HarmonyOS 鸿蒙Next启动的闪屏页怎么配置

可以使用创建子窗口的方式实现您的需求，可参考以下demo思路：

//EntryAbility ,在EntryAbility 里加载根页面以及创建子窗口100%宽高
import { AbilityConstant, UIAbility, Want } from '@kit.AbilityKit';
import { hilog } from '@kit.PerformanceAnalysisKit';
import { display, window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';
import { calendarManager } from '@kit.CalendarKit';
import common from '@ohos.app.ability.common';
import { JSON } from '@kit.ArkTS';

let windowStage_: window.WindowStage | null = null;
let sub_windowClass: window.Window | null = null;

export let calendarMgr: calendarManager.CalendarManager;
export let mContext: common.UIAbilityContext;

export default class EntryAbility extends UIAbility {
  onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onCreate');
  }

  onDestroy(): void {
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onDestroy');
  }

  showSubWindow() {
    // 1.创建应用子窗口。
    if (windowStage_ == null) {
      console.error('Failed to create the subwindow. Cause: windowStage_ is null');
    } else {
      windowStage_.createSubWindow("mySubWindow", (err: BusinessError, data) => {
        let errCode: number = err.code;
        if (errCode) {
          console.error('Failed to create the subwindow. Cause: ' + JSON.stringify(err));
          return;
        }
        sub_windowClass = data;
        console.info('Succeeded in creating the subwindow. Data: ' + JSON.stringify(data));
        // 2.子窗口创建成功后，设置子窗口的位置、大小及相关属性等。
        let displayClass: display.Display = display.getDefaultDisplaySync(); //获取屏幕大小
        sub_windowClass.resize(displayClass.width, displayClass.height, (err: BusinessError) => {
          let errCode: number = err.code;
          if (errCode) {
            console.error('Failed to change the window size. Cause:' + JSON.stringify(err));
            return;
          }
          console.info('Succeeded in changing the window size.');
        });
        // 3.为子窗口加载对应的目标页面。
        sub_windowClass.setUIContent("components/media/Video", (err: BusinessError) => {
          let errCode: number = err.code;
          if (errCode) {
            console.error('Failed to load the content. Cause:' + JSON.stringify(err));
            return;
          }
          console.info('Succeeded in loading the content.');
          // 3.显示子窗口。
          (sub_windowClass as window.Window).showWindow((err: BusinessError) => {
            let errCode: number = err.code;
            if (errCode) {
              console.error('Failed to show the window. Cause: ' + JSON.stringify(err));
              return;
            }
            console.info('Succeeded in showing the window.');
          });
        });
      })
    }
  }

  destroySubWindow() {
    // 4.销毁子窗口。当不再需要子窗口时，可根据具体实现逻辑，使用destroy对其进行销毁。
    (sub_windowClass as window.Window).destroyWindow((err: BusinessError) => {
      let errCode: number = err.code;
      if (errCode) {
        console.error('Failed to destroy the window. Cause: ' + JSON.stringify(err));
        return;
      }
      console.info('Succeeded in destroying the window.');
    });
  }

  onWindowStageCreate(windowStage: window.WindowStage): void {
    // Main window is created, set main page for this ability
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageCreate');
    windowStage.loadContent('pages/Index', (err, data) => {
      if (err.code) {
        hilog.error(0x0000, 'testTag', 'Failed to load the content. Cause: %{public}s', JSON.stringify(err) ?? '');
        return;
      }
      AppStorage.setOrCreate('windowStage',windowStage)
      windowStage_ = windowStage
      this.showSubWindow();
    });
  }

  onWindowStageDestroy(): void {
    // Main window is destroyed, release UI related resources
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageDestroy');
  }

  onForeground(): void {
    // Ability has brought to foreground
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onForeground');
  }

  onBackground(): void {
    // Ability has back to background
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onBackground');
  }
}

在子窗口文件中使用计时函数，到时间后使用window.findWindow(“mySubWindow”).destroyWindow()销毁子窗口显示首页