定时器¶

LVGL 内置了一个定时器系统。您可以注册一个函数，使其周期性地被调用。定时器在 lv_timer_handler() 中处理和调用，该函数需要每隔几毫秒调用一次。有关更多信息，请参阅移植。

定时器是非抢占式的，这意味着一个定时器不能中断另一个定时器。因此，您可以在定时器中调用任何与 LVGL 相关的函数。

创建定时器¶

要创建一个新的定时器，请使用 lv_timer_create(timer_cb, period_ms, user_data)。它将创建一个 lv_timer_t * 变量，稍后可以用它来修改定时器的参数。也可以使用 lv_timer_create_basic()。这允许您在不指定任何参数的情况下创建一个新的定时器。

定时器回调函数应具有 void (*lv_timer_cb_t)(lv_timer_t *); 的原型。

例如：

void my_timer(lv_timer_t * timer)
{
  /*使用 user_data*/
  uint32_t * user_data = timer->user_data;
  printf("my_timer 被调用，用户数据为: %d\n", *user_data);

  /*执行一些与 LVGL 相关的操作*/
  if(something_happened) {
    something_happened = false;
    lv_btn_create(lv_scr_act(), NULL);
  }
}

...

static uint32_t user_data = 10;
lv_timer_t * timer = lv_timer_create(my_timer, 500,  &user_data);

就绪和重置¶

lv_timer_ready(timer) 使定时器在下一次调用 lv_timer_handler() 时运行。

lv_timer_reset(timer) 重置定时器的周期。它将在定义的毫秒周期经过后再次被调用。

设置参数¶

您可以稍后修改一些定时器参数：

lv_timer_set_cb(timer, new_cb)
lv_timer_set_period(timer, new_period)

重复计数¶

您可以使用 lv_timer_set_repeat_count(timer, count) 使定时器仅重复指定的次数。定时器将在调用定义的次数后自动删除。将计数设置为 -1 以无限重复。

测量空闲时间¶

您可以使用 lv_timer_get_idle() 获取 lv_timer_handler 的空闲百分比时间。请注意，它不会测量整个系统的空闲时间，仅测量 lv_timer_handler 的空闲时间。如果您使用操作系统并在定时器中调用 lv_timer_handler，这可能会产生误导，因为它实际上不会测量操作系统在空闲线程中花费的时间。

异步调用¶

在某些情况下，您无法立即执行某个操作。例如，您无法删除一个对象，因为其他地方仍在使用它，或者您不希望现在阻塞执行。对于这些情况，可以使用 lv_async_call(my_function, data_p) 在下一次调用 lv_timer_handler 时调用 my_function。data_p 将在函数调用时传递给它。请注意，仅保存数据指针，因此您需要确保变量在函数调用时仍然“存活”。它可以是 static、全局或动态分配的数据。如果您想取消异步调用，请调用 lv_async_call_cancel(my_function, data_p)，它将清除所有与 my_function 和 data_p 匹配的异步调用。

例如：

void my_screen_clean_up(void * scr)
{
  /*释放与 `scr` 相关的一些资源*/

  /*最后删除屏幕*/
  lv_obj_del(scr);
}

...

/*对当前屏幕上的对象执行一些操作*/

/*在下一次调用 `lv_timer_handler` 时删除屏幕，而不是现在。*/
lv_async_call(my_screen_clean_up, lv_scr_act());

/*屏幕仍然有效，因此您可以对其执行其他操作*/

如果您只想删除一个对象，而不需要在 my_screen_cleanup 中清理任何内容，可以直接使用 lv_obj_del_async，它将在下一次调用 lv_timer_handler 时删除对象。

API¶

Typedefs

typedef void (*lv_timer_cb_t)(struct _lv_timer_t*)¶: Timers execute this type of functions.

typedef struct _lv_timer_t lv_timer_t¶: Descriptor of a lv_timer

Functions

void _lv_timer_core_init(void)¶: Init the lv_timer module

static inline LV_ATTRIBUTE_TIMER_HANDLER uint32_t lv_timer_handler_run_in_period (uint32_t ms)

Call it in the super-loop of main() or threads. It will run lv_timer_handler() with a given period in ms. You can use it with sleep or delay in OS environment. This function is used to simplify the porting.

Parameters: __ms -- the period for running lv_timer_handler()

lv_timer_t *lv_timer_create_basic(void)¶

Create an "empty" timer. It needs to initialized with at least lv_timer_set_cb and lv_timer_set_period

Returns: pointer to the created timer

lv_timer_t *lv_timer_create(lv_timer_cb_t timer_xcb, uint32_t period, void *user_data)¶

Create a new lv_timer

Parameters

timer_xcb -- a callback to call periodically. (the 'x' in the argument name indicates that it's not a fully generic function because it not follows the func_name(object, callback, ...) convention)
period -- call period in ms unit
user_data -- custom parameter

Returns

pointer to the new timer

void lv_timer_del(lv_timer_t *timer)¶

Delete a lv_timer

Parameters: timer -- pointer to an lv_timer

void lv_timer_pause(lv_timer_t *timer)¶

Pause/resume a timer.

Parameters: timer -- pointer to an lv_timer

void lv_timer_resume(lv_timer_t *timer)¶

void lv_timer_set_cb(lv_timer_t *timer, lv_timer_cb_t timer_cb)¶

Set the callback the timer (the function to call periodically)

Parameters

timer -- pointer to a timer
timer_cb -- the function to call periodically

void lv_timer_set_period(lv_timer_t *timer, uint32_t period)¶

Set new period for a lv_timer

Parameters

timer -- pointer to a lv_timer
period -- the new period

void lv_timer_ready(lv_timer_t *timer)¶

Make a lv_timer ready. It will not wait its period.

Parameters: timer -- pointer to a lv_timer.

void lv_timer_set_repeat_count(lv_timer_t *timer, int32_t repeat_count)¶

Set the number of times a timer will repeat.

Parameters

timer -- pointer to a lv_timer.
repeat_count -- -1 : infinity; 0 : stop ; n>0: residual times

void lv_timer_reset(lv_timer_t *timer)¶

Reset a lv_timer. It will be called the previously set period milliseconds later.

Parameters: timer -- pointer to a lv_timer.

void lv_timer_enable(bool en)¶

Enable or disable the whole lv_timer handling

Parameters: en -- true: lv_timer handling is running, false: lv_timer handling is suspended

uint8_t lv_timer_get_idle(void)¶

Get idle percentage

Returns: the lv_timer idle in percentage

lv_timer_t *lv_timer_get_next(lv_timer_t *timer)¶

Iterate through the timers

Parameters: timer -- NULL to start iteration or the previous return value to get the next timer
Returns: the next timer or NULL if there is no more timer

struct _lv_timer_t¶

#include <lv_timer.h>

Descriptor of a lv_timer

Public Members

uint32_t period¶: How often the timer should run

uint32_t last_run¶: Last time the timer ran

lv_timer_cb_t timer_cb¶: Timer function

void *user_data¶: Custom user data

int32_t repeat_count¶: 1: One time; -1 : infinity; n>0: residual times

uint32_t paused¶

Typedefs

typedef void (*lv_async_cb_t)(void*)¶: Type for async callback.

Functions

lv_res_t lv_async_call(lv_async_cb_t async_xcb, void *user_data)¶

Call an asynchronous function the next time lv_timer_handler() is run. This function is likely to return before the call actually happens!

Parameters

async_xcb -- a callback which is the task itself. (the 'x' in the argument name indicates that it's not a fully generic function because it not follows the func_name(object, callback, ...) convention)
user_data -- custom parameter

lv_res_t lv_async_call_cancel(lv_async_cb_t async_xcb, void *user_data)¶

Cancel an asynchronous function call

Parameters

async_xcb -- a callback which is the task itself.
user_data -- custom parameter