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首頁 web前端 js教程 級聯(lián)表單 React Native 高級

級聯(lián)表單 React Native 高級

Dec 08, 2024 pm 01:00 PM

我想分享我處理級聯(lián)表單字段的 3 種方法。

  1. 第一種方法是通用的，使用狀態(tài)變量。
  2. 第二種是使用普通變量和一個(gè)布爾狀態(tài)變量來觸發(fā)狀態(tài)效果（刷新頁面）。
  3. 第三種是帶有普通變量的動態(tài)表單字段。

這是第三種方法，我們將處理動態(tài)表單字段。

注意，如果你看看前面的兩種方法，會更容易理解這篇文章。

第一種方法，Cascade Form Basic
第二種方法，改進(jìn)級聯(lián)形式

我們開始吧，

內(nèi)容

  • 基本形式
  • 表單字段對象
  • 動態(tài)場渲染
  • 示例數(shù)據(jù)
  • 頁面加載
  • 加載國家
  • OnChange
  • 加載狀態(tài)
  • 負(fù)載休息（城市、村莊、街道）
  • 驗(yàn)證
  • 重置表格

基本形式

這是帶有 5 個(gè)下拉字段的靜態(tài)表單頁面。

import React, { useState, useEffect } from "react";
import { ScrollView, View, Text, StyleSheet, TouchableOpacity } from "react-native";
import { Dropdown } from "react-native-element-dropdown";
import { Snackbar } from "react-native-paper";

var snackMsg = "";
export default function App() {
  const [refreshPage, setRefreshPage] = useState(false);
  const [visible, setVisible] = useState(false);

  const onToggleSnackBar = () => setVisible(!visible);
  const onDismissSnackBar = () => setVisible(false);

  const resetForm = () => {
  };

  return (
    <ScrollView>



<p>refreshPage state variable is used to refresh the page in all the situations. </p>

<p><img src="/static/imghw/default1.png"  data-src="https://img.php.cn/upload/article/000/000/000/173363402014343.jpg"  class="lazy" alt="Cascading Form React Native Advanced" /></p>

<p>Now, These fields are going to be converted as dynamic. </p>

<h3>
  
  
  Form Field Object
</h3>

<p>Previously we had 3 separate objects for 3 different fields, but here all fields data placed under one form field object.<br>
</p>

<pre class="brush:php;toolbar:false"> . . .
const formFields = {
  country: {
    fieldId: "country",
    label: "Country",
    labelField: "name",
    valueField: "countryId",
    parents: [],
    list: [],
    selectedItem: {},
    selectedValue: null,
    onValueSelected: () => null,
  },
  state: {
    fieldId: "state",label: "State",labelField: "name",valueField: "stateId",
    parents: ["country"],list: [],selectedItem: {},selectedValue: null,
    onValueSelected: () => null,
  },
  city: {
    fieldId: "city",label: "City",labelField: "name",valueField: "cityId",
    parents: ["country", "state"],list: [],selectedItem: {},
    selectedValue: null,onValueSelected: () => null,
  },
  village: {
    fieldId: "village",label: "Village",labelField: "name",
    valueField: "villageId",
    parents: ["country", "state", "city"],
    list: [],selectedItem: {},selectedValue: null,
    onValueSelected: () => null,
  },
  street: {
    fieldId: "street",label: "Street",labelField: "name",
    valueField: "streetId",
    parents: ["country", "state", "city", "village"],
    list: [],selectedItem: {},selectedValue: null,onValueSelected: () => null,
  },
};

 . . .
export default function App() {
   . . .
}

字段的所有這些屬性都有好處，對于處理動態(tài)渲染將很有用。

  • fieldId 字段 ID
  • label 顯示字段名稱
  • labelField 表示下拉列表數(shù)組中的下拉標(biāo)簽字段
  • valueField 表示下拉值字段
  • 父字段的parents 數(shù)組，將用于驗(yàn)證
  • 列表下拉列表數(shù)組
  • selectedItem 下拉列表的整個(gè)選定項(xiàng)目對象
  • selectedValue 所選值
  • onValueSelected 它是一個(gè)函數(shù)屬性，當(dāng)選擇/更改下拉值時(shí)將使用/調(diào)用。最初分配為空方法。

動態(tài)場渲染

通過迭代表單字段對象鍵，我們動態(tài)渲染下拉字段，所有必需的屬性都可以在表單字段對象中使用。

export default function App() {
  . . .
    return (
    <View>



<p>handle focus / blur<br>
</p>

<pre class="brush:php;toolbar:false">var focusField = "";
export default function App() {
. . .

 const changeFocusField = (fld = "") => {
  focusField = fld;
  setRefreshPage(!refreshPage);
 };
. . .
}

<ZDropDown
. . .
  isFocus={focusField === ele}
  onFocus={() => {
    changeFocusField(ele);
  }}
  onBlur={() => changeFocusField("")}
  onChange={(item) => {}}
 />

樣本數(shù)據(jù)

國家、州、城市、村莊和街道字段的示例數(shù)據(jù)。

const listCountry = [
  { countryId: "1", name: "india" },
  { countryId: "2", name: "uk" },
  { countryId: "3", name: "canada" },
  { countryId: "4", name: "us" },
];

const listSate = [
  { stateId: "1", countryId: "1", name: "state1_india" },
  { stateId: "4", countryId: "2", name: "state1_uk" },
  { stateId: "7", countryId: "3", name: "state1_canada" },
  { stateId: "10", countryId: "4", name: "state1_us" },
];

const listCity = [
  { cityId: "1", stateId: "1", countryId: "1", name: "city1_state1_country1" },
  { cityId: "5", stateId: "2", countryId: "1", name: "city5_state2_country1" },
  {
    cityId: "21",stateId: "7",countryId: "3",name:"city21_state7_country3",
  },
  {
    cityId: "26",stateId: "9",countryId: "3",name: "city26_state9_country3",
  },
];

const listVillage = [
  { cityId: "1", villageId: "1", name: "village 1  city 1" },
  { cityId: "2", villageId: "5", name: "village 5  city 2" },
  { cityId: "3", villageId: "9", name: "village 9  city 3" },
  { cityId: "4", villageId: "10", name: "village 10  city 4" },
];

const listStreet = [
  { villageId: "1", streetId: "1", name: "village 1 street 1" },
  { villageId: "1", streetId: "109", name: "village 1 street 109" },
  { villageId: "2", streetId: "2", name: "village 2 street 2" },
  { villageId: "2", streetId: "110", name: "village 2 street 110" },
];
 . . .
export default function App() {
  . . .
}
 . . .

頁面加載

首先在功能方面我們必須設(shè)置一些重要的東西。 請記住，我們?yōu)?onValueSelected 屬性分配了一個(gè)空方法，現(xiàn)在是時(shí)候分配實(shí)際方法了。因此我們需要?jiǎng)?chuàng)建 5 個(gè)方法并將它們分配給各自的表單字段。

export default function App() {
  . . .
  const allValuesSelected = () => {
    console.log("All fields value selected");
  };

  const loadStreet = async () => {};

  const loadVillage = async () => {};

  const loadCity = async () => {};

  const loadState = async () => {};

  const loadCountry = async () => {};

  const loadPageData = () => {
    formFields.country.onValueSelected = loadState;
    formFields.state.onValueSelected = loadCity;
    formFields.city.onValueSelected = loadVillage;
    formFields.village.onValueSelected = loadStreet;
    formFields.street.onValueSelected = allValuesSelected;    
  };

  return (. . .);
}

當(dāng)選擇 Country 值時(shí)，必須加載 STATE 列表，這就是為什么這里將 loadState 方法分配給 Country 的 onValueSelected。同樣分配了其他方法。

  useEffect(() => {
    loadPageData();
  }, []);

  return (. . .);

負(fù)載國家

從示例數(shù)據(jù)加載國家/地區(qū)列表并在初始頁面加載時(shí)調(diào)用它。

  const loadCountry = async () => {
    formFields.country.list = [...listCountry];
    setRefreshPage(!refreshPage);
  };

  const loadPageData = () => {
    formFields.country.onValueSelected = loadState;
    formFields.state.onValueSelected = loadCity;
    formFields.city.onValueSelected = loadVillage;
    formFields.village.onValueSelected = loadStreet;
    formFields.street.onValueSelected = allValuesSelected;

    loadCountry();
  };

變化時(shí)

選擇下拉字段值后，我們需要設(shè)置相應(yīng)的表單字段值，移除焦點(diǎn)并加載下一個(gè)下拉列表。

return (
  . . .
  <ZDropDown
    // . . .
    onChange={(item) => {
      fld.selectedItem = item;
      fld.selectedValue = item[fld.valueField];
      focusField = "";
      fld.onValueSelected();
    }}
  />
  . . .
);

onValueSelected 很有用吧？

負(fù)載狀態(tài)

當(dāng)?shù)谝粋€(gè)下拉列表（國家/地區(qū)）更改時(shí)，其余字段將發(fā)生更改。因此需要清除所有其他表單字段的列表和數(shù)據(jù)。為此，我們編寫了一個(gè)方法，可以清除給定字段到結(jié)束字段的值。

import React, { useState, useEffect } from "react";
import { ScrollView, View, Text, StyleSheet, TouchableOpacity } from "react-native";
import { Dropdown } from "react-native-element-dropdown";
import { Snackbar } from "react-native-paper";

var snackMsg = "";
export default function App() {
  const [refreshPage, setRefreshPage] = useState(false);
  const [visible, setVisible] = useState(false);

  const onToggleSnackBar = () => setVisible(!visible);
  const onDismissSnackBar = () => setVisible(false);

  const resetForm = () => {
  };

  return (
    <ScrollView>



<p>refreshPage state variable is used to refresh the page in all the situations. </p>

<p><img src="/static/imghw/default1.png"  data-src="https://img.php.cn/upload/article/000/000/000/173363402014343.jpg"  class="lazy" alt="Cascading Form React Native Advanced" /></p>

<p>Now, These fields are going to be converted as dynamic. </p>

<h3>
  
  
  Form Field Object
</h3>

<p>Previously we had 3 separate objects for 3 different fields, but here all fields data placed under one form field object.<br>
</p>

<pre class="brush:php;toolbar:false"> . . .
const formFields = {
  country: {
    fieldId: "country",
    label: "Country",
    labelField: "name",
    valueField: "countryId",
    parents: [],
    list: [],
    selectedItem: {},
    selectedValue: null,
    onValueSelected: () => null,
  },
  state: {
    fieldId: "state",label: "State",labelField: "name",valueField: "stateId",
    parents: ["country"],list: [],selectedItem: {},selectedValue: null,
    onValueSelected: () => null,
  },
  city: {
    fieldId: "city",label: "City",labelField: "name",valueField: "cityId",
    parents: ["country", "state"],list: [],selectedItem: {},
    selectedValue: null,onValueSelected: () => null,
  },
  village: {
    fieldId: "village",label: "Village",labelField: "name",
    valueField: "villageId",
    parents: ["country", "state", "city"],
    list: [],selectedItem: {},selectedValue: null,
    onValueSelected: () => null,
  },
  street: {
    fieldId: "street",label: "Street",labelField: "name",
    valueField: "streetId",
    parents: ["country", "state", "city", "village"],
    list: [],selectedItem: {},selectedValue: null,onValueSelected: () => null,
  },
};

 . . .
export default function App() {
   . . .
}

此方法可用于所有其他下拉字段和頁面重置目的。

export default function App() {
  . . .
    return (
    <View>



<p>handle focus / blur<br>
</p>

<pre class="brush:php;toolbar:false">var focusField = "";
export default function App() {
. . .

 const changeFocusField = (fld = "") => {
  focusField = fld;
  setRefreshPage(!refreshPage);
 };
. . .
}

狀態(tài)下拉列表現(xiàn)已完美加載。

加載其余部分（城市、村莊、街道）

就像之前一樣，我們加載其余字段的數(shù)據(jù)。

<ZDropDown
. . .
  isFocus={focusField === ele}
  onFocus={() => {
    changeFocusField(ele);
  }}
  onBlur={() => changeFocusField("")}
  onChange={(item) => {}}
 />

很好，所有下拉菜單都填充了各自的列表。

Cascading Form React Native Advanced

驗(yàn)證

在顯示下拉列表之前，我們需要驗(yàn)證其父字段。因此，我們將從表單字段對象中獲取父字段。然后逐一迭代它們，驗(yàn)證其值并在必要時(shí)顯示警告。

const listCountry = [
  { countryId: "1", name: "india" },
  { countryId: "2", name: "uk" },
  { countryId: "3", name: "canada" },
  { countryId: "4", name: "us" },
];

const listSate = [
  { stateId: "1", countryId: "1", name: "state1_india" },
  { stateId: "4", countryId: "2", name: "state1_uk" },
  { stateId: "7", countryId: "3", name: "state1_canada" },
  { stateId: "10", countryId: "4", name: "state1_us" },
];

const listCity = [
  { cityId: "1", stateId: "1", countryId: "1", name: "city1_state1_country1" },
  { cityId: "5", stateId: "2", countryId: "1", name: "city5_state2_country1" },
  {
    cityId: "21",stateId: "7",countryId: "3",name:"city21_state7_country3",
  },
  {
    cityId: "26",stateId: "9",countryId: "3",name: "city26_state9_country3",
  },
];

const listVillage = [
  { cityId: "1", villageId: "1", name: "village 1  city 1" },
  { cityId: "2", villageId: "5", name: "village 5  city 2" },
  { cityId: "3", villageId: "9", name: "village 9  city 3" },
  { cityId: "4", villageId: "10", name: "village 10  city 4" },
];

const listStreet = [
  { villageId: "1", streetId: "1", name: "village 1 street 1" },
  { villageId: "1", streetId: "109", name: "village 1 street 109" },
  { villageId: "2", streetId: "2", name: "village 2 street 2" },
  { villageId: "2", streetId: "110", name: "village 2 street 110" },
];
 . . .
export default function App() {
  . . .
}
 . . .

Cascading Form React Native Advanced

重置表格

最后，我們提供了重置表單字段的選項(xiàng)。

export default function App() {
  . . .
  const allValuesSelected = () => {
    console.log("All fields value selected");
  };

  const loadStreet = async () => {};

  const loadVillage = async () => {};

  const loadCity = async () => {};

  const loadState = async () => {};

  const loadCountry = async () => {};

  const loadPageData = () => {
    formFields.country.onValueSelected = loadState;
    formFields.state.onValueSelected = loadCity;
    formFields.city.onValueSelected = loadVillage;
    formFields.village.onValueSelected = loadStreet;
    formFields.street.onValueSelected = allValuesSelected;    
  };

  return (. . .);
}

全部完成?，F(xiàn)在我們看到了如何處理動態(tài)表單字段、呈現(xiàn)字段、加載數(shù)據(jù)并驗(yàn)證它們。

這是我處理級聯(lián)表單字段的 3 種方法。

希望這篇文章/系列有一些您喜歡的有用的東西。謝謝。

完整代碼在這里

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