Android Studio – How to filter devices shown in ListView from bluetooth on discover

I’m writing an app and it has a part which, on button click, scans for Bluetooth devices and shows them in a ListView. It works fine, but i need it to show only devices starting with a word in the name, for example: "MyArduino/123", so I need it to look for the "MyArduino/" part in device names and only show those that have it.

XML:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.test.app.MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/title"
        android:textSize="20sp"
        android:textAlignment="center"
        android:text="@string/title"
        android:gravity="center_horizontal" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/title"
        android:text="@string/bt_menu"
        android:background="@color/button"
        android:onClick="showBt"
        android:id="@+id/to_bt_menu"
        android:layout_margin="10sp"
        tools:ignore="UsingOnClickInXml" />

    <Button
        android:id="@+id/to_vars_menu"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/title"
        android:layout_marginLeft="10sp"
        android:layout_marginStart="10sp"
        android:layout_toEndOf="@id/to_bt_menu"
        android:layout_toRightOf="@id/to_bt_menu"
        android:onClick="showVars"
        android:text="@string/vars_menu"
        android:background="@color/button"
        android:layout_margin="10sp"
        tools:ignore="UsingOnClickInXml" />

    <TextView
        android:id="@+id/status"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/to_bt_menu"
        android:visibility="gone"
        android:ellipsize="end"
        android:maxLines="1"
        android:text="@string/status"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/bluetooth_status"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/to_bt_menu"
        android:visibility="gone"
        android:layout_toEndOf="@id/status"
        android:layout_toRightOf="@id/status"
        android:layout_marginLeft="20sp"
        android:layout_marginStart="20sp"
        android:ellipsize="end"
        android:maxLines="1"
        android:text="@string/bluetooth_status" />

    <Button
        android:id="@+id/scan"
        android:layout_width="150sp"
        android:layout_height="wrap_content"
        android:layout_below="@id/bluetooth_status"
        android:layout_margin="10sp"
        android:visibility="gone"
        android:text="@string/bluetooth_on"
        android:background="@color/button" />

    <Button
        android:id="@+id/off"
        android:layout_width="150sp"
        android:layout_height="wrap_content"
        android:layout_below="@id/bluetooth_status"
        android:layout_margin="10sp"
        android:visibility="gone"
        android:layout_toRightOf="@id/scan"
        android:layout_toEndOf="@id/scan"
        android:background="@color/button"
        android:text="@string/bluetooth_off" />

    <Button
        android:id="@+id/paired_btn"
        android:layout_width="150sp"
        android:layout_height="wrap_content"
        android:layout_below="@id/off"
        android:layout_margin="10sp"
        android:visibility="gone"
        android:text="@string/show_paired_devices"
        android:background="@color/button" />

    <Button
        android:id="@+id/discover"
        android:layout_width="150sp"
        android:layout_height="wrap_content"
        android:layout_below="@id/off"
        android:layout_margin="10sp"
        android:visibility="gone"
        android:layout_toEndOf="@+id/paired_btn"
        android:layout_toRightOf="@id/paired_btn"
        android:text="@string/discover_new_devices"
        android:background="@color/button" />

    <ListView
        android:id="@+id/devices_list_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/discover"
        android:visibility="gone"
        android:choiceMode="singleChoice" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20sp"
        android:onClick="reqVars"
        android:text="@string/req_btn"
        android:layout_below="@id/user_edit"
        android:visibility="gone"
        android:id="@+id/req_btn"
        android:layout_margin="10sp"
        android:background="@color/button" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/to_vars_menu"
        android:layout_margin="10sp"
        android:visibility="gone"
        android:id="@+id/user_edit"
        android:hint="@string/hint_edit"
        tools:ignore="TextFields"/>

    <Button
        android:id="@+id/send_edit_btn"
        android:layout_margin="10sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/user_edit"
        android:visibility="gone"
        android:layout_marginStart="20sp"
        android:layout_marginLeft="20sp"
        android:layout_marginTop="20sp"
        android:layout_toEndOf="@+id/req_btn"
        android:layout_toRightOf="@+id/req_btn"
        android:onClick="editVar"
        android:text="@string/send_edit_btn"
        android:background="@color/button" />

    <ListView
        android:layout_below="@id/req_btn"
        android:visibility="gone"
        android:id="@+id/vars"
        android:choiceMode="singleChoice"
        android:listSelector="@color/list"
        android:layout_width="300sp"
        android:layout_height="wrap_content" />
</RelativeLayout>

MainActivity:

package com.test.app;

import android.Manifest;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.os.SystemClock;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.Set;
import java.util.UUID;

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {

    private final String TAG = MainActivity.class.getSimpleName();

    private static final UUID BT_MODULE_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"); // "random" unique identifier

    // #defines for identifying shared types between calling functions
    private final static int REQUEST_ENABLE_BT = 1; // used to identify adding bluetooth names
    public final static int MESSAGE_READ = 2; // used in bluetooth handler to identify message update
    private final static int CONNECTING_STATUS = 3; // used in bluetooth handler to identify message status

    // GUI Components
    private TextView mBluetoothStatus;
    private Button mScanBtn;
    private Button mOffBtn;
    private Button mListPairedDevicesBtn;
    private Button mDiscoverBtn;
    private ListView mDevicesListView;
    private TextView mStatus;
    private EditText mUserEdit;
    private Button mReqBtn;
    private Button mSendEdit;
    private ListView mVars;
    private String mSelecVar;
    private String mMessage;

    private BluetoothAdapter mBTAdapter;
    private Set<BluetoothDevice> mPairedDevices;
    private ArrayList<BluetoothDevice> mBTDevices;
    private ArrayAdapter<String> mBTArrayAdapter;

    private Handler mHandler; // Our main handler that will receive callback notifications
    private ConnectedThread mConnectedThread; // bluetooth background worker thread to send and receive data
    private BluetoothSocket mBTSocket = null; // bi-directional client-to-client data path

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            Objects.requireNonNull(getSupportActionBar()).hide();
        } else {
            getSupportActionBar().hide();
        }
        setContentView(R.layout.activity_main);

        mBluetoothStatus = (TextView)findViewById(R.id.bluetooth_status);
        mScanBtn = (Button)findViewById(R.id.scan);
        mOffBtn = (Button)findViewById(R.id.off);
        mDiscoverBtn = (Button)findViewById(R.id.discover);
        mListPairedDevicesBtn = (Button)findViewById(R.id.paired_btn);
        mStatus = (TextView)findViewById(R.id.status);
        mUserEdit = (EditText)findViewById(R.id.user_edit);
        mReqBtn = (Button)findViewById(R.id.req_btn);
        mSendEdit = (Button)findViewById(R.id.send_edit_btn);
        mVars = (ListView)findViewById(R.id.vars);

        mBTArrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1);
        mBTDevices = new ArrayList<>();
        mBTAdapter = BluetoothAdapter.getDefaultAdapter(); // get a handle on the bluetooth radio

        mDevicesListView = (ListView)findViewById(R.id.devices_list_view);
        assert mDevicesListView != null;
        mDevicesListView.setAdapter(mBTArrayAdapter); // assign model to view
        mDevicesListView.setOnItemClickListener(mDeviceClickListener);

        mVars.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                mSelecVar = mVars.getItemAtPosition(position).toString().split(",")[0];
            }
        });

        // Ask for location permission if not already allowed
        if(ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, 1);


        mHandler = new Handler(Looper.getMainLooper()){
            @Override
            public void handleMessage(Message msg){
                if(msg.what == MESSAGE_READ){
                    String readMessage = null;
                    try {
                        readMessage = new String((byte[]) msg.obj, "UTF-8");
                    } catch (UnsupportedEncodingException e) {
                        e.printStackTrace();
                    }
                    mMessage = readMessage;
                    if (mMessage != null) {
                        for (int i = 0; i < mMessage.length(); i++) {
                            if (mMessage.toCharArray()[i] == ';') {
                                getVars(mMessage);
                                break;
                            }
                        }
                    }
                }

                if(msg.what == CONNECTING_STATUS){
                    if(msg.arg1 == 1) {
                        mBluetoothStatus.setText("Connected to Device: " + msg.obj);
                        mConnectedThread.write("list");
                    } else
                        mBluetoothStatus.setText("Connection Failed");
                }
            }
        };

        if (mBTArrayAdapter == null) {
            // Device does not support Bluetooth
            mBluetoothStatus.setText("Status: Bluetooth not found");
            Toast.makeText(getApplicationContext(),"Bluetooth device not found!",Toast.LENGTH_SHORT).show();
        }
        else {

            mScanBtn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    bluetoothOn();
                }
            });

            mOffBtn.setOnClickListener(new View.OnClickListener(){
                @Override
                public void onClick(View v){
                    bluetoothOff();
                }
            });

            mListPairedDevicesBtn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v){
                    listPairedDevices();
                }
            });

            mDiscoverBtn.setOnClickListener(new View.OnClickListener(){
                @Override
                public void onClick(View v){
                    discover();
                }
            });
        }
    }

    private void bluetoothOn(){
        if (!mBTAdapter.isEnabled()) {
            Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
            mBluetoothStatus.setText("Bluetooth enabled");
            Toast.makeText(getApplicationContext(),"Bluetooth turned on",Toast.LENGTH_SHORT).show();

        }
        else{
            Toast.makeText(getApplicationContext(),"Bluetooth is already on", Toast.LENGTH_SHORT).show();
        }
    }

    // Enter here after user selects "yes" or "no" to enabling radio
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent Data){
        // Check which request we're responding to
        if (requestCode == REQUEST_ENABLE_BT) {
            // Make sure the request was successful
            if (resultCode == RESULT_OK) {
                // The user picked a contact.
                // The Intent's data Uri identifies which contact was selected.
                mBluetoothStatus.setText("Enabled");
            }
            else
                mBluetoothStatus.setText("Disabled");
        }
    }

    private void bluetoothOff(){
        mBTAdapter.disable(); // turn off
        mBluetoothStatus.setText("Bluetooth disabled");
        Toast.makeText(getApplicationContext(),"Bluetooth turned Off", Toast.LENGTH_SHORT).show();
    }

    private void discover(){
        // Check if the device is already discovering
        if(mBTAdapter.isDiscovering()){
            mBTAdapter.cancelDiscovery();
            Toast.makeText(getApplicationContext(),"Discovery stopped",Toast.LENGTH_SHORT).show();
        }
        else{
            if(mBTAdapter.isEnabled()) {
                mBTArrayAdapter.clear(); // clear items
                mBTAdapter.startDiscovery();
                Toast.makeText(getApplicationContext(), "Discovery started", Toast.LENGTH_SHORT).show();
                registerReceiver(blReceiver, new IntentFilter(BluetoothDevice.ACTION_FOUND));
            }
            else{
                Toast.makeText(getApplicationContext(), "Bluetooth not on", Toast.LENGTH_SHORT).show();
            }
        }
    }

    final BroadcastReceiver blReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if(BluetoothDevice.ACTION_FOUND.equals(action)){
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                // add the name to the list
                mBTDevices.add(device);
                mBTArrayAdapter.add(device.getName() + "n" + device.getAddress());
                mBTArrayAdapter.notifyDataSetChanged();
            }
            if (action.equals(BluetoothDevice.ACTION_BOND_STATE_CHANGED)){
                BluetoothDevice mDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                if (mDevice.getBondState() == BluetoothDevice.BOND_BONDED){
                    Log.d(TAG, "BroadcastReceiver: BOND_BONDED");
                }
                if (mDevice.getBondState() == BluetoothDevice.BOND_BONDING){
                    Log.d(TAG, "BroadcastReceiver: BOND_BONDING");
                }
                if (mDevice.getBondState() == BluetoothDevice.BOND_NONE){
                    Log.d(TAG, "BroadcastReceiver: BOND_NONE");
                }
            }
        }
    };

    private void listPairedDevices(){
        mBTArrayAdapter.clear();
        mPairedDevices = mBTAdapter.getBondedDevices();
        if(mBTAdapter.isEnabled()) {
            // put it's one to the adapter
            for (BluetoothDevice device : mPairedDevices)
                if (device.getName().equals("MyArduino/")){
                    mBTArrayAdapter.add(device.getName() + "n" + device.getAddress());
                }
            Toast.makeText(getApplicationContext(), "Show Paired Devices", Toast.LENGTH_SHORT).show();
        }
        else
            Toast.makeText(getApplicationContext(), "Bluetooth not on", Toast.LENGTH_SHORT).show();
    }

    private AdapterView.OnItemClickListener mDeviceClickListener = new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

            if(!mBTAdapter.isEnabled()) {
                Toast.makeText(getBaseContext(), "Bluetooth not on", Toast.LENGTH_SHORT).show();
                return;
            }

            mBluetoothStatus.setText("Connecting...");
            // Get the device MAC address, which is the last 17 chars in the View
            String info = ((TextView) view).getText().toString();
            final String address = info.substring(info.length() - 17);
            final String name = info.substring(0,info.length() - 17);

            // Spawn a new thread to avoid blocking the GUI one
            new Thread()
            {
                @Override
                public void run() {
                    boolean fail = false;

                    BluetoothDevice device = mBTAdapter.getRemoteDevice(address);

                    try {
                        mBTSocket = createBluetoothSocket(device);
                    } catch (IOException e) {
                        fail = true;
                        Toast.makeText(getBaseContext(), "Socket creation failed", Toast.LENGTH_SHORT).show();
                    }
                    // Establish the Bluetooth socket connection.
                    try {
                        mBTSocket.connect();
                    } catch (IOException e) {
                        try {
                            fail = true;
                            mBTSocket.close();
                            mHandler.obtainMessage(CONNECTING_STATUS, -1, -1)
                                    .sendToTarget();
                        } catch (IOException e2) {
                            //insert code to deal with this
                            Toast.makeText(getBaseContext(), "Socket creation failed", Toast.LENGTH_SHORT).show();
                        }
                    }
                    if(!fail) {
                        mConnectedThread = new ConnectedThread(mBTSocket, mHandler);
                        mConnectedThread.start();

                        mHandler.obtainMessage(CONNECTING_STATUS, 1, -1, name)
                                .sendToTarget();
                    }
                }
            }.start();
        }
    };

    private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
        try {
            final Method m = device.getClass().getMethod("createInsecureRfcommSocketToServiceRecord", UUID.class);
            return (BluetoothSocket) m.invoke(device, BT_MODULE_UUID);
        } catch (Exception e) {
            Log.e(TAG, "Could not create Insecure RFComm Connection",e);
        }
        return  device.createRfcommSocketToServiceRecord(BT_MODULE_UUID);
    }

    public void showBt(View view) {
        mBluetoothStatus.setVisibility(View.VISIBLE);
        mScanBtn.setVisibility(View.VISIBLE);
        mOffBtn.setVisibility(View.VISIBLE);
        mDiscoverBtn.setVisibility(View.VISIBLE);
        mListPairedDevicesBtn.setVisibility(View.VISIBLE);
        mDevicesListView.setVisibility(View.VISIBLE);
        mStatus.setVisibility(View.VISIBLE);
        mVars.setVisibility(View.GONE);
        mUserEdit.setVisibility(View.GONE);
        mSendEdit.setVisibility(View.GONE);
        mReqBtn.setVisibility(View.GONE);
    }

    public void showVars(View view) {
        mBluetoothStatus.setVisibility(View.GONE);
        mScanBtn.setVisibility(View.GONE);
        mOffBtn.setVisibility(View.GONE);
        mDiscoverBtn.setVisibility(View.GONE);
        mListPairedDevicesBtn.setVisibility(View.GONE);
        mDevicesListView.setVisibility(View.GONE);
        mStatus.setVisibility(View.GONE);
        mVars.setVisibility(View.VISIBLE);
        mUserEdit.setVisibility(View.VISIBLE);
        mSendEdit.setVisibility(View.VISIBLE);
        mReqBtn.setVisibility(View.VISIBLE);
    }

    public void reqVars(View view) {
        if (mConnectedThread != null){
            mConnectedThread.write("list");
        }
    }

    public void getVars(String string) {
        String[] str = string.split(";");
        List<String> al;
        al = Arrays.asList(str);
        ArrayAdapter<String> mVarsArrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, al);
        mVars.setAdapter(mVarsArrayAdapter);
    }

    public void editVar(View view) {
        if (mConnectedThread != null) {
            mConnectedThread.write("edit " + mSelecVar + " " + mUserEdit.getText());
            mUserEdit.setText("");
            SystemClock.sleep(2000);
            mConnectedThread.write("list");
        }
    }

    @Override
    public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
        mBTAdapter.cancelDiscovery();

        Log.d(TAG, "onItemClick: You clicked on a device.");
        String deviceName = mBTDevices.get(i).getName();
        String deviceAddress = mBTDevices.get(i).getAddress();

        Log.d(TAG, "onItemClick: deviceName = " + deviceName);
        Log.d(TAG, "onItemClick: deviceAddress = " + deviceAddress);

        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN_MR2){
            Log.d(TAG, "Trying to pair with " + deviceName);
            mBTDevices.get(i).createBond();
        }
    }
}

ConnectedThread:

package com.test.app;

import android.bluetooth.BluetoothSocket;
import android.os.Handler;
import android.os.SystemClock;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class ConnectedThread extends Thread {
    private final BluetoothSocket mmSocket;
    private final InputStream mmInStream;
    private final OutputStream mmOutStream;
    private final Handler mHandler;

    public ConnectedThread(BluetoothSocket socket, Handler handler) {
        mmSocket = socket;
        mHandler = handler;
        InputStream tmpIn = null;
        OutputStream tmpOut = null;

        // Get the input and output streams, using temp objects because
        // member streams are final
        try {
            tmpIn = socket.getInputStream();
            tmpOut = socket.getOutputStream();
        } catch (IOException e) { }

        mmInStream = tmpIn;
        mmOutStream = tmpOut;
    }

    @Override
    public void run() {
        byte[] buffer = new byte[1024];  // buffer store for the stream
        int bytes; // bytes returned from read()
        // Keep listening to the InputStream until an exception occurs
        while (true) {
            try {
                // Read from the InputStream
                bytes = mmInStream.available();
                if(bytes != 0) {
                    buffer = new byte[1024];
                    SystemClock.sleep(100); //pause and wait for rest of data. Adjust this depending on your sending speed.
                    bytes = mmInStream.available(); // how many bytes are ready to be read?
                    bytes = mmInStream.read(buffer, 0, bytes); // record how many bytes we actually read
                    mHandler.obtainMessage(MainActivity.MESSAGE_READ, bytes, -1, buffer)
                            .sendToTarget(); // Send the obtained bytes to the UI activity
                }
            } catch (IOException e) {
                e.printStackTrace();

                break;
            }
        }
    }

    /* Call this from the main activity to send data to the remote device */
    public void write(String input) {
        byte[] bytes = input.getBytes();           //converts entered String into bytes
        try {
            mmOutStream.write(bytes);
        } catch (IOException e) { }
    }

    /* Call this from the main activity to shutdown the connection */
    public void cancel() {
        try {
            mmSocket.close();
        } catch (IOException e) { }
    }
}

Right now, the ListView shows all the devices that the Bluetooth founds, and sometimes, even shows them 2 or 3 times in the same list. As you can see in the MainActivity, i tried to make some sort of a filter in line 272 but it just does not work. Thanks