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Android Bluetooth Tutorial

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.

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

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 getBondedDevices() returns a set of paired (bonded) BluetoothDevice objects.
  • boolean startDiscovery() starts the discovery process.

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

File: activity_main.xml 

<RelativeLayout xmlns:androclass="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" >  
  
    <TextView android:text=""  
     android:id="@+id/out"   
     android:layout_width="wrap_content"   
     android:layout_height="wrap_content">  
    </TextView>  
    <Button  
        android:id="@+id/button1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignParentLeft="true"  
        android:layout_alignParentTop="true"  
        android:layout_marginLeft="30dp"  
        android:layout_marginTop="49dp"  
        android:text="TURN_ON" />  
  
    <Button  
        android:id="@+id/button2"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignLeft="@+id/button1"  
        android:layout_below="@+id/button1"  
        android:layout_marginTop="27dp"  
        android:text="DISCOVERABLE" />  
  
    <Button  
        android:id="@+id/button3"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignLeft="@+id/button2"  
        android:layout_below="@+id/button2"  
        android:layout_marginTop="28dp"  
        android:text="TURN_OFF" />  
  
</RelativeLayout>

Provide Permission

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

<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:androclass="http://schemas.android.com/apk/res/android"  
    package="com.example.bluetooth"  
    android:versionCode="1"  
    android:versionName="1.0" >  
  
    <uses-sdk  
        android:minSdkVersion="8"  
        android:targetSdkVersion="16" />  
  
    <uses-permission android:name="android.permission.BLUETOOTH" />  
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />  
  
    <application  
        android:allowBackup="true"  
        android:icon="@drawable/ic_launcher"  
        android:label="@string/app_name"  
        android:theme="@style/AppTheme" >  
        <activity  
            android:name="com.example.bluetooth.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 write the code to enable, disable and make bluetooth discoverable.
File: MainActivity.java 

import android.os.Bundle;  
import android.app.Activity;  
import android.view.Menu;  
import android.app.Activity;  
import android.bluetooth.BluetoothAdapter;  
import android.content.Context;  
import android.content.Intent;  
import android.os.Bundle;  
import android.util.Log;  
import android.view.View;  
import android.widget.Button;  
import android.widget.TextView;  
import android.widget.Toast;  
  
public class MainActivity extends Activity {  
      private static final int REQUEST_ENABLE_BT = 0;  
      private static final int REQUEST_DISCOVERABLE_BT = 0;  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
    final TextView out=(TextView)findViewById(R.id.out);  
    final Button button1 = (Button) findViewById(R.id.button1);  
    final Button button2 = (Button) findViewById(R.id.button2);  
    final Button button3 = (Button) findViewById(R.id.button3);  
    final BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();  
    if (mBluetoothAdapter == null) {  
       out.append("device not supported");  
    }  
    button1.setOnClickListener(new View.OnClickListener() {  
        public void onClick(View v) {  
            if (!mBluetoothAdapter.isEnabled()) {  
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);  
                startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);  
            }  
        }  
    });  
    button2.setOnClickListener(new View.OnClickListener() {  
     @Override  
        public void onClick(View arg0) {  
            if (!mBluetoothAdapter.isDiscovering()) {  
                  //out.append("MAKING YOUR DEVICE DISCOVERABLE");  
                   Toast.makeText(getApplicationContext(), "MAKING YOUR DEVICE DISCOVERABLE",  
             Toast.LENGTH_LONG);  
  
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);  
                startActivityForResult(enableBtIntent, REQUEST_DISCOVERABLE_BT);  
                    
            }  
        }  
    });  
    button3.setOnClickListener(new View.OnClickListener() {  
        @Override  
        public void onClick(View arg0) {     
            mBluetoothAdapter.disable();  
            //out.append("TURN_OFF BLUETOOTH");  
            Toast.makeText(getApplicationContext(), "TURNING_OFF BLUETOOTH", Toast.LENGTH_LONG);  
           
            }  
    });  
}  
  
    @Override  
    public boolean onCreateOptionsMenu(Menu menu) {  
        // Inflate the menu; this adds items to the action bar if it is present.  
        getMenuInflater().inflate(R.menu.activity_main, menu);  
        return true;  
    }  
  
}

Android Wifi Example

The android.net.wifi.WifiManager class can be used to manage the wifi connectivity. It can be used to add network, disable network, scan for access points, disconnect etc.

Android wifi example to enable and disable wifi

Let's see the simple example of wifi to enable and disable the wifi service.
File: activity_main.xml 


<RelativeLayout xmlns:androclass="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" >  
  
    <Button  
        android:id="@+id/button1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignParentLeft="true"  
        android:layout_alignParentTop="true"  
        android:layout_marginLeft="76dp"  
        android:layout_marginTop="67dp"  
        android:text="Enable Wifi" />  
  
    <Button  
        android:id="@+id/button2"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignLeft="@+id/button1"  
        android:layout_below="@+id/button1"  
        android:layout_marginTop="44dp"  
        android:text="Disable Wifi" />  
  
</RelativeLayout>
File: MainActivity.java 

import android.net.wifi.WifiManager;  
import android.os.Bundle;  
import android.app.Activity;  
import android.content.Context;  
import android.view.Menu;  
import android.view.View;  
import android.view.View.OnClickListener;  
import android.widget.Button;  
  
public class MainActivity extends Activity {  
    Button enableButton,disableButton;  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
          
        enableButton=(Button)findViewById(R.id.button1);  
        disableButton=(Button)findViewById(R.id.button2);  
          
        enableButton.setOnClickListener(new OnClickListener(){  
            public void onClick(View v){  
                WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);  
                wifi.setWifiEnabled(true);  
            }  
        });  
        disableButton.setOnClickListener(new OnClickListener(){  
            public void onClick(View v){  
                WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);  
                wifi.setWifiEnabled(false);  
            }  
        });  
    }  
  
    @Override  
    public boolean onCreateOptionsMenu(Menu menu) {  
        // Inflate the menu; this adds items to the action bar if it is present.  
        getMenuInflater().inflate(R.menu.activity_main, menu);  
        return true;  
    }  
  
}

Add Permission in AndroidManifest.xml

You need to add following permissions in AndroidManifest.xml file.
File: AndroidManifest.xml 

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />  
<uses-permission android:name="android.permission.INTERNET" />  
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
OUTPUT :

Android Sensor Tutorial

  • Sensors can be used to monitor the three-dimensional device movement or change in the environment of the device.
  • Android provides sensor api to work with different types of sensors.

Types of Sensors

Android supports three types of sensors:
  1. Motion Sensors :
    These are used to measure acceleration forces and rotational forces along with three axes.
  2. Position Sensors :
    These are used to measure the physical position of device.
  3. Environmental Sensors :
    These are used to measure the environmental changes such as temperature, humidity etc.

Android Sensor API

Android sensor api provides many classes and interface. The important classes and interfaces of sensor api are as follows:

1) SensorManager class

The android.hardware.SensorManager class provides methods :
  • to get sensor instance,
  • to access and list sensors,
  • to register and unregister sensor listeners etc.
You can get the instance of SensorManager by calling the method getSystemService() and passing the SENSOR_SERVICE constant in it.
SensorManager sm = (SensorManager)getSystemService(SENSOR_SERVICE);

2) Sensor class

The android.hardware.Sensor class provides methods to get information of the sensor such as sensor name, sensor type, sensor resolution, sensor type etc.

3) SensorEvent class

Its instance is created by the system. It provides information about the sensor.

4) SensorEventListener interface

Android simple sensor app example

Let's see the two sensor examples.
  • A sensor example that prints x, y and z axis values. Here, we are going to see that.
  • A sensor example that changes the background color when device is shuffled.
File: activity_main.xml 

<RelativeLayout xmlns:androclass="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" >  
  
    <TextView  
        android:id="@+id/textView1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignParentLeft="true"  
        android:layout_alignParentTop="true"  
        android:layout_marginLeft="92dp"  
        android:layout_marginTop="114dp"  
        android:text="TextView" />  
  
</RelativeLayout>
Let's write the code that prints values of x axis, y axis and z axis.
File: MainActivity.java 

import android.app.Activity;  
import android.os.Bundle;  
import android.widget.TextView;  
import android.widget.Toast;  
import android.hardware.SensorManager;  
import android.hardware.SensorEventListener;  
import android.hardware.SensorEvent;  
import android.hardware.Sensor;  
import java.util.List;  
public class MainActivity extends Activity {  
    SensorManager sm = null;  
    TextView textView1 = null;  
    List list;  
  
    SensorEventListener sel = new SensorEventListener(){  
        public void onAccuracyChanged(Sensor sensor, int accuracy) {}  
        public void onSensorChanged(SensorEvent event) {  
            float[] values = event.values;  
            textView1.setText("x: "+values[0]+"\ny: "+values[1]+"\nz: "+values[2]);  
        }  
    };  
  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
  
        /* Get a SensorManager instance */  
        sm = (SensorManager)getSystemService(SENSOR_SERVICE);  
  
        textView1 = (TextView)findViewById(R.id.textView1);  
  
        list = sm.getSensorList(Sensor.TYPE_ACCELEROMETER);  
        if(list.size()>0){  
            sm.registerListener(sel, (Sensor) list.get(0), SensorManager.SENSOR_DELAY_NORMAL);  
        }else{  
            Toast.makeText(getBaseContext(), "Error: No Accelerometer.", Toast.LENGTH_LONG).show();  
        }  
    }  
  
    @Override  
    protected void onStop() {  
        if(list.size()>0){  
          sm.unregisterListener(sel);  
        }  
        super.onStop();  
    }  
}
OUTPUT :