Flutter：同时使用平移和缩放手势？

Question

我正在创建一个带有颤动的绘图画布，我想同时使用缩放（用于缩放、平移和旋转）和平移（用于用手指绘图）手势，但颤动不允许这样做，因为缩放是平移的超集。有什么解决方法吗？

我尝试创建自己的自定义手势识别器来检测屏幕上的指针数量，以便如果两个指针在很短的时间间隔内（假设为 1 秒）与屏幕接触，则 Scale 接管，否则 pan 开始使用第一个触摸屏幕的指针。我正在使用matrix_gesture_detector包来做缩放部分。

这是我的自定义手势识别器代码

class ScaleAndPanRecognizer extends OneSequenceGestureRecognizer {
  var manager = GestureArenaManager();
  final Function onPanDown;
  final Function onPanUpdate;
  final Function onPanEnd;
  ScaleAndPanRecognizer({
    @required this.onPanDown,
    @required this.onPanUpdate,
    @required this.onPanEnd,
  });

  int numPointers = 0;
  int timeFrame = 1;
  int pointer1;
  int pointer2;
  var time1;
  var time2;
  var position1;

  @override
  void addPointer(PointerDownEvent event) {
    print(numPointers);
    if (numPointers == 0) {
      pointer1 = event.pointer;
      print(pointer1);
      position1 = event.localPosition;
      manager.hold(pointer1); //hold the assignment for this pointer for now
      startTrackingPointer(pointer1);

      numPointers += 1;
      time1 = DateTime.now();
    } else if (numPointers == 1) {
      pointer2 = event.pointer;
      print(pointer2);
      resolvePointer(pointer2, GestureDisposition.rejected);
      time2 = DateTime.now();
      var diff = time2.difference(time1);
      print(diff);
      if (diff <= Duration(seconds: timeFrame)) {
        manager.release(pointer1);
        resolvePointer(pointer1, GestureDisposition.rejected);
      } else {
        resolvePointer(pointer1, GestureDisposition.accepted);
        manager.release(pointer1);
        onPanDown(position1);
      }
      numPointers = 0;
    }
  }

  @override
  void handleEvent(PointerEvent event) {
    if (event is PointerMoveEvent) {
      onPanUpdate(event.localPosition);
    }
    if (event is PointerUpEvent) {
      onPanEnd();
      stopTrackingPointer(event.pointer);
    }
  }

  @override
  String get debugDescription => 'only one pointer recognizer';

  @override
  void didStopTrackingLastPointer(int pointer) {}

}

Answer 1

使用侦听器小部件侦听指针事件，然后处理指针事件以根据需要检测缩放和平移手势。

• 1 个指针（短时间间隔内向下和向上）=> 点击
• 1 个指针（长间隔时间内向下和向上）=> 双击
• 1 个指针（向下并移动）=> 平移
• 2 指针 => 缩放和旋转

您可以使用gesture_x_Detector来完全支持手势（点击，双击，缩放，旋转，长按，..）。