Added a text mapper to customize number text

lib/numberpicker.dart

@@ -7,6 +7,9 @@ import 'package:infinite_listview/infinite_listview.dart';
 
 /// Created by Marcin Szałek
 
+///Define a text mapper to transform the text displayed by the picker
+typedef String TextMapper(String numberText);
+
 ///NumberPicker is a widget designed to pick a number between #minValue and #maxValue
 class NumberPicker extends StatelessWidget {
   ///height of every list element for normal number picker
@@ -24,6 +27,7 @@ class NumberPicker extends StatelessWidget {
     @required this.minValue,
     @required this.maxValue,
     @required this.onChanged,
+    this.textMapper,
     this.itemExtent = kDefaultItemExtent,
     this.listViewHeight = kDefaultListViewCrossAxisSize,
     this.step = 1,
@@ -56,6 +60,7 @@ class NumberPicker extends StatelessWidget {
     @required this.minValue,
     @required this.maxValue,
     @required this.onChanged,
+    this.textMapper,
     this.itemExtent = kDefaultItemExtent,
     this.listViewWidth = kDefaultListViewCrossAxisSize,
     this.step = 1,
@@ -95,6 +100,7 @@ class NumberPicker extends StatelessWidget {
     @required this.minValue,
     @required this.maxValue,
     @required this.onChanged,
+    this.textMapper,
     this.decimalPlaces = 1,
     this.itemExtent = kDefaultItemExtent,
     this.listViewWidth = kDefaultListViewCrossAxisSize,
@@ -135,6 +141,9 @@ class NumberPicker extends StatelessWidget {
 
   ///max value user can pick
   final int maxValue;
+
+  ///build the text of each item on the picker
+  final TextMapper textMapper;
 
   ///inidcates how many decimal places to show
   /// e.g. 0=>[1,2,3...], 1=>[1.0, 1.1, 1.2...]  2=>[1.00, 1.01, 1.02...]
@@ -410,9 +419,10 @@ class NumberPicker extends StatelessWidget {
   }
 
   String getDisplayedValue(int value) {
-    return zeroPad
+    final text = zeroPad
         ? value.toString().padLeft(maxValue.toString().length, '0')
         : value.toString();
+    return textMapper != null ? textMapper(text) : text;
   }
 
   //

test/integer_numberpicker_test.dart

@@ -113,4 +113,16 @@ void main() {
       decoration: decoration,
     );
   });
+
+  testWidgets('Text mapper works', (WidgetTester tester) async {
+    await testMultipleValuesInPicker(
+        tester: tester,
+        minValue: 0,
+        maxValue: 10,
+        initialValue: 2,
+        scrollBy: 1,
+        textMapper: (text) => '$text days',
+        expectedDisplayValues: ['2 days', '3 days', '4 days']);
+  });
+
 }

test/test_utils.dart

@@ -22,6 +22,7 @@ Future<NumberPicker> testNumberPicker({
   int initialValue,
   int scrollBy,
   int step = 1,
+  TextMapper textMapper,
   int expectedValue,
   bool animateToItself = false,
   Axis axis = Axis.vertical,
@@ -40,6 +41,7 @@ Future<NumberPicker> testNumberPicker({
               minValue: minValue,
               maxValue: maxValue,
               step: step,
+              textMapper: textMapper,
               infiniteLoop: infiniteLoop,
               decoration: decoration,
               highlightSelectedValue: highlightSelectedValue,
@@ -50,6 +52,7 @@ Future<NumberPicker> testNumberPicker({
               minValue: minValue,
               maxValue: maxValue,
               step: step,
+              textMapper: textMapper,
               decoration: decoration,
               highlightSelectedValue: highlightSelectedValue,
               onChanged: (newValue) => setState(() => value = newValue),
@@ -85,6 +88,7 @@ Future<NumberPicker> testMultipleValuesInPicker({
   int initialValue,
   int scrollBy,
   int step = 1,
+  TextMapper textMapper,
   bool animateToItself = false,
   Axis axis = Axis.vertical,
   bool zeroPad = false,
@@ -102,6 +106,7 @@ Future<NumberPicker> testMultipleValuesInPicker({
               minValue: minValue,
               maxValue: maxValue,
               step: step,
+              textMapper: textMapper,
               infiniteLoop: infiniteLoop,
               onChanged: (newValue) => setState(() => value = newValue),
               zeroPad: zeroPad,
@@ -111,6 +116,7 @@ Future<NumberPicker> testMultipleValuesInPicker({
               minValue: minValue,
               maxValue: maxValue,
               step: step,
+              textMapper: textMapper,
               zeroPad: zeroPad,
               onChanged: (newValue) => setState(() => value = newValue),
             );