根据所选值更改离子选择的背景颜色

Question

我使用的是 Ionic 5.0，并且我有一个离子选择字段。我需要根据所选选项更改字段的背景。

我已经尝试了几件事。我目前在下面的代码中的尝试是在离子选择中插入 [ngStyle]="SetBackground(item.id)" 但这不起作用。我也试过 [ngStyle]="SetBackground($event)"。我考虑过以某种方式将其添加到 (ionChange)="OnChange($event)" 但无法弄清楚如何做到这一点。似乎我只需要使用 item.id 来更改背景，但对于我来说，我就是想不通。

这是我的 HTML 代码。我希望这足以帮助我找到答案。

<ion-content>

  <div id="game-board">

    <ion-img class="map-img" src="../assets/img/map-a.png"></ion-img>

    <ion-select [(ngModel)]="selectedVal" class="square" interface="popover" [ngStyle]="SetBackground(item.id)">

      <ion-select-option *ngFor="let item of data" [value]="item.id" >

        {{ item.name }}

      </ion-select-option>

    </ion-select>

  </div>

</ion-content>

还有我的 ts

import { Component } from '@angular/core';
import { Platform } from '@ionic/angular';

@Component({
  selector: 'app-home',
  templateUrl: 'home.page.html',
  styleUrls: ['home.page.scss'],
})
export class HomePage {
  data: { id: string; name: string; }[];

  constructor(private platform: Platform) {
    this.platform.ready().then(() => {
      this.data = [
        {
          id: "transparent", name: ""
        },
        {
          id: "green", name: "Forest"
        },
        {
          id: "red", name: "Village"
        },
        {
          id: "yellow", name: "Field"
        },
        {
          id: "blue", name: "Water"
        },
        {
          id: "purple", name: "Monster"
        },
      ]
    })
  }

  SetBackground(bg) {
    let newColor = {
      'background-color': bg.target.value,
    };
    return newColor
  }

我得到的错误...

HomePage.html:12 ERROR TypeError: Cannot read property 'id' of undefined
    at Object.eval [as updateDirectives] (HomePage.html:14)
    at Object.debugUpdateDirectives [as updateDirectives] (core.js:45259)
    at checkAndUpdateView (core.js:44271)
    at callViewAction (core.js:44637)
    at execComponentViewsAction (core.js:44565)
    at checkAndUpdateView (core.js:44278)
    at callViewAction (core.js:44637)
    at execEmbeddedViewsAction (core.js:44594)
    at checkAndUpdateView (core.js:44272)
    at callViewAction (core.js:44637)

Answer 1

哇哦！有用！非常感谢阿伦！

这是包含离子材料的最终 HTML 代码...

 <ion-select [(ngModel)]="selectedVal" [ngStyle]="styleObj" (ionChange)="SetBackground($event)" class="square" interface="popover">

      <ion-select-option *ngFor="let item of data" [value]="item.id" >

        {{ item.name }}

      </ion-select-option>

    </ion-select>

还有 ts...

  styleObj = {};

  SetBackground(bg) {
    this.styleObj = {
      'background-color': bg.target.value,
    };
  }

再次感谢！

ps。这是下一步...

我想在屏幕上显示这些选择语句的 11x11 网格，并且每个语句都有独立的颜色。你会怎么做呢？

Answer 2

<ion-select [(ngModel)]="selectedVal" class="square" interface="popover" [ngStyle]="SetBackground(item.id)">

  <ion-select-option *ngFor="let item of data" [value]="item.id" >

您的 SetBackground 函数在循环之前被调用。所以没有 item.id 的引用。

你可以这样。

html

<select [ngStyle]="styleObj" (change)="SetBackground($event)">

  <option *ngFor="let item of data"  value={{item.id}}>

    {{ item.name }}

  </option>

</select>

ts

 data = [
        {
          id: "transparent", name: ""
        },
        {
          id: "green", name: "Forest"
        },
        {
          id: "red", name: "Village"
        },
        {
          id: "yellow", name: "Field"
        },
        {
          id: "blue", name: "Water"
        },
        {
          id: "purple", name: "Monster"
        },
      ];

  styleObj = {};

  SetBackground(e) {
    this.styleObj = {
      'background-color': e.target.value,
    };
  }