LaurentL LaurentL - 5 days ago 6
React JSX Question

How can I create a progress bar for an api request in React Native?

I'm trying to make a simple progress counter that goes from 0% to 100% while my program fetches weather data. The api request is made by getLocation() inside of index.ios.js which calls fetchWeather() inside of weatherApi.js. Is there a way to measure the progress of my API request made by the fetch function? If not, what would be a good way to implement a loading bar? Any help is very much appreciated!

weatherAPI.js

const rootUrl ='http://api.openweathermap.org/data/2.5/weather?appid=fcea54d0ceade8f08ab838e55bc3f3c0'

export const fetchWeather = (lat,lon) => {

const url = rootUrl+'&lat='+lat+'&lon='+lon+"&units=metric"
console.log(url)

return fetch(url)
.then(res => res.json())
.then(json => ({
temp: json.main.temp,
weather: json.weather[0].main
}))

}


index.ios.js

import React, {Component} from 'react';
import {
AppRegistry,
StyleSheet,
Text,
View,
StatusBar
} from 'react-native'

import Icon from 'react-native-vector-icons/Ionicons'
import {fetchWeather} from './weatherAPI'
import Highlight from 'react-native-highlight-words'

const iconNames = {
Default: 'md-time',
Clear: 'md-sunny',
Rain: 'md-rainy',
Thunderstorm: 'md-thunderstorm',
Clouds: 'md-cloudy',
Snow: 'md-snow',
Drizzle: 'md-umbrella',
}

const phrases = {

Default:{
title: "Fetchin the Fucking Weather",
subtitle: "Be patient, you're witnessing a miracle",
highlight: ["Fucking"],
color: "#636363",
background: "#9C9C9C"
},

Clear: {
title: "FUCK YEAH, CLEAR AS FUCK.",
subtitle: "You Better Go Outside",
highlight: ["Fuck"],
color:"#E32500",
background: "#FFD017"
},
Rain: {
title: "It's Fucking Raining",
subtitle: "You guessed it",
highlight: ["Fucking"],
color:"#004A96",
background:"#2F343A"
},
Thunderstorm: {
title: "Not Just Raining, It's Storming",
subtitle: "Free shower",
highlight: ["Storming"],
color:"#FBFF46",
background:"#020202"
},
Clouds: {
title: "Clouds for Days",
subtitle: "Cotton candy skies",
highlight: ["Days"],
color:"#0044FF",
background: "#939393"

},
Snow: {
title: "Oh Fuck Yeah Bud. It's Snowin'",
subtitle: "Make a fuckin snow angel bud",
highlight: ["Fuck","Snowin'"],
color:"#021D4C",
background:"#15A678"

},
Drizzle: {
title: "Just a Wee Ol' Drizzle Lads",
subtitle: "Free shower",
highlight: ["Wee", "Ol'"],
color:"#dbdbdb",
background:"#1FBB68"

},
}

class App extends Component {


componentWillMount() {

this.state = {

temp: 0,
weather: 'Default'
}

}

componentDidMount() {
this.getLocation()
}

getLocation() {
navigator.geolocation.getCurrentPosition(
posData => fetchWeather(posData.coords.latitude,posData.coords.longitude)
.then(res => this.setState({
temp:Math.round(res.temp),
weather: res.weather
})),
error => alert(error),
{timeout: 10000}
)
}


render(){
console.log(this.state.weather)
return(
<View style={[styles.container, {backgroundColor: phrases[this.state.weather].background}]}>
<StatusBar hidden={true}/>
<View style={styles.header}>
<Icon name={iconNames[this.state.weather]} size={80} color={'white'}/>
<Text style={styles.temp}>{this.state.temp}°</Text>
</View>
<View style={styles.body}>
<Highlight
style={styles.title}
highlightStyle={{color: phrases[this.state.weather].color}}
searchWords={phrases[this.state.weather].highlight}
textToHighlight={phrases[this.state.weather].title}
/>
<Text style={styles.subtitle}>{phrases[this.state.weather].subtitle}</Text>
</View>
</View>
)
}
}

const styles = StyleSheet.create({

container: {
flex:1,
backgroundColor:'#FFD017'
},


header: {
flexDirection:'row',
alignItems:'center',
justifyContent:'space-around',
flex:1,

},
temp: {
fontFamily: 'HelveticaNeue-Bold',
fontSize: 45,
color:'white'

},

body: {
alignItems:'flex-start',
justifyContent:'flex-end',
flex:5,
margin:10

},

title: {
fontFamily: 'HelveticaNeue-Bold',
fontSize: 90,
color:'white',
marginBottom:5

},
subtitle: {
fontFamily: 'HelveticaNeue-Medium',
fontSize: 16,
color:'white'

}



});

AppRegistry.registerComponent('IsItRaining', () => App)

Answer

The fetch API does not include any progress callbacks, so your options are either use XMLHttpRequest, which is fully supported in React Native, or a library that essentially is going to build atop of that. For example, you can modify your fetchWeather function to do:

export const fetchWeather = (lat,lon, progress) => {
return new Promise((resolve, reject) => {
    const url = rootUrl+'&lat='+lat+'&lon='+lon+"&units=metric"
    console.log(url)
    var oReq = new XMLHttpRequest();

    oReq.addEventListener("progress", progress);
    oReq.open('GET', url);
    oReq.send();
    xhr.onreadystatechange = function() {
        if (xhr.readyState == XMLHttpRequest.DONE) {
            let data = JSON.parse(xhr.responseText);
            resolve({temp: data.main.temp, weather: json.weather[0].main});
        }
    }
});
}

Where progress is a callback in which you update the state. For instance, in your component, add the function:

function updateProgress (oEvent) {
  if (oEvent.lengthComputable) {
    var progress = oEvent.loaded / oEvent.total;
    this.setState({progress})
  } else {
    // Unable to compute progress information since the total size is unknown
  }
}

Then, the call becomes:

fetchWeather(posData.coords.latitude,posData.coords.longitude, this.updateProgress.bind(this)) fetchWeather(posData.coords.latitude,posData.coords.longitude)

The example is adapted from MDN.

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