# 应用被拉起时如何获取外部传入参数

#### 问题现象

外部启动应用，如何在应用中接收到外部传入的参数？如何把参数传到启动页面？例如首页根据参数显示不同的样式。

#### 效果预览

#### 背景知识

*   startAbility()：启动一个UIAbility。
*   Want是一种对象，用于在应用组件之间传递信息。
*   onNewWant()：当应用的UIAbility实例已创建，再次调用方法启动该UIAbility实例时，系统触发该UIAbility的onNewWant()回调。
*   onCreate()：在首次创建UIAbility实例时，系统触发onCreate()回调。
*   getSharedLocalStorage()：获取当前stage共享的LocalStorage实例。
*   为了能够支持被其他应用访问，目标应用需要在module.json5配置文件中配置skills标签。本示例使用Deep Linking实现应用间跳转。

#### 解决方案

实现思路：

1.  在拉起方应用TestA中设置参数Want，调用startAbility()触发应用跳转。
    
    src/main/ets/pages/Index.ets：
    
    ```
    import { common, Want } from '@kit.AbilityKit';
    import { BusinessError } from '@kit.BasicServicesKit';
    
    @Entry
    @Component
    struct Index {
      message: string = 'Hello TestA';
    
      build() {
        Column() {
          Text(this.message)
            .id('HelloWorld')
            .fontSize($r('app.float.page_text_font_size'))
            .fontWeight(FontWeight.Bold)
            .alignRules({
              center: { anchor: '__container__', align: VerticalAlign.Center },
              middle: { anchor: '__container__', align: HorizontalAlign.Center }
            });
    
          // 跳转到TestB应用并携带msg参数
          Button('to TestB')
            .onClick(() => {
              let context: common.UIAbilityContext = this.getUIContext().getHostContext() as common.UIAbilityContext;
              let want: Want = {
                uri: 'link://www.testb.com',
                parameters: {
                  msg: 'Hello TestB, I am TestA.'
                }
              };
              try {
                context.startAbility(want).then(() => {
                  console.info('start ability success.');
                }).catch((err: BusinessError) => {
                  console.error(`start ability failed. Code is ${err.code}, message is ${err.message}`);
                });
              } catch (paramError) {
                console.error(`Failed to start ability. Code is ${paramError.code}, message is ${paramError.message}`);
              }
            });
        }
        .justifyContent(FlexAlign.Center)
        .height('100%')
        .width('100%');
      }
    }
    ```
    
2.  在目标应用TestB的module.json5配置文件中的skills标签下新增以下skill对象，用于被其他应用访问。
    
    src/main/module.json5：
    
    ```
    {
      "actions": [
        // actions不能为空，actions为空会造成目标方匹配失败。
        "ohos.want.action.viewData"
      ],
      "uris": [
        {
          // scheme必选，可以自定义，以link为例，需要替换为实际的scheme
          "scheme": "link",
          // host必选，配置待匹配的域名
          "host": "www.testb.com"
        }
      ]
    }
    ```
    
3.  目标应用TestB是冷启动则在onCreate()中接收外部传入的参数Want，是热启动则在onNewWant()中接收外部传入的参数Want。
4.  目标应用TestB将接收到的Want参数存入LocalStorage实例中。
    
    src/main/ets/entryability/EntryAbility.ets：
    
    ```
    import { ConfigurationConstant, UIAbility, Want } from '@kit.AbilityKit';
    import { hilog } from '@kit.PerformanceAnalysisKit';
    import { window } from '@kit.ArkUI';
    
    const DOMAIN = 0x0000;
    
    export default class EntryAbility extends UIAbility {
      onCreate(want: Want): void {
        try {
          this.context.getApplicationContext().setColorMode(ConfigurationConstant.ColorMode.COLOR_MODE_NOT_SET);
        } catch (err) {
          hilog.error(DOMAIN, 'testTag', 'Failed to set colorMode. Cause: %{public}s', JSON.stringify(err));
        }
        hilog.info(DOMAIN, 'testTag', '%{public}s', 'Ability onCreate');
        // 应用冷启动，调用getAndSetParameter方法获取外部参数并存入
        this.getAndSetParameter(want);
      }
    
      onDestroy(): void {
        hilog.info(DOMAIN, 'testTag', '%{public}s', 'Ability onDestroy');
      }
    
      onWindowStageCreate(windowStage: window.WindowStage): void {
        // Main window is created, set main page for this ability
        hilog.info(DOMAIN, 'testTag', '%{public}s', 'Ability onWindowStageCreate');
    
        windowStage.loadContent('pages/Index', this.storage, (err) => {
          if (err.code) {
            hilog.error(DOMAIN, 'testTag', 'Failed to load the content. Cause: %{public}s', JSON.stringify(err));
            return;
          }
          hilog.info(DOMAIN, 'testTag', 'Succeeded in loading the content.');
        });
      }
    
      onWindowStageDestroy(): void {
        // Main window is destroyed, release UI related resources
        hilog.info(DOMAIN, 'testTag', '%{public}s', 'Ability onWindowStageDestroy');
      }
    
      onForeground(): void {
        // Ability has brought to foreground
        hilog.info(DOMAIN, 'testTag', '%{public}s', 'Ability onForeground');
      }
    
      onBackground(): void {
        // Ability has back to background
        hilog.info(DOMAIN, 'testTag', '%{public}s', 'Ability onBackground');
      }
    
      onNewWant(want: Want) {
        hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onNewWant');
        // 应用热启动，调用getAndSetParameter方法获取外部参数并存入
        this.getAndSetParameter(want);
      }
    
      // 获取LocalStorage实例
      storage: LocalStorage = new LocalStorage();
    
      // 获取外部参数并存入LocalStorage实例中
      getAndSetParameter(want: Want): void {
        let parameters = want.parameters;
        if (parameters === null || parameters === undefined) {
          console.error('获取外部参数失败');
          return;
        }
        let msg = want.parameters?.msg;
        this.storage.setOrCreate('msg', msg);
      }
    };
    ```
    
5.  目标应用TestB在页面中通过getSharedLocalStorage()获取LocalStorage实例。
6.  目标应用TestB获取LocalStorage实例中的Want参数并使用。
    
    src/main/ets/pages/Index.ets：
    
    ```
    @Entry
    @Component
    struct Index {
      localStorage = this.getUIContext().getSharedLocalStorage();
    
      message: string = 'Hello TestB';
      @State msg: string = 'I am TestB';
    
      onPageShow(): void {
        let val: string = this.localStorage?.get('msg') as string;
        if (val === null || val === undefined) {
          return;
        }
        this.msg = val;
      }
    
      build() {
        Column() {
          Text(this.message)
            .fontSize($r('app.float.page_text_font_size'))
            .fontWeight(FontWeight.Bold);
          Text(this.msg)
            .fontSize(25)
            .fontWeight(FontWeight.Bold);
        }
        .justifyContent(FlexAlign.Center)
        .height('100%')
        .width('100%');
      }
    }
    ```