create gesture recognizers on attach and dispose on detach to avoid leaks (#42076)

packages/flutter/lib/src/rendering/editable.dart

@@ -229,11 +229,6 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
     assert(_showCursor != null);
     assert(!_showCursor.value || cursorColor != null);
     this.hasFocus = hasFocus ?? false;
-    _tap = TapGestureRecognizer(debugOwner: this)
-      ..onTapDown = _handleTapDown
-      ..onTap = _handleTap;
-    _longPress = LongPressGestureRecognizer(debugOwner: this)
-      ..onLongPress = _handleLongPress;
   }
 
   /// Character used to obscure text if [obscureText] is true.
@@ -1173,12 +1168,18 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   @override
   void attach(PipelineOwner owner) {
     super.attach(owner);
+    _tap = TapGestureRecognizer(debugOwner: this)
+      ..onTapDown = _handleTapDown
+      ..onTap = _handleTap;
+    _longPress = LongPressGestureRecognizer(debugOwner: this)..onLongPress = _handleLongPress;
     _offset.addListener(markNeedsPaint);
     _showCursor.addListener(markNeedsPaint);
   }
 
   @override
   void detach() {
+    _tap.dispose();
+    _longPress.dispose();
     _offset.removeListener(markNeedsPaint);
     _showCursor.removeListener(markNeedsPaint);
     if (_listenerAttached)

packages/flutter/test/rendering/editable_gesture_test.dart

+// Copyright 2017 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 'package:flutter/gestures.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mockito/mockito.dart';
+
+void main() {
+  setUp(() => _GestureBindingSpy());
+
+  test('attach and detach correctly handle gesture', () {
+    final TextSelectionDelegate delegate = FakeEditableTextState();
+    final RenderEditable editable = RenderEditable(
+      backgroundCursorColor: Colors.grey,
+      selectionColor: Colors.black,
+      textDirection: TextDirection.ltr,
+      cursorColor: Colors.red,
+      offset: ViewportOffset.zero(),
+      textSelectionDelegate: delegate,
+      text: const TextSpan(
+        text: 'test',
+        style: TextStyle(
+          height: 1.0, fontSize: 10.0, fontFamily: 'Ahem',
+        ),
+      ),
+      startHandleLayerLink: LayerLink(),
+      endHandleLayerLink: LayerLink(),
+      selection: const TextSelection(
+        baseOffset: 0,
+        extentOffset: 3,
+        affinity: TextAffinity.upstream,
+      ),
+      onSelectionChanged: (_, __, ___) { },
+    );
+    final PipelineOwner owner = PipelineOwner(onNeedVisualUpdate: () { });
+    final _PointerRouterSpy spy = GestureBinding.instance.pointerRouter;
+    editable.attach(owner);
+    // This should register pointer into GestureBinding.instance.pointerRouter.
+    editable.handleEvent(const PointerDownEvent(), BoxHitTestEntry(editable, const Offset(10,10)));
+    expect(spy.routeCount, greaterThan(0));
+    editable.detach();
+    expect(spy.routeCount, 0);
+  });
+}
+
+class _GestureBindingSpy extends AutomatedTestWidgetsFlutterBinding {
+  final PointerRouter _testPointerRouter = _PointerRouterSpy();
+
+  @override
+  PointerRouter get pointerRouter => _testPointerRouter;
+}
+
+class FakeEditableTextState extends TextSelectionDelegate with Mock { }
+
+class _PointerRouterSpy extends PointerRouter {
+  int routeCount = 0;
+  @override
+  void addRoute(int pointer, PointerRoute route, [Matrix4 transform]) {
+    super.addRoute(pointer, route, transform);
+    routeCount++;
+  }
+
+  @override
+  void removeRoute(int pointer, PointerRoute route) {
+    super.removeRoute(pointer, route);
+    routeCount--;
+  }
+}

packages/flutter/test/rendering/editable_test.dart

@@ -2,11 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
-import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/services.dart';
-import 'package:flutter/material.dart';
-import 'package:flutter/foundation.dart';
+import 'package:flutter_test/flutter_test.dart';
 
 import '../rendering/mock_canvas.dart';
 import '../rendering/recording_canvas.dart';