添加loading 动画

app/src/main/ets/pages/system/SystemEventPage.ets

@@ -0,0 +1,42 @@
+import commonEventManager from '@ohos.commonEventManager';
+import Base from '@ohos.base';
+
+
+@Component
+@Entry
+export struct SystemEventPage {
+  // 用于保存创建成功的订阅者对象，后续使用其完成订阅及退订的动作
+  subscriber: commonEventManager.CommonEventSubscriber | null = null;
+  // 订阅者信息
+  subscribeInfo: commonEventManager.CommonEventSubscribeInfo = {
+    events: ["usual.event.SCREEN_OFF"], // 订阅灭屏公共事件
+  }
+
+  aboutToAppear(): void {
+    // 创建订阅者回调
+    commonEventManager.createSubscriber(this.subscribeInfo, (err: Base.BusinessError, data: commonEventManager.CommonEventSubscriber) => {
+      if (err) {
+        console.error(`Failed to create subscriber. Code is ${err.code}, message is ${err.message}`);
+        return;
+      }
+      console.info('Succeeded in creating subscriber.');
+      this.subscriber = data;
+      // 订阅公共事件回调
+    })
+
+    // 订阅公共事件回调
+    if (this.subscriber !== null) {
+      commonEventManager.subscribe(this.subscriber, (err: Base.BusinessError, data: commonEventManager.CommonEventData) => {
+        if (err) {
+          console.error(`Failed to subscribe common event. Code is ${err.code}, message is ${err.message}`);
+          return;
+        }
+      })
+    } else {
+      console.error(`Need create subscriber`);
+    }
+  }
+
+  build() {
+  }
+}