在Picker值更改呼叫函数或React Native中的数组

Question

在这里试图做的是，在选择器值更改上调用该函数并试图呼叫循环并绘制5个文本输入，但会出现错误。当我试图直接在价值上调用myloop数组时，请帮助解决这个小错误，以更改其生成错误，该错误无法称呼为函数。

import * as React from 'react';
import { Text, View, StyleSheet, Alert, Picker } from 'react-native';
import { Constants } from 'react-native';
import { TextInput } from 'react-native-gesture-handler';
var myloop = [];
;
export default class UiDynamic extends React.Component {
  // add a selectValue to your state to stop the overwriting
  state = {
    PickerValueHolder: [],
    selectedValue: ''
  }
  componentDidMount() {
    // remove the return 
   fetch('http:///Dsenze/userapi/inventory/viewinventorytype', {  
        method: 'POST',
        headers: {
          'Accept': 'application/json',
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          "username" :"admin",
          "password" :"admin"
        })
      }).then((response) => response.json())
      .then((responseJson) => {
        // use the inventoryTypeData as it is already an array
       let PickerValueHolder = responseJson.inventoryTypeData;
        console.log("Array data" , PickerValueHolder)
        this.setState({ PickerValueHolder }); // Set the new state
      })
      .catch((error) => {
        console.error(error);
      });
    }
onPickerValueChange=()=>{
    {myloop}
    console.log("Picker change" , myloop);
    //  this.onPickerValueTextinput();
    }
  render() {
        for (let i = 0; i < 5; i++) {
            myloop.push(
              <View key={<TextInput></TextInput>}>
              <TextInput style={{ textAlign: 'center', marginTop: 5 }} 
              placeholder="Enter your name ">
              </TextInput>
              </View>
            )
            }

    return (
      <View style={styles.container}>
      {/* {myloop} */}
        {<Picker
                selectedValue={this.state.selectedValue}
               onValueChange={this.onPickerValueChange}>
                { this.state.PickerValueHolder.map((item, key)=>
                  <Picker.Item label={item.name} value={item.name} key={key} />
                )}
              </Picker>}
      </View>
    );
  }
}
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    backgroundColor: '#ecf0f1',
    padding: 8,
  }
});

谢谢

Answer 1

您的目标渲染5个文本输入

和您所在州的布尔值

state = {
    PickerValueHolder: [],
    selectedValue: '',
    isChange : false,
  }

您的Onchange功能，应用任何条件来通过设置布尔值来渲染这些项目：

onPickerValueChange=(itemValue, itemPosition)=>{
      this.setState({isChange:true});
    }

制作一个函数显示项目，呈现5个输入;

const displayItems =  () => {
 if (this.state.isChange) {
  return  for (let i=0; i<5; i++) {
     return (
           <View key={<TextInput></TextInput>}>
              <TextInput style={{ textAlign: 'center', marginTop: 5 }} 
              placeholder="Enter your name ">
              </TextInput>
              </View>
      );
    }
 }
};

渲染

return (
      <View style={styles.container}>
        {displayItems()}
        <Picker
                selectedValue={this.state.selectedValue}
               onValueChange={this.onPickerValueChange}>
                { this.state.PickerValueHolder.map((item, key)=>
                  <Picker.Item label={item.name} value={item.name} key={key} />
                )}
              </Picker>
      </View>
);