Question

我有一个购物车图标作为几乎所有屏幕的右上角按钮。我正在使用react-navigation5。我想从组件中更新该按钮上的徽章计数。没有使用redux或flux库的任何可能的方法来实现它？以下是我的代码，例如：

route.js

import * as React from 'react';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator } from '@react-navigation/stack';
import { Home, Cart, Wishlist, Login, Signup, Contact, Profile, Search } from './scenes';
import { Primary, Secondary } from './assets/color';
import { HeaderButton } from './components'
const Stack = createStackNavigator();
function Route() {
    return (
        <Stack.Navigator initialRouteName="Profile" screenOptions={({ navigation, route }) =>({ headerRight:()=>(<HeaderButton navigation={navigation} nav='Cart'/>)})}>
            <Stack.Screen name="Home" component={Home} />
            <Stack.Screen name="Cart" component={Cart} options={{headerRight:null}}/>
            <Stack.Screen name="Search" component={Search} />
        </Stack.Navigator>
);
}

export default Route;

headerButton.js

import React, { Component } from "react";
import { View } from 'react-native'
import { Button, Icon, Badge, Text } from 'native-base';
import { Primary, Danger } from '../../assets/color'
export class HeaderButton extends Component{
    render(){
        return(
            <>
            <Button rounded transparent onPress={()=>this.props.navigation.push('Cart')}>
                <Icon type='MaterialIcons' name='shopping-cart' style={{color:Primary,right:6,top:2}}/>
            </Button>
           <Text>{this.props.count}</Text>
            </>
        );
    }
}

home.js

import React, { Component } from "react";
import { View } from 'react-native'
import { Button, Icon, Badge, Text } from 'native-base';
import { Primary, Danger } from '../../assets/color'
export class Home extends Component{
    constructor(){
        super();
        this.state={
            count:1
        }
    }
    addToCart=()=>{
        var varcount=this.state.count;
        varcount=varcount+1;
        this.setState({count:varcount})
    }
    render(){
        return(
            <Button onPress={this.addToCart}>
            <Text>Add to cart</Text>
            </Button>

        );
    }
}

无论何时在应用程序中更改计数，它都必须反映在route.js中的headerbutton组件中，标题为headerRight

Answer 1

我自己解决了这个问题，使用了将参数从父级传递到子级，反之亦然的方法。以下是我在代码中所做的更改。

route.js

import * as React from 'react';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator } from '@react-navigation/stack';
import { Home, Cart, Wishlist, Login, Signup, Contact, Profile, Search } from './scenes';
import { Primary, Secondary } from './assets/color';
import { HeaderButton } from './components'
const Stack = createStackNavigator();
function Route() {
   const [count, setCount] = React.useState(0);
     const onCount=(value)=>{
        setCount(value);
        console.log(count, value);
    }
    return (
        <Stack.Navigator initialRouteName="Profile" screenOptions={({ navigation, route }) =>({ headerRight:props =>(<HeaderButton navigation={navigation} nav='Cart' {...props} badgeCount={count}/>)})}>
            <Stack.Screen name="Home" component={Home} />
            <Stack.Screen name="Cart" component={Cart} options={{headerRight:null}}/>
            <Stack.Screen name="Search" component={Search} />
        </Stack.Navigator>
);
}

export default Route;

headerButton.js

import React, { Component } from "react";
import { View } from 'react-native'
import { Button, Icon, Badge, Text } from 'native-base';
import { Primary, Danger } from '../../assets/color'
export class HeaderButton extends Component{
    render(){
        return(
            <>
            <Button rounded transparent onPress={()=>this.props.navigation.push('Cart')}>
                <Icon type='MaterialIcons' name='shopping-cart' style={{color:Primary,right:6,top:2}}/>
            </Button>
           <Text>{this.props.badgeCount}</Text>
            </>
        );
    }
}

home.js

import React, { Component } from "react";
import { View } from 'react-native'
import { Button, Icon, Badge, Text } from 'native-base';
import { Primary, Danger } from '../../assets/color'
export class Home extends Component{
    constructor(){
        super();
        this.state={
            count:1
        }
    }
    addToCart=()=>{
        var varcount=this.state.count;
        varcount=varcount+1;
        this.setState({count:varcount})
        this.props.onCountChange(this.state.count);

    }
    render(){
        return(
            <Button onPress={this.addToCart}>
            <Text>Add to cart</Text>
            </Button>

        );
    }
}

Answer 2

每次调用addToCart时，都应该在其中加上括号，因为它具有函数值，应该为addToCart()。另外，每当您调用addToCart()时，该值都不会更改，因为varcount的作用域仅是本地的，我建议您将其设置为全局，这样就不会重置该值

如何在React Native中将数据传递到导航标题？

2 个答案: