[lvgl] Fix msgbox content (#7912)

esphome/components/lvgl/widgets/msgbox.py

@@ -29,7 +29,7 @@ from ..lvcode import (
 )
 from ..schemas import STYLE_SCHEMA, STYLED_TEXT_SCHEMA, container_schema, part_schema
 from ..types import LV_EVENT, char_ptr, lv_obj_t
-from . import Widget, set_obj_properties
+from . import Widget, add_widgets, set_obj_properties
 from .button import button_spec
 from .buttonmatrix import (
     BUTTONMATRIX_BUTTON_SCHEMA,
@@ -119,6 +119,7 @@ async def msgbox_to_code(top_layer, conf):
         button_style = {CONF_ITEMS: button_style}
         await set_obj_properties(buttonmatrix_widget, button_style)
     await set_obj_properties(msgbox_widget, conf)
+    await add_widgets(msgbox_widget, conf)
     async with LambdaContext(EVENT_ARG, where=messagebox_id) as close_action:
         outer_widget.add_flag("LV_OBJ_FLAG_HIDDEN")
     if close_button:

tests/components/lvgl/lvgl-package.yaml

@@ -109,6 +109,10 @@ lvgl:
       close_button: true
       title: Messagebox
       bg_color: 0xffff
+      widgets:
+        - label:
+            text: Hello Msgbox
+            id: msgbox_label
       body:
         text: This is a sample messagebox
         bg_color: 0x808080
@@ -137,6 +141,9 @@ lvgl:
         - lvgl.widget.focus: mark
         - lvgl.widget.redraw: hello_label
         - lvgl.widget.redraw:
+        - lvgl.label.update:
+            id: msgbox_label
+            text: Unloaded
       on_all_events:
         logger.log:
           format: "Event %s"