鸿蒙HarmonyO实战-ArkTS语言(状态管理)

🚀前言
状态管理是指在应用程序中维护和更新应用程序状态的过程。在一个程序中,可能有很多不同的组件和模块,它们需要共享和相互作用的状态。如果没有一个明确的方式来管理这些状态,就会导致代码混乱、不易维护和难以扩展。

状态管理的目标是提供一种机制,使得所有的组件和模块都可以访问和更新同一个状态。这个状态通常是存储在一个中央存储区域中,被称为状态存储或状态容器。状态管理通常与应用程序的响应式设计紧密相连,以便在状态改变时自动更新应用程序的界面。

🚀一、ArkTS语言状态管理
🔎1.概述
在声明式UI编程框架中,应用程序的UI是由程序状态驱动的。用户构建一个UI模型,其中应用的运行时状态作为参数传递进去。当参数改变时,UI会根据新的参数重新渲染。这个运行时状态的变化是由状态管理机制来处理的,它会监控状态的变化,并自动更新UI的渲染。在ArkUI中,自定义组件的变量必须被装饰器装饰为状态变量,这样它们的改变才能引起UI的重新渲染。如果不使用状态变量,UI只能在初始化时渲染,后续将不会再刷新。状态变量和UI之间的关系如下图所示:

View(UI):UI渲染,指将build方法内的UI描述和@Builder装饰的方法内的UI描述映射到界面。

State:状态,指驱动UI更新的数据。用户通过触发组件的事件方法,改变状态数据。状态数据的改变,引起UI的重新渲染。

🦋1.1 基本概念

@Component
struct MyComponent {
  //状态变量:被状态装饰器装饰的变量,状态变量值的改变会引起UI的渲染更新
  @State count: number = 0;
  //常规变量:没有被状态装饰器装饰的变量,通常应用于辅助计算。
  private increaseBy: number = 1;

  build() {
  }
}

@Component
struct Parent {
  build() {
    Column() {
      // 从父组件初始化,覆盖本地定义的默认值
      MyComponent({ count: 1, increaseBy: 2 })
    }
  }
}

🦋1.2 装饰器总览
ArkUI提供了多种装饰器主要分为:管理组件拥有的状态、管理应用拥有的状态、其他状态管理功能,主要图形如下:

☀️1.2.1 管理组件拥有的状态

🌈1.2.1.1 @State 组件内状态


@State变量装饰器只支持Object、class、string、number、boolean、enum类型,以及这些类型的数组。不支持复杂类型(比如Date类型)

父子组件初始化和传递装饰图如下:

🍬1.2.1.1.1 变化规则
1、可变类型(boolean、string、number)

// for simple type
@State count: number = 0;
// value changing can be observed
this.count = 1;
2、可变类型(class、Object)

class ClassA {
  public value: string;

  constructor(value: string) {
    this.value = value;
  }
}

class Model {
  public value: string;
  public name: ClassA;
  constructor(value: string, a: ClassA) {
    this.value = value;
    this.name = a;
  }
}

// class类型
@State title: Model = new Model('Hello', new ClassA('World'));

// class类型赋值
this.title = new Model('Hi', new ClassA('ArkUI'));

// class属性的赋值
this.title.value = 'Hi'

// 嵌套的属性赋值观察不到
this.title.name.value = 'ArkUI'

3、可变类型(array)

class Model {
  public value: number;
  constructor(value: number) {
    this.value = value;
  }
}
@State title: Model[] = [new Model(11), new Model(1)]

this.title = [new Model(2)]

this.title[0] = new Model(2)

this.title.pop()

this.title.push(new Model(12))

🍬1.2.1.1.2 使用场景
1、简单类型

@Entry
@Component
struct MyComponent {
  @State count: number = 0;

  build() {
    Button(`click times: ${this.count}`)
      .onClick(() => {
        this.count += 1;
      })
  }
}

2、其他类型

class Model {
  public value: string;

  constructor(value: string) {
    this.value = value;
  }
}

@Entry
@Component
struct EntryComponent {
  build() {
    Column() {
      // 此处指定的参数都将在初始渲染时覆盖本地定义的默认值,并不是所有的参数都需要从父组件初始化
      MyComponent({ count: 1, increaseBy: 2 })
      MyComponent({ title: new Model('Hello, World 2'), count: 7 })
    }
  }
}

@Component
struct MyComponent {
  @State title: Model = new Model('Hello World');
  @State count: number = 0;
  private increaseBy: number = 1;

  build() {
    Column() {
      Text(`${this.title.value}`)
      Button(`Click to change title`).onClick(() => {
        // @State变量的更新将触发上面的Text组件内容更新
        this.title.value = this.title.value === 'Hello ArkUI' ? 'Hello World' : 'Hello ArkUI';
      })

      Button(`Click to increase count=${this.count}`).onClick(() => {
        // @State变量的更新将触发该Button组件的内容更新
        this.count += this.increaseBy;
      })
    }
  }
}

🌈1.2.1.2 @Prop 父子单向同步

@Prop变量装饰器只支持string、number、boolean、enum类型,以及这些类型的数组。不支持复杂类型(比如any类型)

父子组件初始化和传递装饰图如下:

1.2.1.2.1 变化规则
1、简单类型

// 简单类型
@Prop count: number;
// 赋值的变化可以被观察到
this.count = 1;

对于@State和@Prop的同步场景:

  • 使用父组件中@State变量的值初始化子组件中的@Prop变量。当@State变量变化时,该变量值也会同步更新至@Prop变量。

  • @Prop装饰的变量的修改不会影响其数据源@State装饰变量的值。

  • 除了@State,数据源也可以用@Link或@Prop装饰,对@Prop的同步机制是相同的。

  • 数据源和@Prop变量的类型需要相同。

🍬1.2.1.2.2 使用场景
1、父组件@State到子组件@Prop简单数据类型同步

@Component
struct CountDownComponent {
  @Prop count: number;
  costOfOneAttempt: number = 1;

  build() {
    Column() {
      if (this.count > 0) {
        Text(`You have ${this.count} Nuggets left`)
      } else {
        Text('Game over!')
      }
      // @Prop装饰的变量不会同步给父组件
      Button(`Try again`).onClick(() => {
        this.count -= this.costOfOneAttempt;
      })
    }
  }
}
@Entry
@Component
struct ParentComponent {
  @State countDownStartValue: number = 10;
  build() {
    Column() {
      Text(`Grant ${this.countDownStartValue} nuggets to play.`)
      // 父组件的数据源的修改会同步给子组件
      Button(`+1 - Nuggets in New Game`).onClick(() => {
        this.countDownStartValue += 1;
      })
      // 父组件的修改会同步给子组件
      Button(`-1  - Nuggets in New Game`).onClick(() => {
        this.countDownStartValue -= 1;
      })
      CountDownComponent({ count: this.countDownStartValue, costOfOneAttempt: 2 })
    }
  }
}

2、父组件@State数组项到子组件@Prop简单数据类型同步

@Component
struct Child {
  @Prop value: number;

  build() {
    Text(`${this.value}`)
      .fontSize(50)
      .onClick(()=>{this.value++})
  }
}
@Entry
@Component
struct Index {
  @State arr: number[] = [1,2,3];
  build() {
    Row() {
      Column() {
        Child({value: this.arr[0]})
        Child({value: this.arr[1]})
        Child({value: this.arr[2]})
        Divider().height(5)
        ForEach(this.arr, 
          item => {
            Child({value: item})
          }, 
          item => item.toString()
        )
        Text('replace entire arr')
        .fontSize(50)
        .onClick(()=>{
          // 两个数组都包含项“3”。
          this.arr = this.arr[0] == 1 ? [3,4,5] : [1,2,3];
        })
      }
    }
  }
}

3、从父组件中的@State类对象属性到@Prop简单类型的同步

class Book {
  public title: string;
  public pages: number;
  public readIt: boolean = false;

  constructor(title: string, pages: number) {
    this.title = title;
    this.pages = pages;
  }
}

@Component
struct ReaderComp {
  @Prop title: string;
  @Prop readIt: boolean;

  build() {
    Row() {
      Text(this.title)
      Text(`... ${this.readIt ? 'I have read' : 'I have not read it'}`)
        .onClick(() => this.readIt = true)
    }
  }
}
@Entry
@Component
struct Library {
  @State book: Book = new Book('100 secrets of C++', 765);
  build() {
    Column() {
      ReaderComp({ title: this.book.title, readIt: this.book.readIt })
      ReaderComp({ title: this.book.title, readIt: this.book.readIt })
    }
  }
}

4、@Prop本地初始化不和父组件同步

@Component
struct MyComponent {
  @Prop customCounter: number;
  @Prop customCounter2: number = 5;

  build() {
    Column() {
      Row() {
        Text(`From Main: ${this.customCounter}`).width(90).height(40).fontColor('#FF0010')
      }

      Row() {
        Button('Click to change locally !').width(180).height(60).margin({ top: 10 })
          .onClick(() => {
            this.customCounter2++
          })
      }.height(100).width(180)
      Row() {
        Text(`Custom Local: ${this.customCounter2}`).width(90).height(40).fontColor('#FF0010')
      }
    }
  }
}
@Entry
@Component
struct MainProgram {
  @State mainCounter: number = 10;
  build() {
    Column() {
      Row() {
        Column() {
          Button('Click to change number').width(480).height(60).margin({ top: 10, bottom: 10 })
            .onClick(() => {
              this.mainCounter++
            })
        }
      }
      Row() {
        Column()
        // customCounter必须从父组件初始化,因为MyComponent的customCounter成员变量缺少本地初始化;此处,customCounter2可以不做初始化。
        MyComponent({ customCounter: this.mainCounter })
        // customCounter2也可以从父组件初始化,父组件初始化的值会覆盖子组件customCounter2的本地初始化的值
        MyComponent({ customCounter: this.mainCounter, customCounter2: this.mainCounter })
      }
    }
  }
}

🌈1.2.1.3 @Link 父子双向同步
父组件中@State, @StorageLink和@Link 和子组件@Link可以建立双向数据同步。

@Link 变量装饰器只支持string、number、boolean、enum类型,以及这些类型的数组。不支持复杂类型(比如any类型)

父子组件初始化和传递装饰图如下:

🍬1.2.1.3.1 变化规则

  • 当装饰的数据类型为boolean、string、number类型时,可以同步观察到数值的变化。

  • 当装饰的数据类型为class或者Object时,可以观察到赋值和属性赋值的变化,即Object.keys(observedObject)返回的所有属性。

  • 当装饰的对象是array时,可以观察到数组添加、删除、更新数组单元的变化。

🍬1.2.1.3.2 使用场景
1、简单类型和类对象类型的@Link

class GreenButtonState {
  width: number = 0;
  constructor(width: number) {
    this.width = width;
  }
}
@Component
struct GreenButton {
  @Link greenButtonState: GreenButtonState;
  build() {
    Button('Green Button')
      .width(this.greenButtonState.width)
      .height(150.0)
      .backgroundColor('#00ff00')
      .onClick(() => {
        if (this.greenButtonState.width < 700) {
          // 更新class的属性,变化可以被观察到同步回父组件
          this.greenButtonState.width += 125;
        } else {
          // 更新class,变化可以被观察到同步回父组件
          this.greenButtonState = new GreenButtonState(100);
        }
      })
  }
}
@Component
struct YellowButton {
  @Link yellowButtonState: number;
  build() {
    Button('Yellow Button')
      .width(this.yellowButtonState)
      .height(150.0)
      .backgroundColor('#ffff00')
      .onClick(() => {
        // 子组件的简单类型可以同步回父组件
        this.yellowButtonState += 50.0;
      })
  }
}
@Entry
@Component
struct ShufflingContainer {
  @State greenButtonState: GreenButtonState = new GreenButtonState(300);
  @State yellowButtonProp: number = 100;
  build() {
    Column() {
      // 简单类型从父组件@State向子组件@Link数据同步
      Button('Parent View: Set yellowButton')
        .onClick(() => {
          this.yellowButtonProp = (this.yellowButtonProp < 700) ? this.yellowButtonProp + 100 : 100;
        })
      // class类型从父组件@State向子组件@Link数据同步
      Button('Parent View: Set GreenButton')
        .onClick(() => {
          this.greenButtonState.width = (this.greenButtonState.width < 700) ? this.greenButtonState.width + 100 : 100;
        })
      // class类型初始化@Link
      GreenButton({ greenButtonState: $greenButtonState })
      // 简单类型初始化@Link
      YellowButton({ yellowButtonState: $yellowButtonProp })
    }
  }
}

2、数组类型的@Link

@Component
struct Child {
  @Link items: number[];

  build() {
    Column() {
      Button(`Button1: push`).onClick(() => {
        this.items.push(this.items.length + 1);
      })
      Button(`Button2: replace whole item`).onClick(() => {
        this.items = [100, 200, 300];
      })
    }
  }
}
@Entry
@Component
struct Parent {
  @State arr: number[] = [1, 2, 3];
  build() {
    Column() {
      Child({ items: $arr })
      ForEach(this.arr,
        item => {
          Text(`${item}`)
        },
        item => item.toString()
      )
    }
  }
}

🌈1.2.1.4 @Provide/@Consume 与后代组件双向同步

@Prop变量装饰器只支持string、number、boolean、enum类型,以及这些类型的数组。不支持复杂类型(比如any类型)

父子组件初始化和传递装饰图如下:

🍬1.2.1.4.1 变化规则

  • 当装饰的数据类型为boolean、string、number类型时,可以观察到数值的变化。

  • 当装饰的数据类型为class或者Object的时候,可以观察到赋值和属性赋值的变化(属性为Object.keys(observedObject)返回的所有属性)。

  • 当装饰的对象是array的时候,可以观察到数组的添加、删除、更新数组单元。

🍬1.2.1.4.2 使用场景

@Component
struct CompD {
  // @Consume装饰的变量通过相同的属性名绑定其祖先组件CompA内的@Provide装饰的变量
  @Consume reviewVotes: number;

  build() {
    Column() {
      Text(`reviewVotes(${this.reviewVotes})`)
      Button(`reviewVotes(${this.reviewVotes}), give +1`)
        .onClick(() => this.reviewVotes += 1)
    }
    .width('50%')
  }
}
@Component
struct CompC {
  build() {
    Row({ space: 5 }) {
      CompD()
      CompD()
    }
  }
}
@Component
struct CompB {
  build() {
    CompC()
  }
}
@Entry
@Component
struct CompA {
  // @Provide装饰的变量reviewVotes由入口组件CompA提供其后代组件
  @Provide reviewVotes: number = 0;
  build() {
    Column() {
      Button(`reviewVotes(${this.reviewVotes}), give +1`)
        .onClick(() => this.reviewVotes += 1)
      CompB()
    }
  }
}

🌈1.2.1.5 @Observed/@ObjectLink 嵌套类对象属性变化


类型必须是@Observed装饰的class,可用于初始化常规变量、@State、@Link、@Prop、@Provide

嵌套类对象装饰图如下:

🍬1.2.1.5.1 变化规则

class ClassA {
  public c: number;

  constructor(c: number) {
    this.c = c;
  }
}

@Observed
class ClassB {
  public a: ClassA;
  public b: number;

  constructor(a: ClassA, b: number) {
    this.a = a;
    this.b = b;
  }
}

@ObjectLink b: ClassB

// 赋值变化可以被观察到
this.b.a = new ClassA(5)
this.b.b = 5

// ClassA没有被@Observed装饰,其属性的变化观察不到
this.b.a.c = 5

🍬1.2.1.5.2 使用场景
1、嵌套对象

// objectLinkNestedObjects.ets
let NextID: number = 1;

@Observed
class ClassA {
  public id: number;
  public c: number;

  constructor(c: number) {
    this.id = NextID++;
    this.c = c;
  }
}

@Observed
class ClassB {
  public a: ClassA;

  constructor(a: ClassA) {
    this.a = a;
  }
}

@Component
struct ViewA {
  label: string = 'ViewA1';
  @ObjectLink a: ClassA;

  build() {
    Row() {
      Button(`ViewA [${this.label}] this.a.c=${this.a.c} +1`)
        .onClick(() => {
          this.a.c += 1;
        })
    }
  }
}
@Entry
@Component
struct ViewB {
  @State b: ClassB = new ClassB(new ClassA(0));
  build() {
    Column() {
      ViewA({ label: 'ViewA #1', a: this.b.a })
      ViewA({ label: 'ViewA #2', a: this.b.a })
      Button(`ViewB: this.b.a.c+= 1`)
        .onClick(() => {
          this.b.a.c += 1;
        })
      Button(`ViewB: this.b.a = new ClassA(0)`)
        .onClick(() => {
          this.b.a = new ClassA(0);
        })
      Button(`ViewB: this.b = new ClassB(ClassA(0))`)
        .onClick(() => {
          this.b = new ClassB(new ClassA(0));
        })
    }
  }
}

2、对象数组

@Component
struct ViewA {
  // 子组件ViewA的@ObjectLink的类型是ClassA
  @ObjectLink a: ClassA;
  label: string = 'ViewA1';

  build() {
    Row() {
      Button(`ViewA [${this.label}] this.a.c = ${this.a.c} +1`)
        .onClick(() => {
          this.a.c += 1;
        })
    }
  }
}
@Entry
@Component
struct ViewB {
  // ViewB中有@State装饰的ClassA[]
  @State arrA: ClassA[] = [new ClassA(0), new ClassA(0)];
  build() {
    Column() {
      ForEach(this.arrA,
        (item) => {
          ViewA({ label: `#${item.id}`, a: item })
        },
        (item) => item.id.toString()
      )
      // 使用@State装饰的数组的数组项初始化@ObjectLink,其中数组项是被@Observed装饰的ClassA的实例
      ViewA({ label: `ViewA this.arrA[first]`, a: this.arrA[0] })
      ViewA({ label: `ViewA this.arrA[last]`, a: this.arrA[this.arrA.length-1] })
      Button(`ViewB: reset array`)
        .onClick(() => {
          this.arrA = [new ClassA(0), new ClassA(0)];
        })
      Button(`ViewB: push`)
        .onClick(() => {
          this.arrA.push(new ClassA(0))
        })
      Button(`ViewB: shift`)
        .onClick(() => {
          this.arrA.shift()
        })
      Button(`ViewB: chg item property in middle`)
        .onClick(() => {
          this.arrA[Math.floor(this.arrA.length / 2)].c = 10;
        })
      Button(`ViewB: chg item property in middle`)
        .onClick(() => {
          this.arrA[Math.floor(this.arrA.length / 2)] = new ClassA(11);
        })
    }
  }
}

3、二维数组

@Observed
class StringArray extends Array<String> {
}

@Observed
class StringArray extends Array<String> {
}

@Component
struct ItemPage {
  @ObjectLink itemArr: StringArray;

  build() {
    Row() {
      Text('ItemPage')
        .width(100).height(100)

      ForEach(this.itemArr,
        item => {
          Text(item)
            .width(100).height(100)
        },
        item => item
      )
    }
  }
}

@Entry
@Component
struct IndexPage {
  @State arr: Array<StringArray> = [new StringArray(), new StringArray(), new StringArray()];

  build() {
    Column() {
      ItemPage({ itemArr: this.arr[0] })
      ItemPage({ itemArr: this.arr[1] })
      ItemPage({ itemArr: this.arr[2] })

      Divider()

      ForEach(this.arr,
        itemArr => {
          ItemPage({ itemArr: itemArr })
        },
        itemArr => itemArr[0]
      )

      Divider()

      Button('update')
        .onClick(() => {
          console.error('Update all items in arr');
          if (this.arr[0][0] !== undefined) {
            // 正常情况下需要有一个真实的ID来与ForEach一起使用,但此处没有
            // 因此需要确保推送的字符串是唯一的。
            this.arr[0].push(`${this.arr[0].slice(-1).pop()}${this.arr[0].slice(-1).pop()}`);
            this.arr[1].push(`${this.arr[1].slice(-1).pop()}${this.arr[1].slice(-1).pop()}`);
            this.arr[2].push(`${this.arr[2].slice(-1).pop()}${this.arr[2].slice(-1).pop()}`);
          } else {
            this.arr[0].push('Hello');
            this.arr[1].push('World');
            this.arr[2].push('!');
          }
        })
    }
  }
}

☀️1.2.2 管理应用拥有的状态

🌈1.2.2.1 LocalStorage:页面级UI状态存储
🍬1.2.2.1.1 变化规则

  • 当@LocalStorageLink(key)装饰的数值改变被观察到时,修改将被同步回LocalStorage对应属性键值key的属性中。

  • LocalStorage中属性键值key对应的数据一旦改变,属性键值key绑定的所有的数据(包括双向@LocalStorageLink和单向@LocalStorageProp)都将同步修改;

  • 当@LocalStorageLink(key)装饰的数据本身是状态变量,它的改变不仅仅会同步回LocalStorage中,还会引起所属的自定义组件的重新渲染。

🍬1.2.2.1.2 使用场景
1、应用逻辑使用LocalStorage

let storage = new LocalStorage({ 'PropA': 47 }); // 创建新实例并使用给定对象初始化
let propA = storage.get('PropA') // propA == 47
let link1 = storage.link('PropA'); // link1.get() == 47
let link2 = storage.link('PropA'); // link2.get() == 47
let prop = storage.prop('PropA'); // prop.get() = 47
link1.set(48); // two-way sync: link1.get() == link2.get() == prop.get() == 48
prop.set(1); // one-way sync: prop.get()=1; but link1.get() == link2.get() == 48
link1.set(49); // two-way sync: link1.get() == link2.get() == prop.get() == 49

2、从UI内部使用LocalStorage

// 创建新实例并使用给定对象初始化
let storage = new LocalStorage({ 'PropA': 47 });

@Component
struct Child {
  // @LocalStorageLink变量装饰器与LocalStorage中的'PropA'属性建立双向绑定
  @LocalStorageLink('PropA') storLink2: number = 1;

  build() {
    Button(`Child from LocalStorage ${this.storLink2}`)
      // 更改将同步至LocalStorage中的'PropA'以及Parent.storLink1
      .onClick(() => this.storLink2 += 1)
  }
}
// 使LocalStorage可从@Component组件访问
@Entry(storage)
@Component
struct CompA {
  // @LocalStorageLink变量装饰器与LocalStorage中的'PropA'属性建立双向绑定
  @LocalStorageLink('PropA') storLink1: number = 1;
  build() {
    Column({ space: 15 }) {
      Button(`Parent from LocalStorage ${this.storLink1}`) // initial value from LocalStorage will be 47, because 'PropA' initialized already
        .onClick(() => this.storLink1 += 1)
      // @Component子组件自动获得对CompA LocalStorage实例的访问权限。
      Child()
    }
  }
}

3、@LocalStorageProp和LocalStorage单向同步的简单场景

// 创建新实例并使用给定对象初始化
let storage = new LocalStorage({ 'PropA': 47 });
// 使LocalStorage可从@Component组件访问
@Entry(storage)
@Component
struct CompA {
  // @LocalStorageProp变量装饰器与LocalStorage中的'PropA'属性建立单向绑定
  @LocalStorageProp('PropA') storProp1: number = 1;

  build() {
    Column({ space: 15 }) {
      // 点击后从47开始加1,只改变当前组件显示的storProp1,不会同步到LocalStorage中
      Button(`Parent from LocalStorage ${this.storProp1}`)
        .onClick(() => this.storProp1 += 1)
      Child()
    }
  }
}
@Component
struct Child {
  // @LocalStorageProp变量装饰器与LocalStorage中的'PropA'属性建立单向绑定
  @LocalStorageProp('PropA') storProp2: number = 2;
  build() {
    Column({ space: 15 }) {
      // 当CompA改变时,当前storProp2不会改变,显示47
      Text(`Parent from LocalStorage ${this.storProp2}`)
    }
  }
}

4、@LocalStorageLink和LocalStorage双向同步的简单场景

// 构造LocalStorage实例
let storage = new LocalStorage({ 'PropA': 47 });
// 调用link9+接口构造'PropA'的双向同步数据,linkToPropA 是全局变量
let linkToPropA = storage.link('PropA');

@Entry(storage)
@Component
struct CompA {

  // @LocalStorageLink('PropA')在CompA自定义组件中创建'PropA'的双向同步数据,初始值为47,因为在构造LocalStorage已经给“PropA”设置47
  @LocalStorageLink('PropA') storLink: number = 1;

  build() {
    Column() {
      Text(`incr @LocalStorageLink variable`)
        // 点击“incr @LocalStorageLink variable”,this.storLink加1,改变同步回storage,全局变量linkToPropA也会同步改变 

        .onClick(() => this.storLink += 1)
      // 并不建议在组件内使用全局变量linkToPropA.get(),因为可能会有生命周期不同引起的错误。
      Text(`@LocalStorageLink: ${this.storLink} - linkToPropA: ${linkToPropA.get()}`)
    }
  }
}

5、兄弟节点之间同步状态变量

let storage = new LocalStorage({ countStorage: 1 });

@Component
struct Child {
  // 子组件实例的名字
  label: string = 'no name';
  // 和LocalStorage中“countStorage”的双向绑定数据
  @LocalStorageLink('countStorage') playCountLink: number = 0;

  build() {
    Row() {
      Text(this.label)
        .width(50).height(60).fontSize(12)
      Text(`playCountLink ${this.playCountLink}: inc by 1`)
        .onClick(() => {
          this.playCountLink += 1;
        })
        .width(200).height(60).fontSize(12)
    }.width(300).height(60)
  }
}
@Entry(storage)
@Component
struct Parent {
  @LocalStorageLink('countStorage') playCount: number = 0;
  build() {
    Column() {
      Row() {
        Text('Parent')
          .width(50).height(60).fontSize(12)
        Text(`playCount ${this.playCount} dec by 1`)
          .onClick(() => {
            this.playCount -= 1;
          })
          .width(250).height(60).fontSize(12)
      }.width(300).height(60)
      Row() {
        Text('LocalStorage')
          .width(50).height(60).fontSize(12)
        Text(`countStorage ${this.playCount} incr by 1`)
          .onClick(() => {
            storage.set<number>('countStorage', 1 + storage.get<number>('countStorage'));
          })
          .width(250).height(60).fontSize(12)
      }.width(300).height(60)
      Child({ label: 'ChildA' })
      Child({ label: 'ChildB' })
      Text(`playCount in LocalStorage for debug ${storage.get<number>('countStorage')}`)
        .width(300).height(60).fontSize(12)
    }
  }
}

6、将LocalStorage实例从UIAbility共享到一个或多个视图

// EntryAbility.ts
import UIAbility from '@ohos.app.ability.UIAbility';
import window from '@ohos.window';
let para:Record<string,number> = { 'PropA': 47 };
let localStorage: LocalStorage = new LocalStorage(para);
export default class EntryAbility extends UIAbility {
  storage: LocalStorage = localStorage

  onWindowStageCreate(windowStage: window.WindowStage) {
    windowStage.loadContent('pages/Index', this.storage);
  }
}
// 通过GetShared接口获取stage共享的LocalStorage实例
let storage = LocalStorage.GetShared()

@Entry(storage)
@Component
struct CompA {
  // can access LocalStorage instance using 
  // @LocalStorageLink/Prop decorated variables
  @LocalStorageLink('PropA') varA: number = 1;

  build() {
    Column() {
      Text(`${this.varA}`).fontSize(50)
    }
  }
}

🌈1.2.2.2 AppStorage:AppStorage
🍬1.2.2.2.1 变化规则
和前面一样传递的参数变成@StorageProp和@StorageLink

  • 当装饰的数据类型为boolean、string、number类型时,可以观察到数值的变化。
  • 当装饰的数据类型为class或者Object时,可以观察到赋值和属性赋值的变化,即Object.keys(observedObject)返回的所有属性。
  • 当装饰的对象是array时,可以观察到数组添加、删除、更新数组单元的变化。
    🍬1.2.2.2.2 使用场景
    1、从应用逻辑使用AppStorage和LocalStorage
AppStorage.SetOrCreate('PropA', 47);

let storage: LocalStorage = new LocalStorage({ 'PropA': 17 });
let propA: number = AppStorage.Get('PropA') // propA in AppStorage == 47, propA in LocalStorage == 17
var link1: SubscribedAbstractProperty<number> = AppStorage.Link('PropA'); // link1.get() == 47
var link2: SubscribedAbstractProperty<number> = AppStorage.Link('PropA'); // link2.get() == 47
var prop: SubscribedAbstractProperty<number> = AppStorage.Prop('PropA'); // prop.get() == 47

link1.set(48); // two-way sync: link1.get() == link2.get() == prop.get() == 48
prop.set(1); // one-way sync: prop.get() == 1; but link1.get() == link2.get() == 48
link1.set(49); // two-way sync: link1.get() == link2.get() == prop.get() == 49

storage.get('PropA') // == 17 
storage.set('PropA', 101);
storage.get('PropA') // == 101

AppStorage.Get('PropA') // == 49
link1.get() // == 49
link2.get() // == 49
prop.get() // == 49

2、从UI内部使用AppStorage和LocalStorage

AppStorage.SetOrCreate('PropA', 47);
let storage = new LocalStorage({ 'PropA': 48 });

@Entry(storage)
@Component
struct CompA {
  @StorageLink('PropA') storLink: number = 1;
  @LocalStorageLink('PropA') localStorLink: number = 1;

  build() {
    Column({ space: 20 }) {
      Text(`From AppStorage ${this.storLink}`)
        .onClick(() => this.storLink += 1)
      Text(`From LocalStorage ${this.localStorLink}`)
        .onClick(() => this.localStorLink += 1)
    }
  }
}

3、不建议借助@StorageLink的双向同步机制实现事件通知

// xxx.ets
class ViewData {
  title: string;
  uri: Resource;
  color: Color = Color.Black;

  constructor(title: string, uri: Resource) {
    this.title = title;
    this.uri = uri
  }
}

@Entry
@Component
struct Gallery2 {
  dataList: Array<ViewData> = [new ViewData('flower', $r('app.media.icon')), new ViewData('OMG', $r('app.media.icon')), new ViewData('OMG', $r('app.media.icon'))]
  scroller: Scroller = new Scroller()

  build() {
    Column() {
      Grid(this.scroller) {
        ForEach(this.dataList, (item: ViewData, index?: number) => {
          GridItem() {
            TapImage({
              uri: item.uri,
              index: index
            })
          }.aspectRatio(1)
        }, (item: ViewData, index?: number) => {
          return JSON.stringify(item) + index;
        })
      }.columnsTemplate('1fr 1fr')
    }
  }
}
@Component
export struct TapImage {
  @StorageLink('tapIndex') @Watch('onTapIndexChange') tapIndex: number = -1;
  @State tapColor: Color = Color.Black;
  private index: number = 0;
  private uri: Resource = {
    id: 0,
    type: 0,
    moduleName: "",
    bundleName: ""
  };
  // 判断是否被选中
  onTapIndexChange() {
    if (this.tapIndex >= 0 && this.index === this.tapIndex) {
      console.info(`tapindex: ${this.tapIndex}, index: ${this.index}, red`)
      this.tapColor = Color.Red;
    } else {
      console.info(`tapindex: ${this.tapIndex}, index: ${this.index}, black`)
      this.tapColor = Color.Black;
    }
  }
  build() {
    Column() {
      Image(this.uri)
        .objectFit(ImageFit.Cover)
        .onClick(() => {
          this.tapIndex = this.index;
        })
        .border({ width: 5, style: BorderStyle.Dotted, color: this.tapColor })
    }
  }
}
// xxx.ets
import emitter from '@ohos.events.emitter';

let NextID: number = 0;

class ViewData {
  title: string;
  uri: Resource;
  color: Color = Color.Black;
  id: number;

  constructor(title: string, uri: Resource) {
    this.title = title;
    this.uri = uri
    this.id = NextID++;
  }
}

@Entry
@Component
struct Gallery2 {
  dataList: Array<ViewData> = [new ViewData('flower', $r('app.media.icon')), new ViewData('OMG', $r('app.media.icon')), new ViewData('OMG', $r('app.media.icon'))]
  scroller: Scroller = new Scroller()
  private preIndex: number = -1

  build() {
    Column() {
      Grid(this.scroller) {
        ForEach(this.dataList, (item: ViewData) => {
          GridItem() {
            TapImage({
              uri: item.uri,
              index: item.id
            })
          }.aspectRatio(1)
          .onClick(() => {
            if (this.preIndex === item.id) {
              return
            }
            let innerEvent: emitter.InnerEvent = { eventId: item.id }
            // 选中态:黑变红
            let eventData: emitter.EventData = {
              data: {
                "colorTag": 1
              }
            }
            emitter.emit(innerEvent, eventData)
            if (this.preIndex != -1) {
              console.info(`preIndex: ${this.preIndex}, index: ${item.id}, black`)
              let innerEvent: emitter.InnerEvent = { eventId: this.preIndex }
              // 取消选中态:红变黑
              let eventData: emitter.EventData = {
                data: {
                  "colorTag": 0
                }
              }
              emitter.emit(innerEvent, eventData)
            }
            this.preIndex = item.id
          })
        }, (item: ViewData) => JSON.stringify(item))
      }.columnsTemplate('1fr 1fr')
    }
  }
}
@Component
export struct TapImage {
  @State tapColor: Color = Color.Black;
  private index: number = 0;
  private uri: Resource = {
    id: 0,
    type: 0,
    moduleName: "",
    bundleName: ""
  };
  onTapIndexChange(colorTag: emitter.EventData) {
    if (colorTag.data != null) {
      this.tapColor = colorTag.data.colorTag ? Color.Red : Color.Black
    }
  }
  aboutToAppear() {
    //定义事件ID
    let innerEvent: emitter.InnerEvent = { eventId: this.index }
    emitter.on(innerEvent, data => {
      this.onTapIndexChange(data)
    })
  }
  build() {
    Column() {
      Image(this.uri)
        .objectFit(ImageFit.Cover)
        .border({ width: 5, style: BorderStyle.Dotted, color: this.tapColor })
    }
  }
}

以上通知事件逻辑简化成三元表达式

// xxx.ets
class ViewData {
  title: string;
  uri: Resource;
  color: Color = Color.Black;

  constructor(title: string, uri: Resource) {
    this.title = title;
    this.uri = uri
  }
}

@Entry
@Component
struct Gallery2 {
  dataList: Array<ViewData> = [new ViewData('flower', $r('app.media.icon')), new ViewData('OMG', $r('app.media.icon')), new ViewData('OMG', $r('app.media.icon'))]
  scroller: Scroller = new Scroller()

  build() {
    Column() {
      Grid(this.scroller) {
        ForEach(this.dataList, (item: ViewData, index?: number) => {
          GridItem() {
            TapImage({
              uri: item.uri,
              index: index
            })
          }.aspectRatio(1)
        }, (item: ViewData, index?: number) => {
          return JSON.stringify(item) + index;
        })
      }.columnsTemplate('1fr 1fr')
    }
  }
}
@Component
export struct TapImage {
  @StorageLink('tapIndex') tapIndex: number = -1;
  @State tapColor: Color = Color.Black;
  private index: number = 0;
  private uri: Resource = {
    id: 0,
    type: 0,
    moduleName: "",
    bundleName: ""
  };
  build() {
    Column() {
      Image(this.uri)
        .objectFit(ImageFit.Cover)
        .onClick(() => {
          this.tapIndex = this.index;
        })
        .border({
          width: 5,
          style: BorderStyle.Dotted,
          color: (this.tapIndex >= 0 && this.index === this.tapIndex) ? Color.Red : Color.Black
        })
    }
  }
}

AppStorage与PersistentStorage以及Environment配合使用时,需要注意以下几点:

  • 在AppStorage中创建属性后,调用PersistentStorage.persistProp()接口时,会使用在AppStorage中已经存在的值,并覆盖PersistentStorage中的同名属性,所以建议要使用相反的调用顺序,反例可见在PersistentStorage之前访问AppStorage中的属性;

  • 如果在AppStorage中已经创建属性后,再调用Environment.envProp()创建同名的属性,会调用失败。因为AppStorage已经有同名属性,Environment环境变量不会再写入AppStorage中,所以建议AppStorage中属性不要使用Environment预置环境变量名。

  • 状态装饰器装饰的变量,改变会引起UI的渲染更新,如果改变的变量不是用于UI更新,只是用于消息传递,推荐使用 emitter方式。例子可见不建议借助@StorageLink的双向同步机制实现事件通知。

🌈1.2.2.3 PersistentStorage:持久化存储UI状态

🍬1.2.2.3.1 变化规则
类似AppStorage,流程图如下:

🍬1.2.2.3.2 使用场景

PersistentStorage.PersistProp('aProp', 47);

@Entry
@Component
struct Index {
  @State message: string = 'Hello World'
  @StorageLink('aProp') aProp: number = 48

  build() {
    Row() {
      Column() {
        Text(this.message)
        // 应用退出时会保存当前结果。重新启动后,会显示上一次的保存结果
        Text(`${this.aProp}`)
          .onClick(() => {
            this.aProp += 1;
          })
      }
    }
  }
}

🌈1.2.2.4 Environment:设备环境查询
Environment是ArkUI框架在应用程序启动时创建的单例对象。它为AppStorage提供了一系列描述应用程序运行状态的属性。Environment的所有属性都是不可变的(即应用不可写入),所有的属性都是简单类型。

🍬1.2.2.4.1 变化规则
不可读写

🍬1.2.2.4.2 使用场景
1、从UI中访问Environment参数

// 将设备languageCode存入AppStorage中
Environment.EnvProp('languageCode', 'en');
let enable = AppStorage.Get('languageCode');

@Entry
@Component
struct Index {
  @StorageProp('languageCode') languageCode: string = 'en';

  build() {
    Row() {
      Column() {
        // 输出当前设备的languageCode
        Text(this.languageCode)
      }
    }
  }
}

2、应用逻辑使用Environment

// 使用Environment.EnvProp将设备运行languageCode存入AppStorage中;
Environment.EnvProp('languageCode', 'en');
// 从AppStorage获取单向绑定的languageCode的变量
const lang: SubscribedAbstractProperty<string> = AppStorage.Prop('languageCode');

if (lang.get() === 'zh') {
  console.info('你好');
} else {
  console.info('Hello!');
}

☀️1.2.3 其他状态管理功能

  • @Watch:用于监听状态变量的变化。
    运算符:给内置组件提供TS变量的引用,使得TS变量和内置组件的内部状态保持同步。

🌈1.2.2.1 使用场景

1、@Watch和自定义组件更新

clike @Component struct TotalView { @Prop @Watch('onCountUpdated') count: number; @State total: number = 0; // @Watch cb onCountUpdated(propName: string): void { this.total += this.count; } build() { Text(`Total: ${this.total}`) } } @Entry @Component struct CountModifier { @State count: number = 0; build() { Column() { Button('add to basket') .onClick(() => { this.count++ }) TotalView({ count: this.count }) } } } 

2、@Watch与@Link组合使用

clike class PurchaseItem { static NextId: number = 0; public id: number; public price: number; constructor(price: number) { this.id = PurchaseItem.NextId++; this.price = price; } } @Component struct BasketViewer { @Link @Watch('onBasketUpdated') shopBasket: PurchaseItem[]; @State totalPurchase: number = 0; updateTotal(): number { let total = this.shopBasket.reduce((sum, i) => sum + i.price, 0); // 超过100欧元可享受折扣 if (total >= 100) { total = 0.9 * total; } return total; } // @Watch 回调 onBasketUpdated(propName: string): void { this.totalPurchase = this.updateTotal(); } build() { Column() { ForEach(this.shopBasket, (item) => { Text(`Price: ${item.price.toFixed(2)} €`) }, item => item.id.toString() ) Text(`Total: ${this.totalPurchase.toFixed(2)} €`) } } } @Entry @Component struct BasketModifier { @State shopBasket: PurchaseItem[] = []; build() { Column() { Button('Add to basket') .onClick(() => { this.shopBasket.push(new PurchaseItem(Math.round(100 * Math.random()))) }) BasketViewer({ shopBasket: $shopBasket }) } } }

🌈1.2.2.2 $$语法:

内置组件双向同步

clike // xxx.ets @Entry @Component struct RefreshExample { @State isRefreshing: boolean = false @State counter: number = 0 build() { Column() { Text('Pull Down and isRefreshing: ' + this.isRefreshing) .fontSize(30) .margin(10) Refresh({ refreshing: $$this.isRefreshing, offset: 120, friction: 100 }) { Text('Pull Down and refresh: ' + this.counter) .fontSize(30) .margin(10) } .onStateChange((refreshStatus: RefreshStatus) => { console.info('Refresh onStatueChange state is ' + refreshStatus) }) } } }