显示原文
Events are triggered in LVGL when something happens which might be interesting to the user, e.g. when an object:
- is clicked
- is scrolled
- has its value changed
- is redrawn, etc.
Besides widgets, events can registered from displays and input devices too.
当发生某些对用户可能感兴趣的事情时，LVGL中的事件将被触发，例如：
- 被点击
- 被滚动
- 值发生改变
- 重新绘制等。
除了部件，事件还可以从显示和输入设备进行注册。
显示原文
The user can assign callback functions to an object to see its events. In practice, it looks like this:
lv_obj_t * btn = lv_button_create(lv_screen_active());
lv_obj_add_event_cb(btn, my_event_cb, LV_EVENT_CLICKED, NULL); /*Assign an event callback*/
...
static void my_event_cb(lv_event_t * event)
{
printf("Clicked\n");
}In the example :cppLV_EVENT_CLICKED means that only the click event will call my_event_cb. See the list of event codes <events_codes> for all the options. :cppLV_EVENT_ALL can be used to receive all events.
The last parameter of :cpplv_obj_add_event is a pointer to any custom data that will be available in the event. It will be described later in more detail.
More events can be added to an object, like this:
lv_obj_add_event_cb(obj, my_event_cb_1, LV_EVENT_CLICKED, NULL);
lv_obj_add_event_cb(obj, my_event_cb_2, LV_EVENT_PRESSED, NULL);
lv_obj_add_event_cb(obj, my_event_cb_3, LV_EVENT_ALL, NULL); /*No filtering, receive all events*/Even the same event callback can be used on an object with different user_data. For example:
lv_obj_add_event_cb(obj, increment_on_click, LV_EVENT_CLICKED, &num1);
lv_obj_add_event_cb(obj, increment_on_click, LV_EVENT_CLICKED, &num2);The events will be called in the order as they were added.
Other objects can use the same event callback.
In the very same way events can attached to the input devices and displays like this
lv_display_add_event_cb(disp, event_cb, LV_EVENT_RESOLUTION_CHANGED, NULL);
lv_indev_add_event_cb(indev, event_cb, LV_EVENT_CLICKED, NULL);用户可以为对象指定回调函数以查看其事件。 实际操作是这样的：
lv_obj_t * btn = lv_button_create(lv_screen_active());
lv_obj_add_event_cb(btn, my_event_cb, LV_EVENT_CLICKED, NULL); /*分配一个事件回调*/
...
static void my_event_cb(lv_event_t * event)
{
printf("Clicked\n");
}在示例中 :cppLV_EVENT_CLICKED 意味着只有点击事件会调用 my_event_cb。查看 事件代码列表 <events_codes> 以获取所有选项。 :cppLV_EVENT_ALL 可用于接收所有事件。
:cpplv_obj_add_event 的最后一个参数是指向事件中可用的任何自定义数据的指针。稍后将更详细地描述它。
可以向对象添加更多事件，像这样：
lv_obj_add_event_cb(obj, my_event_cb_1, LV_EVENT_CLICKED, NULL);
lv_obj_add_event_cb(obj, my_event_cb_2, LV_EVENT_PRESSED, NULL);
lv_obj_add_event_cb(obj, my_event_cb_3, LV_EVENT_ALL, NULL); /*无过滤，接收所有事件*/甚至相同的事件回调也可以在具有不同“user_data”的对象上使用。例如：
lv_obj_add_event_cb(obj, increment_on_click, LV_EVENT_CLICKED, &num1);
lv_obj_add_event_cb(obj, increment_on_click, LV_EVENT_CLICKED, &num2);事件将按其被添加的顺序调用。
其他对象可以使用相同的 事件回调。
以完全相同的方式，事件可以附加到输入设备和显示器上，像这样：
lv_display_add_event_cb(disp, event_cb, LV_EVENT_RESOLUTION_CHANGED, NULL);
lv_indev_add_event_cb(indev, event_cb, LV_EVENT_CLICKED, NULL);uint32_t i;
uint32_t event_cnt = lv_obj_get_event_count(obj);
for(i = 0; i < event_cnt; i++) {
lv_event_dsc_t * event_dsc = lv_obj_get_event_dsc(obj, i);
if(lv_event_dsc_get_cb(event_dsc) == some_event_cb) {
lv_obj_remove_event(obj, i);
break;
}
}显示原文
The event codes can be grouped into these categories: - Input device events - Drawing events - Other events - Special events - Custom events
All objects (such as Buttons/Labels/Sliders etc.) regardless their type receive the Input device, Drawing and Other events.
However, the Special events are specific to a particular widget type. See the widgets' documentation <widgets> to learn when they are sent,
Custom events are added by the user and are never sent by LVGL.
The following event codes exist:
事件代码可以分为以下类别：- 输入设备事件 - 绘图事件 - 其他事件 - 特殊事件 - 自定义事件
所有对象（如按钮/标签/滑块等）无论其类型，都会接收 输入设备、 绘图 和 其他 事件。
然而， 特殊事件 是特定于特定部件类型的。请参阅 widgets' documentation <widgets> 以了解它们何时被发送。
自定义事件 是用户添加的，并且永远不会被LVGL发送。
存在以下事件代码：
显示原文
- :cpp
LV_EVENT_PRESSED: The object has been pressed - :cpp
LV_EVENT_PRESSING: The object is being pressed (called continuously while pressing) - :cpp
LV_EVENT_PRESS_LOST: The object is still being pressed but slid cursor/finger off of the object - :cpp
LV_EVENT_SHORT_CLICKED: The object was pressed for a short period of time, then released it. Not called if scrolled. - :cpp
LV_EVENT_LONG_PRESSED: Object has been pressed for at least long_press_time. Not called if scrolled. - :cpp
LV_EVENT_LONG_PRESSED_REPEAT: Called after long_press_time in every long_press_repeat_time ms. Not called if scrolled. - :cpp
LV_EVENT_CLICKED: Called on release if not scrolled (regardless to long press) - :cpp
LV_EVENT_RELEASED: Called in every cases when the object has been released - :cpp
LV_EVENT_SCROLL_BEGIN: Scrolling begins. The event parameter is a pointer to the animation of the scroll. Can be modified - :cpp
LV_EVENT_SCROLL_THROW_BEGIN: - :cpp
LV_EVENT_SCROLL_END: Scrolling ends - :cpp
LV_EVENT_SCROLL: Scrolling - :cpp
LV_EVENT_GESTURE: A gesture is detected. Get the gesture with :cpplv_indev_get_gesture_dir(lv_indev_active()); - :cpp
LV_EVENT_KEY: A key is sent to the object. Get the key with :cpplv_indev_get_key(lv_indev_active()); - :cpp
LV_EVENT_FOCUSED: The object is focused - :cpp
LV_EVENT_DEFOCUSED: The object is defocused - :cpp
LV_EVENT_LEAVE: The object is defocused but still selected - :cpp
LV_EVENT_HIT_TEST: Perform advanced hit-testing - :cpp
LV_EVENT_INDEV_RESET: Indev has been reset
- :cpp
LV_EVENT_PRESSED: 对象已被按下 - :cpp
LV_EVENT_PRESSING: 对象正在被按下（在持续按压时被调用） - :cpp
LV_EVENT_PRESS_LOST: 对象仍在被按下，但滑动光标/手指离开对象 - :cpp
LV_EVENT_SHORT_CLICKED: 对象被按下一小段时间，然后释放。如果被滚动，则不会被调用。 - :cpp
LV_EVENT_LONG_PRESSED: 对象至少被按下`long_press_time`。如果被滚动，则不会被调用。 - :cpp
LV_EVENT_LONG_PRESSED_REPEAT: 在每`long_press_repeat_time`毫秒后，调用一次。如果被滚动，则不会被调用。 - :cpp
LV_EVENT_CLICKED: 如果没有被滚动，在释放时被调用（不管长按） - :cpp
LV_EVENT_RELEASED: 在所有对象释放时被调用 - :cpp
LV_EVENT_SCROLL_BEGIN: 滚动开始。事件参数是滚动动画的指针。可以被修改 - :cpp
LV_EVENT_SCROLL_THROW_BEGIN: - :cpp
LV_EVENT_SCROLL_END: 滚动结束 - :cpp
LV_EVENT_SCROLL: 滚动 - :cpp
LV_EVENT_GESTURE: 检测到手势。使用 :cpplv_indev_get_gesture_dir(lv_indev_active());获取手势 - :cpp
LV_EVENT_KEY: 将键发送给对象。使用 :cpplv_indev_get_key(lv_indev_active());获取键 - :cpp
LV_EVENT_FOCUSED: 对象被聚焦 - :cpp
LV_EVENT_DEFOCUSED: 对象失去焦点 - :cpp
LV_EVENT_LEAVE: 对象失去焦点但仍然被选中 - :cpp
LV_EVENT_HIT_TEST: 执行高级点击测试 - :cpp
LV_EVENT_INDEV_RESET: 输入设备已重置
显示原文
- :cpp
LV_EVENT_COVER_CHECK: Check if the object fully covers an area. The event parameter is :cpplv_cover_check_info_t *. - :cpp
LV_EVENT_REFR_EXT_DRAW_SIZE: Get the required extra draw area around the object (e.g. for shadow). The event parameter is :cppint32_t *to store the size. - :cpp
LV_EVENT_DRAW_MAIN_BEGIN: Starting the main drawing phase - :cpp
LV_EVENT_DRAW_MAIN: Perform the main drawing - :cpp
LV_EVENT_DRAW_MAIN_END: Finishing the main drawing phase - :cpp
LV_EVENT_DRAW_POST_BEGIN: Starting the post draw phase (when all children are drawn) - :cpp
LV_EVENT_DRAW_POST: Perform the post draw phase (when all children are drawn) - :cpp
LV_EVENT_DRAW_POST_END: Finishing the post draw phase (when all children are drawn) - :cpp
LV_EVENT_DRAW_TASK_ADDED: Adding a draw task
- :cpp
LV_EVENT_COVER_CHECK: 检查对象是否完全覆盖了一个区域。事件参数是 :cpplv_cover_check_info_t *。 - :cpp
LV_EVENT_REFR_EXT_DRAW_SIZE: 获取对象周围所需的额外绘制区域（例如用于阴影）。事件参数是 :cppint32_t *来存储大小。 - :cpp
LV_EVENT_DRAW_MAIN_BEGIN: 开始主绘制阶段 - :cpp
LV_EVENT_DRAW_MAIN: 执行主绘制 - :cpp
LV_EVENT_DRAW_MAIN_END: 结束主绘制阶段 - :cpp
LV_EVENT_DRAW_POST_BEGIN: 开始后绘制阶段（当所有子对象都绘制完成时） - :cpp
LV_EVENT_DRAW_POST: 执行后绘制阶段（当所有子对象都绘制完成时） - :cpp
LV_EVENT_DRAW_POST_END: 结束后绘制阶段（当所有子对象都绘制完成时） - :cpp
LV_EVENT_DRAW_TASK_ADDED: 添加绘制任务
显示原文
- :cpp
LV_EVENT_VALUE_CHANGED: The object's value has changed (i.e. slider moved) - :cpp
LV_EVENT_INSERT: A text is inserted to the object. The event data is char * being inserted. - :cpp
LV_EVENT_REFRESH: Notify the object to refresh something on it (for the user) - :cpp
LV_EVENT_READY: A process has finished - :cpp
LV_EVENT_CANCEL: A process has been cancelled
- :cpp
LV_EVENT_VALUE_CHANGED: 对象的值已更改（例如，滑块移动） - :cpp
LV_EVENT_INSERT: 文本已插入到对象中。事件数据是被插入的 char *。 - :cpp
LV_EVENT_REFRESH: 通知对象刷新其上的某些内容（用户用） - :cpp
LV_EVENT_READY: 进程已结束 - :cpp
LV_EVENT_CANCEL: 进程已取消
显示原文
- :cpp
LV_EVENT_CREATE: Object is being created - :cpp
LV_EVENT_DELETE: Object is being deleted - :cpp
LV_EVENT_CHILD_CHANGED: Child was removed, added, or its size, position were changed - :cpp
LV_EVENT_CHILD_CREATED: Child was created, always bubbles up to all parents - :cpp
LV_EVENT_CHILD_DELETED: Child was deleted, always bubbles up to all parents - :cpp
LV_EVENT_SCREEN_UNLOAD_START: A screen unload started, fired immediately when scr_load is called - :cpp
LV_EVENT_SCREEN_LOAD_START: A screen load started, fired when the screen change delay is expired - :cpp
LV_EVENT_SCREEN_LOADED: A screen was loaded - :cpp
LV_EVENT_SCREEN_UNLOADED: A screen was unloaded - :cpp
LV_EVENT_SIZE_CHANGED: Object coordinates/size have changed - :cpp
LV_EVENT_STYLE_CHANGED: Object's style has changed - :cpp
LV_EVENT_LAYOUT_CHANGED: The children position has changed due to a layout recalculation - :cpp
LV_EVENT_GET_SELF_SIZE: Get the internal size of a widget
- :cpp
LV_EVENT_CREATE: 对象正在被创建 - :cpp
LV_EVENT_DELETE: 对象正在被删除 - :cpp
LV_EVENT_CHILD_CHANGED: 子对象已被移除、添加，或其大小、位置已被修改 - :cpp
LV_EVENT_CHILD_CREATED: 子对象已被创建，总是向上冒泡到所有父对象 - :cpp
LV_EVENT_CHILD_DELETED: 子对象已被删除，总是向上冒泡到所有父对象 - :cpp
LV_EVENT_SCREEN_UNLOAD_START: 屏幕卸载已开始，在调用scr_load时立即触发 - :cpp
LV_EVENT_SCREEN_LOAD_START: 屏幕加载已开始，在屏幕切换延迟过后触发 - :cpp
LV_EVENT_SCREEN_LOADED: 屏幕已加载 - :cpp
LV_EVENT_SCREEN_UNLOADED: 屏幕已卸载 - :cpp
LV_EVENT_SIZE_CHANGED: 对象坐标/大小已更改 - :cpp
LV_EVENT_STYLE_CHANGED: 对象的样式已更改 - :cpp
LV_EVENT_LAYOUT_CHANGED: 由于布局重新计算，子对象位置已更改 - :cpp
LV_EVENT_GET_SELF_SIZE: 获取部件的内部大小
- :cpp
LV_EVENT_INVALIDATE_AREA - :cpp
LV_EVENT_RESOLUTION_CHANGED - :cpp
LV_EVENT_COLOR_FORMAT_CHANGED - :cpp
LV_EVENT_REFR_REQUEST - :cpp
LV_EVENT_REFR_START - :cpp
LV_EVENT_REFR_READY - :cpp
LV_EVENT_RENDER_START - :cpp
LV_EVENT_RENDER_READY - :cpp
LV_EVENT_FLUSH_START - :cpp
LV_EVENT_FLUSH_FINISH
显示原文
Any custom event codes can be registered by uint32_t MY_EVENT_1 = :cpplv_event_register_id
They can be sent to any object with :cpplv_event_send(obj, MY_EVENT_1, &some_data)
任何自定义事件代码都可以通过 uint32_t MY_EVENT_1 = :cpplv_event_register_id 来注册。
它们可以发送到任何对象中，使用 :cpplv_event_send(obj, MY_EVENT_1, &some_data)
显示原文
To manually send events to an object, use :cpplv_obj_send_event(obj, <EVENT_CODE>, &some_data).
For example, this can be used to manually close a message box by simulating a button press (although there are simpler ways to do this):
/*Simulate the press of the first button (indexes start from zero)*/
uint32_t btn_id = 0;
lv_event_send(mbox, LV_EVENT_VALUE_CHANGED, &btn_id);The same works for display and input devices with :cpplv_display_send_event(obj, <EVENT_CODE>, &some_data) and :cpplv_indev_send_event(obj, <EVENT_CODE>, &some_data).
手动发送事件到对象，使用以下代码 :cpplv_obj_send_event(obj, <EVENT_CODE>, &some_data)。
例如，这可以用于通过模拟按钮按下来手动关闭消息框（尽管有更简单的方法来做到这一点）：
/*模拟第一个按钮的按下（索引从零开始）*/
uint32_t btn_id = 0;
lv_event_send(mbox, LV_EVENT_VALUE_CHANGED, &btn_id);对于显示器和输入设备也同样适用： :cpplv_display_send_event(obj, <EVENT_CODE>, &some_data) 和 :cpplv_indev_send_event(obj, <EVENT_CODE>, &some_data)。
显示原文
:cppLV_EVENT_REFRESH is a special event because it's designed to let the user notify an object to refresh itself. Some examples:
- notify a label to refresh its text according to one or more variables (e.g. current time)
- refresh a label when the language changes
- enable a button if some conditions are met (e.g. the correct PIN is entered)
- add/remove styles to/from an object if a limit is exceeded, etc
:cppLV_EVENT_REFRESH 是一个特殊事件，因为它被设计用来让用户通知对象刷新自身。一些例子包括：
- 通知标签根据一个或多个变量刷新其文本（比如当前时间）
- 当语言发生变化时刷新标签
- 如果满足一些条件（比如输入了正确的PIN码），则启用一个按钮
- 当超出限制时，为对象添加/移除样式，等等
显示原文
:cpplv_event_t is the only parameter passed to the event callback and it contains all data about the event. The following values can be gotten from it:
- :cpp
lv_event_get_code(e): get the event code - :cpp
lv_event_get_current_target(e): get the object to which an event was sent. I.e. the object whose event handler is being called. - :cpp
lv_event_get_target(e): get the object that originally triggered the event (different from :cpplv_event_get_targetifevent bubbling <events_bubbling>is enabled) - :cpp
lv_event_get_user_data(e): get the pointer passed as the last parameter of :cpplv_obj_add_event. - :cpp
lv_event_get_param(e): get the parameter passed as the last parameter of :cpplv_event_send
:cpplv_event_t 是传递给事件回调函数的唯一参数，它包含了该事件的所有数据。可以从中获取以下值：
- :cpp
lv_event_get_code(e)：获取事件代码 - :cpp
lv_event_get_current_target(e)：获取发送事件的对象。即，正在被调用事件处理器的对象。 - :cpp
lv_event_get_target(e)： 获取最初触发事件的对象（如果启用了event bubbling <events_bubbling>，则与 :cpplv_event_get_target不同） - :cpp
lv_event_get_user_data(e)： 获取作为 :cpplv_obj_add_event的最后一个参数传递的指针。 - :cpp
lv_event_get_param(e)： 获取作为 :cpplv_event_send的最后一个参数传递的参数。
显示原文
If :cpplv_obj_add_flag(obj, LV_OBJ_FLAG_EVENT_BUBBLE) is enabled all events will be sent to an object's parent too. If the parent also has :cppLV_OBJ_FLAG_EVENT_BUBBLE enabled the event will be sent to its parent and so on.
The target parameter of the event is always the current target object, not the original object. To get the original target call :cpplv_event_get_target_obj(e) in the event handler.
如果启用了 :cpplv_obj_add_flag(obj, LV_OBJ_FLAG_EVENT_BUBBLE)，那么所有事件也会发送给对象的父级。如果父级也启用了 :cppLV_OBJ_FLAG_EVENT_BUBBLE，那么该事件将继续被发送给其父级，依此类推。
事件的 target 参数始终是当前的目标对象，而不是原始对象。要获取原始目标，可以在事件处理函数中调用 :cpplv_event_get_target_obj(e)。