Bluetooth functionality in Android

Bluetooth is a way to send or receive data between two different devices. Android platform includes support for the Bluetooth framework that allows a device to wirelessly exchange data with other Bluetooth devices.

Android provides Bluetooth API to perform these different operations.

  • Scan for other Bluetooth devices

  • Get a list of paired devices

  • Connect to other devices through service discovery


src/MainActivity.java


import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;

import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;

import android.widget.Toast;
import java.util.ArrayList;
import java.util.Set;

public class MainActivity extends Activity  {
   Button b1,b2,b3,b4;
   private BluetoothAdapter BA;
   private Set<BluetoothDevice>pairedDevices;
   ListView lv;

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

      b1 = (Button) findViewById(R.id.button);
      b2=(Button)findViewById(R.id.button2);
      b3=(Button)findViewById(R.id.button3);
      b4=(Button)findViewById(R.id.button4);

      BA = BluetoothAdapter.getDefaultAdapter();
      lv = (ListView)findViewById(R.id.listView);
   }

   public void on(View v){
      if (!BA.isEnabled()) {
         Intent turnOn = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
         startActivityForResult(turnOn, 0);
         Toast.makeText(getApplicationContext(), "Turned on",Toast.LENGTH_LONG).show();
      } else {
         Toast.makeText(getApplicationContext(), "Already on", Toast.LENGTH_LONG).show();
      }
   }

   public void off(View v){
      BA.disable();
      Toast.makeText(getApplicationContext(), "Turned off" ,Toast.LENGTH_LONG).show();
   }

    
   public  void visible(View v){
      Intent getVisible = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
      startActivityForResult(getVisible, 0);
   }

    
   public void list(View v){
      pairedDevices = BA.getBondedDevices();
        
      ArrayList list = new ArrayList();

      for(BluetoothDevice bt : pairedDevices) list.add(bt.getName());
      Toast.makeText(getApplicationContext(), "Showing Paired Devices",Toast.LENGTH_SHORT).show();

      final ArrayAdapter adapter = new  ArrayAdapter(this,android.R.layout.simple_list_item_1, list);
        
      lv.setAdapter(adapter);
   }
}

activity_main.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:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   android:paddingBottom="@dimen/activity_vertical_margin"
   tools:context=".MainActivity"
   android:transitionGroup="true">
   
   <TextView android:text="Bluetooth Example" 
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/textview"
      android:textSize="35dp"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true" />
      
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="My Example"
      android:id="@+id/textView"
      android:layout_below="@+id/textview"
      android:layout_centerHorizontal="true"
      android:textColor="#ff7aff24"
      android:textSize="35dp" />
      
   <ImageView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/imageView"
      android:src="@drawable/abc"
      android:layout_below="@+id/textView"
      android:layout_centerHorizontal="true"
      android:theme="@style/Base.TextAppearance.AppCompat" />
      
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Turn On"
      android:id="@+id/button"
      android:layout_below="@+id/imageView"
      android:layout_toStartOf="@+id/imageView"
      android:layout_toLeftOf="@+id/imageView"
      android:clickable="true"
      android:onClick="on" />
      
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Get visible"
      android:onClick="visible"
      android:id="@+id/button2"
      android:layout_alignBottom="@+id/button"
      android:layout_centerHorizontal="true" />
      
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="List devices"
      android:onClick="list"
      android:id="@+id/button3"
      android:layout_below="@+id/imageView"
      android:layout_toRightOf="@+id/imageView"
      android:layout_toEndOf="@+id/imageView" />
      
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="turn off"
      android:onClick="off"
      android:id="@+id/button4"
      android:layout_below="@+id/button"
      android:layout_alignParentLeft="true"
      android:layout_alignParentStart="true" />
      
   <ListView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/listView"
      android:layout_alignParentBottom="true"
      android:layout_alignLeft="@+id/button"
      android:layout_alignStart="@+id/button"
      android:layout_below="@+id/textView2" />
      
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Paired devices:"
      android:id="@+id/textView2"
      android:textColor="#ff34ff06"
      android:textSize="25dp"
      android:layout_below="@+id/button4"
      android:layout_alignLeft="@+id/listView"
      android:layout_alignStart="@+id/listView" />

</RelativeLayout>

Strings.xml

<resources>
   <string name="app_name">My Application</string>
</resources>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.myapplication" >
   <uses-permission android:name="android.permission.BLUETOOTH"/>
   <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
   
   <application
      android:allowBackup="true"
      android:icon="@mipmap/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>