add the Draggable,DragTarget widget.

Author: nb312

lib/const/page_item_const.dart

@@ -252,4 +252,9 @@ const PAGE_ITEMS = [
     "img": PageImage.FLUTTER_OPEN,
     "click": PageName.ANIM_OPACITY,
   },
+  {
+    "title": PageName.INTER_DRAG,
+    "img": PageImage.FLUTTER_OPEN,
+    "click": PageName.INTER_DRAG,
+  },
 ];

lib/const/page_name_const.dart

@@ -55,4 +55,5 @@ class PageName {
   static const ANIM_WIDGET = "AnimatedWidget";
   static const ANIM_PYH_MODEL = "PyhModel";
   static const ANIM_OPACITY = "OpacityPage";
+  static const INTER_DRAG = "Draggable";
 }

lib/main.dart

@@ -69,6 +69,7 @@ class FlutterOpenApp extends StatelessWidget {
         PageName.ANIM_WIDGET: (context) => AnimWidgetPage(),
         PageName.ANIM_PYH_MODEL: (context) => PyhModelPage(),
         PageName.ANIM_OPACITY: (context) => AnimOpacityPage(),
+        PageName.INTER_DRAG: (context) => DraggablePage(),
       },
     );
   }

lib/page/_page.dart

@@ -36,3 +36,4 @@ export 'layoutsingle/_layout_single.dart';
 export 'muti/_muti.dart';
 export 'assets/_assets.dart';
 export 'anim/_anim.dart';
+export 'interation/_interaction.dart';

lib/page/interation/DraggablePage.dart

@@ -0,0 +1,80 @@
+///
+/// Created by NieBin on 2019/6/11
+/// Github: https://github.com/nb312
+/// Email: niebin312@gmail.com
+///
+import "package:flutter/material.dart";
+import "package:flutter_widgets/const/_const.dart";
+
+class DraggablePage extends StatefulWidget {
+  @override
+  _DragState createState() => _DragState();
+}
+
+class _DragState extends State<DraggablePage> {
+  String _value = "";
+
+  Widget _draggable(String _data) => Draggable<String>(
+        child: Text(
+          "$_data",
+          style: TextStyle(color: RED_LIGHT, fontSize: 30),
+        ),
+        feedback: Text(
+          "$_data",
+          style: TextStyle(color: BLUE_DEEP),
+        ),
+        childWhenDragging: Container(),
+        maxSimultaneousDrags: 1,
+        onDragCompleted: () {
+          print("Complete.");
+        },
+        onDragStarted: () {
+          print("Start");
+        },
+        onDraggableCanceled: (v, off) {
+          print("Cancel");
+        },
+        data: _data,
+      );
+
+  Widget _target() => DragTarget<String>(
+        builder: (context, List<String> candidateData, rejectedData) =>
+            Container(
+              constraints: BoxConstraints.expand(height: 100),
+              color: GREEN,
+              alignment: Alignment.center,
+              child: Text(
+                candidateData.length > 0 ? candidateData[0] : _value,
+                style: TextStyle(color: Colors.white, fontSize: 30),
+              ),
+            ),
+        onAccept: (value) {
+          print("Accept value= $value");
+          _value = value;
+        },
+        onLeave: (value) {
+          print("leave = $value");
+        },
+        onWillAccept: (value) {
+          print("Will Accept: value = $value");
+          return true;
+        },
+      );
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+        appBar: AppBar(
+          title: Text(PageName.INTER_DRAG),
+        ),
+        body: Column(
+          children: <Widget>[
+            Text(" You should drag the text and put it into the green area,"
+                "then you can see the text changed."),
+            _draggable("Hello"),
+            _draggable("World"),
+            _target(),
+          ],
+        ));
+  }
+}

lib/page/interation/_interaction.dart

@@ -0,0 +1,6 @@
+///
+/// Created by NieBin on 2019/6/11
+/// Github: https://github.com/nb312
+/// Email: niebin312@gmail.com
+///
+export "DraggablePage.dart";