lvgl8.2 圆弧渐变

### 如何在 LVGL 8.2 中创建圆弧渐变效果 #### 创建圆弧对象并应用渐变样式 为了在 LVGL 8.2 版本中实现圆弧渐变的效果，可以利用 `lv_arc` 组件以及自定义绘制函数来完成。具体来说，通过设置不同的颜色节点和调整这些节点的位置比例，可以在圆弧的不同位置显示不同颜色。 以下是具体的代码示例： ```c #include "lvgl/lvgl.h" static void draw_event_cb(lv_event_t * e) { lv_obj_draw_part_dsc_t * dsc = (lv_obj_draw_part_dsc_t *)e->param; if(dsc->part == LV_ARC_DRAW_PART_BG || dsc->part == LV_ARC_DRAW_PART_INDIC){ /* Create gradient color */ uint32_t c1 = lv_color_hex(0xFF0000).full; // Start Color Red uint32_t c2 = lv_color_hex(0x00FF00).full; // End Color Green int i; for(i = 0; i < dsc->length; i++) { float ratio = ((float)i / (float)dsc->length); uint32_t col = lv_color_mix(c1, c2, ratio).full; lv_opa_t opa_scale = LV_OPA_COVER; lv_draw_rect_dsc_t rect_draw_desc; lv_draw_rect_dsc_init(&rect_draw_desc); rect_draw_desc.bg_color.full = col; rect_draw_desc.bg_grad_dir = LV_GRAD_DIR_VER; rect_draw_desc.bg_grad_color.full = col; rect_draw_desc.radius = LV_RADIUS_CIRCLE; rect_draw_desc.opa = opa_scale; lv_area_t coords_tmp; lv_area_copy(&coords_tmp, &dsc->draw_area); coords_tmp.x1 += i; coords_tmp.x2 = coords_tmp.x1; lv_draw_rect(&coords_tmp, &rect_draw_desc, dsc->layer); } } } void create_arc_with_gradient(void) { static lv_style_t style_arc; lv_style_init(&style_arc); lv_style_set_bg_opa(&style_arc, LV_STATE_DEFAULT, LV_OPA_TRANSP); lv_style_set_pad_all(&style_arc, LV_STATE_DEFAULT, 0); lv_obj_t * arc = lv_arc_create(lv_scr_act()); lv_obj_add_style(arc, &style_arc, 0); lv_obj_center(arc); lv_obj_set_size(arc, 150, 150); lv_arc_set_rotation(arc, 270); lv_arc_set_range(arc, 0, 100); lv_arc_set_value(arc, 70); lv_obj_add_event_cb(arc, draw_event_cb, LV_EVENT_DRAW_PART_BEGIN, NULL); } ``` 此段代码展示了如何在一个圆形路径上生成线性的色彩过渡[^4]。需要注意的是，在实际开发过程中可能还需要根据需求微调参数以达到最佳视觉效果。