从自定义组件响应本机更改状态

Question

我有自定义选取器组件，我想更新 selectedValue 和 onValueChange 事件的状态。如果我直接在渲染部分添加选择器，它可以正常工作，但由于代码重复，我决定将我的选择器转换为自定义组件。所以我这样做了：

    import React, { Component } from 'react';
import {
    StyleSheet,
    View,
    Modal,
    ActivityIndicator
} from 'react-native';
import { Item, Picker } from 'native-base'
const CustomPicker = props => {
    const {
        pickerLabel,
        selectedVal,
        onChangeVal,
        pickerStyle,
        pickerData,
        ...attributes
    } = props;
    return (
        <Picker
            selectedValue={selectedVal}
            style={[pickerStyle]}
            onValueChange={(itemValue, itemIndex) => this.setState({onChangeVal: itemValue})}>
            <Picker.Item label={pickerLabel} value={''}/>
            {pickerData.map((item, key) => (
                <Picker.Item label={item} value={item} key={key}/>)
            )}
        </Picker>
    )
}
const styles = StyleSheet.create({
});
export default CustomPicker;

我像这样调用不同的组件：

<CustomPicker pickerLabel={"Select User"} selectedVal={this.state.selectedUser} pickerStyle={styles.picker} pickerData={this.state.userList} onChangeVal={this.state.selectedUser} />

标签 + 数据很好地填充在选择器中，但问题即将出现在事件中。它没有更新拾取数据的状态，我错过了什么？

Answer 1

您需要

在父组件中创建一个函数来更改值，因为您正在尝试更改stateless component中的state

相反，您需要做的是

父组件

onChange = (itemValue, itemIndex) => {
  // Set the state here and update as required
}
<CustomPicker pickerLabel={"Select User"} selectedVal={this.state.selectedUser} pickerStyle={styles.picker} pickerData={this.state.userList} onChangeVal={this.onChange} />

子组件

onValueChange={onChangeVal}>

对于多个选择器：

父组件

state = {
  user: [
         {value: 'Something', key: 0, label: 'Select User', userList: [//...Some Array here]},
         {value: 'Something Else', key: 1, label: 'Dont Select User', userList: [//...Some Array here]}
    ]
}
onChange = (itemValue, itemIndex, pickerIndex) => {
      // Update the states based on the pickerIndex
    }
const {user} = this.state
// Use a map here
user.map((data, index) => (
      <CustomPicker key={index} index={index} pickerLabel={data.label} selectedVal={data.value} pickerStyle={styles.picker} pickerData={data.userList} onChangeVal={this.onChange} />
))

子组件

const {
        index, <== Picker Index
        pickerLabel,
        selectedVal,
        onChangeVal,
        pickerStyle,
        pickerData,
        ...attributes
    } = props;
<Picker
            selectedValue={selectedVal}
            style={[pickerStyle]}
            onValueChange={(itemValue, itemIndex) => this.props.onChangeVal(itemValue, itemIndex, index)}> <== Pass picker value to the parent