GestureAbout.dart

import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter_starter_notes/component/CommonTitle.dart';

class GestureAbout extends StatelessWidget {
  GestureAbout({Key key, this.title});

  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: SingleChildScrollView(
        child: Column(
          children: <Widget>[
            CommonTitle('Gesture 点击、双击、长按'),
            GestureDetectorTestRoute(),
            CommonTitle('Gesture 拖动、滑动'),
            Container(
              child: _Drag(),
              height: 150,
              width: double.infinity,
            ),
            CommonTitle('Gesture 单一方向拖动'),
            Container(
              child: _DragVertical(),
              height: 150,
              width: double.infinity,
            ),
            CommonTitle('Gesture 缩放'),
            _ScaleTestRoute(),
            CommonTitle('GestureRecognizer 介绍与示例'),
            Container(
              padding: EdgeInsets.all(16),
              child: Text(
                  "GestureDetector内部是使用一个或多个GestureRecognizer来识别各种手势的，而GestureRecognizer的作用就是通过Listener来将原始指针事件转换为语义手势，GestureDetector直接可以接收一个子Widget。"),
            ),
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: _GestureRecognizerTestRoute(),
            ),
            CommonTitle('手势竞争与冲突'),
            Container(
              padding: EdgeInsets.all(16),
              child: Text(
                  "Flutter中的手势识别引入了一个Arena的概念，Arena直译为“竞技场”的意思，每一个手势识别器（GestureRecognizer）都是一个“竞争者”（GestureArenaMember），当发生滑动事件时，他们都要在“竞技场”去竞争本次事件的处理权，而最终只有一个“竞争者”会胜出(win)。"),
            ),
            Container(
                height: 150,
                width: double.infinity,
                child: BothDirectionTestRoute()),
            Container(
              padding: EdgeInsets.all(16),
              child: Text(
                  "由于手势竞争最终只有一个胜出者，所以，当有多个手势识别器时，可能会产生冲突。假设有一个widget，它可以左右拖动，现在我们也想检测在它上面手指按下和抬起的事件,下面的例子会有冲突"),
            ),
            Container(
                height: 150,
                width: double.infinity,
                child: GestureConflictTestRoute()),
            Container(
              padding: EdgeInsets.all(16),
              child: Text(
                  "手势冲突只是手势级别的，而手势是对原始指针的语义化的识别，所以在遇到复杂的冲突场景时，都可以通过Listener直接识别原始指针事件来解决冲突。下面的例子用 Listener 成功解决冲突"),
            ),
            Container(
                height: 150,
                width: double.infinity,
                child: FixGestureConflictByListenerRoute()),
          ],
        ),
      ),
    );
  }
}

class GestureDetectorTestRoute extends StatefulWidget {
  @override
  _GestureDetectorTestRouteState createState() =>
      new _GestureDetectorTestRouteState();
}

class _GestureDetectorTestRouteState extends State<GestureDetectorTestRoute> {
  String _operation = "No Gesture detected!"; //保存事件名
  @override
  Widget build(BuildContext context) {
    return Center(
      child: GestureDetector(
        child: Container(
          alignment: Alignment.center,
          color: Colors.blue,
          width: 200.0,
          height: 100.0,
          child: Text(
            _operation,
            style: TextStyle(color: Colors.white),
          ),
        ),
        onTap: () => updateText("Tap"), //点击
        onDoubleTap: () => updateText("DoubleTap"), //双击
        onLongPress: () => updateText("LongPress"), //长按
      ),
    );
  }

  void updateText(String text) {
    //更新显示的事件名
    setState(() {
      _operation = text;
    });
  }
}

class _Drag extends StatefulWidget {
  @override
  _DragState createState() => new _DragState();
}

class _DragState extends State<_Drag> with SingleTickerProviderStateMixin {
  double _top = 0.0; //距顶部的偏移
  double _left = 0.0; //距左边的偏移

  @override
  Widget build(BuildContext context) {
    return Stack(
      fit: StackFit.expand,
      children: <Widget>[
        Positioned(
          top: _top,
          left: _left,
          child: GestureDetector(
            child: CircleAvatar(child: Text("A")),
            //手指按下时会触发此回调
            onPanDown: (DragDownDetails e) {
              //打印手指按下的位置(相对于屏幕)
              print("用户手指按下：${e.globalPosition}");
            },
            //手指滑动时会触发此回调
            onPanUpdate: (DragUpdateDetails e) {
              //用户手指滑动时，更新偏移，重新构建
              setState(() {
                _left += e.delta.dx;
                _top += e.delta.dy;
              });
            },
            onPanEnd: (DragEndDetails e) {
              //打印滑动结束时在x、y轴上的速度
              print(e.velocity);
            },
          ),
        )
      ],
    );
  }
}

class _DragVertical extends StatefulWidget {
  @override
  _DragVerticalState createState() => new _DragVerticalState();
}

class _DragVerticalState extends State<_DragVertical> {
  double _top = 0.0;

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        Positioned(
          top: _top,
          child: GestureDetector(
              child: CircleAvatar(child: Text("A")),
              //垂直方向拖动事件
              onVerticalDragUpdate: (DragUpdateDetails details) {
                setState(() {
                  _top += details.delta.dy;
                });
              }),
        )
      ],
    );
  }
}

class _ScaleTestRoute extends StatefulWidget {
  @override
  _ScaleTestRouteState createState() => new _ScaleTestRouteState();
}

class _ScaleTestRouteState extends State<_ScaleTestRoute> {
  double _width = 200.0; //通过修改图片宽度来达到缩放效果

  @override
  Widget build(BuildContext context) {
    return Center(
      child: GestureDetector(
        //指定宽度，高度自适应
        child: Image.asset("imgs/avatar.png", width: _width),
        onScaleUpdate: (ScaleUpdateDetails details) {
          setState(() {
            //缩放倍数在0.8到10倍之间
            _width = 200 * details.scale.clamp(.8, 10.0);
          });
        },
      ),
    );
  }
}

class _GestureRecognizerTestRoute extends StatefulWidget {
  @override
  _GestureRecognizerTestRouteState createState() =>
      new _GestureRecognizerTestRouteState();
}

class _GestureRecognizerTestRouteState
    extends State<_GestureRecognizerTestRoute> {
  TapGestureRecognizer _tapGestureRecognizer = new TapGestureRecognizer();
  bool _toggle = false; //变色开关

  @override
  void dispose() {
    //用到GestureRecognizer的话一定要调用其dispose方法释放资源
    _tapGestureRecognizer.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text.rich(TextSpan(children: [
        TextSpan(text: "你好世界"),
        TextSpan(
          text: "点我变色",
          style: TextStyle(
              fontSize: 30.0, color: _toggle ? Colors.blue : Colors.red),
          recognizer: _tapGestureRecognizer
            ..onTap = () {
              setState(() {
                _toggle = !_toggle;
              });
            },
        ),
        TextSpan(text: "你好世界"),
      ])),
    );
  }
}

class BothDirectionTestRoute extends StatefulWidget {
  @override
  BothDirectionTestRouteState createState() =>
      new BothDirectionTestRouteState();
}

class BothDirectionTestRouteState extends State<BothDirectionTestRoute> {
  double _top = 0.0;
  double _left = 0.0;

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        Positioned(
          top: _top,
          left: _left,
          child: GestureDetector(
            child: CircleAvatar(child: Text("A")),
            //垂直方向拖动事件
            onVerticalDragUpdate: (DragUpdateDetails details) {
              setState(() {
                _top += details.delta.dy;
              });
            },
            onHorizontalDragUpdate: (DragUpdateDetails details) {
              setState(() {
                _left += details.delta.dx;
              });
            },
          ),
        )
      ],
    );
  }
}

class GestureConflictTestRoute extends StatefulWidget {
  @override
  GestureConflictTestRouteState createState() =>
      new GestureConflictTestRouteState();
}

class GestureConflictTestRouteState extends State<GestureConflictTestRoute> {
  double _left = 0.0;

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        Positioned(
          left: _left,
          child: GestureDetector(
            child: CircleAvatar(child: Text("A")),
            //要拖动和点击的widget
            onHorizontalDragUpdate: (DragUpdateDetails details) {
              setState(() {
                _left += details.delta.dx;
              });
            },
            onHorizontalDragEnd: (details) {
              print("onHorizontalDragEnd");
            },
            onTapDown: (details) {
              print("down");
            },
            onTapUp: (details) {
              print("up");
            },
          ),
        )
      ],
    );
  }
}

class FixGestureConflictByListenerRoute extends StatefulWidget {
  @override
  _FixGestureConflictByListenerRouteState createState() {
    // TODO: implement createState
    return _FixGestureConflictByListenerRouteState();
  }
}

class _FixGestureConflictByListenerRouteState
    extends State<FixGestureConflictByListenerRoute> {
  double _leftB = 0.0;

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        Positioned(
          top: 80.0,
          left: _leftB,
          child: Listener(
            onPointerDown: (details) {
              print("down");
            },
            onPointerUp: (details) {
              //会触发
              print("up");
            },
            child: GestureDetector(
              child: CircleAvatar(child: Text("B")),
              onHorizontalDragUpdate: (DragUpdateDetails details) {
                setState(() {
                  _leftB += details.delta.dx;
                });
              },
              onHorizontalDragEnd: (details) {
                print("onHorizontalDragEnd");
              },
            ),
          ),
        ),
      ],
    );
  }
}