Add button

src/main.rs

@@ -17,5 +17,19 @@ fn build_ui(app: &Application) {
         .title("Hello, World!")
         .build();
 
+    let button = Button::builder()
+        .label("Press me!")
+        .margin_top(12)
+        .margin_bottom(12)
+        .margin_start(12)
+        .margin_end(12)
+        .build();
+
+    button.connect_clicked(move |button| {
+        button.set_label("Hello, World!");
+    });
+
+    window.set_child(Some(&button));
+
     window.present();
 }