break;
                } else {
                    connection = null;
                    device = null;
                }
            }
            if (device==null) {
                // There are no USB devices connected (but usb host were listed). Send an intent to MainActivity.
                Intent intent = new Intent(ACTION_NO_USB);
                sendBroadcast(intent);
            }
        } else {
            Log.d(TAG, "findSerialPortDevice() usbManager returned empty device list." );
            // There is no USB devices connected. Send an intent to MainActivity
            Intent intent = new Intent(ACTION_NO_USB);
            sendBroadcast(intent);
        }
    }

    private void setFilter() {
        IntentFilter filter = new IntentFilter();
        filter.addAction(ACTION_USB_PERMISSION);
        filter.addAction(ACTION_USB_DETACHED);
        filter.addAction(ACTION_USB_ATTACHED);
        registerReceiver(usbReceiver, filter);
    }

    /*
     * Request user permission. The response will be received in the BroadcastReceiver
     */
    private void requestUserPermission() {
        Log.d(TAG, String.format("requestUserPermission(%X:%X)", device.getVendorId(), device.getProductId() ) );
        PendingIntent mPendingIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
        usbManager.requestPermission(device, mPendingIntent);
    }

    public class UsbBinder extends Binder {
        public UsbService getService() {
            return UsbService.this;
        }
    }

    /*
     * A simple thread to open a serial port.
     * Although it should be a fast operation. moving usb operations away from UI thread is a good thing.
     */
    private class ConnectionThread extends Thread {
        @Override
        public void run() {
            serialPort = UsbSerialDevice.createUsbSerialDevice(device, connection);
            if (serialPort != null) {
                if (serialPort.open()) {
                    serialPortConnected = true;
                    serialPort.setBaudRate(BAUD_RATE);
                    serialPort.setDataBits(UsbSerialInterface.DATA_BITS_8);
                    serialPort.setStopBits(UsbSerialInterface.STOP_BITS_1);
                    serialPort.setParity(UsbSerialInterface.PARITY_NONE);
                    /**
                     * Current flow control Options:
                     * UsbSerialInterface.FLOW_CONTROL_OFF
                     * UsbSerialInterface.FLOW_CONTROL_RTS_CTS only for CP2102 and FT232
                     * UsbSerialInterface.FLOW_CONTROL_DSR_DTR only for CP2102 and FT232
                     */
                    serialPort.setFlowControl(UsbSerialInterface.FLOW_CONTROL_OFF);
                    serialPort.read(mCallback);
                    serialPort.getCTS(ctsCallback);
                    serialPort.getDSR(dsrCallback);

                    //
                    // Some Arduinos would need some sleep because firmware wait some time to know whether a new sketch is going
                    // to be uploaded or not
                    //Thread.sleep(2000); // sleep some. YMMV with different chips.

                    // Everything went as expected. Send an intent to MainActivity
                    Intent intent = new Intent(ACTION_USB_READY);
                    context.sendBroadcast(intent);
                } else {
                    // Serial port could not be opened, maybe an I/O error or if CDC driver was chosen, it does not really fit
                    // Send an Intent to Main Activity
                    if (serialPort instanceof CDCSerialDevice) {
                        Intent intent = new Intent(ACTION_CDC_DRIVER_NOT_WORKING);
                        context.sendBroadcast(intent);
                    } else {
                        Intent intent = new Intent(ACTION_USB_DEVICE_NOT_WORKING);
                        context.sendBroadcast(intent);
                    }
                }
            } else {
                // No driver for given device, even generic CDC driver could not be loaded
                Intent intent = new Intent(ACTION_USB_NOT_SUPPORTED);
                context.sendBroadcast(intent);
            }
        }
    }
}

private UsbService usbService;
...
Button swchBtn = (Button) findViewById(R.id.buttonSwitch);
        swchBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick (View v)
            {

                if(usbService != null)
                {
                    Intent swIntent = new Intent(MainActivity.this, SecondActivity.class);
                    swIntent.putExtra("USBService", usbService);
                    startActivity(swIntent);
                }
            }