Scan Bluetooth Devices

To start scan bluetooth device, simple call bluetoothAdapter.startDiscovery().

In order to receive the list of found bluetooth devices, we have to implement a BroadcastReceiver for BluetoothDevice.ACTION_FOUND.



AndroidBluetooth.java

package com.exercise.AndroidBluetooth;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;

public class AndroidBluetooth extends Activity {
 
 private static final int REQUEST_ENABLE_BT = 1;
 
    ListView listDevicesFound;
 Button btnScanDevice;
 TextView stateBluetooth;
 BluetoothAdapter bluetoothAdapter;
 
 ArrayAdapter<String> btArrayAdapter;
 
 /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        btnScanDevice = (Button)findViewById(R.id.scandevice);
        
        stateBluetooth = (TextView)findViewById(R.id.bluetoothstate);
        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        
        listDevicesFound = (ListView)findViewById(R.id.devicesfound);
        btArrayAdapter = new ArrayAdapter<String>(AndroidBluetooth.this, android.R.layout.simple_list_item_1);
        listDevicesFound.setAdapter(btArrayAdapter);
        
        CheckBlueToothState();
        
        btnScanDevice.setOnClickListener(btnScanDeviceOnClickListener);

        registerReceiver(ActionFoundReceiver, 
          new IntentFilter(BluetoothDevice.ACTION_FOUND));
    }
    
    @Override
 protected void onDestroy() {
  // TODO Auto-generated method stub
  super.onDestroy();
  unregisterReceiver(ActionFoundReceiver);
 }

 private void CheckBlueToothState(){
     if (bluetoothAdapter == null){
         stateBluetooth.setText("Bluetooth NOT support");
        }else{
         if (bluetoothAdapter.isEnabled()){
          if(bluetoothAdapter.isDiscovering()){
           stateBluetooth.setText("Bluetooth is currently in device discovery process.");
          }else{
           stateBluetooth.setText("Bluetooth is Enabled.");
           btnScanDevice.setEnabled(true);
          }
         }else{
          stateBluetooth.setText("Bluetooth is NOT Enabled!");
          Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
             startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
         }
        }
    }
    
    private Button.OnClickListener btnScanDeviceOnClickListener
    = new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   btArrayAdapter.clear();
   bluetoothAdapter.startDiscovery();
  }};

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  // TODO Auto-generated method stub
  if(requestCode == REQUEST_ENABLE_BT){
   CheckBlueToothState();
  }
 }
    
 private final BroadcastReceiver ActionFoundReceiver = new BroadcastReceiver(){

  @Override
  public void onReceive(Context context, Intent intent) {
   // TODO Auto-generated method stub
   String action = intent.getAction();
   if(BluetoothDevice.ACTION_FOUND.equals(action)) {
             BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
             btArrayAdapter.add(device.getName() + "\n" + device.getAddress());
             btArrayAdapter.notifyDataSetChanged();
         }
  }};
    
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<TextView 
    android:id="@+id/bluetoothstate" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    />
<TextView
    android:id="@+id/bluetoothstate" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    />
<TextView
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="Set Discoverable Duration" 
    />
<Button
    android:id="@+id/scandevice" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:text="Scan Bluetooth Devices" 
    android:enabled="false"
    /> 
<ListView
    android:id="@+id/devicesfound" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    /> 
</LinearLayout>

Modify AndroidManifest.xml to grant permission of "android.permission.BLUETOOTH", and "android.permission.BLUETOOTH_ADMIN".

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.exercise.AndroidBluetooth"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="7" />
    <uses-permission android:name="android.permission.BLUETOOTH"></uses-permission>
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"></uses-permission>

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".AndroidBluetooth"
                  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>

Download the files.


Related:
- Start Bluetooth Discoverable and register BroadcastReceiver for ACTION_SCAN_MODE_CHANGED

---

Updated@2016-03-07: 
Android 6.0 Changes - Access to Hardware Identifier

To provide users with greater data protection, starting in this release, Android removes programmatic access to the device’s local hardware identifier for apps using the Wi-Fi and Bluetooth APIs. The WifiInfo.getMacAddress() and the BluetoothAdapter.getAddress() methods now return a constant value of 02:00:00:00:00:00.

To access the hardware identifiers of nearby external devices via Bluetooth and Wi-Fi scans, your app must now have the ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION permissions:

WifiManager.getScanResults()
BluetoothDevice.ACTION_FOUND
BluetoothLeScanner.startScan()

Note: When a device running Android 6.0 (API level 23) initiates a background Wi-Fi or Bluetooth scan, the operation is visible to external devices as originating from a randomized MAC address.

link: http://developer.android.com/about/versions/marshmallow/android-6.0-changes.html#behavior-hardware-id

I have no Android 6.0 devices, So I can't figure it out if it is related!