example(micropython): updated MicroPython examples according to LVGL changes (#4031)

examples/widgets/arc/lv_example_arc_1.py

@@ -1,8 +1,23 @@
+def value_changed_event_cb(e,label):
+    arc = e.get_target_obj()
+
+    txt = "{:d}%".format(arc.get_value())
+    label.set_text(txt)
+
+    # Rotate the label to the current position of the arc
+    arc.rotate_obj_to_angle(label, 25)
+
+label = lv.label(lv.scr_act())
+
 # Create an Arc
 arc = lv.arc(lv.scr_act())
-arc.set_end_angle(200)
 arc.set_size(150, 150)
+arc.set_rotation(135)
+arc.set_bg_angles(0, 270)
+arc.set_value(10)
 arc.center()
+arc.add_event(lambda e: value_changed_event_cb(e,label),lv.EVENT.VALUE_CHANGED, None)
 
-
+# Manually update the label for the first time
+arc.send_event(lv.EVENT.VALUE_CHANGED, None)