Improvements to Edge Fade in and out.

Fix Zoom To Fit for hidden graphs

Author: nabil6391

example/lib/large_tree_graphview.dart

@@ -101,7 +101,8 @@ class _LargeTreeViewPageState extends State<LargeTreeViewPage> with TickerProvid
                 controller: _controller,
                 graph: graph,
                 algorithm: algorithm,
-                // initialNode: ValueKey(1),
+                centerGraph: true,
+                initialNode: ValueKey(1),
                 panAnimationDuration: Duration(milliseconds: 750),
                 toggleAnimationDuration: Duration(milliseconds: 750),
                 // edgeBuilder: (Edge edge, EdgeGeometry geometry) {

example/lib/tree_graphview.dart

@@ -218,7 +218,6 @@ class _TreeViewPageState extends State<TreeViewPage> with TickerProviderStateMix
       Node.Id(36),  // Yoga
     ];
 
-    _controller.setInitiallyCollapsedNodes([tech, business, personal]);
     // Build the graph structure
     graph.addEdge(root, tech);
     graph.addEdge(root, business, paint: Paint()..color = Colors.blue);
@@ -277,6 +276,7 @@ class _TreeViewPageState extends State<TreeViewPage> with TickerProviderStateMix
     for (final exerciseNode in exerciseDetails) {
       graph.addEdge(healthDetails[0], exerciseNode, paint: Paint()..color = Colors.amber);
     }
+    _controller.setInitiallyCollapsedNodes(graph, [tech, business, personal]);
 
     builder
       ..siblingSeparation = (100)