1# 业务模块并发加载场景
2
3在应用启动过程中，会有多个业务模块需要加载，例如地图类应用的定位、打车、导航等不同的模块，如果全部在UI主线程初始化，则会严重影响冷启动耗时。此时需要在不同子线程并行化加载这些模块功能，降低启动耗时。
4
5通过使用ArkTS提供的TaskPool能力，可以将不同业务初始化任务移到子线程中，业务模块通过下沉C++实现成[NativeBinding对象](transferabled-object.md)、或者在ArkTS层定义[Sendable对象](arkts-sendable.md)，就可以将初始化的模块返回UI主线程调用，实现如下。
6
71. 各业务功能（SDK）模块定义（这里以Sendable对象为例）。
8   计算器业务模块定义如下：
9
10   ```ts
11   // sdk/Calculator.ets
12   import { collections } from '@kit.ArkTS'
13
14   @Sendable
15   export class Calculator {
16     history?: collections.Array<collections.Array<string>>
17     totalCount: number = 0
18
19     static init(): Calculator {
20       let calc = new Calculator()
21       calc.totalCount = 0
22       calc.history = collections.Array.create(calc.totalCount, collections.Array.create(2, ""));
23       return calc
24     }
25
26     add(a: number, b: number) {
27       let result = a + b;
28       this.newCalc(`${a} + ${b}`, `${result}`);
29       return result
30     }
31
32     sub(a: number, b: number) {
33       let result = a - b;
34       this.newCalc(`${a} - ${b}`, `${result}`);
35       return result
36     }
37
38     mul(a: number, b: number) {
39       let result = a * b;
40       this.newCalc(`${a} * ${b}`, `${result}`);
41       return result
42     }
43
44     div(a: number, b: number) {
45       let result = a / b;
46       this.newCalc(`${a} / ${b}`, `${result}`);
47       return result
48     }
49
50     getHistory(): collections.Array<collections.Array<string>> {
51       return this.history!;
52     }
53
54     showHistory() {
55       for (let i = 0; i < this.totalCount; i++) {
56         console.info(`${i}: ${this.history![i][0]} = ${this.history![i][1]}`)
57       }
58     }
59
60     private newCalc(opt: string, ret: string) {
61       let newRecord = new collections.Array<string>(opt, ret)
62       this.totalCount = this.history!.unshift(newRecord)
63     }
64   }
65   ```
66
67   定时器业务模块定义如下：
68
69   ```ts
70   // sdk/TimerSdk.ets
71   @Sendable
72   export class TimerSdk {
73     static init(): TimerSdk {
74       let timer = new TimerSdk()
75       return timer
76     }
77
78     async Countdown(time: number) {
79       return new Promise((resolve: (value: boolean) => void) => {
80         setTimeout(() => {
81           resolve(true)
82         }, time)
83       })
84     }
85   }
86   ```
87
882. 在UI主线程触发各业务模块分发到子线程，加载完成后在UI主线程使用。
89
90   ```ts
91   // Index.ets
92   import { Calculator } from '../sdk/Calculator'
93   import { TimerSdk } from '../sdk/TimerSdk'
94   import { taskpool } from '@kit.ArkTS';
95
96   @Concurrent
97   function initCalculator(): Calculator {
98     return Calculator.init()
99   }
100
101   @Concurrent
102   function initTimerSdk(): TimerSdk {
103     return TimerSdk.init()
104   }
105
106   @Entry
107   @Component
108   struct Index {
109     calc?: Calculator
110     timer?: TimerSdk
111
112     aboutToAppear(): void {
113       taskpool.execute(initCalculator).then((ret) => {
114         this.calc = ret as Calculator
115       })
116       taskpool.execute(initTimerSdk).then((ret) => {
117         this.timer = ret as TimerSdk
118       })
119     }
120
121     build() {
122       Row() {
123         Column() {
124           Text("calculate add")
125             .id('add')
126             .fontSize(50)
127             .fontWeight(FontWeight.Bold)
128             .alignRules({
129               center: { anchor: '__container__', align: VerticalAlign.Center },
130               middle: { anchor: '__container__', align: HorizontalAlign.Center }
131             })
132             .onClick(async () => {
133               let result = this.calc?.add(1, 2)
134               console.info(`Result is ${result}`)
135             })
136           Text("show history")
137             .id('show')
138             .fontSize(50)
139             .fontWeight(FontWeight.Bold)
140             .alignRules({
141               center: { anchor: '__container__', align: VerticalAlign.Center },
142               middle: { anchor: '__container__', align: HorizontalAlign.Center }
143             })
144             .onClick(async () => {
145               this.calc?.showHistory()
146             })
147           Text("countdown")
148             .id('get')
149             .fontSize(50)
150             .fontWeight(FontWeight.Bold)
151             .alignRules({
152               center: { anchor: '__container__', align: VerticalAlign.Center },
153               middle: { anchor: '__container__', align: HorizontalAlign.Center }
154             })
155             .onClick(async () => {
156               console.info(`Timer start`)
157               await this.timer?.Countdown(1000);
158               console.info(`Timer end`)
159             })
160         }
161         .width('100%')
162       }
163       .height('100%')
164     }
165   }
166   ```
167