Android Bluetooth

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To exchange data with other devices wirelessly, Bluetooth is used. The Bluetooth framework supported by the Android platform allows a device to send or receive data between two different devices. The Bluetooth API of Android is used to perform these tasks and many more:

  • To scan Bluetooth devices
  • To connect and transfer data from and to other devices
  • To manage multiple connections

Android Bluetooth API:

The interfaces classes to work with Bluetooth are included in the android.bluetooth package. These are:

  • BluetoothAdapter
  • BluetoothDevice
  • BluetoothSocket
  • BluetoothServerSocket
  • BluetoothClass
  • BluetoothProfile
  • BluetoothProfile.ServiceListener
  • BluetoothHeadset
  • BluetoothA2dp
  • BluetoothHealth
  • BluetoothHealthCallback
  • BluetoothHealthAppConfiguration

BluetoothAdapter class:

To perform the fundamental tasks, like to initiate a device discovery, to query a list of paired or bonded devices, to create a BluetoothServerSocket instance to listen for connection requests, etc, the BluetoothAdapter class is used.

Constants of BluetoothAdapter class:

There are various constants provided by the BluetoothAdapter class. Some of these constants are:

  • String ACTION_REQUEST_ENABLE
  • String ACTION_REQUEST_DISCOVERABLE
  • String ACTION_DISCOVERY_STARTED
  • String ACTION_DISCOVERY_FINISHED

Methods of BluetoothAdapter class:

The BluetoothAdapter class contains various methods. Some of the important methods of the BluetoothAdapter class are:

  • static synchronized BluetoothAdapter getDefaultAdapter(): Used to return the instance of BluetoothAdapter.
  • boolean enable(): Used to enable the Bluetooth adapter, if it is disabled.
  • boolean isEnabled(): Used to return true if the Bluetooth adapter is enabled.
  • boolean disable(): Used to disable the Bluetooth adapter, if it is enabled.
  • String getName(): Used to return the name of the Bluetooth adapter.
  • boolean setName(String name): Used to change the Bluetooth name.
  • int getState(): Used to return the current state of the local Bluetooth adapter.
  • Set<BluetoothDevice> getBondedDevices(): Used to return a set of paired or bonded BluetoothDevice objects.
  • boolean startDiscovery(): Used to start the discovery process.

Example: To enable, disable, and make discoverable Bluetooth programmatically:

activity_main.xml:

In the activity_main.xml file, we will drag a Textview and three buttons from the pallet.

<?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"
    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="Bluetooth"
        android:id="@+id/textView"
        android:layout_below="@+id/textview"
        android:layout_centerHorizontal="true"
        android:textColor="#db5a6b"
        android:textSize="35dp" />
 
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Turn On"
        android:id="@+id/button"
        android:layout_below="@+id/textView"
        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/button2" />
 
    <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/button3" />
 
    <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="#db5a6b"
        android:textSize="25dp"
        android:layout_below="@+id/button4"
        android:layout_alignLeft="@+id/listView"
        android:layout_alignStart="@+id/listView" />
 
</RelativeLayout>

AndroidManifest.xml:

In the AndroidManifest.xml file, we will provide the below permissions:

Syntax:

<uses-permission android:name="android.permission.BLUETOOTH" />  
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />

File: AndroidManifest.xml:

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

Activity class:(File: MainActivity.java)

In the MainActivity.java file, we will write the code to enable, disable, and to make the Bluetooth discoverable.

package com.example.radioapp;
 
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);
    }
}

Output: