update fab position and hide fab button when page open

lib/src/power_logger.dart

@@ -34,6 +34,8 @@ class _LoggerFABState extends State<LoggerFAB> {
   double get screenWidth => MediaQuery.of(context).size.width;
   double get screenHeight => MediaQuery.of(context).size.height;
   bool _moving = false;
+
+  bool showSubPage = false;
   @override
   Widget build(BuildContext context) {
     return AnimatedPositioned(
@@ -41,6 +43,10 @@ class _LoggerFABState extends State<LoggerFAB> {
       duration: _moving ? Duration.zero : Duration(milliseconds: 300),
       left: _x - 25,
       top: _y - 25,
+      child: AnimatedOpacity(
+        duration: Duration(milliseconds: 300),
+        curve: Curves.easeInOutCubic,
+        opacity: showSubPage ? 0 : 1,
         child: GestureDetector(
           onPanStart: (detail) {
             _moving = true;
@@ -56,17 +62,23 @@ class _LoggerFABState extends State<LoggerFAB> {
               _x = 50;
             } else
               _x = screenWidth - 50;
-          if ((_y < screenHeight / 2)) {
-            _y = 70;
-          } else
+            if (_y > screenHeight - 50) {
               _y = screenHeight - 50;
+            } else if (_y < 50) _y = 50;
+
             _moving = false;
             setState(() {});
           },
-        onTap: () => Navigator.push(
+          onTap: showSubPage
+              ? null
+              : () async {
+                  showSubPage = true;
+                  await Navigator.push(
                     context,
                     MaterialPageRoute(builder: (context) => PowerLoggerView()),
-        ),
+                  );
+                  showSubPage = false;
+                },
           child: ClipOval(
             child: BackdropFilter(
               filter: ImageFilter.blur(sigmaX: 5, sigmaY: 5),
@@ -85,6 +97,7 @@ class _LoggerFABState extends State<LoggerFAB> {
             ),
           ),
         ),
+      ),
     );
   }
 }