Question

我试图在react-navigation的帮助下在两个屏幕之间导航。我可以在navigate方法中访问render，因为它的范围也在该方法内。

我应该在哪里声明，以便我可以访问此component的任何方法。我正在尝试访问navigate方法中的onPressButton，但它会出错。

无法找到变量：导航

import React, { Component } from "react";
import { View, Text, Image, Button, Alert, StyleSheet } from "react-native";
import styles from "./Styles";
import * as strings from "./Strings";
import RoundButton from "./RoundButton";
var DialogAndroid = require("react-native-dialogs");
import { StackNavigator } from "react-navigation";

export default class CreateMessageScreen extends Component {
  render() {  
    const { navigate } = this.props.navigation;

    return (
      <View style={styles.container}>
        <Image source={require("./img/create_message.png")} />
        <Text style={styles.textStyle}>{strings.create_message}</Text>

        <RoundButton
          textStyle={styles.roundTextStyle}
          buttonStyle={styles.roundButtonStyle}
          onPress={this.onPressButton}
        >
          CREATE MESSAGE
        </RoundButton>

      </View>
    );
  }

  onPressButton() {
    var options = {
      title: strings.app_name,
      content: strings.create_message,
      positiveText: strings.OK,
      onPositive: () => navigate("DashboardScreen")
    };
    var dialog = new DialogAndroid();
    dialog.set(options);
    dialog.show();
  }
}

Answer 1

您需要将const { navigate } = this.props.navigation;移至onPressButton函数而不是render函数（不要忘记bind函数，以便{{1} }具有正确的值）：

this

Answer 2

像这样的对象解构工作，

解构对象：

const obj = { first: 'Jane', last: 'Doe' };
const {first: f, last: l} = obj;
    // f = 'Jane'; l = 'Doe'

// {prop} is short for {prop: prop}
const {first, last} = obj;
    // first = 'Jane'; last = 'Doe'

在你的情况下：

1. const { navigation:navigate } = this.props;

或：

2. const {navigation} = this.props;





export default class CreateMessageScreen extends Component {
  render() {  
 const { navigation:navigate } = this.props;

    return (
      <View style={styles.container}>
        <Image source={require("./img/create_message.png")} />
        <Text style={styles.textStyle}>{strings.create_message}</Text>

        <RoundButton
          textStyle={styles.roundTextStyle}
          buttonStyle={styles.roundButtonStyle}
          onPress={this.onPressButton}
        >
          CREATE MESSAGE
        </RoundButton>

      </View>
    );
  }



    onPressButton() {
  const { navigation:navigate } = this.props;
        var options = {
          title: strings.app_name,
          content: strings.create_message,
          positiveText: strings.OK,
          onPositive: () => navigate("DashboardScreen")
        };
        var dialog = new DialogAndroid();
        dialog.set(options);
        dialog.show();
      }
    }

Answer 3

之所以发生这种情况，是因为你没有像在render（）函数中那样从道具中解构它

onPressButton = () => {
    var {navigate} = this.props.navigation;
    var options = {
      title: strings.app_name,
      content: strings.create_message,
      positiveText: strings.OK,
      onPositive: () => navigate("DashboardScreen")
    };
    var dialog = new DialogAndroid();
    dialog.set(options);
    dialog.show();
  }

找不到变量：导航

3 个答案: