Update timecard File

MainAppDMT/lib/screens/timecard/timercard.dart

+import 'dart:async';
+import 'package:flutter/material.dart';
+
+class TimerCard extends StatefulWidget {
+  const TimerCard({Key key}) : super(key: key);
+
+  @override
+  TimerCardState createState() => TimerCardState();
+}
+
+class TimerCardState extends State<TimerCard> {
+  // The timer's value shown on app's UI.
+  int _timerValue = 0;
+  bool _paused = true;
+  // A stream that updates every second. The stream's value is the number of
+  // seconds elapsed since the app is started. We simply print this stream value
+  // out in command-line. The value shown on UI is this._timerValue.
+  final Stream<int> _periodicStream =
+      Stream.periodic(Duration(milliseconds: 1000), (i) => i);
+  // Record of the latest stream value that we saw. Because the StreamBuilder is
+  // rebuilt when we call setState(), and in the re-build we shouldn't increment
+  // this._timerValue if the latest snapshot's value hasn't changed.
+  int _previousStreamValue = 0;
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      alignment: Alignment.center,
+      margin: EdgeInsets.all(8),
+      child: StreamBuilder(
+        stream: this._periodicStream,
+        builder: (BuildContext context, AsyncSnapshot<int> snapshot) {
+          if (snapshot.hasData) {
+            if (snapshot.data != this._previousStreamValue) {
+              print('Latest snapshot from stream: ${snapshot.data}');
+              this._previousStreamValue = snapshot.data;
+              if (!_paused) {
+                this._timerValue++;
+              }
+            }
+          }
+          return Column(
+            mainAxisSize: MainAxisSize.min,
+            children: <Widget>[
+              Card(child: _buildTimerUI()),
+            ],
+          );
+        },
+      ),
+    );
+  }
+
+  Widget _buildTimerUI() {
+    return Column(
+      children: <Widget>[
+        Text(
+          '$_timerValue',
+          style: Theme.of(context).textTheme.headline4,
+        ),
+        ButtonBar(
+          mainAxisSize: MainAxisSize.min,
+          children: <Widget>[
+            IconButton(
+              icon: Icon(this._paused ? Icons.play_arrow : Icons.pause),
+              onPressed: () => setState(() => this._paused = !this._paused),
+            ),
+            IconButton(
+              icon: Icon(Icons.stop),
+              onPressed: () => setState(
+                () {
+                  this._timerValue = 0;
+                  this._paused = true;
+                },
+              ),
+            ),
+          ],
+        ),
+      ],
+    );
+  }
+}