一、GestureDetector 的介绍

GestureDetector：是手势识别的组件，可以识别点击、双击、长按事件、拖动、缩放等手势

二、GestureDetector的源码介绍

GestureDetector({
    Key key,
    this.child,
    this.onTapDown,//按下时回调
    this.onTapUp,//抬起时回调
    this.onTap,//点击事件回调
    this.onTapCancel,//点击取消事件回调
    this.onSecondaryTap,
    this.onSecondaryTapDown,
    this.onSecondaryTapUp,
    this.onSecondaryTapCancel,
    this.onTertiaryTapDown,
    this.onTertiaryTapUp,
    this.onTertiaryTapCancel,
    this.onDoubleTapDown,//短时间内双击按下时回调
    this.onDoubleTap,//短时间内双击回调
    this.onDoubleTapCancel,//短时间内双击取消事件回调
    this.onLongPress,//长按事件回调
    this.onLongPressStart,//长按开始事件回调
    this.onLongPressMoveUpdate,//长按移动事件回调
    this.onLongPressUp,//长按抬起事件回调
    this.onLongPressEnd,//长按结束事件回调
    this.onSecondaryLongPress,
    this.onSecondaryLongPressStart,
    this.onSecondaryLongPressMoveUpdate,
    this.onSecondaryLongPressUp,
    this.onSecondaryLongPressEnd,
    this.onVerticalDragDown,//垂直滑动按下事件回调
    this.onVerticalDragStart,//垂直滑动开始事件回调
    this.onVerticalDragUpdate,//垂直滑动更新事件回调
    this.onVerticalDragEnd,//垂直滑动结束事件回调
    this.onVerticalDragCancel,//垂直滑动取消事件回调
    this.onHorizontalDragDown,//水平滑动按下事件回调
    this.onHorizontalDragStart,///水平滑动开始事件回调
    this.onHorizontalDragUpdate,//水平滑动更新事件回调
    this.onHorizontalDragEnd,//水平滑动结束事件回调
    this.onHorizontalDragCancel,//水平滑动取消事件回调
    this.onForcePressStart,//回调函数只会在有压力的设备上被触发
    this.onForcePressPeak,
    this.onForcePressUpdate,
    this.onForcePressEnd,
    this.onPanDown,//按压时回调
    this.onPanStart,//按压拖动开始回调
    this.onPanUpdate,//按压拖动回调
    this.onPanEnd,//按压拖动结束回调
    this.onPanCancel,//按压拖动取消回调
    this.onScaleStart,//缩放开始事件回调
    this.onScaleUpdate,//缩放更新事件回调
    this.onScaleEnd,//缩放结束事件回调
    this.behavior,//手势检测器在触摸中应该如何工作
    this.excludeFromSemantics = false,
    this.dragStartBehavior = DragStartBehavior.start,
  }) : assert(excludeFromSemantics != null),
       assert(dragStartBehavior != null),
       assert(() {
         final bool haveVerticalDrag = onVerticalDragStart != null || onVerticalDragUpdate != null || onVerticalDragEnd != null;
         final bool haveHorizontalDrag = onHorizontalDragStart != null || onHorizontalDragUpdate != null || onHorizontalDragEnd != null;
         final bool havePan = onPanStart != null || onPanUpdate != null || onPanEnd != null;
         final bool haveScale = onScaleStart != null || onScaleUpdate != null || onScaleEnd != null;
         if (havePan || haveScale) {
           if (havePan && haveScale) {
             throw FlutterError.fromParts(<DiagnosticsNode>[
               ErrorSummary('Incorrect GestureDetector arguments.'),
               ErrorDescription(
                 'Having both a pan gesture recognizer and a scale gesture recognizer is redundant; scale is a superset of pan.'
               ),
               ErrorHint('Just use the scale gesture recognizer.')
             ]);
           }
           final String recognizer = havePan ? 'pan' : 'scale';
           if (haveVerticalDrag && haveHorizontalDrag) {
             throw FlutterError(
               'Incorrect GestureDetector arguments.\n'
               'Simultaneously having a vertical drag gesture recognizer, a horizontal drag gesture recognizer, and a $recognizer gesture recognizer '
               'will result in the $recognizer gesture recognizer being ignored, since the other two will catch all drags.'
             );
           }
         }
         return true;
       }()),
       super(key: key);

三、GestureDetector的属性介绍

四、一些触摸事件，监听的调用顺序

4.1、点击屏幕：onPanDown--onPanCancel--onTapDown--onTapUp--onTap

4.2、点击滑动：onPanDown--onTapDown--onTapCancel--onPanStart--onPanUpdate--onPanEnd

4.3、双击屏幕：onPanDown--onPanCancel--onDoubleTapDown--onPanDown--onPanCancel--onDoubleTap

4.4、长按屏幕：onPanDown--onTapDown--onTapCancel--onPanCancel--onLongPressStart--onLongPress--onLongPressMoveUpdate--onLongPressEnd--onLongPressUp

4.5、手指左右滑动：onVerticalDragDown--onHorizontalDragDown--onVerticalDragCancel--onHorizontalDragStart--onHorizontalDragUpdate--onHorizontalDragEnd

4.6、手指上下滑动：onVerticalDragDown--onHorizontalDragDown--onHorizontalDragCancel--onVerticalDragStart--onVerticalDragUpdate--onVerticalDragEnd

4.7、缩放：onScaleStart--onScaleUpdate--onScaleEnd

五、GestureDetector的demo

5.1、给组件添加按键监听

class _GestureDetectorFulState extends State<GestureDetectorFul> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      appBar: AppBar(
        title: Text("GestureDetector学习"),
      ),
      body: Center(
        child: GestureDetector(
          //一定要加（按钮和文字之间的空白，也添加监听了）
          behavior: HitTestBehavior.opaque,
          onPanDown: (value) {
            print("我是onPanDown");
          },
          child: Row(
            children: [
              OutlinedButton(
                child: Text("按钮"),
                onPressed: () {
                  print("点击了button");
                },
              ),
              SizedBox(width: 80),
              Text("文字")
            ],
          )
        ),
      )
    ));
  }
}