Problem with write data over flutter_blue - flutter

Question

I have a Question to Flutter with Bluetooth.
I Use the Flutter_blue package https://pub.dev/packages/flutter_blue
How I can write data external over a Future or a Void.
I use the code of the documentation Example of Flutter_blue.
Just I will extend this with my own void to write data every 5 seconds.
Here is my code that I want to control
import 'dart:convert';
import 'package:flutter_blue/flutter_blue.dart';
class SecondBlue {
BluetoothCharacteristic targetCharacteristic;
SecondBlue(this.targetCharacteristic);
writeData(String data) async {
if (targetCharacteristic == null) return;
List<int> bytes = utf8.encode(data);
await targetCharacteristic.write(bytes);
}
}
i would like after the first bluetooth part provides the connection
write data about this part at any time.
here is the code of flutter_blue to connect the device.
The main Part:
// Copyright 2017, Paul DeMarco.
// All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'dart:async';
import 'dart:math';
import 'package:flutter/material.dart';
import 'package:flutter_blue/flutter_blue.dart';
import 'package:flutter_blue_example/widgets.dart';
void main() {
runApp(FlutterBlueApp());
}
class FlutterBlueApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
color: Colors.lightBlue,
home: StreamBuilder<BluetoothState>(
stream: FlutterBlue.instance.state,
initialData: BluetoothState.unknown,
builder: (c, snapshot) {
final state = snapshot.data;
if (state == BluetoothState.on) {
return FindDevicesScreen();
}
return BluetoothOffScreen(state: state);
}),
);
}
}
class BluetoothOffScreen extends StatelessWidget {
const BluetoothOffScreen({Key? key, this.state}) : super(key: key);
final BluetoothState? state;
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.lightBlue,
body: Center(
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
Icon(
Icons.bluetooth_disabled,
size: 200.0,
color: Colors.white54,
),
Text(
'Bluetooth Adapter is ${state != null ? state.toString().substring(15) : 'not available'}.',
style: Theme.of(context)
.primaryTextTheme
.subhead
?.copyWith(color: Colors.white),
),
],
),
),
);
}
}
class FindDevicesScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Find Devices'),
),
body: RefreshIndicator(
onRefresh: () =>
FlutterBlue.instance.startScan(timeout: Duration(seconds: 4)),
child: SingleChildScrollView(
child: Column(
children: <Widget>[
StreamBuilder<List<BluetoothDevice>>(
stream: Stream.periodic(Duration(seconds: 2))
.asyncMap((_) => FlutterBlue.instance.connectedDevices),
initialData: [],
builder: (c, snapshot) => Column(
children: snapshot.data!
.map((d) => ListTile(
title: Text(d.name),
subtitle: Text(d.id.toString()),
trailing: StreamBuilder<BluetoothDeviceState>(
stream: d.state,
initialData: BluetoothDeviceState.disconnected,
builder: (c, snapshot) {
if (snapshot.data ==
BluetoothDeviceState.connected) {
return RaisedButton(
child: Text('OPEN'),
onPressed: () => Navigator.of(context).push(
MaterialPageRoute(
builder: (context) =>
DeviceScreen(device: d))),
);
}
return Text(snapshot.data.toString());
},
),
))
.toList(),
),
),
StreamBuilder<List<ScanResult>>(
stream: FlutterBlue.instance.scanResults,
initialData: [],
builder: (c, snapshot) => Column(
children: snapshot.data!
.map(
(r) => ScanResultTile(
result: r,
onTap: () => Navigator.of(context)
.push(MaterialPageRoute(builder: (context) {
r.device.connect();
return DeviceScreen(device: r.device);
})),
),
)
.toList(),
),
),
],
),
),
),
floatingActionButton: StreamBuilder<bool>(
stream: FlutterBlue.instance.isScanning,
initialData: false,
builder: (c, snapshot) {
if (snapshot.data!) {
return FloatingActionButton(
child: Icon(Icons.stop),
onPressed: () => FlutterBlue.instance.stopScan(),
backgroundColor: Colors.red,
);
} else {
return FloatingActionButton(
child: Icon(Icons.search),
onPressed: () => FlutterBlue.instance
.startScan(timeout: Duration(seconds: 4)));
}
},
),
);
}
}
class DeviceScreen extends StatelessWidget {
const DeviceScreen({Key? key, required this.device}) : super(key: key);
final BluetoothDevice device;
List<int> _getRandomBytes() {
final math = Random();
return [
math.nextInt(255),
math.nextInt(255),
math.nextInt(255),
math.nextInt(255)
];
}
List<Widget> _buildServiceTiles(List<BluetoothService> services) {
return services
.map(
(s) => ServiceTile(
service: s,
characteristicTiles: s.characteristics
.map(
(c) => CharacteristicTile(
characteristic: c,
onReadPressed: () => c.read(),
onWritePressed: () async {
await c.write(_getRandomBytes(), withoutResponse: true);
await c.read();
},
onNotificationPressed: () async {
await c.setNotifyValue(!c.isNotifying);
await c.read();
},
descriptorTiles: c.descriptors
.map(
(d) => DescriptorTile(
descriptor: d,
onReadPressed: () => d.read(),
onWritePressed: () => d.write(_getRandomBytes()),
),
)
.toList(),
),
)
.toList(),
),
)
.toList();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(device.name),
actions: <Widget>[
StreamBuilder<BluetoothDeviceState>(
stream: device.state,
initialData: BluetoothDeviceState.connecting,
builder: (c, snapshot) {
VoidCallback? onPressed;
String text;
switch (snapshot.data) {
case BluetoothDeviceState.connected:
onPressed = () => device.disconnect();
text = 'DISCONNECT';
break;
case BluetoothDeviceState.disconnected:
onPressed = () => device.connect();
text = 'CONNECT';
break;
default:
onPressed = null;
text = snapshot.data.toString().substring(21).toUpperCase();
break;
}
return FlatButton(
onPressed: onPressed,
child: Text(
text,
style: Theme.of(context)
.primaryTextTheme
.button
?.copyWith(color: Colors.white),
));
},
)
],
),
body: SingleChildScrollView(
child: Column(
children: <Widget>[
StreamBuilder<BluetoothDeviceState>(
stream: device.state,
initialData: BluetoothDeviceState.connecting,
builder: (c, snapshot) => ListTile(
leading: (snapshot.data == BluetoothDeviceState.connected)
? Icon(Icons.bluetooth_connected)
: Icon(Icons.bluetooth_disabled),
title: Text(
'Device is ${snapshot.data.toString().split('.')[1]}.'),
subtitle: Text('${device.id}'),
trailing: StreamBuilder<bool>(
stream: device.isDiscoveringServices,
initialData: false,
builder: (c, snapshot) => IndexedStack(
index: snapshot.data! ? 1 : 0,
children: <Widget>[
IconButton(
icon: Icon(Icons.refresh),
onPressed: () => device.discoverServices(),
),
IconButton(
icon: SizedBox(
child: CircularProgressIndicator(
valueColor: AlwaysStoppedAnimation(Colors.grey),
),
width: 18.0,
height: 18.0,
),
onPressed: null,
)
],
),
),
),
),
StreamBuilder<int>(
stream: device.mtu,
initialData: 0,
builder: (c, snapshot) => ListTile(
title: Text('MTU Size'),
subtitle: Text('${snapshot.data} bytes'),
trailing: IconButton(
icon: Icon(Icons.edit),
onPressed: () => device.requestMtu(223),
),
),
),
StreamBuilder<List<BluetoothService>>(
stream: device.services,
initialData: [],
builder: (c, snapshot) {
return Column(
children: _buildServiceTiles(snapshot.data!),
);
},
),
],
),
),
);
}
}
and here the second Part:
// Copyright 2017, Paul DeMarco.
// All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'package:flutter/material.dart';
import 'package:flutter_blue/flutter_blue.dart';
class ScanResultTile extends StatelessWidget {
const ScanResultTile({Key? key, required this.result, this.onTap})
: super(key: key);
final ScanResult result;
final VoidCallback? onTap;
Widget _buildTitle(BuildContext context) {
if (result.device.name.length > 0) {
return Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
result.device.name,
overflow: TextOverflow.ellipsis,
),
Text(
result.device.id.toString(),
style: Theme.of(context).textTheme.caption,
)
],
);
} else {
return Text(result.device.id.toString());
}
}
Widget _buildAdvRow(BuildContext context, String title, String value) {
return Padding(
padding: EdgeInsets.symmetric(horizontal: 16.0, vertical: 4.0),
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(title, style: Theme.of(context).textTheme.caption),
SizedBox(
width: 12.0,
),
Expanded(
child: Text(
value,
style: Theme.of(context)
.textTheme
.caption
?.apply(color: Colors.black),
softWrap: true,
),
),
],
),
);
}
String getNiceHexArray(List<int> bytes) {
return '[${bytes.map((i) => i.toRadixString(16).padLeft(2, '0')).join(', ')}]'
.toUpperCase();
}
String getNiceManufacturerData(Map<int, List<int>> data) {
if (data.isEmpty) {
return 'N/A';
}
List<String> res = [];
data.forEach((id, bytes) {
res.add(
'${id.toRadixString(16).toUpperCase()}: ${getNiceHexArray(bytes)}');
});
return res.join(', ');
}
String getNiceServiceData(Map<String, List<int>> data) {
if (data.isEmpty) {
return 'N/A';
}
List<String> res = [];
data.forEach((id, bytes) {
res.add('${id.toUpperCase()}: ${getNiceHexArray(bytes)}');
});
return res.join(', ');
}
#override
Widget build(BuildContext context) {
return ExpansionTile(
title: _buildTitle(context),
leading: Text(result.rssi.toString()),
trailing: RaisedButton(
child: Text('CONNECT'),
color: Colors.black,
textColor: Colors.white,
onPressed: (result.advertisementData.connectable) ? onTap : null,
),
children: <Widget>[
_buildAdvRow(
context, 'Complete Local Name', result.advertisementData.localName),
_buildAdvRow(context, 'Tx Power Level',
'${result.advertisementData.txPowerLevel ?? 'N/A'}'),
_buildAdvRow(context, 'Manufacturer Data',
getNiceManufacturerData(result.advertisementData.manufacturerData)),
_buildAdvRow(
context,
'Service UUIDs',
(result.advertisementData.serviceUuids.isNotEmpty)
? result.advertisementData.serviceUuids.join(', ').toUpperCase()
: 'N/A'),
_buildAdvRow(context, 'Service Data',
getNiceServiceData(result.advertisementData.serviceData)),
],
);
}
}
class ServiceTile extends StatelessWidget {
final BluetoothService service;
final List<CharacteristicTile> characteristicTiles;
const ServiceTile(
{Key? key, required this.service, required this.characteristicTiles})
: super(key: key);
#override
Widget build(BuildContext context) {
if (characteristicTiles.length > 0) {
return ExpansionTile(
title: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text('Service'),
Text('0x${service.uuid.toString().toUpperCase().substring(4, 8)}',
style: Theme.of(context).textTheme.body1?.copyWith(
color: Theme.of(context).textTheme.caption?.color))
],
),
children: characteristicTiles,
);
} else {
return ListTile(
title: Text('Service'),
subtitle:
Text('0x${service.uuid.toString().toUpperCase().substring(4, 8)}'),
);
}
}
}
class CharacteristicTile extends StatelessWidget {
final BluetoothCharacteristic characteristic;
final List<DescriptorTile> descriptorTiles;
final VoidCallback? onReadPressed;
final VoidCallback? onWritePressed;
final VoidCallback? onNotificationPressed;
const CharacteristicTile(
{Key? key,
required this.characteristic,
required this.descriptorTiles,
this.onReadPressed,
this.onWritePressed,
this.onNotificationPressed})
: super(key: key);
#override
Widget build(BuildContext context) {
return StreamBuilder<List<int>>(
stream: characteristic.value,
initialData: characteristic.lastValue,
builder: (c, snapshot) {
final value = snapshot.data;
return ExpansionTile(
title: ListTile(
title: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text('Characteristic'),
Text(
'0x${characteristic.uuid.toString().toUpperCase().substring(4, 8)}',
style: Theme.of(context).textTheme.body1?.copyWith(
color: Theme.of(context).textTheme.caption?.color))
],
),
subtitle: Text(value.toString()),
contentPadding: EdgeInsets.all(0.0),
),
trailing: Row(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
IconButton(
icon: Icon(
Icons.file_download,
color: Theme.of(context).iconTheme.color?.withOpacity(0.5),
),
onPressed: onReadPressed,
),
IconButton(
icon: Icon(Icons.file_upload,
color: Theme.of(context).iconTheme.color?.withOpacity(0.5)),
onPressed: onWritePressed,
),
IconButton(
icon: Icon(
characteristic.isNotifying
? Icons.sync_disabled
: Icons.sync,
color: Theme.of(context).iconTheme.color?.withOpacity(0.5)),
onPressed: onNotificationPressed,
)
],
),
children: descriptorTiles,
);
},
);
}
}
class DescriptorTile extends StatelessWidget {
final BluetoothDescriptor descriptor;
final VoidCallback? onReadPressed;
final VoidCallback? onWritePressed;
const DescriptorTile(
{Key? key,
required this.descriptor,
this.onReadPressed,
this.onWritePressed})
: super(key: key);
#override
Widget build(BuildContext context) {
return ListTile(
title: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text('Descriptor'),
Text('0x${descriptor.uuid.toString().toUpperCase().substring(4, 8)}',
style: Theme.of(context)
.textTheme
.body1
?.copyWith(color: Theme.of(context).textTheme.caption?.color))
],
),
subtitle: StreamBuilder<List<int>>(
stream: descriptor.value,
initialData: descriptor.lastValue,
builder: (c, snapshot) => Text(snapshot.data.toString()),
),
trailing: Row(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
IconButton(
icon: Icon(
Icons.file_download,
color: Theme.of(context).iconTheme.color?.withOpacity(0.5),
),
onPressed: onReadPressed,
),
IconButton(
icon: Icon(
Icons.file_upload,
color: Theme.of(context).iconTheme.color?.withOpacity(0.5),
),
onPressed: onWritePressed,
)
],
),
);
}
}
class AdapterStateTile extends StatelessWidget {
const AdapterStateTile({Key? key, required this.state}) : super(key: key);
final BluetoothState state;
#override
Widget build(BuildContext context) {
return Container(
color: Colors.redAccent,
child: ListTile(
title: Text(
'Bluetooth adapter is ${state.toString().substring(15)}',
style: Theme.of(context).primaryTextTheme.subhead,
),
trailing: Icon(
Icons.error,
color: Theme.of(context).primaryTextTheme.subhead?.color,
),
),
);
}
}
please help me!!!