How to Use the Terminal's Bluetooth Printer Service

This service demonstrates how to use a set of Bluetooth APIs to print image or text. The integrity process of Bluetooth print service includes opening Bluetooth, scanning the Bluetooth devices surrounding， pairing with a Bluetooth device and connecting with the device with SPP, and then sending data, which always shows in types of image and text document, and printing the data.

Introduction

Bluetooth printing is a service, which gets a connection with buletooth printer, sends data to the bluetooth printer through the connection and then printing the data. The connection is built by terminal with SPP(Serial Port Profile). The process of the service:

1. Open bluetooth if doesn't open.
2. Scan and discovery the bluetooth devices surrounding.
3. Select and pair the bluetooth printer.
4. Send data(a series of ESC command).
5. Print the data.

Pre-requisites:

1. Android SDK 24
2. Android Build Tools v27.0.0
3. Android Support Repository
4. Zxing

Getting Started:

This service uses the Gradle build system. To build this project, use the "gradlew build" command or use "Import Project" in Android Studio.

Code Snippet

• Basic PAIs of Bluetooth

    public void openBluetooth(Activity activity) {
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        activity.startActivityForResult(enableBtIntent, 1);
    }
    public void closeBluetooth() {
        this.bluetoothAdapter.disable();
    }
    public void searchDevices() {
        this.bluetoothAdapter.startDiscovery();
    }
    private BroadcastReceiver receiver = new BroadcastReceiver() {
        ProgressDialog progressDialog = null;
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                if (device.getBondState() == BluetoothDevice.BOND_BONDED) {
                    addBondDevice(device);
                } else {
                    addUnbondDevice(device);
                }
            } else if (BluetoothDevice.ACTION_ACL_CONNECTED.equals(action)) {
            	BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            	String msg = "ACTION_ACL_CONNECTED: " + device.getAddress() + "=" + device.getBondState();
            	Toast.makeText(context, msg, Toast.LENGTH_LONG).show();
            	System.out.println(msg);
            } else if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
                progressDialog = ProgressDialog.show(context, "pair...","...", true);
            } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED .equals(action)) {
                bluetoothAdapter.cancelDiscovery();
                if (progressDialog != null)
                	progressDialog.dismiss();
                addUnbondDevicesToListView();
                addBondDevicesToListView();
            } else if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
            	int state = bluetoothAdapter.getState();
                if (state == BluetoothAdapter.STATE_ON) {
                    searchDevices.setEnabled(true);
                    bondDevicesListView.setEnabled(true);
                    unbondDevicesListView.setEnabled(true);
                } else if (state == BluetoothAdapter.STATE_OFF) {
                    searchDevices.setEnabled(false);
                    bondDevicesListView.setEnabled(false);
                    unbondDevicesListView.setEnabled(false);
                } else {
                    System.out.println("Bluetooth.STATE: " + state);
                }
            } else {
                System.out.println("Bluetooth.ACTION: " + action);
            }
        }
    };

• Connection with SPP

public boolean connect() {
	if (!isConnected) {
		try {
			bluetoothSocket = createBluetoothSocket();
			bluetoothSocket.connect();
			outputStream = bluetoothSocket.getOutputStream();
			isConnected = bluetoothSocket.isConnected();
			if (this.bluetoothAdapter.isDiscovering()) {
				Toast.makeText(this.context, "success to connect",1).show();
				this.bluetoothAdapter.isDiscovering();
			}
		} catch (Exception e) {
			e.printStackTrace();
			Toast.makeText(this.context, "fail to  connect", 1).show();

			return false;
		}
	}
	Toast.makeText(this.context, this.device.getName() + "connected",Toast.LENGTH_SHORT).show();
	return true;
}

private BluetoothSocket createBluetoothSocket()
		throws IOException, NoSuchMethodException, IllegalAccessException, InvocationTargetException {
	switch (TYPE_OF_CREATING_SOCKET) {
	case 0:	return device.createRfcommSocketToServiceRecord(uuid);
	case 1: return device.createInsecureRfcommSocketToServiceRecord(uuid);
	default:
		Method m = device.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
		return (BluetoothSocket) m.invoke(device, 1);
	}
}

• Send and print

final byte[][] byteCommands = { { 0x1b, 0x40 }, //printer commands(ESC commands)
		{ 0x1b, 0x4d, 0x00 },
		{ 0x1b, 0x4d, 0x01 },
		{ 0x1d, 0x21, 0x00 },
		{ 0x1d, 0x21, 0x11 },
		{ 0x1b, 0x45, 0x00 },
		{ 0x1b, 0x45, 0x01 },
		{ 0x1b, 0x7b, 0x00 },
		{ 0x1b, 0x7b, 0x01 },
		{ 0x1d, 0x42, 0x00 },
		{ 0x1d, 0x42, 0x01 },
		{ 0x1b, 0x56, 0x00 },
		{ 0x1b, 0x56, 0x01 },
public void selectCommand() {
	new AlertDialog.Builder(context).setTitle("Commands").setItems(items, new DialogInterface.OnClickListener() {
				@Override
				public void onClick(DialogInterface dialog, int which) {
					if (isConnected) {
						try {
							outputStream.write(byteCommands[which]);
						} catch (IOException e) {
							Toast.makeText(context, "write exception",Toast.LENGTH_SHORT).show();
						}
					} else {
						Toast.makeText(context, "connection is lost",Toast.LENGTH_SHORT).show();
					}
				}
			}).create().show();
}
public void write(byte[] buff){
	try {
		outputStream.write(buff);
	} catch (IOException e) {
	}
}