Fragment
Fragment is a concept copied from Android.
It represents a reusable portion of your app's UI. A fragment defines and manages its own layout, has its own lifecycle, and can handle its own events. Like Android's Fragment that must be hosted by an activity or another fragment, Fragment in LVGL needs to be hosted by a Widget, or another fragment. The fragment's view hierarchy becomes part of, or attaches to, the host's view hierarchy.
Such concept also has some similarities to UiViewController on iOS.
Fragment Manager is a manager holding references to fragments attached to it, and has an internal stack to achieve navigation. You can use fragment manager to build navigation stack, or multi pane application easily.
Usage
Enable LV_USE_FRAGMENT in lv_conf.h.
Create Fragment Class
struct sample_fragment_t {
/* IMPORTANT: don't miss this part */
lv_fragment_t base;
/* States, object references and data fields for this fragment */
const char *title;
};
const lv_fragment_class_t sample_cls = {
/* Initialize something needed */
.constructor_cb = sample_fragment_ctor,
/* Create view objects */
.create_obj_cb = sample_fragment_create_obj,
/* IMPORTANT: size of your fragment struct */
.instance_size = sizeof(struct sample_fragment_t),
};
Use lv_fragment_manager
/* Create fragment instance, and Widgets will be added to container */
lv_fragment_manager_t *manager = lv_fragment_manager_create(container, NULL);
/* Replace current fragment with instance of sample_cls, and init_argument is user defined pointer */
lv_fragment_manager_replace(manager, &sample_cls, init_argument);
Example
Basic fragment usage
C code
View on GitHub/**
* @file lv_example_fragment_1.c
* @brief Basic usage of obj fragment
*/
#include "../../lv_examples.h"
#if LV_USE_FRAGMENT && LV_BUILD_EXAMPLES
static void sample_fragment_ctor(lv_fragment_t * self, void * args);
static lv_obj_t * sample_fragment_create_obj(lv_fragment_t * self, lv_obj_t * parent);
static void sample_container_delete(lv_event_t * e);
static lv_obj_t * root = NULL;
struct sample_fragment_t {
lv_fragment_t base;
const char * name;
};
static const lv_fragment_class_t sample_cls = {
.constructor_cb = sample_fragment_ctor,
.create_obj_cb = sample_fragment_create_obj,
.instance_size = sizeof(struct sample_fragment_t),
};
void lv_example_fragment_1(void)
{
root = lv_obj_create(lv_screen_active());
lv_obj_set_size(root, LV_PCT(100), LV_PCT(100));
lv_fragment_manager_t * manager = lv_fragment_manager_create(NULL);
/* Clean up the fragment manager before objects in containers got deleted */
lv_obj_add_event_cb(root, sample_container_delete, LV_EVENT_DELETE, manager);
lv_fragment_t * fragment = lv_fragment_create(&sample_cls, "Fragment");
lv_fragment_manager_replace(manager, fragment, &root);
}
static void sample_fragment_ctor(lv_fragment_t * self, void * args)
{
((struct sample_fragment_t *) self)->name = args;
}
static lv_obj_t * sample_fragment_create_obj(lv_fragment_t * self, lv_obj_t * parent)
{
lv_obj_t * label = lv_label_create(parent);
lv_obj_set_style_bg_opa(label, LV_OPA_COVER, 0);;
lv_label_set_text_fmt(label, "Hello, %s!", ((struct sample_fragment_t *) self)->name);
return label;
}
static void sample_container_delete(lv_event_t * e)
{
lv_fragment_manager_t * manager = (lv_fragment_manager_t *) lv_event_get_user_data(e);
lv_fragment_manager_delete(manager);
}
#endif