Ionic 2：如何根据 json 在 ionic 2 中先前的下拉选择显示第二个下拉数据

Question

我有一个注册页面，其中有 3 个组合框。一个包含国家名称，第二个包含州，第三个包含district.so 当i select 一个国家对应的州应该来，而当i select 州对应的地区应该来。我有 json 包含在文件位置 assets/data/region.js 中的地区和州，我该怎么做？请帮忙

import { Component } from '@angular/core';
import { NavController, AlertController, LoadingController, Loading, IonicPage } from 'ionic-angular';
import { ObsAuthService } from '../../services/obs_auth.services';
import { MatriproPage } from '../matripro/matripro';
import { LocationService } from '../../services/loc.service';

@Component({
    selector: 'page-matriloc',
    templateUrl: 'matriloc.html',
    
    providers: [ObsAuthService]
    
})
export class MatrilocPage{
    myjsondata: any;
    
    constructor(private nav: NavController, private auth: ObsAuthService,
        private alertCtrl: AlertController, private loadingCtrl: LoadingController,
        private myService: LocationService) {
        }

    selectChange(e) {
        console.log(e);
    }  
    
    public nxt(){
        this.nav.push(MatriproPage);
        
    }
    goback() {
             this.nav.pop();
}
}

<ion-header>
    <ion-navbar>
        <ion-title>Location Information</ion-title>
    </ion-navbar>
</ion-header>

<ion-content>
    <h1 class="h1">Location</h1>

    <ion-row>
        <ion-col>
            <ion-label>Country Living in:</ion-label>
        </ion-col>
    </ion-row>
    <ion-row>
        <ion-col>
            <ion-select  placeholder="Select">
                <ion-option [value]="sCountry" >India</ion-option>
            </ion-select>
        </ion-col>
    </ion-row>
    <ion-row>
        <ion-col>
            <ion-label>Residing State:</ion-label>
        </ion-col>
        <ion-col>
            <ion-label>Residing City/District:</ion-label>
        </ion-col>
    </ion-row>
    <ion-row>
        <ion-col >
            <ion-select  [(ngModel)]="sState" placeholder="Select">
                <ion-option [value]="state"></ion-option>
            </ion-select>
        </ion-col>
        <ion-col >
            <ion-select  [(ngModel)]="sDistrict" placeholder="Select">
                <ion-option [value]="districts"></ion-option>
            </ion-select>
        </ion-col>
    </ion-row>
    <ion-row>
            <ion-col>
                <button ion-button full color="secondary" block>Save</button>
            </ion-col>
            <ion-col>
                <button (click)="nxt()" ion-button full color="primary" block>Next</button>
            </ion-col>
        </ion-row>
</ion-content>

Answer 1

我已经为州和地区创建了。所以当你点击州时，selected州的地区将被加载到这里。

将状态数组从 json 分配给 states。当您 select 状态时，将加载该状态的相应分区。我已经为州和地区做了这个，你也可以为国家做同样的事情。

在html

<ion-content>
    <ion-item>
      <ion-select [(ngModel)]="selectedState">
        <ion-option *ngFor="let stateObj of states" [value]="stateObj">{{stateObj.state}}</ion-option>
      </ion-select>
    </ion-item>

    <ion-item>
      <ion-select [(ngModel)]="selectedDistrict">
        <ion-option *ngFor="let district of selectedState.districts" [value]="district">{{district}}</ion-option>
      </ion-select>
    </ion-item>
</ion-content>

在 ts

states  = []; // Assign the states from the json file
selectedState: any = {
districts : []
};
selectedDistrict: string;

Answer 2

您想根据所选州更改选区下拉列表的值。所以你要做的是首先在页面加载时加载状态并将它们分配给状态数组。每当用户更改状态时，重新加载地区数组。所以你的代码将是这样的：

在ts文件中

selectedState;
selectedDistrict;
states = [];
districts = [];

ionPageDidEnter(){
   //Load all the states and assign to states array
}

loadDistrictsForSelectedState(selectedState : StateObject){
   //write your logic to get districts from json
   districts = newArrayOfDistrictsFetchedFromJson;
}

html:

<ion-row>
        <ion-col >
            <ion-select  [(ngModel)]="selectedState" ionChange = "loadDistrictsForSelectedState(selectedState) placeholder="Select">
                <ion-option *ngFor="let state of states" [value]="state">
                    {{state.name}}
                </ion-option>
            </ion-select>
        </ion-col>
        <ion-col >
            <ion-select  [(ngModel)]="selectedDistrict" placeholder="Select">
                <ion-option *ngFor="let district of districts" [value]="district">
                   {{district.name}}
                </ion-option>
            </ion-select>
        </ion-col>
    </ion-row>

您可以根据选择的国家使用相同的逻辑加载状态。

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ionic-framework

ionic2