Connect to specific Bluetooth device with a click

Question

I'm trying to connect to a specific device using my Android APP, until now what I was able to do is get the paired items doing this :

BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
Set < BluetoothDevice > pairedDevices = bluetoothAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
    for (BluetoothDevice device: pairedDevices) {
        mDeviceName.add(device.getName());
        mDeviceMAC.add(device.getAddress());

    }
}
bluetoothClass.setDeviceName(mDeviceName);
bluetoothClass.setDeviceMac(mDeviceMAC);

Where I get the MAC and the Device name of all of my paired devices. The thing that I would like to do is when I select one it connects to the Bluetooth device.

EXAMPLE

On a Samsung S4 when I turn on the Bluetooth it popups a Dialog whitch contains all of my paired devices and when I click on anyone it connects (I've i'm able to ...) so basically I want to do this, since now I've been getting the paired devices (I don't know if it's the best way to get that but it does) and then when user click on anyone it connects to the device.

It's something like this question but it's unfortunately unanswered.

Answer 1

It's impossible to give you an example within this format, so I have provided you with a good sample and helpful links to help you understand the sample.

I recommend you follow the steps I have provided and then, when you have specific problems, you can bring it here, with the code snippet you are having difficulty with.

I recommend you use download this sample code:
http://developer.android.com/samples/BluetoothChat/index.html

If you haven't already, it's good to study this:
http://developer.android.com/reference/android/bluetooth/BluetoothDevice.html

This is a good tutorial and they have many tutorials:
http://www.tutorialspoint.com/android/android_bluetooth.htm

You will need the following permissions in your manifest:

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

This is one intent that is advisable to use, to check to see if BT is enabled:

if (!mBluetoothAdapter.isEnabled()) {
    android.content.Intent enableIntent = new android.content.Intent(
           android.bluetooth.BluetoothAdapter.ACTION_REQUEST_ENABLE);
    startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
}

and to make your device discoverable to other devices:

if (mBluetoothAdapter.getScanMode() !=
        android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
    android.content.Intent discoverableIntent =
        new android.content.Intent(
            android.bluetooth.BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
    discoverableIntent.putExtra(
        android.bluetooth.BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION,
                300); // You are able to set how long it is discoverable.
    startActivity(discoverableIntent);
}

As I mentioned in my answer here:

You can avoid using an intent to search for paired devices. When connecting to a device that is not paired, a notification will pop up asking to pair the devices. Once paired this message should not show again for these devices, the connection should be automatic (according to how you have written your program).

I use an intent to enable bluetooth, and to make my device discoverable, I then set up my code to connect, and press a button to connect. In your case, you will need to ensure your accessories are discoverable also. In my case I use a unique UUID, and both devices must recognise this to connect. This can only be used if you are programming both devices, whether both are android or one android and one other device type.

You will need to understand how to use sockets, this is how the devices communicate.
I recommend studying these two links:

http://developer.android.com/reference/android/bluetooth/BluetoothSocket.html
http://developer.android.com/reference/android/bluetooth/BluetoothServerSocket.html

Sockets are used to set up connections between devices. There will be a server socket and device sockets (determined by many factors, the programmer, the actual devices). The server socket listens for incoming connections, when a connection is accepted the devices connect, each with a simple socket.

I am not sure how much you know about threading. The connection needs to be managed with threads:

http://developer.android.com/guide/components/processes-and-threads.html
http://android-developers.blogspot.com.au/2009/05/painless-threading.html

The connection between the devices is managed on threads separate from the User Interface thread. This is to prevent the phone from locking up while it is setting up, seeking and making a BT connection.

For instance:

AcceptThread - the thread that listens for a connection and accepts the connection (via the serversocket). This thread can run for an extended time waiting for a device to connect with.

ConnectThread - the thread that the device connecting to the server uses to connect to the serversocket.

ConnectedThread - this is the thread that manages the connection between both sockets.

Let me know if this helps you.