implemented tip calculator example

tip_calculator/lib/main.dart

@@ -0,0 +1,65 @@
+import 'package:flutter/material.dart';
+
+void main() {
+  runApp(new MaterialApp(title: 'Tip Calculator', home: new TipCalculator()));
+}
+
+class TipCalculator extends StatelessWidget {
+  double billAmount = 0.0;
+  double tipPercentage = 0.0;
+
+  @override
+  Widget build(BuildContext context) {
+    // Create first input field
+    TextField billAmountField = new TextField(
+      keyboardType: TextInputType.number,
+      onChanged: (String value) {
+        try {
+          billAmount = double.parse(value);
+        } catch (exception) {
+          billAmount = 0.0;
+        }
+      },
+      decoration: new InputDecoration(labelText: "Bill amount(\$)"),
+    );
+
+    // Create another input field
+    TextField tipPercentageField = new TextField(
+        decoration: new InputDecoration(labelText: "Tip %", hintText: "15"),
+        keyboardType: TextInputType.number,
+        onChanged: (String value) {
+          try {
+            tipPercentage = double.parse(value);
+          } catch (exception) {
+            tipPercentage = 0.0;
+          }
+        });
+
+    // Create button
+    RaisedButton calculateButton = new RaisedButton(
+        child: new Text("Calculate"),
+        onPressed: () {
+          // Calculate tip and total
+          double calculatedTip = billAmount * tipPercentage / 100.0;
+          double total = billAmount + calculatedTip;
+
+          // Generate dialog
+          AlertDialog dialog = new AlertDialog(
+              content: new Text("Tip: \$$calculatedTip \n"
+                  "Total: \$$total"));
+
+          // Show dialog
+          showDialog(context: context, child: dialog);
+        });
+
+    Container container = new Container(
+        padding: const EdgeInsets.all(16.0),
+        child: new Column(
+            children: [billAmountField, tipPercentageField, calculateButton]));
+
+    AppBar appBar = new AppBar(title: new Text("Tip Calculator"));
+
+    Scaffold scaffold = new Scaffold(appBar: appBar, body: container);
+    return scaffold;
+  }
+}