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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/overview/obj.rst | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/docs/overview/obj.rst b/docs/overview/obj.rst index ef4726be1..d67631efd 100644 --- a/docs/overview/obj.rst +++ b/docs/overview/obj.rst @@ -167,6 +167,29 @@ using :cpp:expr:`lv_obj_clean(obj)`. You can use :cpp:expr:`lv_obj_delete_delayed(obj, 1000)` to delete an object after some time. The delay is expressed in milliseconds. +Sometimes you're not sure whether an object was deleted and you need some way to +check if it's still "alive". Anytime before the object is deleted, you can use +cpp:expr:`lv_obj_null_on_delete(&obj)` to cause your object pointer to be set to ``NULL`` +when the object is deleted. + +Make sure the pointer variable itself stays valid until the object is deleted. Here +is an example: + +.. code:: c + + void some_timer_callback(lv_timer_t * t) + { + static lv_obj_t * my_label; + if(my_label == NULL) { + my_label = lv_label_create(lv_screen_active()); + lv_obj_delete_delayed(my_label, 1000); + lv_obj_null_on_delete(&my_label); + } + else { + lv_obj_set_x(my_label, lv_obj_get_x(my_label) + 1); + } + } + .. _objects_screens: Screens |