公共事件
OpenHarmony 提供了许多系统事件,比如屏幕息屏亮屏事件、USB插拔事件以及APP的安装卸载等,由于这些事件是系统发出的,如果需要监听这些系统事件,比如设备电量低需要给用户提示充电等场景该怎么办喃?ArkUI开发框架给我们提供了 @ohos.commonEventManager
模块,它不仅可以订阅系统事件,而且还可以订阅和发布自定义事件,本节笔者简单介绍一下该库相关 API 的使用。
commonEventManager定义介绍
declare namespace commonEventManager {
function publish(event: string, callback: AsyncCallback<void>): void;
function publish(event: string, options: CommonEventPublishData, callback: AsyncCallback<void>): void;
function publishAsUser(event: string, userId: number, callback: AsyncCallback<void>): void;
function publishAsUser(event: string, userId: number, options: CommonEventPublishData, callback: AsyncCallback<void>): void;
function createSubscriber(subscribeInfo: CommonEventSubscribeInfo, callback: AsyncCallback<CommonEventSubscriber>): void;
function createSubscriber(subscribeInfo: CommonEventSubscribeInfo): Promise<CommonEventSubscriber>;
function subscribe(subscriber: CommonEventSubscriber, callback: AsyncCallback<CommonEventData>): void;
function unsubscribe(subscriber: CommonEventSubscriber, callback?: AsyncCallback<void>): void;
}
- publish:发送公共事件,
event
表示事件名称。 - publishAsUser:发送指定用户的公共事件。
- createSubscriber:创建事件的订阅者。
- subscribe:订阅事件,可以是公共事件,也可以是自定义事件。
- unsubscribe:取消订阅事件,一旦取消,后续对的事件将不再接收。
@ohos.commonEventManager
模块提供的 API 使用很简单,首先创建接收事件的订阅者,然后开始订阅事件,最后取消订阅。发布事件直接调用 publish()
方法发布事件即可,如果事件匹配到订阅者订阅的事件类型,就会回调给订阅者,
完整源码
import commonEvent from '@ohos.commonEventManager'; // 引入事件包
@Entry
@Component
struct Index {
@State text: string = "";
@State publish: string = "";
private subscriber = null;
private createSubscriber() {
if (this.subscriber) {
this.text = "subscriber already created";
} else {
commonEvent.createSubscriber({
// 创建订阅者
events: ["testEvent"] // 指定订阅的事件名称
}, (err, subscriber) => {
// 创建结果的回调
if (err) {
this.text = "create subscriber failure"
} else {
this.subscriber = subscriber; // 创建订阅成功
this.text = "create subscriber success";
}
})
}
}
private subscribe() {
if (this.subscriber) {
// 根据创建的subscriber开始订阅事件
commonEvent.subscribe(this.subscriber, (err, data) => {
if (err) {
// 异常处理
this.text = "subscribe event failure: " + err;
} else {
// 接收到事件
this.text = "subscribe event success: " + JSON.stringify(data.event) + ", " + JSON.stringify(data);
}
})
} else {
this.text = "please create subscriber";
}
}
private unsubscribe() {
if (this.subscriber) {
commonEvent.unsubscribe(this.subscriber, (err) => {
// 取消订阅事件
if (err) {
this.text = "unsubscribe event failure: " + err;
} else {
this.subscriber = null;
this.text = "unsubscribe event success: ";
}
})
} else {
this.text = "already subscribed";
}
}
private publishEvent() {
commonEvent.publish("testEvent", (err) => {
// 发布事件,事件名称为testEvent
if (err) {
// 结果回调
this.publish = "publish event error: " + err.code + ", " + err.message + ", " + err.name + ", " + err.stack;
} else {
this.publish = "publish event success";
}
})
}
private publishEventWithData() {
commonEvent.publish("testEvent", {
// 发布事件,事件名称为testEvent
code: 10086, // 事件携带的参数
data: "publish with data",
parameters: {
id: 1,
content: "坚果"
}
// 事件携带的参数
}, (err) => {
// 结果回调
if (err) {
this.publish = "publish event error: " + err.code + ", " + err.message + ", " + err.name + ", " + err.stack;
} else {
this.publish = "publish event with data success";
}
})
}
build() {
Column({
space: 10 }) {
Button("创建订阅者")
.size({
width: 260, height: 50 })
.onClick(() => {
this.createSubscriber();
})
Button("订阅公共事件")
.size({
width: 260, height: 50 })
.onClick(() => {
this.subscribe();
})
Button("取消订阅")
.size({
width: 260, height: 50 })
.onClick(() => {
this.unsubscribe();
})
Text(this.text)
.size({
width: 260, height: 260 })
.fontSize(22)
.backgroundColor("#dbdbdb")
Divider()
.size({
width: 260, height: 5 })
Button("发布公共事件")
.size({
width: 260, height: 50 })
.onClick(() => {
this.publishEvent();
})
Button("发布公共事件指定公共信息")
.size({
width: 260, height: 50 })
.onClick(() => {
this.publishEventWithData();
})
Text(this.publish)
.size({
width: 260, height: 150 })
.fontSize(22)
.backgroundColor("#dbdbdb")
}
.padding(10)
.size({
width: "100%", height: '100%' })
}
}
完毕