Fixed center problem of buttons. (#459)

* Fixed center problem of buttons of the issue #458

* Fixed center problem of buttons of the issue #458 for toast_context page

example/android/build.gradle

@@ -26,6 +26,6 @@ subprojects {
     project.evaluationDependsOn(':app')
 }
 
-task clean(type: Delete) {
+tasks.register("clean", Delete) {
     delete rootProject.buildDir
 }

example/lib/main.dart

@@ -25,7 +25,8 @@ class _MyAppState extends State<MyApp> {
       appBar: AppBar(
         title: Text("Toast"),
       ),
-      body: Column(
+      body: Center(
+        child: Column(
           mainAxisAlignment: MainAxisAlignment.center,
           children: [
             ElevatedButton(
@@ -49,6 +50,7 @@ class _MyAppState extends State<MyApp> {
             ),
           ],
         ),
+      ),
     );
   }
 }

example/lib/toast_context.dart

@@ -139,7 +139,8 @@ class _ToastContextState extends State<ToastContext> {
       appBar: AppBar(
         title: Text("Custom Toasts"),
       ),
-      body: Column(
+      body: Center(
+        child: Column(
           children: [
             SizedBox(
               height: 24.0,
@@ -194,6 +195,7 @@ class _ToastContextState extends State<ToastContext> {
             ),
           ],
         ),
+      ),
     );
   }
 }