Make BlueTooth connection between Android devices

The previous post show how to List paired BlueTooth devices. Here I show how to make connection between Android devices with Bluetooth.

In order to make it simple, I separate its functionality in two app:

• AndroidBlueToothBeCOnnected:
  It start a BluetoothServerSocket by calling bluetoothAdapter.listenUsingRfcommWithServiceRecord().
  Then wait for connection with accept().
• AndroidBlueTooth:
  It search for paired bluetooth devices, and request connect.

This example show making connection only, nothing else can do.

---

AndroidBlueToothBeCOnnected:

MainActivity.java

package com.example.androidbluetoothbeconnected;

import java.io.IOException;
import java.util.UUID;

import android.support.v7.app.ActionBarActivity;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {
 
 private static final int REQUEST_ENABLE_BT = 1;
 
 BluetoothAdapter bluetoothAdapter;
 
 private UUID myUUID;
 private String myName;

 TextView textInfo, textStatus;
 
 ThreadBeConnected myThreadBeConnected;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  textInfo = (TextView)findViewById(R.id.info);
  textStatus = (TextView)findViewById(R.id.status);
  
  if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH)){
   Toast.makeText(this, 
    "FEATURE_BLUETOOTH NOT support", 
    Toast.LENGTH_LONG).show();
            finish();
            return;
  }

  //generate UUID on web: http://www.famkruithof.net/uuid/uuidgen
  //have to match the UUID on the another device of the BT connection
  myUUID = UUID.fromString("ec79da00-853f-11e4-b4a9-0800200c9a66");
  myName = myUUID.toString();
  
  bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
  if (bluetoothAdapter == null) {
   Toast.makeText(this, 
    "Bluetooth is not supported on this hardware platform", 
    Toast.LENGTH_LONG).show();
            finish();
            return;
  }
  
  String stInfo = bluetoothAdapter.getName() + "\n" +
      bluetoothAdapter.getAddress();
  textInfo.setText(stInfo);
 }
 
 @Override
 protected void onStart() {
  super.onStart();
  
  //Turn ON BlueTooth if it is OFF
  if (!bluetoothAdapter.isEnabled()) {
            Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
        }
  
  setup();
 }
 
 private void setup() {
  textStatus.setText("setup()");
  myThreadBeConnected = new ThreadBeConnected();
  myThreadBeConnected.start();
 }
 
 @Override
 protected void onDestroy() {
  super.onDestroy();
  
  if(myThreadBeConnected!=null){
   myThreadBeConnected.cancel();
  }
 }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  
  if(requestCode==REQUEST_ENABLE_BT){
   if(resultCode == Activity.RESULT_OK){
    setup();
   }else{
    Toast.makeText(this, 
     "BlueTooth NOT enabled", 
     Toast.LENGTH_SHORT).show();
             finish();
   }
  } 
 }


 private class ThreadBeConnected extends Thread {
  
  private BluetoothServerSocket bluetoothServerSocket = null;
  
  public ThreadBeConnected() {
   try {
    bluetoothServerSocket = 
      bluetoothAdapter.listenUsingRfcommWithServiceRecord(myName, myUUID);
    
    textStatus.setText("Waiting\n" 
     + "bluetoothServerSocket :\n"
     + bluetoothServerSocket);
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }

  @Override
  public void run() {
   BluetoothSocket bluetoothSocket = null;
   
   if(bluetoothServerSocket!=null){
    try {
     bluetoothSocket = bluetoothServerSocket.accept();
     
     BluetoothDevice remoteDevice = bluetoothSocket.getRemoteDevice();
     
     final String strConnected = "Connected:\n" +
       remoteDevice.getName() + "\n" +
       remoteDevice.getAddress();
     
     //connected
     runOnUiThread(new Runnable(){

      @Override
      public void run() {
       textStatus.setText(strConnected);
      }});
     
    } catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
     
     final String eMessage = e.getMessage();
     runOnUiThread(new Runnable(){

      @Override
      public void run() {
       textStatus.setText("something wrong: \n" + eMessage);
      }});
    }
   }else{
    runOnUiThread(new Runnable(){

     @Override
     public void run() {
      textStatus.setText("bluetoothServerSocket == null");
     }});
   }
  }
  
  public void cancel() {
   
   Toast.makeText(getApplicationContext(), 
    "close bluetoothServerSocket", 
    Toast.LENGTH_LONG).show();
   
   try {
    bluetoothServerSocket.close();
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
        }
 }
}

/res/layout/activity_main.xml

<LinearLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.example.androidbluetoothbeconnected.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />
    
    <TextView
        android:id="@+id/info"
        android:textStyle="bold|italic"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/status"
        android:textSize="28sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

Modify AndroidManifest.xml to add permission of "android.permission.BLUETOOTH".

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.androidbluetoothbeconnected"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />
    <uses-permission android:name="android.permission.BLUETOOTH"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

Download the files.

---

AndroidBlueTooth:

MainActivity.java

package com.example.androidbluetooth;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Set;
import java.util.UUID;

import android.support.v7.app.ActionBarActivity;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {
 
 private static final int REQUEST_ENABLE_BT = 1;
 
 BluetoothAdapter bluetoothAdapter;
 
 ArrayList<BluetoothDevice> pairedDeviceArrayList;
 
 TextView textInfo, textStatus;
 ListView listViewPairedDevice;
 ArrayAdapter<BluetoothDevice> pairedDeviceAdapter;
 private UUID myUUID;
 
 ThreadConnectBTdevice myThreadConnectBTdevice;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  textInfo = (TextView)findViewById(R.id.info);
  textStatus = (TextView)findViewById(R.id.status);
  listViewPairedDevice = (ListView)findViewById(R.id.pairedlist);
  
  if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH)){
   Toast.makeText(this, 
    "FEATURE_BLUETOOTH NOT support", 
    Toast.LENGTH_LONG).show();
            finish();
            return;
  }

  //generate UUID on web: http://www.famkruithof.net/uuid/uuidgen
  //have to match the UUID on the another device of the BT connection
  myUUID = UUID.fromString("ec79da00-853f-11e4-b4a9-0800200c9a66");
  
  bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
  if (bluetoothAdapter == null) {
   Toast.makeText(this, 
    "Bluetooth is not supported on this hardware platform", 
    Toast.LENGTH_LONG).show();
            finish();
            return;
  }
  
  String stInfo = bluetoothAdapter.getName() + "\n" +
    bluetoothAdapter.getAddress();
  textInfo.setText(stInfo);
 }

 @Override
 protected void onStart() {
  super.onStart();
  
  //Turn ON BlueTooth if it is OFF
  if (!bluetoothAdapter.isEnabled()) {
            Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
        }
  
  setup();
 }
 
 private void setup() {
  Set<BluetoothDevice> pairedDevices = bluetoothAdapter.getBondedDevices();
  if (pairedDevices.size() > 0) {
   pairedDeviceArrayList = new ArrayList<BluetoothDevice>();
   
   for (BluetoothDevice device : pairedDevices) {
    pairedDeviceArrayList.add(device);
            }
   
   pairedDeviceAdapter = new ArrayAdapter<BluetoothDevice>(this,
                 android.R.layout.simple_list_item_1, pairedDeviceArrayList);
   listViewPairedDevice.setAdapter(pairedDeviceAdapter);
   
   listViewPairedDevice.setOnItemClickListener(new OnItemClickListener(){

    @Override
    public void onItemClick(AdapterView<?> parent, View view,
      int position, long id) {
     BluetoothDevice device = 
       (BluetoothDevice)parent.getItemAtPosition(position);
      Toast.makeText(MainActivity.this, 
       "Name: " + device.getName() + "\n"
       + "Address: " + device.getAddress() + "\n"
       + "BondState: " + device.getBondState() + "\n"
       + "BluetoothClass: " + device.getBluetoothClass() + "\n"
       + "Class: " + device.getClass(),
       Toast.LENGTH_LONG).show();
      
      textStatus.setText("start ThreadConnectBTdevice");
      myThreadConnectBTdevice = new ThreadConnectBTdevice(device);
      myThreadConnectBTdevice.start();
    }});
  }
 }
 
 

 @Override
 protected void onDestroy() {
  super.onDestroy();
  
  if(myThreadConnectBTdevice!=null){
   myThreadConnectBTdevice.cancel();
  }
 }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  
  if(requestCode==REQUEST_ENABLE_BT){
   if(resultCode == Activity.RESULT_OK){
    setup();
   }else{
    Toast.makeText(this, 
     "BlueTooth NOT enabled", 
     Toast.LENGTH_SHORT).show();
             finish();
   }
  } 
 }
 
 private class ThreadConnectBTdevice extends Thread {
  private BluetoothSocket bluetoothSocket = null;
        private final BluetoothDevice bluetoothDevice;
        
        
        public ThreadConnectBTdevice(BluetoothDevice device) {
         bluetoothDevice = device;

         try {
    bluetoothSocket = device.createRfcommSocketToServiceRecord(myUUID);
    textStatus.setText("bluetoothSocket: \n" + bluetoothSocket);
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
        }

  @Override
  public void run() {
   boolean success = false;
   try {
    bluetoothSocket.connect();
    success = true;
   } catch (IOException e) {
    e.printStackTrace();
    
    final String eMessage = e.getMessage();
    runOnUiThread(new Runnable(){

     @Override
     public void run() {
      textStatus.setText("something wrong bluetoothSocket.connect(): \n" + eMessage);
     }});
    
    try {
     bluetoothSocket.close();
    } catch (IOException e1) {
     // TODO Auto-generated catch block
     e1.printStackTrace();
    }
   }
   
   if(success){
    //connect successful
    runOnUiThread(new Runnable(){

     @Override
     public void run() {
      textStatus.setText("connect successful");
     }});
   }else{
    //fail
   }
  }
  
  public void cancel() {
   
   Toast.makeText(getApplicationContext(), 
     "close bluetoothSocket", 
     Toast.LENGTH_LONG).show();
   
   try {
    bluetoothSocket.close();
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
   
        }
 }
 
}

/res/layout/activity_main.xml

<LinearLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.example.androidbluetooth.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />
    
    <TextView
        android:id="@+id/info"
        android:textStyle="bold|italic"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/status"
        android:textSize="28sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    
    <ListView 
        android:id="@+id/pairedlist"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

AndroidManifest.xml with permission of "android.permission.BLUETOOTH"

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.androidbluetooth"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />
    <uses-permission android:name="android.permission.BLUETOOTH"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

Download the files.

Next:
- Bluetooth communication between Android devices