ArkUI（eTS）开发问题汇总

问题1.aboutToAppear和onAppear的区别?

aboutToAppear：是被@Component修饰自定义组件的生命周期方法，函数在创建自定义组件的新实例后，在执行其build函数之前执行。

onAppear：是每个组件的属性方法，在该组件显示时触发此回调。

eTS里面object类型有办法更新吗?

lis:Array<object> = [
  {
    'id': 0,
    'name': '计划',
    'image': $rawfile('index/ic_public_view_list_filled2.png'),
    'number':0
  },
this.lis['0'].name = 1

然后用这种方式更新前端不会跟着更新,文档里面看到有@State装饰,但是不支持object类型,有其他方式解决吗?

“number”最好不要作为属性，因为“number”是字段类型。Object请改为class，示例代码如下：

@Observed export class xxx {
​
 id: number;
​
 name: string;
​
 image: string;
​
 number: number;
​
 constructor(id: number, name: string, image:string,number:number) {
​
  this.id = id;
​
  this.name = name;
​
  this.image = name;
​
  this.number = number;
​
 }
​
}
​
lis: Array<xxx> = [{
​
   'id': 0,
​
   'name': '计划',
​
   'image': xxx,
​
   'number': 0
​
}]
​
this.lis[0].name='new Name'

问题2.ets 的【TextArea】组件如何做到清空操作？

@State text: string = 'test'
TextArea({ placeholder: this.text })
//...
Button().onClick((value: string) => {
          this.text = ''
        })

问题3.怎么获取鸿蒙系统的小时制

可以使用DateFormatUtil.is24HourClock方法。

问题4.使用ArkUI开发的App能在安卓设备上安装吗？

不可以。HarmonyOS的应用只能运行在鸿蒙系统里。鸿蒙系统能运行HarmonyOS的应用和安卓应用。但是安卓系统只能运行安卓应用。

问题5.如何实现遮罩效果

使用onTouch实现按下抬起事件，.mask()实现遮罩的效果。代码如下：

@Entry
@Component
struct Index {
  @State mask:boolean=false
  build() {
    Column() {
      Image('/comment/bg.jpg')
        .mask(this.mask?new Rect({ width: '500px', height: '280px' }).fill(Color.Gray):null)
        .width('500px').height('280px')
        .onTouch((event: TouchEvent) => {
          switch(event.type){
            case TouchType.Down:
              this.mask=true
              break;
            case TouchType.Up:
              this.mask=false
              break;
          }
        })
    }.width('100%').margin({ top: 5 })
  }
}

问题6.ets声明式ui开发，怎么获取当前系统时间

在这里，我们将字符串用@state包裹，这样可以监听数据的更新

我们给Text绑定点击时间，然后点击，即可显示当前时间，下面是效果。

@Entry
@Component
struct Index {
  @State message: string = 'Hello World'
​
  build() {
    Row() {
      Column() {
        Text(this.message)
          .fontSize(50)
          .fontWeight(FontWeight.Bold).onClick(()=>{
          let date = new Date()
​
//获取当前时间
//          this.message=date.toLocaleString();
          //周几
//          this.message=date.getUTCDay().toString();
​
//日期
//          this.message=date.getUTCDate().toString();
//          //农历月份
//          this.message=date.getUTCMonth().toString();
​
​
          this.message=date.getFullYear() + "年" + (date.getMonth() + 1) + "月" + date.getDate() + "日" + date.getHours() + "时" + date.getMinutes() + "分" + date.getSeconds()+ "秒"
​
​
        })
      }
      .width('100%')
    }
    .height('100%')
  }
}

https://developer.harmonyos.com/cn/docs/documentation/doc-guides/ui-js-fa-call-pa-0000001050435961

档上的例子是ArkUI的js版本连接ServiceAbility（注意不是Internal Ability方式）的例子，想依葫芦画瓢调一下eTS的，理论上应该是语法上的差异，但是没有复现效果，各位火眼精金帮看一下是我用错了吗？

ets页面布局（就一个按钮，点击调用ServiceSync函数连接pa并发送数据）

Button('发送数据')
        .width(200)
        .height(50)
        .margin({bottom:10})
        .onClick(ServiceSync)复制
export async function ServiceSync(): Promise<void> {
  console.log("ServiceSync")
​
  // abilityType: 0-Ability; 1-Internal Ability
  const ABILITY_TYPE_EXTERNAL: number = 0
  // syncOption(Optional, default sync): 0-Sync; 1-Async
  const ACTION_SYNC: number = 0
​
  //请求类型（code）
  const ACTION_MESSAGE_CODE_TYPE1: number = 1001
  //请求数据
  let actionData: Object = {
    "firstNum": 1024,
    "secondNum": 2048
  }
​
  let action: CallAbilityParam
  action.bundleName = "com.example.test"
  action.abilityName = "com.example.test.ComputeServiceAbility"
  action.messageCode = ACTION_MESSAGE_CODE_TYPE1
  action.data = actionData
  action.abilityType = ABILITY_TYPE_EXTERNAL
  action.syncOption = ACTION_SYNC
​
  let result = await FeatureAbility.callAbility(action)
  let ret = JSON.parse(result)
  if (ret.code == 0) {
    console.info('plus result is:' + JSON.stringify(ret.abilityResult))
  } else {
    console.error('plus error code:' + JSON.stringify(ret.code))
  }
}复制

PA端（和官方文档例子相同）

package com.example.test;
​
// ohos相关接口包
import ohos.aafwk.ability.Ability;
import ohos.aafwk.content.Intent;
import ohos.hiviewdfx.HiLog;
import ohos.hiviewdfx.HiLogLabel;
import ohos.rpc.IRemoteBroker;
import ohos.rpc.IRemoteObject;
import ohos.rpc.RemoteObject;
import ohos.rpc.MessageParcel;
import ohos.rpc.MessageOption;
import ohos.utils.zson.ZSONObject;
​
import java.util.HashMap;
import java.util.Map;
​
public class ComputeServiceAbility extends Ability {
    // 定义日志标签
    private static final HiLogLabel LABEL = new HiLogLabel(HiLog.LOG_APP, 0x00210, "MY_TAG");
​
    private MyRemote remote = new MyRemote();
    // FA在请求PA服务时会调用Ability.connectAbility连接PA，连接成功后，需要在onConnect返回一个remote对象，供FA向PA发送消息
    @Override
    protected IRemoteObject onConnect(Intent intent) {
        HiLog.info(LABEL, "onConnect");
        super.onConnect(intent);
        return remote.asObject();
    }
    class MyRemote extends RemoteObject implements IRemoteBroker {
        private static final int SUCCESS = 0;
        private static final int ERROR = 1;
        private static final int PLUS = 1001;
​
        MyRemote() {
            super("MyService_MyRemote");
        }
​
        @Override
        public boolean onRemoteRequest(int code, MessageParcel data, MessageParcel reply, MessageOption option) {
            HiLog.info(LABEL, "onRemoteRequest:%d|%s" , code , data.readString());
            switch (code) {
                case PLUS: {
                    String dataStr = data.readString();
                    RequestParam param = new RequestParam();
                    try {
                        param = ZSONObject.stringToClass(dataStr, RequestParam.class);
                    } catch (RuntimeException e) {
                        HiLog.error(LABEL, "convert failed.");
                    }
​
                    // 返回结果当前仅支持String，对于复杂结构可以序列化为ZSON字符串上报
                    Map<String, Object> result = new HashMap<String, Object>();
                    result.put("code", SUCCESS);
                    result.put("abilityResult", param.getFirstNum() + param.getSecondNum());
                    reply.writeString(ZSONObject.toZSONString(result));
                    break;
                }
                default: {
                    Map<String, Object> result = new HashMap<String, Object>();
                    result.put("abilityError", ERROR);
                    reply.writeString(ZSONObject.toZSONString(result));
                    return false;
                }
            }
            return true;
        }
​
        @Override
        public IRemoteObject asObject() {
            return this;
        }
    }
}

const ABILITY_TYPE_EXTERNAL = 0;
const ACTION_SYNC = 0;
const ACTION_MESSAGE_CODE_PLUS = 1001;
​
export default {
    plus: async function () {
        let data = {
            'first': 123,
            'second': 234
        }
        let dataJson:String = JSON.stringify(data)
        var action = {
            'bundleName': 'com.huawei.myapplication',
            'abilityName': 'com.huawei.myapplication.ComputeServiceAbility',
            'messageCode': ACTION_MESSAGE_CODE_PLUS,
            'abilityType': ABILITY_TYPE_EXTERNAL,
            'data': dataJson,
            'syncOption': ACTION_SYNC
        };
​
        var result = await FeatureAbility.callAbility(action);
        var ret = JSON.parse(result);
        if (ret.code == 0) {
            console.info('plus result is:' + JSON.stringify(ret.abilityResult));
        } else {
            console.error('plus error code:' + JSON.stringify(ret.code));
        }
    }
}

找到原因了，之前跟进调试发现callAbility的参数是callAbilityParam，文档里也没有详细定义，想当然以为是个类，就直接实例化对象了

let action: CallAbilityParam复制

后来在gloabl.ets发现这是个ingerface，所以这样用

let result = await FeatureAbility.callAbility({
    bundleName: 'com.example.test' ,
    abilityName: 'com.example.test.ComputeServiceAbility' ,
    messageCode: ACTION_MESSAGE_CODE_TYPE1 ,
    data: { firstNum : 1024, secondNum : 2048 },
    abilityType: ABILITY_TYPE_EXTERNAL,
    syncOption: ACTION_SYNC
  })