Introduction

Bluetooth Print Plus is a Bluetooth plugin used to print thermal printers in Flutter, a new mobile SDK to help developers build bluetooth thermal printer apps for iOS and Android.

Important, important, important. First, you need to run the demo to confirm the printer command type ! ! ! now support tspl/tsc、cpcl、esc pos. If this plugin is helpful to you, please give it a like, Thanks.

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Plan

Version	plan
1.1.x	blue and tsc command, esc print image command
1.5.x	support cpcl command
2.x.x	improve esc command
3.x.x	support zpl command

Features

	Android	iOS	Description
scan	:white_check_mark:	:white_check_mark:	Starts a scan for Bluetooth Low Energy devices.
connect	:white_check_mark:	:white_check_mark:	Establishes a connection to the device.
disconnect	:white_check_mark:	:white_check_mark:	Cancels an active or pending connection to the device.
state	:white_check_mark:	:white_check_mark:	Stream of state changes for the Bluetooth Device.

Usage

Example

To use this plugin :

• add the dependency to your pubspec.yaml file.

dependencies:
  flutter:
    sdk: flutter
  bluetooth_print_plus: ^2.4.2

Add permissions for Bluetooth

---

We need to add the permission to use Bluetooth and access location:

Android

In the android/app/src/main/AndroidManifest.xml let’s add:

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

IOS

In the ios/Runner/Info.plist let’s add:

<key>NSBluetoothAlwaysUsageDescription</key>
<string>Need BLE permission</string>
<key>NSBluetoothPeripheralUsageDescription</key>
<string>Need BLE permission</string>

import

import 'package:bluetooth_print_plus/bluetooth_print_plus.dart';

BluetoothPrintPlus useful property

BluetoothPrintPlus.isBlueOn;
BluetoothPrintPlus.isScanning;
BluetoothPrintPlus.isConnected;

listen

---

late StreamSubscription<bool> _isScanningSubscription;
late StreamSubscription<BlueState> _blueStateSubscription;
late StreamSubscription<ConnectState> _connectStateSubscription;
late StreamSubscription<Uint8List> _receivedDataSubscription;
late StreamSubscription<List<BluetoothDevice>> _scanResultsSubscription;
late List<BluetoothDevice> _scanResults;

• scan results

/// listen scanResults
_scanResultsSubscription = BluetoothPrintPlus.scanResults.listen((event) {
  if (mounted) {
    setState(() {
      _scanResults = event;
    });
  }
});

• state

/// listen isScanning
_isScanningSubscription = BluetoothPrintPlus.isScanning.listen((event) {
  print('********** isScanning: $event **********');
  if (mounted) {
    setState(() {});
  }
});

/// listen blue state
_blueStateSubscription = BluetoothPrintPlus.blueState.listen((event) {
  print('********** blueState change: $event **********');
  /// blue state changed, do something...
});

/// listen connect state
_blueStateSubscription = _BluetoothPrintPlus.connectState.listen((event) {
  print('********** connectState change: $event **********');
  /// connect state changed, do something...
});

• received Data

_BluetoothPrintPlus.receivedData.listen((data) {
  print('********** received data: $data **********');
  /// received data, do something...
});

scan

---

// begin scan
await BluetoothPrintPlus.startScan(timeout: Duration(seconds: 10));

// get devices
_scanResultsSubscription = BluetoothPrintPlus.scanResults.listen((event) {
  if (mounted) {
    setState(() {
      _scanResults = event;
    });
  }
});

connect

---

await BluetoothPrintPlus.connect(_device);

disconnect

---

await BluetoothPrintPlus.disconnect();

print/write

---

final ByteData bytes = await rootBundle.load("assets/dithered-image.png");

/// write tsc command, for example:
final Uint8List image = bytes.buffer.asUint8List();
await tscCommand.cleanCommand();
await tscCommand.size(width: 76, height: 130);
await tscCommand.cls(); // most after size
await tscCommand.image(image: image, x: 50, y: 60);
await tscCommand.print(1);
final cmd = await tscCommand.getCommand();
if (cmd == null) return;
BluetoothPrintPlus.write(cmd);

/// write cpcl command, for example:
await cpclCommand.cleanCommand();
await cpclCommand.size(width: 76 * 8, height: 76 * 8);
await cpclCommand.image(image: image, x: 10, y: 10);
await cpclCommand.print();
final cmd = await cpclCommand.getCommand();
if (cmd == null) return;
BluetoothPrintPlus.write(cmd);

/// write esc command, for example:
await escCommand.cleanCommand();
await escCommand.print();
await escCommand.image(image: image);
await escCommand.print();
final cmd = await escCommand.getCommand();
if (cmd == null) return;
BluetoothPrintPlus.write(cmd);

Cancel Subscription

@override
void dispose() {
  super.dispose();
  _isScanningSubscription.cancel();
  _blueStateSubscription.cancel();
  _connectStateSubscription.cancel();
  _receivedDataSubscription.cancel();
  _scanResultsSubscription.cancel();
  _scanResults.clear();
  _device = null;
}

Troubleshooting

error:'State restoration of CBCentralManager is only allowed for applications that have specified the "bluetooth-central" background mode'

info.plist add:

<key>NSBluetoothAlwaysUsageDescription</key>
<string>Allow App use bluetooth?</string>
<key>NSBluetoothPeripheralUsageDescription</key>
<string>Allow App use bluetooth?</string>
<key>UIBackgroundModes</key>
<array>
    <string>bluetooth-central</string>
    <string>bluetooth-peripheral</string>
</array>

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