Input devices（输入设备）

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An input device usually means:

Pointer-like input device like touchpad or mouse
Keypads like a normal keyboard or simple numeric keypad
Encoders with left/right turn and push options
External hardware buttons which are assigned to specific points on the screen

important:: Before reading further, please read the Porting section of Input devices

输入设备通常指：

像触摸板或鼠标这样的类似指针的输入设备
像普通键盘或简单数字键盘这样的键盘
左/右旋转和推按钮的编码器
分配给屏幕特定点的外部硬件按钮

important:: 在继续阅读前，请阅读「输入设备」的移植部分

Pointers（光标）

Cursor（光标）

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Pointer input devices (like a mouse) can have a cursor.

...
lv_indev_t * mouse_indev = lv_indev_create();
...
LV_IMAGE_DECLARE(mouse_cursor_icon);                          /*Declare the image source.*/
lv_obj_t * cursor_obj = lv_image_create(lv_screen_active());      /*Create an image object for the cursor */
lv_image_set_src(cursor_obj, &mouse_cursor_icon);           /*Set the image source*/
lv_indev_set_cursor(mouse_indev, cursor_obj);               /*Connect the image  object to the driver*/

Note that the cursor object should have lv_obj_remove_flag(cursor_obj, LV_OBJ_FLAG_CLICKABLE). For images, clicking is disabled by default.

指针输入设备（如鼠标）可以有一个指针。

代码示例：

...
lv_indev_t *mouse_indev = lv_indev_create();
...
LV_IMG_DECLARE(mouse_cursor_icon);                           /*  声明图片源   */
lv_obj_t *cursor_obj = lv_image_create(lv_screen_active());    /*  为光标创建一个图片对象  */
lv_image_set_src(cursor_obj, &mouse_cursor_icon);            /*  设置图片源  */
lv_indev_set_cursor(mouse_indev, cursor_obj);                /*  将图片对象与驱动程序连接  */

注意，光标对象应该有这样的设置 lv_obj_remove_flag(cursor_obj, LV_OBJ_FLAG_CLICKABLE)。对于图片，默认情况下是不能点击的。

Gestures (手势)

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Pointer input devices can detect basic gestures. By default, most of the widgets send the gestures to its parent, so finally the gestures can be detected on the screen object in a form of an LV_EVENT_GESTURE event. For example:

void my_event(lv_event_t * e)
{
  lv_obj_t * screen = lv_event_get_current_target(e);
  lv_dir_t dir = lv_indev_get_gesture_dir(lv_indev_active());
  switch(dir) {
    case LV_DIR_LEFT:
      ...
      break;
    case LV_DIR_RIGHT:
      ...
      break;
    case LV_DIR_TOP:
      ...
      break;
    case LV_DIR_BOTTOM:
      ...
      break;
  }
}

...

lv_obj_add_event_cb(screen1, my_event, LV_EVENT_GESTURE, NULL);

To prevent passing the gesture event to the parent from an object use lv_obj_remove_flag(obj, LV_OBJ_FLAG_GESTURE_BUBBLE).

Note that, gestures are not triggered if an object is being scrolled.

If you did some action on a gesture you can call lv_indev_wait_release(lv_indev_active()) in the event handler to prevent LVGL sending further input device related events.

指针输入设备可以检测基本手势。默认情况下，大多数小部件将手势发送给其父对象，因此最终手势可以以 LV_EVENT_GESTURE 事件的形式在屏幕对象上被检测到。例如：

void my_event(lv_event_t * e)
{
  lv_obj_t * screen = lv_event_get_current_target(e);
  lv_dir_t dir = lv_indev_get_gesture_dir(lv_indev_active());
  switch(dir) {
    case LV_DIR_LEFT:
      ...
      break;
    case LV_DIR_RIGHT:
      ...
      break;
    case LV_DIR_TOP:
      ...
      break;
    case LV_DIR_BOTTOM:
      ...
      break;
  }
}

...

lv_obj_add_event_cb(screen1, my_event, LV_EVENT_GESTURE, NULL);

要阻止将手势事件从对象传递给其父对象，请使用 lv_obj_remove_flag(obj, LV_OBJ_FLAG_GESTURE_BUBBLE)。

注意，如果对象正在滚动，手势不会触发。

如果您在手势上执行了某个操作，可以在事件处理程序中调用 lv_indev_wait_release(lv_indev_active()) 来防止 LVGL 发送进一步的与输入设备相关的事件。

Keypad and encoder（键盘和编码器）

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You can fully control the user interface without a touchpad or mouse by using a keypad or encoder(s). It works similar to the TAB key on the PC to select an element in an application or a web page.

您可以通过使用键盘或编码器来完全控制用户界面，而无需触摸板或鼠标。它类似于在电脑上使用 TAB 键来选择应用程序或网页中的元素。

Groups（组）

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Objects you want to control with a keypad or encoder need to be added to a Group. In every group there is exactly one focused object which receives the pressed keys or the encoder actions. For example, if a Text area is focused and you press some letter on a keyboard, the keys will be sent and inserted into the text area. Similarly, if a Slider is focused and you press the left or right arrows, the slider's value will be changed.

You need to associate an input device with a group. An input device can send key events to only one group but a group can receive data from more than one input device.

To create a group use lv_group_t * g = lv_group_create() and to add an object to the group use lv_group_add_obj(g, obj).

To associate a group with an input device use lv_indev_set_group(indev, g).

你想要使用键盘或编码器控制的对象需要添加到一个 Group 中。每个组中只有一个焦点对象，它接收按键或编码器动作。例如，如果一个文本区域被聚焦，你按键盘上的字母，这些按键会被发送并插入到文本区域中。同样，如果一个滑块被聚焦，你按下左右箭头键，滑块的数值会改变。

你需要将输入设备与一个组关联起来。一个输入设备只能发送按键事件到一个组，但一个组可以接收来自多个输入设备的数据。

使用 lv_group_t * g = lv_group_create() 来创建一个组，使用 lv_group_add_obj(g, obj) 来将一个对象添加到组中。

使用 lv_indev_set_group(indev, g) 来将一个组与一个输入设备关联起来。

Keys（按键）

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There are some predefined keys which have special meaning:

LV_KEY_NEXT: Focus on the next object
LV_KEY_PREV: Focus on the previous object
LV_KEY_ENTER: Triggers LV_EVENT_PRESSED, LV_EVENT_CLICKED, or LV_EVENT_LONG_PRESSED etc. events
LV_KEY_UP: Increase value or move upwards
LV_KEY_DOWN: Decrease value or move downwards
LV_KEY_RIGHT: Increase value or move to the right
LV_KEY_LEFT: Decrease value or move to the left
LV_KEY_ESC: Close or exit (E.g. close a Drop down list)
LV_KEY_DEL: Delete (E.g. a character on the right in a Text area)
LV_KEY_BACKSPACE: Delete a character on the left (E.g. in a Text area)
LV_KEY_HOME: Go to the beginning/top (E.g. in a Text area)
LV_KEY_END: Go to the end (E.g. in a Text area)

The most important special keys in your read_cb() function are:

You should translate some of your keys to these special keys to support navigation in a group and interact with selected objects.

Usually, it's enough to use only LV_KEY_LEFT and LV_KEY_RIGHT because most objects can be fully controlled with them.

With an encoder you should use only LV_KEY_LEFT, LV_KEY_RIGHT, and LV_KEY_ENTER.

有一些预定义的键具有特殊含义：

LV_KEY_NEXT：焦点移至下一个对象
LV_KEY_PREV：焦点移至上一个对象
LV_KEY_ENTER：触发 LV_EVENT_PRESSED 、LV_EVENT_CLICKED 或 LV_EVENT_LONG_PRESSED 等事件
LV_KEY_UP：增加值或向上移动
LV_KEY_DOWN：减少值或向下移动
LV_KEY_RIGHT：增加值或向右移动
LV_KEY_LEFT：减少值或向左移动
LV_KEY_ESC：关闭或退出（例如，关闭下拉列表）
LV_KEY_DEL：删除（例如，在文本区中删除右侧的字符）
LV_KEY_BACKSPACE：删除左侧的字符（例如，在文本区中）
LV_KEY_HOME：跳至开头/顶部（例如，在文本区中）
LV_KEY_END：跳至末尾（例如，在文本区中）

在你的 read_cb() 函数中，最重要的特殊键是：

你应该将一些键转换为这些特殊键，以支持在组内导航和与选定对象交互。

通常，只使用 LV_KEY_LEFT 和 LV_KEY_RIGHT 就足够了，因为大多数对象可以完全通过它们进行控制。

在使用编码器时，只需使用 LV_KEY_LEFT、LV_KEY_RIGHT 和 LV_KEY_ENTER。

Edit and navigate mode（编辑和导航模式）

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Since a keypad has plenty of keys, it's easy to navigate between objects and edit them using the keypad. But encoders have a limited number of "keys" and hence it is difficult to navigate using the default options. Navigate and Edit modes are used to avoid this problem with encoders.

In Navigate mode, an encoder's LV_KEY_LEFT or LV_KEY_RIGHT is translated to LV_KEY_NEXT or LV_KEY_PREV. Therefore, the next or previous object will be selected by turning the encoder. Pressing LV_KEY_ENTER will change to Edit mode.

In Edit mode, LV_KEY_NEXT and LV_KEY_PREV is usually used to modify an object. Depending on the object's type, a short or long press of LV_KEY_ENTER changes back to Navigate mode. Usually, an object which cannot be pressed (like a Slider) leaves Edit mode upon a short click. But with objects where a short click has meaning (e.g. Button), a long press is required.

由于键盘有大量按键，因此可以轻松使用键盘在对象之间导航并对其进行编辑。但是编码器的“按键”数量有限，因此使用默认选项进行导航很困难。导航和编辑模式被用来避免这一问题。

在导航模式下，编码器的 LV_KEY_LEFT 或 LV_KEY_RIGHT 被转换为 LV_KEY_NEXT 或 LV_KEY_PREV。因此，可以通过旋转编码器选择下一个或上一个对象。按下 LV_KEY_ENTER 将切换到编辑模式。

在编辑模式下，通常使用 LV_KEY_NEXT 和 LV_KEY_PREV 来修改对象。根据对象的类型，短按或长按 LV_KEY_ENTER 可切换回导航模式。通常，无法按压的对象（比如滑块）在短按时会离开编辑模式。但是需要在有短按功能的对象上进行长按，比如按钮。

Default group（默认组）

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Interactive widgets - such as buttons, checkboxes, sliders, etc. - can be automatically added to a default group. Just create a group with lv_group_t * g = lv_group_create() and set the default group with lv_group_set_default(g)

Don't forget to assign one or more input devices to the default group with lv_indev_set_group(my_indev, g).

交互式小部件，比如按钮、复选框、滑块等，可以自动添加到默认组中。只需创建一个组 lv_group_t * g = lv_group_create() 并将默认组设为 :g:cpp:expr:`lv_group_set_default(g)`。

不要忘记用 lv_indev_set_group(my_indev, g) 将一个或多个输入设备分配给默认组。

Styling（风格样式）

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If an object is focused either by clicking it via touchpad or focused via an encoder or keypad it goes to the LV_STATE_FOCUSED state. Hence, focused styles will be applied to it.

If an object switches to edit mode it enters the LV_STATE_FOCUSED | LV_STATE_EDITED states so these style properties will be shown.

For a more detailed description read the Style section.

如果通过触控板点击或通过编码器或键盘输入来聚焦一个对象，它会进入 LV_STATE_FOCUSED 状态。因此，聚焦的样式将被应用于该对象。

如果一个对象切换到编辑模式，它会进入:cpp:expr:LV_STATE_FOCUSED | LV_STATE_EDITED 状态，因此这些样式属性将会显示出来。

要获取更详细的描述，请阅读 Style 部分。

API