LVGL (Light and Versatile Graphics Library) is a powerful open-source graphics library widely used for embedded systems and beyond. A core component of any LVGL application is the screen, the visual canvas where all graphical elements reside. This article will delve into the intricacies of LVGL screens, covering their creation, loading, management, and accessing relevant information like screen names. We'll explore the functions involved, best practices, and potential pitfalls to help developers effectively leverage this crucial aspect of the library.
LVGL Screen Name: A Conceptual Understanding
The concept of a "screen name" in LVGL isn't directly implemented as a built-in string attribute of an `lv_obj_t` object representing a screen. LVGL doesn't inherently assign names to screens. Instead, screen identification and management rely on pointers to the `lv_obj_t` objects themselves. However, developers can easily implement their own naming mechanism by associating a string with each screen object, either through a separate data structure or by leveraging user data within the `lv_obj_t` structure. We'll discuss how to implement this custom naming later in the article.
Creating an LVGL Screen: The `lv_
The foundation of any LVGL screen is its creation. This is primarily achieved using the `lv_
The function signature is as follows:
lv_obj_t * lv_obj_create(lv_obj_t * parent, const lv_obj_t * copy);
* `lv_obj_t * parent`: This parameter specifies the parent object. For a screen, this should be `NULL`, indicating that the screen is a top-level object, not nested within another object.
* `const lv_obj_t * copy`: This is an optional parameter. If provided, it allows you to create a new screen by copying the structure and contents of an existing screen. This is incredibly useful for creating multiple screens with similar layouts, saving significant development time. If `NULL`, a blank screen is created.
Example: Creating a new, blank screen:
lv_obj_t * scr = lv_obj_create(NULL, NULL);
Example: Creating a new screen by copying an existing screen:
lv_obj_t * existing_screen = ...; // Assume this is an existing screen object
lv_obj_t * new_screen = lv_obj_create(NULL, existing_screen);
Loading an LVGL Screen: The `lv_scr_load()` Function
Once a screen is created, it needs to be displayed. This is done using the `lv_scr_load()` function:
void lv_scr_load(lv_obj_t * scr);
This function takes a pointer to the `lv_obj_t` representing the screen as an argument. Calling `lv_scr_load()` makes the specified screen the active screen, making its contents visible to the user.
Example: Loading the newly created screen:
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