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HarmonyOS NEXT 组件通信与状态共享：构建高效的组件协作机制

1. 组件通信基础

1.1 通信方式概述

通信方式	使用场景	优点	缺点
属性传递	父子组件	简单直接	层级限制
事件机制	子到父通信	解耦合	单向流动
状态管理	全局状态	统一管理	复杂度高
依赖注入	跨组件共享	高度解耦	配置繁琐

1.2 基本属性传递

// 子组件
@Component
struct ChildComponent {@Prop title: string;  // 接收父组件传递的属性@State private count: number = 0;build() {Column() {Text(this.title)Button(`Count: ${this.count}`).onClick(() => {this.count++;})}}
}// 父组件
@Component
struct ParentComponent {@State private pageTitle: string = 'Hello';build() {Column() {ChildComponent({title: this.pageTitle})}}
}

2. 状态共享机制

2.1 状态管理器

// 全局状态定义
class AppState {@Observedclass UserState {isLoggedIn: boolean = false;username: string = '';preferences: Map<string, any> = new Map();}@Observedclass ThemeState {isDark: boolean = false;primaryColor: string = '#000000';fontSize: number = 14;}user: UserState = new UserState();theme: ThemeState = new ThemeState();
}// 状态管理器
class StateManager {private static instance: StateManager;private state: AppState = new AppState();static getInstance(): StateManager {if (!this.instance) {this.instance = new StateManager();}return this.instance;}getState(): AppState {return this.state;}// 更新用户状态updateUserState(updates: Partial<AppState['user']>) {Object.assign(this.state.user, updates);}// 更新主题状态updateThemeState(updates: Partial<AppState['theme']>) {Object.assign(this.state.theme, updates);}
}

2.2 状态注入与使用

@Component
struct ThemeAwareComponent {@ObjectLink themeState: AppState['theme'];build() {Column() {Text('Current Theme').fontSize(this.themeState.fontSize).fontColor(this.themeState.primaryColor)Toggle({ type: ToggleType.Switch, isOn: this.themeState.isDark }).onChange((isOn: boolean) => {this.themeState.isDark = isOn;})}}
}

3. 事件总线实现

3.1 事件总线定义

type EventCallback = (...args: any[]) => void;class EventBus {private static instance: EventBus;private events: Map<string, Set<EventCallback>> = new Map();static getInstance(): EventBus {if (!this.instance) {this.instance = new EventBus();}return this.instance;}// 订阅事件on(event: string, callback: EventCallback): void {if (!this.events.has(event)) {this.events.set(event, new Set());}this.events.get(event).add(callback);}// 取消订阅off(event: string, callback: EventCallback): void {if (this.events.has(event)) {this.events.get(event).delete(callback);}}// 触发事件emit(event: string, ...args: any[]): void {if (this.events.has(event)) {this.events.get(event).forEach(callback => {callback(...args);});}}
}

3.2 事件总线使用

@Component
struct EventComponent {private eventBus = EventBus.getInstance();@State private message: string = '';aboutToAppear() {// 订阅事件this.eventBus.on('updateMessage', (msg: string) => {this.message = msg;});}aboutToDisappear() {// 取消订阅this.eventBus.off('updateMessage', this.handleMessage);}build() {Column() {Text(this.message)Button('Send Message').onClick(() => {this.eventBus.emit('updateMessage', 'Hello from EventBus!');})}}
}

4. 依赖注入

4.1 服务定义

interface UserService {getCurrentUser(): Promise<User>;updateProfile(data: Partial<User>): Promise<void>;
}@Injectable
class UserServiceImpl implements UserService {async getCurrentUser(): Promise<User> {// 实现获取用户信息的逻辑return null;}async updateProfile(data: Partial<User>): Promise<void> {// 实现更新用户信息的逻辑}
}// 依赖注入容器
class Container {private static instance: Container;private services: Map<string, any> = new Map();static getInstance(): Container {if (!this.instance) {this.instance = new Container();}return this.instance;}// 注册服务register<T>(token: string, implementation: T): void {this.services.set(token, implementation);}// 获取服务resolve<T>(token: string): T {if (!this.services.has(token)) {throw new Error(`Service ${token} not found`);}return this.services.get(token);}
}

4.2 服务使用

@Component
struct UserProfileComponent {@Inject('UserService') userService: UserService;@State private user: User = null;async aboutToAppear() {try {this.user = await this.userService.getCurrentUser();} catch (error) {console.error('Failed to load user:', error);}}build() {Column() {if (this.user) {Text(this.user.name)Button('Update Profile').onClick(async () => {await this.userService.updateProfile({name: 'New Name'});})}}}
}

5. 实战案例

5.1 购物车状态管理

// 购物车状态
@Observed
class CartState {items: Map<string, CartItem> = new Map();total: number = 0;addItem(item: Product, quantity: number = 1) {const cartItem = this.items.get(item.id) || {product: item,quantity: 0};cartItem.quantity += quantity;this.items.set(item.id, cartItem);this.calculateTotal();}removeItem(itemId: string) {this.items.delete(itemId);this.calculateTotal();}private calculateTotal() {this.total = Array.from(this.items.values()).reduce((sum, item) => sum + item.product.price * item.quantity, 0);}
}// 购物车组件
@Component
struct CartComponent {@ObjectLink cartState: CartState;build() {Column() {// 购物车列表List() {ForEach(Array.from(this.cartState.items.values()), (item: CartItem) => {ListItem() {CartItemComponent({ item })}})}// 总计Row() {Text(`Total: $${this.cartState.total.toFixed(2)}`)Button('Checkout').onClick(() => {// 处理结算逻辑})}}}
}

5.2 主题切换实现

// 主题定义
interface Theme {primaryColor: string;backgroundColor: string;textColor: string;fontSize: {small: number;medium: number;large: number;};
}// 主题服务
@Injectable
class ThemeService {private currentTheme: Theme;private eventBus = EventBus.getInstance();setTheme(theme: Theme) {this.currentTheme = theme;this.eventBus.emit('themeChanged', theme);}getTheme(): Theme {return this.currentTheme;}
}// 主题感知组件
@Component
struct ThemeAwareButton {@Inject('ThemeService') themeService: ThemeService;private text: string;@State private theme: Theme;aboutToAppear() {this.theme = this.themeService.getTheme();EventBus.getInstance().on('themeChanged', (newTheme: Theme) => {this.theme = newTheme;});}build() {Button(this.text).backgroundColor(this.theme.primaryColor).fontColor(this.theme.textColor).fontSize(this.theme.fontSize.medium)}
}

5.3 表单状态管理

// 表单状态
@Observed
class FormState {values: Map<string, any> = new Map();errors: Map<string, string> = new Map();isDirty: boolean = false;setValue(field: string, value: any) {this.values.set(field, value);this.isDirty = true;this.validate(field);}setError(field: string, error: string) {this.errors.set(field, error);}validate(field: string) {// 实现字段验证逻辑}isValid(): boolean {return this.errors.size === 0;}
}// 表单组件
@Component
struct FormComponent {@ObjectLink formState: FormState;build() {Column() {TextInput({placeholder: 'Username'}).onChange((value: string) => {this.formState.setValue('username', value);})if (this.formState.errors.has('username')) {Text(this.formState.errors.get('username')).fontColor(Color.Red)}Button('Submit').enabled(this.formState.isValid()).onClick(() => {// 处理表单提交})}}
}

5.4 最佳实践建议

1. 状态管理

   • 合理划分状态范围
   • 避免状态重复
   • 实现状态同步机制

2. 组件通信

   • 选择合适的通信方式
   • 保持单向数据流
   • 避免过度耦合

3. 依赖注入

   • 合理使用服务抽象
   • 实现依赖的解耦
   • 便于单元测试

4. 性能优化

   • 避免不必要的状态更新
   • 合理使用事件解绑
   • 优化组件重渲染

通过合理使用组件通信和状态共享机制，可以构建出结构清晰、易于维护的应用。在实际开发中，要根据具体需求选择合适的通信方式，并注意性能优化和代码质量。