我正在使用Flutter创建一个绘图画布，想要同时使用缩放（用于缩放、平移和旋转）和手势绘制。但由于缩放是Pan的超集，Flutter不允许这样做。是否有任何解决方法？
我尝试创建自己的自定义手势识别器，以检测屏幕上的指针数量。如果两个指针在短时间内（比如1秒）接触屏幕，则缩放接管；否则，平移将使用第一个触摸屏幕的指针。我正在使用matrix_gesture_detector包来实现缩放部分。
以下是我的自定义手势识别器的代码：
我尝试创建自己的自定义手势识别器，以检测屏幕上的指针数量。如果两个指针在短时间内（比如1秒）接触屏幕，则缩放接管；否则，平移将使用第一个触摸屏幕的指针。我正在使用matrix_gesture_detector包来实现缩放部分。
以下是我的自定义手势识别器的代码：
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) {}
}