Android Bluetooth

Bluetooth is a way to exchange data with other devices wirelessly. Android provides Bluetooth API to perform several tasks such as:

• scan bluetooth devices
• Connect and transfer data from and to other devices
• manage multiple connections etc.

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Android Bluetooth API

The android.bluetooth package provides a lot of interfaces classes to work with bluetooth such as:

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

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BluetoothAdapter class

By the help of BluetoothAdapter class, we can perform fundamental tasks such as initiate device discovery, query a list of paired (bonded) devices, create a BluetoothServerSocket instance to listen for connection requests etc.

Constants of BluetoothAdapter class

BluetoothAdapter class provides many constants. Some of them are as follows:

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

Methods of BluetoothAdapter class

Commonly used methods of BluetoothAdapter class are as follows:

• static synchronized BluetoothAdapter getDefaultAdapter() returns the instance of BluetoothAdapter.
• boolean enable() enables the bluetooth adapter if it is disabled.
• boolean isEnabled() returns true if the bluetooth adapter is enabled.
• boolean disable() disables the bluetooth adapter if it is enabled.
• String getName() returns the name of the bluetooth adapter.
• boolean setName(String name) changes the bluetooth name.
• int getState() returns the current state of the local bluetooth adapter.
• Set<BluetoothDevice> getBondedDevices() returns a set of paired bonded) BluetoothDevice objects.
• boolean startDiscovery() starts the discovery process.

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Android Bluetooth Example: enable, disable and make discovrable bluetooth programmatically

You need to write few lines of code only, to enable or disable the bluetooth.

activity_main.xml

Drag one textview and three buttons from the pallete, now the activity_main.xml file will like this:

File: activity_main.xml

1. <RelativeLayout xmlns:androclass="http://schemas.android.com/apk/res/android"  
2.     xmlns:tools="http://schemas.android.com/tools"  
3.     android:layout_width="match_parent"  
4.     android:layout_height="match_parent"  
5.     tools:context=".MainActivity" >  
6.   
7.     <TextView android:text=""  
8.      android:id="@+id/out"   
9.      android:layout_width="wrap_content"   
10.      android:layout_height="wrap_content">  
11.     </TextView>  
12.     <Button  
13.         android:id="@+id/button1"  
14.         android:layout_width="wrap_content"  
15.         android:layout_height="wrap_content"  
16.         android:layout_alignParentLeft="true"  
17.         android:layout_alignParentTop="true"  
18.         android:layout_marginLeft="30dp"  
19.         android:layout_marginTop="49dp"  
20.         android:text="TURN_ON" />  
21.   
22.     <Button  
23.         android:id="@+id/button2"  
24.         android:layout_width="wrap_content"  
25.         android:layout_height="wrap_content"  
26.         android:layout_alignLeft="@+id/button1"  
27.         android:layout_below="@+id/button1"  
28.         android:layout_marginTop="27dp"  
29.         android:text="DISCOVERABLE" />  
30.   
31.     <Button  
32.         android:id="@+id/button3"  
33.         android:layout_width="wrap_content"  
34.         android:layout_height="wrap_content"  
35.         android:layout_alignLeft="@+id/button2"  
36.         android:layout_below="@+id/button2"  
37.         android:layout_marginTop="28dp"  
38.         android:text="TURN_OFF" />  
39.   
40. </RelativeLayout>  

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Provide Permission

You need to provide following permissions in AndroidManifest.xml file.

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

The full code of AndroidManifest.xml file is given below.

File: AndroidManifest.xml

1. <?xml version="1.0" encoding="utf-8"?>  
2. <manifest xmlns:androclass="http://schemas.android.com/apk/res/android"  
3.     package="com.example.bluetooth"  
4.     android:versionCode="1"  
5.     android:versionName="1.0" >  
6.   
7.     <uses-sdk  
8.         android:minSdkVersion="8"  
9.         android:targetSdkVersion="16" />  
10.   
11.     <uses-permission android:name="android.permission.BLUETOOTH" />  
12.     <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />  
13.   
14.     <application  
15.         android:allowBackup="true"  
16.         android:icon="@drawable/ic_launcher"  
17.         android:label="@string/app_name"  
18.         android:theme="@style/AppTheme" >  
19.         <activity  
20.             android:name="com.example.bluetooth.MainActivity"  
21.             android:label="@string/app_name" >  
22.             <intent-filter>  
23.                 <action android:name="android.intent.action.MAIN" />  
24.   
25.                 <category android:name="android.intent.category.LAUNCHER" />  
26.             </intent-filter>  
27.         </activity>  
28.     </application>  
29.   
30. </manifest>  

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Activity class

Let's write the code to enable, disable and make bluetooth discoverable.

File: MainActivity.java

1. package com.example.bluetooth;  
2. import android.os.Bundle;  
3. import android.app.Activity;  
4. import android.view.Menu;  
5. import android.app.Activity;  
6. import android.bluetooth.BluetoothAdapter;  
7. import android.content.Context;  
8. import android.content.Intent;  
9. import android.os.Bundle;  
10. import android.util.Log;  
11. import android.view.View;  
12. import android.widget.Button;  
13. import android.widget.TextView;  
14. import android.widget.Toast;  
15.   
16. public class MainActivity extends Activity {  
17.       private static final int REQUEST_ENABLE_BT = 0;  
18.       private static final int REQUEST_DISCOVERABLE_BT = 0;  
19.     @Override  
20.     protected void onCreate(Bundle savedInstanceState) {  
21.         super.onCreate(savedInstanceState);  
22.         setContentView(R.layout.activity_main);  
23.     final TextView out=(TextView)findViewById(R.id.out);  
24.     final Button button1 = (Button) findViewById(R.id.button1);  
25.     final Button button2 = (Button) findViewById(R.id.button2);  
26.     final Button button3 = (Button) findViewById(R.id.button3);  
27.     final BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();  
28.     if (mBluetoothAdapter == null) {  
29.        out.append("device not supported");  
30.     }  
31.     button1.setOnClickListener(new View.OnClickListener() {  
32.         public void onClick(View v) {  
33.             if (!mBluetoothAdapter.isEnabled()) {  
34.                 Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);  
35.                 startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);  
36.             }  
37.         }  
38.     });  
39.     button2.setOnClickListener(new View.OnClickListener() {  
40.      @Override  
41.         public void onClick(View arg0) {  
42.             if (!mBluetoothAdapter.isDiscovering()) {  
43.                   //out.append("MAKING YOUR DEVICE DISCOVERABLE");  
44.                    Toast.makeText(getApplicationContext(), "MAKING YOUR DEVICE DISCOVERABLE",  
45.              Toast.LENGTH_LONG);  
46.   
47.                 Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);  
48.                 startActivityForResult(enableBtIntent, REQUEST_DISCOVERABLE_BT);  
49.                     
50.             }  
51.         }  
52.     });  
53.     button3.setOnClickListener(new View.OnClickListener() {  
54.         @Override  
55.         public void onClick(View arg0) {     
56.             mBluetoothAdapter.disable();  
57.             //out.append("TURN_OFF BLUETOOTH");  
58.             Toast.makeText(getApplicationContext(), "TURNING_OFF BLUETOOTH", Toast.LENGTH_LONG);  
59.            
60.             }  
61.     });  
62. }  
63.   
64.     @Override  
65.     public boolean onCreateOptionsMenu(Menu menu) {  
66.         // Inflate the menu; this adds items to the action bar if it is present.  
67.         getMenuInflater().inflate(R.menu.activity_main, menu);  
68.         return true;  
69.     }  
70.   
71. }  

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You need to run it on the real device (e.g. mobile) to test the application.