How to implement Toast using ReactNative

This article mainly introduces the example of implementing Toast in ReactNative. Now I share it with you and give it as a reference.

For Android development engineers, Toast is very familiar. It is used to display a prompt message and automatically hide it. When we develop RN applications, it is a bit difficult for us to achieve such an effect, but it is not difficult at all. It just requires us to adapt. RN officially provides an API ToastAndroid. You should guess it when you see the name. It can only be used in Android, and has no effect when used in iOS. Therefore, we need to adapt or customize one. Today’s article is to customize a Toast so that it can run on both Android and iOS, and has the same operating effect.

Source code portal

Define components

import React, {Component} from 'react'; import { StyleSheet, View, Easing, Dimensions, Text, Animated } from 'react-native'; import PropTypes from 'prop-types'; import Toast from "./index"; const {width, height} = Dimensions.get("window"); const viewHeight = 35; class ToastView extends Component { static propTypes = { message:PropTypes.string, }; dismissHandler = null; constructor(props) { super(props); this.state = { message: props.message !== undefined ? props.message : '' } } render() { return (  {this.state.message}  ) } componentDidMount() { this.timingDismiss() } componentWillUnmount() { clearTimeout(this.dismissHandler) } timingDismiss = () => { this.dismissHandler = setTimeout(() => { this.onDismiss() }, 1000) }; onDismiss = () => { if (this.props.onDismiss) { this.props.onDismiss() } } } const styles = StyleSheet.create({ textContainer: { backgroundColor: 'rgba(0,0,0,.6)', borderRadius: 8, padding: 10, bottom:height/8, maxWidth: width / 2, alignSelf: "flex-end", }, defaultText: { color: "#FFF", fontSize: 15, }, container: { position: "absolute", left: 0, right: 0, top: 0, bottom: 0, flexDirection: "row", justifyContent: "center", } }); export default ToastView

First import our necessary basic components and API, our custom components need to inherit it, Dimensions Used to implement animation, Easing is used to set the trajectory running effect of animation, and PropTypes is used to define property types.

The render method is the entrance for us to define component rendering. The outermost view uses position as absolute, and sets left, right, top, and bottom to 0 so that it fills the screen. In this way, it will not be displayed during Toast display. Let the interface listen for click events. The inner View is a black frame container displayed by Toast. The backgroundColor attribute is set to rgba format, and the color is black and the transparency is 0.6. And set rounded corners and max-width to half the screen width. Then the Text component is used to display specific prompt information.

We also see that propTypes is used to limit the type of attribute message to string. The constructor is the construction method of our component. It has a props parameter, which is some properties passed over. It should be noted that super(props) must be called first in the constructor, otherwise an error will be reported. Here, I set the passed value into the state.

For Toast, the display will disappear automatically after a while. We can achieve this effect through setTimeout. Call this method on componentDidMount. The time here is set to 1000ms. Then the hidden destruction is exposed. When we use setTimeout, we also need to clear the timer when the component is unloaded. componentWillUnmount is called back when the component is unmounted. So clear the timer here.

Achieve animation effect

We have implemented the Toast effect above, but the display and hiding are not overly animated, which is slightly stiff. Then we add some translation and transparency animations, and then modify componentDidMount to achieve animation effects

Add two variables in the component

moveAnim = new Animated.Value(height / 12); opacityAnim = new Animated.Value(0);

In the previous style of the inner view, the bottom set is height/8. Here we set the view style as follows

style={[styles.textContainer, {bottom: this.moveAnim, opacity: this.opacityAnim}]}

and then modify componentDidMount

componentDidMount() { Animated.timing( this.moveAnim, { toValue: height / 8, duration: 80, easing: Easing.ease }, ).start(this.timingDismiss); Animated.timing( this.opacityAnim, { toValue: 1, duration: 100, easing: Easing.linear }, ).start(); }

That is, when the bottom is displayed, it moves from height/12 to height/8, the time is 80ms, and the transparency changes from 0 to 1 Execution time 100ms. Above we see that there is an easing attribute, which passes the curve speed of animation execution. You can implement it yourself. There are many different effects in the Easing API. You can check out the implementation yourself. The source code address is https://github.com/facebook/react-native/blob/master/Libraries/Animated/src/Easing.js. If you want to implement it yourself, just give it a calculation function. You can watch and imitate yourself.

Define the display time

In the front we set the Toast display to 1000ms, we customize the display time, and limit the type number,

time: PropTypes.number

In the construction The processing of time in the method

time: props.time && props.time < 1500 ? Toast.SHORT : Toast.LONG,

Here I have processed the time display into two values, SHORT and LONG. Of course, you can process it yourself to the desired effect.

Then you only need to modify the time 1000 in timingDismiss and write it as this.state.time.

Component update

When updating properties again when the component already exists, we need to process this, update the message and time in the state, and clear the timer, Retime.

componentWillReceiveProps(nextProps) { this.setState({ message: nextProps.message !== undefined ? nextProps.message : '', time: nextProps.time && nextProps.time < 1500 ? Toast.SHORT : Toast.LONG, }) clearTimeout(this.dismissHandler) this.timingDismiss() }

Component registration

In order for our defined components to be called in the form of API instead of written in the render method, we define a follow component

import React, {Component} from "react"; import {StyleSheet, AppRegistry, View, Text} from 'react-native'; viewRoot = null; class RootView extends Component { constructor(props) { super(props); console.log("constructor:setToast") viewRoot = this; this.state = { view: null, } } render() { console.log("RootView"); return ( {this.state.view} ) } static setView = (view) => { //此处不能使用this.setState viewRoot.setState({view: view}) }; } const originRegister = AppRegistry.registerComponent; AppRegistry.registerComponent = (appKey, component) => { return originRegister(appKey, function () { const OriginAppComponent = component(); return class extends Component { render() { return (     ); }; }; }); }; const styles = StyleSheet.create({ container: { flex: 1, position: 'relative', }, rootView: { position: "absolute", left: 0, right: 0, top: 0, bottom: 0, flexDirection: "row", justifyContent: "center", } }); export default RootView

RootView is the root component we defined. It is implemented as above and registered through AppRegistry.registerComponent.

Packaging for external calls

import React, { Component, } from 'react'; import RootView from '../RootView' import ToastView from './ToastView' class Toast { static LONG = 2000; static SHORT = 1000; static show(msg) { RootView.setView( { RootView.setView() }}/>) } static show(msg, time) { RootView.setView( { RootView.setView() }}/>) } } export default Toast

Two static variables are defined in Toast, indicating that the displayed time is for external use. Then provide two static methods, in which the setView method of RootView is called to set the ToastView to the root view.

Use

First import the above Toast, and then call it through the following method

Toast.show("测试,我是Toast"); //能设置显示时间的Toast Toast.show("测试",Toast.LONG);

The above is what I compiled for everyone, I hope it will be helpful to everyone in the future helpful.

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