Print multiple times.

example/blue/lib/main.dart

+import 'dart:async';
 import 'dart:convert';
 import 'package:flutter/material.dart';
 import 'package:flutter_bluetooth_basic/flutter_bluetooth_basic.dart';
@@ -29,20 +30,60 @@ class MyHomePage extends StatefulWidget {
 class _MyHomePageState extends State<MyHomePage> {
   BluetoothManager bluetoothManager = BluetoothManager.instance;
   bool _connected = false;
+  bool _isScanning = false;
+  List<BluetoothDevice> _devices = [];
+  StreamSubscription _scanResultsSubscription;
+  StreamSubscription _isScanningSubscription;
+  // Buffers used for rescan before sending the data
+  List<BluetoothDevice> _bufDevices = [];
+  StreamSubscription _bufScanSubscription;
+  // StreamSubscription _isScanningSubscription;
 
-  Future sleep3() {
-    return Future<dynamic>.delayed(const Duration(seconds: 7), () => "1");
+  void _startScanDevices() {
+    setState(() {
+      _devices = [];
+    });
+
+    bluetoothManager.startScan(timeout: Duration(seconds: 4));
+
+    _scanResultsSubscription =
+        bluetoothManager.scanResults.listen((devices) async {
+      setState(() {
+        _devices = devices;
+      });
+    });
+
+    _isScanningSubscription =
+        bluetoothManager.isScanning.listen((isScanningCurrent) async {
+      // if isScanning value changed (scan just stopped)
+      if (_isScanning && !isScanningCurrent) {
+        _scanResultsSubscription.cancel();
+        _isScanningSubscription.cancel();
+      }
+      setState(() {
+        _isScanning = isScanningCurrent;
+      });
+    });
+  }
+
+  void _stopScanDevices() {
+    bluetoothManager.stopScan();
+  }
+
+  Future _sleep(int seconds) {
+    return Future<dynamic>.delayed(Duration(seconds: seconds));
   }
 
   void _testPrint(BluetoothDevice printer) async {
-    // print('Test print.... name: ${printer.name}');
-    if (printer != null && printer.address != null) {
+    // We have to rescan before connecting, otherwise we can connect only once
+    await bluetoothManager.startScan(timeout: Duration(seconds: 1));
+    await bluetoothManager.stopScan();
+
     // Connect
     await bluetoothManager.connect(printer);
 
     // Subscribe to the events
     bluetoothManager.state.listen((state) async {
-        // print('**************cur device status: $state');
       switch (state) {
         case BluetoothManager.CONNECTED:
           print('********************* CONNECTED');
@@ -51,14 +92,13 @@ class _MyHomePageState extends State<MyHomePage> {
             print('@@@@SEND DATA......');
             final List<int> bytes = latin1.encode('test!\n\n\n').toList();
             await bluetoothManager.writeData(bytes);
-              // print('################## print send #############');
-              // bluetoothManager.
+            // TODO show message "Data sent"
           }
-            sleep3().then((dynamic printer) async {
+          // TODO sending disconnect signal should be event-based
+          _sleep(3).then((dynamic printer) async {
             print('@@@@DISCONNECTING......');
             await bluetoothManager.disconnect();
           });
-
           _connected = true;
           break;
         case BluetoothManager.DISCONNECTED:
@@ -69,11 +109,6 @@ class _MyHomePageState extends State<MyHomePage> {
           break;
       }
     });
-
-      // TODO show message "Data sent"
-    } else {
-      // TODO show message "Can't connect to the device"
-    }
   }
 
   @override
@@ -82,13 +117,11 @@ class _MyHomePageState extends State<MyHomePage> {
       appBar: AppBar(
         title: Text(widget.title),
       ),
-      body: StreamBuilder<List<BluetoothDevice>>(
-        stream: bluetoothManager.scanResults,
-        initialData: [],
-        builder: (c, snapshot) => Column(
-          children: snapshot.data
-              .map((d) => InkWell(
-                    onTap: () => _testPrint(d),
+      body: ListView.builder(
+          itemCount: _devices.length,
+          itemBuilder: (BuildContext context, int index) {
+            return InkWell(
+              onTap: () => _testPrint(_devices[index]),
               child: Column(
                 children: <Widget>[
                   Container(
@@ -104,8 +137,8 @@ class _MyHomePageState extends State<MyHomePage> {
                             crossAxisAlignment: CrossAxisAlignment.start,
                             mainAxisAlignment: MainAxisAlignment.center,
                             children: <Widget>[
-                                    Text(d.name ?? ''),
-                                    Text(d.address),
+                              Text(_devices[index].name ?? ''),
+                              Text(_devices[index].address),
                               Text(
                                 'Click to print a test receipt',
                                 style: TextStyle(color: Colors.grey[700]),
@@ -119,27 +152,17 @@ class _MyHomePageState extends State<MyHomePage> {
                   Divider(),
                 ],
               ),
-                  ))
-              .toList(),
-        ),
-      ),
-      floatingActionButton: StreamBuilder<bool>(
-        stream: bluetoothManager.isScanning,
-        initialData: false,
-        builder: (c, snapshot) {
-          if (snapshot.data) {
-            return FloatingActionButton(
+            );
+          }),
+      floatingActionButton: _isScanning
+          ? FloatingActionButton(
               child: Icon(Icons.stop),
-              onPressed: () => bluetoothManager.stopScan(),
+              onPressed: _stopScanDevices,
               backgroundColor: Colors.red,
-            );
-          } else {
-            return FloatingActionButton(
+            )
+          : FloatingActionButton(
               child: Icon(Icons.search),
-                onPressed: () =>
-                    bluetoothManager.startScan(timeout: Duration(seconds: 4)));
-          }
-        },
+              onPressed: _startScanDevices,
             ),
     );
   }