Android - Bluetooth

There are some practices that you can follow while developing android application. These are suggested by the android itself and they keep on improving with respect to time.

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

Android provides BluetoothAdapter class to communicate with Bluetooth. Create an object of this calling by calling the static method getDefaultAdapter(). Its syntax is given below.

private BluetoothAdapter BA;
BA = BluetoothAdapter.getDefaultAdapter();

In order to enable the Bluetooth of your device, call the intent with the following Bluetooth constant ACTION_REQUEST_ENABLE. Its syntax is.

Intent turnOn = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(turnOn, 0);

Apart from this constant, there are other constants provided the API , that supports different tasks. They are listed below.

Once you enable the Bluetooth , you can get a list of paired devices by calling getBondedDevices() method. It returns a set of bluetooth devices. Its syntax is.

private SetpairedDevices;
pairedDevices = BA.getBondedDevices();

Apart form the parried Devices , there are other methods in the API that gives more control over Blueetooth. They are listed below.

Example

This example provides demonstration of BluetoothAdapter class to manipulate Bluetooth and show list of paired devices by the Bluetooth.
To experiment with this example , you need to run this on an actual device.

Here is the content of src/MainActivity.java

package com.example.sairamkrishna.myapplication;

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 SetpairedDevices;
   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);
   }
}

Here is the content of 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="Mca tutorials"
      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>

Here is the content of Strings.xml

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

Here is the content of AndroidManifest.xml.

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

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from Android studio, open one of your project's activity files and click Runicon from the tool bar.If your Bluetooth will not be turned on then, it will ask your permission to enable the Bluetooth.

Now just select the Get Visible button to turn on your visibility. The following screen would appear asking your permission to turn on discovery for 120 seconds.

Now just select the List Devices option. It will list down the paired devices in the list view. In my case , I have only one paired device. It is shown below.

Now just select the Turn off button to switch off the Bluetooth. Following message would appear when you switch off the bluetooth indicating the successful switching off of Bluetooth.