Added TextField.onTap() (#24536)

packages/flutter/lib/src/material/text_field.dart

@@ -127,6 +127,7 @@ class TextField extends StatefulWidget {
     this.keyboardAppearance,
     this.scrollPadding = const EdgeInsets.all(20.0),
     this.enableInteractiveSelection = true,
+    this.onTap,
   }) : assert(textAlign != null),
        assert(autofocus != null),
        assert(obscureText != null),
@@ -144,9 +145,44 @@ class TextField extends StatefulWidget {
   /// If null, this widget will create its own [TextEditingController].
   final TextEditingController controller;
 
-  /// Controls whether this widget has keyboard focus.
+  /// Defines the keyboard focus for this widget.
+  ///
+  /// The [focusNode] is a long-lived object that's typically managed by a
+  /// [StatefulWidget] parent. See [FocusNode] for more information.
+  ///
+  /// To give the keyboard focus to this widget, provide a [focusNode] and then
+  /// use the current [FocusScope] to request the focus:
+  ///
+  /// ```dart
+  /// FocusScope.of(context).requestFocus(myFocusNode);
+  /// ```
+  ///
+  /// This happens automatically when the widget is tapped.
+  ///
+  /// To be notified when the widget gains or loses the focus, add a listener
+  /// to the [focusNode]:
+  ///
+  /// ```dart
+  /// focusNode.addListener(() { print(myFocusNode.hasFocus); });
+  /// ```
   ///
   /// If null, this widget will create its own [FocusNode].
+  ///
+  /// ## Keyboard
+  ///
+  /// Requesting the focus will typically cause the the keyboard to be shown
+  /// if it's not showing already.
+  ///
+  /// On Android, the user can hide the keyboard - withouth changing the focus -
+  /// with the system back button. They can restore the keyboard's visibility
+  /// by tapping on a text field.  The user might hide the keyboard and
+  /// switch to a physical keyboard, or they might just need to get it
+  /// out of the way for a moment, to expose something it's
+  /// obscuring. In this case requesting the focus again will not
+  /// cause the focus to change, and will not make the keyboard visible.
+  ///
+  /// This widget builds an [EditableText] and will ensure that the keyboard is
+  /// showing when it is tapped by calling [EditableTextState.requestKeyboard()].
   final FocusNode focusNode;
 
   /// The decoration to show around the text field.
@@ -298,6 +334,26 @@ class TextField extends StatefulWidget {
   /// {@macro flutter.widgets.editableText.enableInteractiveSelection}
   final bool enableInteractiveSelection;
 
+  /// Called when the user taps on this textfield.
+  ///
+  /// The textfield builds a [GestureDetector] to handle input events like tap,
+  /// to trigger focus requests, to move the caret, adjust the selection, etc.
+  /// Handling some of those events by wrapping the textfield with a competing
+  /// GestureDetector is problematic.
+  ///
+  /// To unconditionally handle taps, without interfering with the textfield's
+  /// internal gesture detector, provide this callback.
+  ///
+  /// If the textfield is created with [enabled] false, taps will not be
+  /// recognized.
+  ///
+  /// To be notified when the textfield gains or loses the focus, provide a
+  /// [focusNode] and add a listener to that.
+  ///
+  /// To listen to arbitrary pointer events without competing with the
+  /// textfield's internal gesture detector, use a [Listener].
+  final GestureTapCallback onTap;
+
   @override
   _TextFieldState createState() => _TextFieldState();
 
@@ -306,6 +362,7 @@ class TextField extends StatefulWidget {
     super.debugFillProperties(properties);
     properties.add(DiagnosticsProperty<TextEditingController>('controller', controller, defaultValue: null));
     properties.add(DiagnosticsProperty<FocusNode>('focusNode', focusNode, defaultValue: null));
+    properties.add(DiagnosticsProperty<bool>('enabled', enabled, defaultValue: null));
     properties.add(DiagnosticsProperty<InputDecoration>('decoration', decoration));
     properties.add(DiagnosticsProperty<TextInputType>('keyboardType', keyboardType, defaultValue: TextInputType.text));
     properties.add(DiagnosticsProperty<TextStyle>('style', style, defaultValue: null));
@@ -315,6 +372,7 @@ class TextField extends StatefulWidget {
     properties.add(IntProperty('maxLines', maxLines, defaultValue: 1));
     properties.add(IntProperty('maxLength', maxLength, defaultValue: null));
     properties.add(FlagProperty('maxLengthEnforced', value: maxLengthEnforced, ifTrue: 'max length enforced'));
+    properties.add(DiagnosticsProperty<GestureTapCallback>('onTap', onTap, defaultValue: false));
   }
 }
 
@@ -453,6 +511,8 @@ class _TextFieldState extends State<TextField> with AutomaticKeepAliveClientMixi
       _renderEditable.handleTap();
     _requestKeyboard();
     _confirmCurrentSplash();
+    if (widget.onTap != null)
+      widget.onTap();
   }
 
   void _handleTapCancel() {

packages/flutter/test/material/text_field_test.dart

@@ -67,11 +67,13 @@ Widget overlay({ Widget child }) {
         child: Overlay(
           initialEntries: <OverlayEntry>[
             OverlayEntry(
-              builder: (BuildContext context) => Center(
-                child: Material(
-                  child: child,
-                ),
-              ),
+              builder: (BuildContext context) {
+                return Center(
+                  child: Material(
+                    child: child,
+                  ),
+                );
+              },
             ),
           ],
         ),
@@ -3341,4 +3343,43 @@ void main() {
     expect(minOffset, 0.0);
     expect(maxOffset, 50.0);
   });
+
+  testWidgets('onTap is called upon tap', (WidgetTester tester) async {
+    int tapCount = 0;
+    await tester.pumpWidget(
+      overlay(
+        child: TextField(
+          onTap: () {
+            tapCount += 1;
+          },
+        ),
+      ),
+    );
+
+    expect(tapCount, 0);
+    await tester.tap(find.byType(TextField));
+    await tester.tap(find.byType(TextField));
+    await tester.tap(find.byType(TextField));
+    expect(tapCount, 3);
+  });
+
+  testWidgets('onTap is not called, field is disabled', (WidgetTester tester) async {
+    int tapCount = 0;
+    await tester.pumpWidget(
+      overlay(
+        child: TextField(
+          enabled: false,
+          onTap: () {
+            tapCount += 1;
+          },
+        ),
+      ),
+    );
+
+    expect(tapCount, 0);
+    await tester.tap(find.byType(TextField));
+    await tester.tap(find.byType(TextField));
+    await tester.tap(find.byType(TextField));
+    expect(tapCount, 0);
+  });
 }