UIExplorer fixes

Summary:
Currently, when reloading uiexplorer, it does not go back to the last visited
component. This fixes it, by only storing the state (which contains the last
visited component), after it has been set.

Reviewed By: bestander

Differential Revision: D3821288

fbshipit-source-id: 5b9ba10765ce402c20016519a3b7f6b5211cc623

Examples/UIExplorer/js/UIExplorerApp.android.js

@@ -50,8 +50,8 @@ type Props = {
   exampleFromAppetizeParams: string,
 };
 
-type State = {
-  initialExampleUri: ?string,
+type State = UIExplorerNavigationState & {
+  externalExample: ?string,
 };
 
 class UIExplorerApp extends React.Component {
@@ -185,8 +185,10 @@ class UIExplorerApp extends React.Component {
     this.drawer && this.drawer.closeDrawer();
     const newState = UIExplorerNavigationReducer(this.state, action);
     if (this.state !== newState) {
-      this.setState(newState);
-      AsyncStorage.setItem('UIExplorerAppState', JSON.stringify(this.state));
+      this.setState(
+        newState,
+        () => AsyncStorage.setItem('UIExplorerAppState', JSON.stringify(this.state))
+      );
       return true;
     }
     return false;