Timers（定时器）¶

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LVGL has a built-in timer system. You can register a function to have it be called periodically. The timers are handled and called in lv_timer_handler(), which needs to be called every few milliseconds. See Porting for more information.

The timers are non-preemptive, which means a timer cannot interrupt another timer. Therefore, you can call any LVGL related function in a timer.

LVGL 有一个内置的定时器系统。您可以注册一个函数以定期调用它。定时器在lv_timer_handler()中被处理和调用，它需要每隔几毫秒调用一次。有关详细信息，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，您可以在计时器中调用任何与 LVGL 相关的函数。

Create a timer（创建定时器）¶

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To create a new timer, use lv_timer_create(timer_cb, period_ms, user_data). It will create an lv_timer_t * variable, which can be used later to modify the parameters of the timer. lv_timer_create_basic() can also be used. This allows you to create a new timer without specifying any parameters.

A timer callback should have void (*lv_timer_cb_t)(lv_timer_t *); prototype.

For example:

要创建一个新的计时器，请使用 lv_timer_create(timer_cb, period_ms, user_data)。它将创建一个 lv_timer_t * 变量，以后可以使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新计时器。

一个定时器回调应该有 void (*lv_timer_cb_t)(lv_timer_t *); 原型。

例如：

void my_timer(lv_timer_t * timer)
{
  /*Use the user_data*/
  uint32_t * user_data = timer->user_data;
  printf("my_timer called with user data: %d\n", *user_data);

  /*Do something with LVGL*/
  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);

Ready and Reset（准备与重置）¶

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lv_timer_ready(timer) makes the timer run on the next call of lv_timer_handler().

lv_timer_reset(timer) resets the period of a timer. It will be called again after the defined period of milliseconds has elapsed.

lv_timer_ready(timer) 使计时器在下一次调用 lv_timer_handler() 时运行。

lv_timer_reset(timer) 重置计时器的周期。它将在定义的毫秒时间段过去后再次调用。

Set parameters（参数设置）¶

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You can modify some parameters of the timers later:

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

您可以修改定时器的一些参数：

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

Repeat count（设置重复次数）¶

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You can make a timer repeat only a given number of times with lv_timer_set_repeat_count(timer, count). The timer will automatically be deleted after being called the defined number of times. Set the count to -1 to repeat indefinitely.

您可以使用 lv_timer_set_repeat_count(timer, count) 使计时器仅重复给定次数。定时器在调用定义的次数后将自动删除。将计数设置为“-1”以无限重复。

Measure idle time（测量空闲时间）¶

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You can get the idle percentage time of lv_timer_handler with lv_timer_get_idle(). Note that, it doesn't measure the idle time of the overall system, only lv_timer_handler. It can be misleading if you use an operating system and call lv_timer_handler in a timer, as it won't actually measure the time the OS spends in an idle thread.

你可以通过 lv_timer_get_idle() 获取 lv_timer_handler 的空闲百分比时间。请注意，它不测量整个系统的空闲时间，只测量 lv_timer_handler。如果您使用操作系统并在计时器中调用 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。

Asynchronous calls（异步调用）¶

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In some cases, you can't do an action immediately. For example, you can't delete an object because something else is still using it or you don't want to block the execution now. For these cases, lv_async_call(my_function, data_p) can be used to make my_function be called on the next call of lv_timer_handler. data_p will be passed to function when it's called. Note that, only the pointer of the data is saved so you need to ensure that the variable will be "alive" while the function is called. It can be static, global or dynamically allocated data.

For example:

在某些情况下，您无法立即执行操作。例如，您不能删除一个对象，因为其他东西仍在使用它，或者您现在不想阻止执行。对于这些情况，可以使用 lv_async_call(my_function, data_p) 使 my_function 在下一次调用 lv_timer_handler 时被调用。 data_p 将在调用时传递给函数。请注意，仅保存数据的指针，因此您需要确保在调用函数时该变量将“处于活动状态”。它可以是静态、全局或动态分配的数据。

例如：

void my_screen_clean_up(void * scr)
{
  /*Free some resources related to `scr`*/

  /*Finally delete the screen*/
  lv_obj_del(scr);  
}

...

/*Do somethings with the object on the current screen*/

/*Delete screen on next call of `lv_timer_handler`, so not now.*/
lv_async_call(my_screen_clean_up, lv_scr_act());

/*The screen is still valid so you can do other things with it*/

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If you just want to delete an object, and don't need to clean anything up in my_screen_cleanup, you could just use lv_obj_del_async, which will delete the object on the next call to lv_timer_handler.

如果你只是想删除一个对象，而不需要在 my_screen_cleanup 中清理任何东西，你可以使用 lv_obj_del_async，它会在下次调用 lv_timer_handler 时删除该对象。

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

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

返回: 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

参数

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

返回

pointer to the new timer

void lv_timer_del(lv_timer_t *timer)¶

Delete a lv_timer

参数: timer -- pointer to an lv_timer

void lv_timer_pause(lv_timer_t *timer)¶

Pause/resume a timer.

参数: 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)

参数

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

参数

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.

参数: 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.

参数

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.

参数: timer -- pointer to a lv_timer.

void lv_timer_enable(bool en)¶

Enable or disable the whole lv_timer handling

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

uint8_t lv_timer_get_idle(void)¶

Get idle percentage

返回: the lv_timer idle in percentage

lv_timer_t *lv_timer_get_next(lv_timer_t *timer)¶

Iterate through the timers

参数: timer -- NULL to start iteration or the previous return value to get the next timer
返回: 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!

参数

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