Google Glass GDK: How to Communicate with Android Device

Question

I'm looking for a way to send data between my Android Device and Google Glass that doesn't rely on Cloud API's. Is this supported? I see the Bluetooth connections in the My Glass app, which makes me think it can be done. Is there an example source code that shows how this is done? Or do I have to decompile the MyGlass app to figure it out?

Is there a preferred method for doing this kind of data transfer? Ideally I'd like to transfer data in both directions.

Answer 1

Ok, for the requesters....

EDIT: The code below still works, but I've put it into a git repo for those who are interested...

https://github.com/NathanielWaggoner/GoogleGlassBlutooth

Here is my Bluetooth Host/Client code. It's not perfect - You're going to need some patience, and there are some bugs on reconnection and such, but it does work. I've been sending data up to Glass From the Hand Held and driving UI updates (publishing live cards, updating live cards etc...) for about three days using this now.

Host:

import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.util.ArrayList; import java.util.UUID;  import android.app.Activity; import android.bluetooth.BluetoothAdapter; import android.bluetooth.BluetoothServerSocket; import android.bluetooth.BluetoothSocket; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.os.Bundle; import android.os.Handler; import android.os.Looper; import android.os.Message; import android.util.Log; import android.view.Menu; import android.widget.TextView;   public class BluetoothHost extends Activity {      public static String msgToSend="";     public static final int STATE_CONNECTION_STARTED = 0;     public static final int STATE_CONNECTION_LOST = 1;     public static final int READY_TO_CONN = 2;     public static final String DEVICE_NAME = "device_name";     public static final String TOAST = "toast";      // our last connection     ConnectedThread mConnectedThread;// = new ConnectedThread(socket);     // track our connections     ArrayList<ConnectedThread> mConnThreads;     // bt adapter for all your bt needs (where we get all our bluetooth powers)     BluetoothAdapter myBt;     // list of sockets we have running (for multiple connections)     ArrayList<BluetoothSocket> mSockets = new ArrayList<BluetoothSocket>();     // list of addresses for devices we've connected to     ArrayList<String> mDeviceAddresses = new ArrayList<String>();     // just a name, nothing more...     String NAME="G6BITCHES";     // We can handle up to 7 connections... or something...     UUID[] uuids = new UUID[2];     // some uuid's we like to use..     String uuid1 = "05f2934c-1e81-4554-bb08-44aa761afbfb";     String uuid2 = "c2911cd0-5c3c-11e3-949a-0800200c9a66";     // just a tag..     String TAG = "G6 Bluetooth Host Activity";       // constant we define and pass to startActForResult (must be >0), that the system passes back to you in your onActivityResult()      // implementation as the requestCode parameter.     int REQUEST_ENABLE_BT = 1;       AcceptThread accThread;     TextView connectedDevices;     Handler handle;     BroadcastReceiver receiver;     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);          // the activity for this is pretty stripped, just a basic selection ui....         setContentView(R.layout.activity_main);         uuids[0] = UUID.fromString(uuid1);         uuids[1] = UUID.fromString(uuid2);         connectedDevices = (TextView) findViewById(R.id.connected_devices_values);         handle = new Handler(Looper.getMainLooper()) {             @Override             public void handleMessage(Message msg) {                 switch (msg.what) {                 case STATE_CONNECTION_STARTED:                     connectedDevices.setText(msg.getData().getString("NAMES"));                     break;                 case STATE_CONNECTION_LOST:                     connectedDevices.setText("");                     startListening();                     break;                 case READY_TO_CONN:                     startListening();                 default:                     break;                 }             }         };          // ....         myBt = BluetoothAdapter.getDefaultAdapter();         // run the "go get em" thread..         accThread = new AcceptThread();         accThread.start();     }     public void startListening() {         if(accThread!=null) {             accThread.cancel();         }else if (mConnectedThread!= null) {             mConnectedThread.cancel();         } else {             accThread = new AcceptThread();             accThread.start();         }     }      @Override     public boolean onCreateOptionsMenu(Menu menu) {         // Inflate the menu; this adds items to the action bar if it is present.         getMenuInflater().inflate(R.menu.main, menu);         return true;     }     private class AcceptThread extends Thread {         private BluetoothServerSocket mmServerSocket;         BluetoothServerSocket tmp;          public AcceptThread() {             BluetoothServerSocket tmp = null;             try {                 tmp = myBt.listenUsingInsecureRfcommWithServiceRecord(NAME, uuids[0]);              } catch (IOException e) { }             mmServerSocket = tmp;         }          public void run() {             Log.e(TAG,"Running?");             BluetoothSocket socket = null;             // Keep listening until exception occurs or a socket is returned             while (true) {                  try {                      socket = mmServerSocket.accept();                 } catch (IOException e) {                     e.printStackTrace();                     break;                 }                 // If a connection was accepted                  if (socket != null) {                     try {                         mmServerSocket.close();                     } catch (IOException e) {                         // TODO Auto-generated catch block                         e.printStackTrace();                     }                     // Do work to manage the connection (in a separate thread)                     manageConnectedSocket(socket);                      break;                 }             }         }          /** Will cancel the listening socket, and cause the thread to finish */         public void cancel() {             try {                 mmServerSocket.close();                 Message msg = handle.obtainMessage(READY_TO_CONN);                 handle.sendMessage(msg);                              } catch (IOException e) { }         }     }       private void manageConnectedSocket(BluetoothSocket socket) {         // start our connection thread         mConnectedThread = new ConnectedThread(socket);         mConnectedThread.start();          // Send the name of the connected device back to the UI Activity         // so the HH can show you it's working and stuff...         String devs="";         for(BluetoothSocket sock: mSockets) {             devs+=sock.getRemoteDevice().getName()+"\n";         }         // pass it to the UI....         Message msg = handle.obtainMessage(STATE_CONNECTION_STARTED);         Bundle bundle = new Bundle();         bundle.putString("NAMES", devs);         msg.setData(bundle);          handle.sendMessage(msg);                     }     private class ConnectedThread extends Thread {         private final BluetoothSocket mmSocket;         private final InputStream mmInStream;         private final OutputStream mmOutStream;          public ConnectedThread(BluetoothSocket socket) {             Log.d(TAG, "create ConnectedThread");             mmSocket = socket;             InputStream tmpIn = null;             OutputStream tmpOut = null;              // Get the BluetoothSocket input and output streams             try {                 tmpIn = socket.getInputStream();                 tmpOut = socket.getOutputStream();             } catch (IOException e) {                 Log.e(TAG, "temp sockets not created", e);             }             mmInStream = tmpIn;             mmOutStream = tmpOut;         }          public void run() {             Log.i(TAG, "BEGIN mConnectedThread");             byte[] buffer = new byte[1024];             int bytes;              // Keep listening to the InputStream while connected             while (true) {                 try {                     //byte[] blah = ("System Time:" +System.currentTimeMillis()).getBytes();                     if(!msgToSend.equals("")) {                         Log.e(TAG,"writing!");                         write(msgToSend.getBytes());                         setMsg("");                     }                     Thread.sleep(1000);                 } catch (Exception e) {                     Log.e(TAG, "disconnected", e);                     connectionLost();                 }             }         }         public void connectionLost() {             Message msg = handle.obtainMessage(STATE_CONNECTION_LOST);             handle.sendMessage(msg);                         }         /**          * Write to the connected OutStream.          * @param buffer  The bytes to write          */         public void write(byte[] buffer) {             try {                 mmOutStream.write(buffer);             } catch (IOException e) {                 Log.e(TAG, "Exception during write", e);                 connectionLost();             }         }          public void cancel() {             try {                 mmSocket.close();                 Message msg = handle.obtainMessage(READY_TO_CONN);                 handle.sendMessage(msg);                             } catch (IOException e) {                 Log.e(TAG, "close() of connect socket failed", e);             }         }     }     public static synchronized void setMsg(String newMsg) {         msgToSend = newMsg;     }     public static class HostBroadRec extends BroadcastReceiver {         @Override         public void onReceive(Context context, Intent intent) {             Bundle b= intent.getExtras();             String vals ="";             for(String key: b.keySet()) {                 vals+=key+"&"+b.getString(key)+"Z";             }             BluetoothHost.setMsg(vals);         }     } } 

Client:

import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.util.ArrayList; import java.util.Set; import java.util.UUID;  import android.app.Activity; import android.bluetooth.BluetoothAdapter; import android.bluetooth.BluetoothDevice; import android.bluetooth.BluetoothSocket; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.os.Bundle; import android.os.Handler; import android.os.Looper; import android.os.Message; import android.text.format.DateFormat; import android.util.Log; import android.view.Menu; import android.view.View; import android.view.WindowManager; import android.widget.AdapterView; import android.widget.AdapterView.OnItemSelectedListener; import android.widget.ArrayAdapter; import android.widget.Spinner; import android.widget.TextView; import android.widget.Toast;  public class BluetoothClient extends Activity {      public static final int READY_TO_CONN =0;     public static final int CANCEL_CONN =1;     public static final int MESSAGE_READ =2;      // holds the bluetooth names/ids that we're associated with.     ArrayAdapter<String> btArray;     // bt adapter for all your bt needs     BluetoothAdapter myBt;     String NAME="G6BITCHES";     String TAG = "G6 Bluetooth Slave Activity";     UUID[] uuids = new UUID[2];     // some uuid's we like to use..     String uuid1 = "05f2934c-1e81-4554-bb08-44aa761afbfb";     String uuid2 = "c2911cd0-5c3c-11e3-949a-0800200c9a66";     //  DateFormat df = new DateFormat("ddyyyy")     ConnectThread mConnThread;     Spinner devices;     Handler handle;     // constant we define and pass to startActForResult (must be >0), that the system passes back to you in your onActivityResult()      // implementation as the requestCode parameter.     int REQUEST_ENABLE_BT = 1;     // bc for discovery mode for BT...     private final BroadcastReceiver mReceiver = new BroadcastReceiver() {         public void onReceive(Context context, Intent intent) {             String action = intent.getAction();             // When discovery finds a device             if (BluetoothDevice.ACTION_FOUND.equals(action)) {                 // Get the BluetoothDevice object from the Intent                 BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);                 // Add the name and address to an array adapter to show in a ListView                 if(device!= null) {                     if(device.getName().contains("Nexus")) {                      } else {                         btArray.add(device.getName() + "\n" + device.getAddress());                      }                 }                 update();             }         }     };      Context ctx;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         //      publishCards(this);         getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);         ctx = this;         handle = new Handler(Looper.getMainLooper()) {             @Override             public void handleMessage(Message msg) {                 switch (msg.what) {                 case READY_TO_CONN:                     mConnThread=null;                     update();                     break;                 case CANCEL_CONN:                     break;                 case MESSAGE_READ:                     byte[] readBuf = (byte[]) msg.obj;                      // construct a string from the valid bytes in the buffer                     String readMessage = new String(readBuf, 0, msg.arg1);                     Log.e(TAG,"received: "+readMessage);                     if (readMessage.length() > 0) {                         // do soemthing...                     }                       //                      updateCards(ctx, readMessage);                     //                          update()                     //  mConversationArrayAdapter.add(mConnectedDeviceName+":  " + readMessage);                      break;                 default:                     break;                 }             }         };         btArray = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, android.R.id.text1);         btArray.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);         uuids[0] = UUID.fromString(uuid1);         uuids[1] = UUID.fromString(uuid2);         // spinner for displaying available devices for pairing         devices = (Spinner) findViewById(R.id.devices_spinner);         devices.setAdapter(btArray);         // use the same UUID across an installation         // should allow clients to find us repeatedly         myBt = BluetoothAdapter.getDefaultAdapter();         if (myBt == null) {             Toast.makeText(this, "Device Does not Support Bluetooth", Toast.LENGTH_LONG).show();         }          else if (!myBt.isEnabled()) {             // we need to wait until bt is enabled before set up, so that's done either in the following else, or              // in the onActivityResult for our code ...             Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);             startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);         } else {             detectAndSetUp();         }         setContentView(R.layout.bluetooth_activity_layout);      }      @Override     public void onDestroy() {         unregisterReceiver(mReceiver);         super.onDestroy();      }      @Override     protected void onActivityResult (int requestCode, int resultCode, Intent data){         if(requestCode == REQUEST_ENABLE_BT) {             if (resultCode != RESULT_OK) {                 Toast.makeText(this, "Failed to enable Bluetooth", Toast.LENGTH_LONG).show();             } else {                 Toast.makeText(this, "Bluetooth Enabled", Toast.LENGTH_LONG).show();                 detectAndSetUp();             }         }     }      private void detectAndSetUp() {         IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);         registerReceiver(mReceiver, filter); // Don't forget to unregister during onDestroy          Set<BluetoothDevice> pairedDevices = myBt.getBondedDevices();         // If there are paired devices         if (pairedDevices.size() > 0) {             // Loop through paired devices             for (BluetoothDevice device : pairedDevices) {                  if(device.getName().contains("Nexus")) {                  } else {                     btArray.add(device.getName() + "\n" + device.getAddress());                  }                 // Add the name and address to an array adapter to show in a ListView                 //              btArray.add(device.getName() + "\n" + device.getAddress());                 //              update();             }         }         myBt.startDiscovery();     }      public void update() {               devices = (Spinner) findViewById(R.id.devices_spinner);         devices.setAdapter(btArray);         devices.setOnItemSelectedListener(new OnItemSelectedListener() {             @Override             public void onItemSelected(AdapterView<?> arg0, View arg1,                     int position, long id) {                 if(mConnThread!=null) {                     Log.e(TAG,"Canceling old connection, and starting new one.");                     mConnThread.cancel();                 } else {                     Log.e(TAG,"got a thing...");                     String str = ((TextView)arg1).getText().toString();                     Log.e(TAG,"tots: "+str);                         String[] vals = str.split("\n");                     Log.e(TAG,"mac: "+vals[1]);                     BluetoothDevice dev = myBt.getRemoteDevice(vals[1]);                     mConnThread = new ConnectThread(dev);                     mConnThread.run();                 }             }              @Override             public void onNothingSelected(AdapterView<?> arg0) {                 // TODO Auto-generated method stub              }          });     }     @Override        public boolean onCreateOptionsMenu(Menu menu) {         // Inflate the menu; this adds items to the action bar if it is present.         getMenuInflater().inflate(R.menu.bluetooth, menu);         return true;     }      private class ConnectThread extends Thread {         private final BluetoothSocket mmSocket;         private final BluetoothDevice mmDevice;          public ConnectThread(BluetoothDevice device) {             Log.e(TAG,"ConnectThread start....");             // Use a temporary object that is later assigned to mmSocket,             // because mmSocket is final             BluetoothSocket tmp = null;             mmDevice = device;              // Get a BluetoothSocket to connect with the given BluetoothDevice             try {                  // this seems to work on the note3...                 // you can remove the Insecure if you want to...                  tmp = device.createInsecureRfcommSocketToServiceRecord(uuids[0]);                 //                  Method m;                 // this is an approach I've seen others use, it wasn't nescesary for me,                 // but your results may vary...                  //                  m = device.getClass().getMethod("createInsecureRfcommSocket", new Class[] {int.class});                 //                  tmp = (BluetoothSocket) m.invoke(device, 1);                 //              } catch (NoSuchMethodException e1) {                 //                  // TODO Auto-generated catch block                 //                  e1.printStackTrace();                 //              } catch (IllegalArgumentException e2) {                 //                  // TODO Auto-generated catch block                 //                  e2.printStackTrace();                 //              } catch (IllegalAccessException e3) {                 //                  // TODO Auto-generated catch block                 //                  e3.printStackTrace();                 //              } catch (InvocationTargetException e4) {                 //                  // TODO Auto-generated catch block                 //                  e4.printStackTrace();                 //              }                    //                  if(tmp.isConnected()) {                 //                      break                 //                  }                } catch (Exception e) {                  Log.e(TAG,"Danger Will Robinson");                 e.printStackTrace();             }             mmSocket = tmp;         }          public void run() {             // Cancel discovery because it will slow down the connection             myBt.cancelDiscovery();             Log.e(TAG,"stopping discovery");              try {                 // Connect the device through the socket. This will block                 // until it succeeds or throws an exception                 Log.e(TAG,"connecting!");                  mmSocket.connect();             } catch (IOException connectException) {                                  Log.e(TAG,"failed to connect");                  // Unable to connect; close the socket and get out                 try {                     Log.e(TAG,"close-ah-da-socket");                      mmSocket.close();                 } catch (IOException closeException) {                      Log.e(TAG,"failed to close hte socket");                  }                 Log.e(TAG,"returning..");                  return;             }              Log.e(TAG,"we can now manage our connection!");              // Do work to manage the connection (in a separate thread)             manageConnectedSocket(mmSocket);         }          /** Will cancel an in-progress connection, and close the socket */         public void cancel() {             try {                 mmSocket.close();                 Message msg = handle.obtainMessage(READY_TO_CONN);                 handle.sendMessage(msg);                              } catch (IOException e) { }         }     }      public void manageConnectedSocket(BluetoothSocket mmSocket) {         ConnectedThread t = new ConnectedThread(mmSocket);         t.start();         // manage your socket... I'll probably do a lot of the boiler plate here later     }     private class ConnectedThread extends Thread {         private final BluetoothSocket mmSocket;         private final InputStream mmInStream;         private final OutputStream mmOutStream;          public ConnectedThread(BluetoothSocket socket) {             Log.d(TAG, "create ConnectedThread");             mmSocket = socket;             InputStream tmpIn = null;             OutputStream tmpOut = null;              // Get the BluetoothSocket input and output streams             try {                 tmpIn = socket.getInputStream();                 tmpOut = socket.getOutputStream();             } catch (IOException e) {                 Log.e(TAG, "temp sockets not created", e);             }              mmInStream = tmpIn;             mmOutStream = tmpOut;         }          public void run() {             Log.i(TAG, "BEGIN mConnectedThread");             byte[] buffer = new byte[1024];             int bytes;              // Keep listening to the InputStream while connected             while (true) {                 try {                     //                  byte[] blah = ("System Time:" +System.currentTimeMillis()).getBytes();                     //                  write(blah);                     //                  Thread.sleep(1000);                     // Read from the InputStream                     bytes = mmInStream.read(buffer);                     // Send the obtained bytes to the UI Activity                     handle.obtainMessage(MESSAGE_READ, bytes, -1, buffer)                     .sendToTarget();                      //                  .sendToTarget();                 } catch (Exception e) {                     Log.e(TAG, "disconnected", e);                     connectionLost();                     //                  break;                 }             }         }         public void connectionLost() {             Message msg = handle.obtainMessage(CANCEL_CONN);             //          Bundle bundle = new Bundle();             //          bundle.putString("NAMES", devs);             //          msg.setData(bundle);              handle.sendMessage(msg);                          }         /**          * Write to the connected OutStream.          * @param buffer  The bytes to write          */         public void write(byte[] buffer) {             try {                 mmOutStream.write(buffer);                  // Share the sent message back to the UI Activity                 //              mHandler.obtainMessage(BluetoothChat.MESSAGE_WRITE, -1, -1, buffer)                 //              .sendToTarget();             } catch (IOException e) {                 Log.e(TAG, "Exception during write", e);             }         }          public void cancel() {             try {                 mmSocket.close();             } catch (IOException e) {                 Log.e(TAG, "close() of connect socket failed", e);             }         }     } } 

Host Manifest:

 <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"     package="transapps.android_bluetooth_host"     android:versionCode="1"     android:versionName="1.0" >      <uses-sdk         android:minSdkVersion="7"         android:targetSdkVersion="17" />      <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" >         <activity             android:name="transapps.android_bluetooth_host.BluetoothHost"             android:label="@string/app_name" >             <intent-filter>                 <action android:name="android.intent.action.MAIN" />                  <category android:name="android.intent.category.LAUNCHER" />             </intent-filter>         </activity>          <receiver android:name=".BluetoothHost$HostBroadRec" >             <intent-filter>                 <action android:name="transapps.g6.new.alert" />             </intent-filter>         </receiver>     </application>   </manifest> 

Client Manifest:

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"     package="transapps.android_blutooth"     android:versionCode="1"     android:versionName="1.0" >      <uses-sdk         android:minSdkVersion="15"         android:targetSdkVersion="15" />      <uses-permission android:name="android.permission.BLUETOOTH" />     <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />      <application         android:allowBackup="true"         android:icon="@drawable/ic_launcher"         android:label="@string/app_name" >         <activity             android:name="transapps.android_blutooth.BluetoothClient"             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> 

I'll leave the UI as an exercise to the reader.

Answer 2

There is no preferred method, but if you're looking to do it wirelessly, a Bluetooth 3.0 RFCOMM does work.

If you provide more specifics about the problem you're trying to solve in your question, I'll be able to provide a more specific answer.

Answer 3

Several things I noticed when following this solution (awesome work by the way!)

1) I could only create a bluetooth connection when my phone and the Google Glass were not already paired through the MyGlass app - If you are having trouble establishing a connection, try forgetting that pairing.

2) The Glass API does not support controlling your bluetooth connection through intents using commands like

Intent discoveryIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoveryIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, DISCOVER_DURATION);
startActivityForResult(discoveryIntent, REQUEST_BLU);

In order to make the Glass headset discoverable (rather than the phone it is connecting to), I needed to follow solutions similar to those like user4934624 provided at this question and shantanu gave at this question. I invoked a hidden method to access bluetooth functionality directly. Warning: the hidden method seems to have been there for years, but there is no guarantee it will continue to be in future APIs.

 // this method allows us to make the device discoverable without alerting the users
// NOTE!!!! This uses a hidden method, so it may be removed from the API in the future
public void makeDiscoverable (){

    Class <?> baClass = BluetoothAdapter.class;
    Method[] methods = baClass.getDeclaredMethods();

    // we want to use method setScanMode(int mode, int duration)
    // there are 2 setScanModes
    // so select the first setScanMode you see

    // test to see which method is the one we want
    //for (int i = 0; i<50; i++) {Log.d(Integer.toString(i), methods[i].getName());}

    //I had trouble calling the first setScanMode, so I called the second.
    // I need to pass in a discoverable time, but it stays discoverable indefinitely
    // Thus you must turn off the setScanMode as soon as the connection is established
    // I should probably write in some other security stuff to turn it off if connection fails
    // maybe a timer running on a different thread?


    Method mSetScanMode = methods[38];
    try {
        mSetScanMode.invoke(myBt, BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE,300);
        //mSetScanMode.invoke(myBt, BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);


    } catch (Exception e) {
        Log.e("discoverable", e.getMessage());
    }
}

// this method allows us to make the device not discoverable without alerting the user
// NOTE!!!! This uses a hidden method, so it may be removed from the API in the future
public void makeNotDiscoverable (){

    // see notes for makeDiscoverable
    Class <?> baClass = BluetoothAdapter.class;
    Method [] methods = baClass.getDeclaredMethods();

    Method mSetScanMode = methods[38];
    try {
       mSetScanMode.invoke(myBt, BluetoothAdapter.SCAN_MODE_CONNECTABLE,300);
    } catch (Exception e) {
        Log.e("discoverable", e.getMessage());
    }
}

Note that I first ran a test that output the names of all the methods in the class I mirrored; that allowed me to narrow my search for which method I wanted to use.