What's new in Android

Google I/O 2014 - What's new in Android

What's new in Android development tools

Google I/O 2014 - What's new in Android development tools

Official Moto 360 Demo at Google I/O

Meet Moto 360, a classic timepiece powered by Android Wear. Get a sneak peek at just some of the functionalities of Moto 360 in demo we are giving at this year's Google I/O.

Implement BroadcastReceiver to monitor Bluetooth state changed

Last example show how to Enable Bluetooth using Intent of BluetoothAdapter.ACTION_REQUEST_ENABLE. In this example, we implement a new class BTStateChangedBroadcastReceiver, extends BroadcastReceiver, to monitor Bluetooth state changed.

BTStateChangedBroadcastReceiver.java

package com.example.androidbluetooth;

import android.bluetooth.BluetoothAdapter;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class BTStateChangedBroadcastReceiver extends BroadcastReceiver {

 @Override
 public void onReceive(Context context, Intent intent) {
  int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, 
    -1);
  
  switch(state){
  case BluetoothAdapter.STATE_CONNECTED:
   Toast.makeText(context, 
    "BTStateChangedBroadcastReceiver: STATE_CONNECTED", 
    Toast.LENGTH_SHORT).show();
   break;
  case BluetoothAdapter.STATE_CONNECTING:
   Toast.makeText(context, 
    "BTStateChangedBroadcastReceiver: STATE_CONNECTING", 
    Toast.LENGTH_SHORT).show();
   break;
  case BluetoothAdapter.STATE_DISCONNECTED:
   Toast.makeText(context, 
    "BTStateChangedBroadcastReceiver: STATE_DISCONNECTED", 
    Toast.LENGTH_SHORT).show();
   break;
  case BluetoothAdapter.STATE_DISCONNECTING:
   Toast.makeText(context, 
    "BTStateChangedBroadcastReceiver: STATE_DISCONNECTING", 
    Toast.LENGTH_SHORT).show();
   break;
  case BluetoothAdapter.STATE_OFF:
   Toast.makeText(context, 
    "BTStateChangedBroadcastReceiver: STATE_OFF", 
    Toast.LENGTH_SHORT).show();
   break;
  case BluetoothAdapter.STATE_ON:
   Toast.makeText(context, 
    "BTStateChangedBroadcastReceiver: STATE_ON", 
    Toast.LENGTH_SHORT).show();
   break;
  case BluetoothAdapter.STATE_TURNING_OFF:
   Toast.makeText(context, 
    "BTStateChangedBroadcastReceiver: STATE_TURNING_OFF", 
    Toast.LENGTH_SHORT).show();
   break;
  case BluetoothAdapter.STATE_TURNING_ON:
   Toast.makeText(context, 
    "BTStateChangedBroadcastReceiver: STATE_TURNING_ON", 
    Toast.LENGTH_SHORT).show();
   break; 
  }
 }

}

Call registerReceiver(...) to register new BTStateChangedBroadcastReceiver(), to the intent of BluetoothAdapter.ACTION_STATE_CHANGED.

package com.example.androidbluetooth;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
 
 TextView textInfo;
 Button buttonEnableBT;
 BluetoothAdapter bluetoothAdapter;
 
 final static int REQUEST_ENABLE_BT = 1;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  textInfo = (TextView)findViewById(R.id.info);
  buttonEnableBT = (Button)findViewById(R.id.enablebt);
  
  bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
  if (bluetoothAdapter == null) {
   textInfo.setText("BlueTooth not supported in this device");
   buttonEnableBT.setEnabled(false);
  }else{
   if (bluetoothAdapter.isEnabled()) {
    buttonEnableBT.setEnabled(false);
    textInfo.setText("BlueTooth enabled");
   }else{
    buttonEnableBT.setEnabled(true);
    textInfo.setText("BlueTooth disabled, click button to turn on BlueTooth.");
   }
   
   //register BroadcastReceiver
   registerReceiver(new BTStateChangedBroadcastReceiver(), 
    new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED));
  }
  
  buttonEnableBT.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View v) {
    Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
       startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
   }});

 }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);
  
  if(requestCode == REQUEST_ENABLE_BT){
   if(resultCode==RESULT_OK){
    Toast.makeText(MainActivity.this, "BlueTooth Turned On", Toast.LENGTH_LONG).show();
   }else{
    Toast.makeText(MainActivity.this, "Cancelled", Toast.LENGTH_LONG).show();
   }
  }
  
  if (bluetoothAdapter.isEnabled()) {
   buttonEnableBT.setEnabled(false);
   textInfo.setText("BlueTooth enabled");
  }else{
   buttonEnableBT.setEnabled(true);
   textInfo.setText("BlueTooth disabled, click button to turn on BlueTooth.");
  }
  
 }

}

activity_main.xml

<LinearLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.example.androidbluetooth.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="android-coding.blogspot.com" />
    <TextView
        android:id="@+id/info"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <Button
        android:id="@+id/enablebt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Enable BlueTooth" />

</LinearLayout>

Permission of "android.permission.BLUETOOTH" is needed in AndroidManifest.xml.

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

Check BlueTooth status, and enable it using Intent of BluetoothAdapter.ACTION_REQUEST_ENABLE

This example check if Bluetooth supported in running device and its ON/OFF status. Then call startActivityForResult() with Intent of BluetoothAdapter.ACTION_REQUEST_ENABLE, when user click button to enable it. Then re-check the status again in onActivityResult() when result returned.


MainActivity.java

package com.example.androidbluetooth;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
 
 TextView textInfo;
 Button buttonEnableBT;
 BluetoothAdapter bluetoothAdapter;
 
 final static int REQUEST_ENABLE_BT = 1;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  textInfo = (TextView)findViewById(R.id.info);
  buttonEnableBT = (Button)findViewById(R.id.enablebt);
  
  bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
  if (bluetoothAdapter == null) {
   textInfo.setText("BlueTooth not supported in this device");
   buttonEnableBT.setEnabled(false);
  }else{
   if (bluetoothAdapter.isEnabled()) {
    buttonEnableBT.setEnabled(false);
    textInfo.setText("BlueTooth enabled");
   }else{
    buttonEnableBT.setEnabled(true);
    textInfo.setText("BlueTooth disabled, click button to turn on BlueTooth.");
   }
   
  }
  
  buttonEnableBT.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View v) {
    Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
       startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
   }});

 }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);
  
  if(requestCode == REQUEST_ENABLE_BT){
   if(resultCode==RESULT_OK){
    Toast.makeText(MainActivity.this, "BlueTooth Turned On", Toast.LENGTH_LONG).show();
   }else{
    Toast.makeText(MainActivity.this, "Cancelled", Toast.LENGTH_LONG).show();
   }
  }
  
  if (bluetoothAdapter.isEnabled()) {
   buttonEnableBT.setEnabled(false);
   textInfo.setText("BlueTooth enabled");
  }else{
   buttonEnableBT.setEnabled(true);
   textInfo.setText("BlueTooth disabled, click button to turn on BlueTooth.");
  }
  
 }

}

activity_main.xml

<LinearLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.example.androidbluetooth.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="android-coding.blogspot.com" />
    <TextView
        android:id="@+id/info"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <Button
        android:id="@+id/enablebt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Enable BlueTooth" />

</LinearLayout>

Add <uses-permission android:name="android.permission.BLUETOOTH"/> in AndroidManifest.xml.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.androidbluetooth"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />
    <uses-permission android:name="android.permission.BLUETOOTH"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.androidbluetooth.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>

Google Nexus 5 Android 4.4.3 KitKat