fix wallet view scroll

lib/screens/wallet_view.dart

@@ -61,10 +61,19 @@ class _WalletViewScreenState extends State<WalletViewScreen> {
       ),
       bottomNavigationBar: const GeckoBottomAppBar(),
       body: SafeArea(
-          child: SingleChildScrollView(
-            child: SizedBox(
-              height: MediaQuery.of(context).size.height - MediaQuery.of(context).padding.top - kBottomNavigationBarHeight,
-              child: Column(children: <Widget>[
+        child: LayoutBuilder(
+          builder: (context, constraints) {
+            return SingleChildScrollView(
+              child: ConstrainedBox(
+                constraints: BoxConstraints(minHeight: constraints.maxHeight),
+                // On divise le contenu en deux parties afin de pouvoir utiliser mainAxisAlignment.spaceBetween
+                // et ainsi faire remonter le bouton de transfert en bas sur grand écran.
+                child: Column(
+                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                  children: <Widget>[
+                    // Partie haute
+                    Column(
+                      children: [
                         WalletHeader(address: address),
                         ScaledSizedBox(height: 20),
                         Row(
@@ -77,10 +86,13 @@ class _WalletViewScreenState extends State<WalletViewScreen> {
                               label: "displayNActivity".tr(),
                               onTap: () => Navigator.push(
                                 context,
-                        PageNoTransit(builder: (context) => ActivityScreen(address: address)),
+                                PageNoTransit(
+                                  builder: (context) => ActivityScreen(address: address),
+                                ),
                               ),
                             ),
-                    Consumer<SubstrateSdk>(builder: (context, sub, _) {
+                            Consumer<SubstrateSdk>(
+                              builder: (context, sub, _) {
                                 return FutureBuilder(
                                   future: sub.certState(address),
                                   builder: (context, AsyncSnapshot<CertState> snapshot) {
@@ -95,7 +107,8 @@ class _WalletViewScreenState extends State<WalletViewScreen> {
                                     );
                                   },
                                 );
-                    }),
+                              },
+                            ),
                             _buildActionButton(
                               context: context,
                               key: keyCopyAddress,
@@ -108,13 +121,23 @@ class _WalletViewScreenState extends State<WalletViewScreen> {
                             ),
                           ],
                         ),
-                const Spacer(),
+                      ],
+                    ),
+                    // Partie basse
+                    Column(
+                      children: [
                         _buildTransferButton(context),
                         ScaledSizedBox(height: isTall ? 40 : 7),
-              ]),
+                      ],
+                    ),
+                  ],
                 ),
               ),
-        ));
+            );
+          },
+        ),
+      ),
+    );
   }
 
   Widget _buildActionButton({