[plcs#8888] 单点触摸

lib/widget/only_one_pointer_widget.dart

@@ -0,0 +1,55 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/gestures.dart';
+
+/**
+ * 单点触摸的方案：https://xbuba.com/questions/51712287
+ */
+class OnlyOnePointerRecognizer extends OneSequenceGestureRecognizer {
+  int _p = 0;
+
+  @override
+  void addAllowedPointer(PointerDownEvent event) {
+    startTrackingPointer(event.pointer);
+    if (_p == 0) {
+      resolve(GestureDisposition.rejected);
+      _p = event.pointer;
+    } else {
+      resolve(GestureDisposition.accepted);
+    }
+  }
+
+  @override
+  String get debugDescription => 'only one pointer recognizer';
+
+  @override
+  void didStopTrackingLastPointer(int pointer) {}
+
+  @override
+  void handleEvent(PointerEvent event) {
+    if (!event.down && event.pointer == _p) {
+      _p = 0;
+    }
+  }
+}
+
+class OnlyOnePointerRecognizerWidget extends StatelessWidget {
+  final Widget child;
+
+  OnlyOnePointerRecognizerWidget({this.child});
+
+  @override
+  Widget build(BuildContext context) {
+    return RawGestureDetector(
+      gestures: <Type, GestureRecognizerFactory>{
+        OnlyOnePointerRecognizer:
+            GestureRecognizerFactoryWithHandlers<OnlyOnePointerRecognizer>(
+          () => OnlyOnePointerRecognizer(),
+          (OnlyOnePointerRecognizer instance) {
+
+          },
+        ),
+      },
+      child: child,
+    );
+  }
+}