HarmonyOS通过CES(Common Event Service,公共事件服务)为应用程序提供订阅、发布、退订公共事件的能力,通过ANS(Advanced Notification Service,即通知增强服务)系统服务来为应用程序提供发布通知的能力。
应用如果需要接收公共事件,需要订阅相应的事件。
公共事件相关基础类包含CommonEventData、CommonEventPublishInfo、CommonEventSubscribeInfo、CommonEventSubscriber和CommonEventManager。基础类之间的关系如下图所示:
图1 公共事件基础类关系图 CommonEventData CommonEventData封装公共事件相关信息。用于在发布、分发和接收时处理数据。在构造CommonEventData对象时,相关参数需要注意以下事项:
CommonEventPublishInfo CommonEventPublishInfo封装公共事件发布相关属性、限制等信息,包括公共事件类型(有序或粘性)、接收者权限等。
CommonEventSubscriber CommonEventSubscriber封装公共事件订阅者及相关参数。
CommonEventManager CommonEventManager是为应用提供订阅、退订和发布公共事件的静态接口类。
效果演示 HarmonyOS 公共事件Demo演示
四种公共事件:无序的公共事件、带权限的公共事件、有序的公共事件、粘性的公共事件。 发布无序的公共事件:构造CommonEventData对象,设置Intent,通过构造operation对象把需要发布的公共事件信息传入intent对象。然后调用 CommonEventManager.publishCommonEvent(CommonEventData) 接口发布公共事件。
public void publishDisorderedEvent() { Intent intent = new Intent(); Operation operation = new Intent.OperationBuilder().withAction(event).build(); intent.setOperation(operation); CommonEventData eventData = new CommonEventData(intent); try { CommonEventManager.publishCommonEvent(eventData); showTips(context, "Publish succeeded"); } catch (RemoteException e) { HiLog.error(LABEL_LOG, "%{public}s", "publishDisorderedEvent remoteException."); } }
发布携带权限的公共事件:构造CommonEventPublishInfo对象,设置订阅者的权限。
"reqPermissions": [ { "name": "ohos.samples.permission", "reason": "get right", "usedScene": { "ability": [ ".MainAbilitySlice" ], "when": "inuse" } } ]
public void publishPermissionEvent() { Intent intent = new Intent(); Operation operation = new Intent.OperationBuilder().withAction(event).build(); intent.setOperation(operation); CommonEventData eventData = new CommonEventData(intent); CommonEventPublishInfo publishInfo = new CommonEventPublishInfo(); String[] permissions = {"ohos.sample.permission"}; publishInfo.setSubscriberPermissions(permissions); try { CommonEventManager.publishCommonEvent(eventData, publishInfo); showTips(context, "Publish succeeded"); } catch (RemoteException e) { HiLog.error(LABEL_LOG, "%{public}s", "publishPermissionEvent remoteException."); } }
发布有序的公共事件:构造CommonEventPublishInfo对象,通过setOrdered(true)指定公共事件属性为有序公共事件,也可以指定一个最后的公共事件接收者。
public void publishOrderlyEvent() { MatchingSkills skills = new MatchingSkills(); Intent intent = new Intent(); Operation operation = new Intent.OperationBuilder().withAction(event).build(); intent.setOperation(operation); CommonEventData eventData = new CommonEventData(intent); skills.addEvent(event); CommonEventPublishInfo publishInfo = new CommonEventPublishInfo(); publishInfo.setOrdered(true); try { CommonEventManager.publishCommonEvent(eventData, publishInfo); showTips(context, "Publish succeeded"); } catch (RemoteException e) { HiLog.error(LABEL_LOG, "%{public}s", "publishOrderlyEvent remoteException."); } }
发布粘性公共事件:构造CommonEventPublishInfo对象,通过setSticky(true)指定公共事件属性为粘性公共事件。
"reqPermissions": [ { "name": "ohos.permission.COMMONEVENT_STICKY", "reason": "get right", "usedScene": { "ability": [ ".MainAbilitySlice" ], "when": "inuse" } } ]
public void publishStickyEvent() { Intent intent = new Intent(); Operation operation = new Intent.OperationBuilder().withAction(event).build(); intent.setOperation(operation); CommonEventData eventData = new CommonEventData(intent); CommonEventPublishInfo publishInfo = new CommonEventPublishInfo(); publishInfo.setSticky(true); try { CommonEventManager.publishCommonEvent(eventData, publishInfo); showTips(context, "Publish succeeded"); } catch (RemoteException e) { HiLog.error(LABEL_LOG, "%{public}s", "publishStickyEvent remoteException."); } }
1、创建CommonEventSubscriber派生类,在onReceiveEvent()回调函数中处理公共事件。
class TestCommonEventSubscriber extends CommonEventSubscriber { TestCommonEventSubscriber(CommonEventSubscribeInfo info) { super(info); } @Override public void onReceiveEvent(CommonEventData commonEventData) { } }
2、构造MyCommonEventSubscriber对象,调用CommonEventManager.subscribeCommonEvent()接口进行订阅。
String event = "测试"; MatchingSkills matchingSkills = new MatchingSkills(); matchingSkills.addEvent(event); // 自定义事件CommonEventSubscribeInfo subscribeInfo = new CommonEventSubscribeInfo(matchingSkills); TestCommonEventSubscribersubscriber = new TestCommonEventSubscriber(subscribeInfo);try { CommonEventManager.subscribeCommonEvent(subscriber); } catch (RemoteException e) { HiLog.error(LABEL, "Exception occurred during subscribeCommonEvent invocation."); }
如果订阅的公共事件是有序的,可以调用setPriority()指定优先级。
String event = "测试"; MatchingSkills matchingSkills = new MatchingSkills(); matchingSkills.addEvent(event); // 自定义事件CommonEventSubscribeInfo subscribeInfo = new CommonEventSubscribeInfo(matchingSkills); subscribeInfo.setPriority(100); // 设置优先级,优先级取值范围[-1000,1000],值默认为0。TestCommonEventSubscribersubscriber subscriber = new TestCommonEventSubscribersubscriber (subscribeInfo);try { CommonEventManager.subscribeCommonEvent(subscriber); } catch (RemoteException e) { HiLog.error(LABEL, "Exception occurred during subscribeCommonEvent invocation."); }
3、针对在onReceiveEvent中不能执行耗时操作的限制,可以使用CommonEventSubscriber的goAsyncCommonEvent()来实现异步操作,函数返回后仍保持该公共事件活跃,且执行完成后必须调用AsyncCommonEventResult .finishCommonEvent()来结束。
EventRunner runner = EventRunner.create(); // EventRunner创建新线程,将耗时的操作放到新的线程上执行MyEventHandler myHandler = new MyEventHandler(runner); // MyEventHandler为EventHandler的派生类,在不同线程间分发和处理事件和Runnable任务@Overridepublic void onReceiveEvent(CommonEventData commonEventData){ final AsyncCommonEventResult result = goAsyncCommonEvent(); Runnable task = new Runnable() { @Override public void run() { ........ // 待执行的操作,由开发者定义 result.finishCommonEvent(); // 调用finish结束异步操作 } }; myHandler.postTask(task); }
在Ability的onStop()中调用CommonEventManager.unsubscribeCommonEvent()方法来退订公共事件。调用后,之前订阅的所有公共事件均被退订。
public void unSubscribeEvent() { if (subscriber == null) { HiLog.info(LABEL_LOG, "%{public}s", "CommonEvent onUnsubscribe commonEventSubscriber is null"); return; } try { CommonEventManager.unsubscribeCommonEvent(subscriber); showTips(context, "UnSubscribe succeeded"); } catch (RemoteException e) { HiLog.error(LABEL_LOG, "%{public}s", "unsubscribeEvent remoteException."); } destroy(); } private void destroy() { subscriber = null; eventListener = null; unSubscribe = true; }
|