Fix #1471 Add double tap gesture

packages/flutter/lib/gestures.dart

@@ -8,6 +8,7 @@ library gestures;
 export 'src/gestures/arena.dart';
 export 'src/gestures/constants.dart';
 export 'src/gestures/drag.dart';
+export 'src/gestures/double_tap.dart';
 export 'src/gestures/long_press.dart';
 export 'src/gestures/pointer_router.dart';
 export 'src/gestures/recognizer.dart';

packages/flutter/lib/src/gestures/double_tap.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:sky' as sky;
+
+import 'package:sky/src/gestures/arena.dart';
+import 'package:sky/src/gestures/constants.dart';
+import 'package:sky/src/gestures/recognizer.dart';
+import 'package:sky/src/gestures/tap.dart';
+
+class DoubleTapGestureRecognizer extends PrimaryPointerGestureRecognizer {
+  DoubleTapGestureRecognizer({ PointerRouter router, this.onDoubleTap })
+    : super(router: router, deadline: kTapTimeout);
+
+  GestureTapListener onDoubleTap;
+  int _numTaps = 0;
+  Timer _longTimer;
+
+  void resolve(GestureDisposition disposition) {
+    super.resolve(disposition);
+    if (disposition == GestureDisposition.rejected) {
+      _numTaps = 0;
+    }
+  }
+
+  void didExceedDeadline() {
+    stopTrackingPointer(primaryPointer);
+    resolve(GestureDisposition.rejected);
+  }
+
+  void didExceedLongDeadline() {
+    _numTaps = 0;
+    _longTimer = null;
+  }
+
+  void handlePrimaryPointer(sky.PointerEvent event) {
+    if (event.type == 'pointerup') {
+      _numTaps++;
+      if (_numTaps == 1) {
+        _longTimer = new Timer(kDoubleTapTimeout, didExceedLongDeadline);
+      } else if (_numTaps == 2) {
+        resolve(GestureDisposition.accepted);
+        onDoubleTap();
+      }
+    }
+  }
+
+
+}

packages/flutter/lib/src/gestures/recognizer.dart

@@ -99,11 +99,13 @@ abstract class PrimaryPointerGestureRecognizer extends GestureRecognizer {
     assert(state != GestureRecognizerState.ready);
     if (state == GestureRecognizerState.possible && event.pointer == primaryPointer) {
       // TODO(abarth): Maybe factor the slop handling out into a separate class?
-      if (event.type == 'pointermove' && _getDistance(event) > kTouchSlop)
+      if (event.type == 'pointermove' && _getDistance(event) > kTouchSlop) {
         resolve(GestureDisposition.rejected);
-      else
+        stopTrackingPointer(event.pointer);
+      } else {
         handlePrimaryPointer(event);
       }
+    }
     stopTrackingIfPointerNoLongerDown(event);
   }
 

packages/flutter/lib/src/gestures/tap.dart

@@ -5,16 +5,22 @@
 import 'dart:sky' as sky;
 
 import 'package:sky/src/gestures/arena.dart';
+import 'package:sky/src/gestures/constants.dart';
 import 'package:sky/src/gestures/recognizer.dart';
 
 typedef void GestureTapListener();
 
 class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
   TapGestureRecognizer({ PointerRouter router, this.onTap })
-    : super(router: router);
+    : super(router: router, deadline: kTapTimeout);
 
   GestureTapListener onTap;
 
+  void didExceedDeadline() {
+    stopTrackingPointer(primaryPointer);
+    resolve(GestureDisposition.rejected);
+  }
+
   void handlePrimaryPointer(sky.PointerEvent event) {
     if (event.type == 'pointerup') {
       resolve(GestureDisposition.accepted);

packages/flutter/lib/src/widgets/gesture_detector.dart

@@ -14,6 +14,7 @@ class GestureDetector extends StatefulComponent {
     Key key,
     this.child,
     this.onTap,
+    this.onDoubleTap,
     this.onShowPress,
     this.onLongPress,
     this.onVerticalDragStart,
@@ -32,6 +33,7 @@ class GestureDetector extends StatefulComponent {
 
   final Widget child;
   final GestureTapListener onTap;
+  final GestureTapListener onDoubleTap;
   final GestureShowPressListener onShowPress;
   final GestureLongPressListener onLongPress;
 
@@ -69,6 +71,13 @@ class GestureDetectorState extends State<GestureDetector> {
     return _tap;
   }
 
+  DoubleTapGestureRecognizer _doubleTap;
+  DoubleTapGestureRecognizer _ensureDoubleTap() {
+    if (_doubleTap == null)
+      _doubleTap = new DoubleTapGestureRecognizer(router: _router);
+    return _doubleTap;
+  }
+
   ShowPressGestureRecognizer _showPress;
   ShowPressGestureRecognizer _ensureShowPress() {
     if (_showPress == null)
@@ -115,6 +124,7 @@ class GestureDetectorState extends State<GestureDetector> {
 
   void dispose() {
     _tap = _ensureDisposed(_tap);
+    _doubleTap = _ensureDisposed(_doubleTap);
     _showPress = _ensureDisposed(_showPress);
     _longPress = _ensureDisposed(_longPress);
     _verticalDrag = _ensureDisposed(_verticalDrag);
@@ -126,6 +136,7 @@ class GestureDetectorState extends State<GestureDetector> {
 
   void didUpdateConfig(GestureDetector oldConfig) {
     _syncTap();
+    _syncDoubleTap();
     _syncShowPress();
     _syncLongPress();
     _syncVerticalDrag();
@@ -141,6 +152,13 @@ class GestureDetectorState extends State<GestureDetector> {
       _ensureTap().onTap = config.onTap;
   }
 
+  void _syncDoubleTap() {
+    if (config.onDoubleTap == null)
+      _doubleTap = _ensureDisposed(_doubleTap);
+    else
+      _ensureDoubleTap().onDoubleTap = config.onDoubleTap;
+  }
+
   void _syncShowPress() {
     if (config.onShowPress == null)
       _showPress = _ensureDisposed(_showPress);
@@ -207,6 +225,8 @@ class GestureDetectorState extends State<GestureDetector> {
   void _handlePointerDown(sky.PointerEvent event) {
     if (_tap != null)
       _tap.addPointer(event);
+    if (_doubleTap != null)
+      _doubleTap.addPointer(event);
     if (_showPress != null)
       _showPress.addPointer(event);
     if (_longPress != null)