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Using placeholder images with react native
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import React, { | |
AppRegistry, | |
Component, | |
StyleSheet, | |
Text, | |
View, | |
Image, | |
Dimensions, | |
StatusBar, | |
ScrollView | |
} from 'react-native'; | |
StatusBar.setBarStyle('light-content'); | |
console.disableYellowBox = true; // This gets in the way! | |
// imageSize is used to statically size <Image/> instances | |
const windowDims = Dimensions.get('window'), | |
itemSize = (windowDims.width / 2) - 20; | |
// This is *the* placeholder image to be used in steps #3 and #5 | |
const placeholder = require('./images/placeholder.png'); | |
const styles = StyleSheet.create({ | |
container : { | |
paddingTop : 30, | |
justifyContent : 'center', | |
alignItems : 'center', | |
backgroundColor : '#F5FCFF', | |
flexDirection : 'row', | |
flexWrap : 'wrap' | |
}, | |
child : { | |
width : itemSize, | |
height : itemSize, | |
margin : 7 | |
}, | |
topBar : { | |
position : 'absolute', | |
top : 0, | |
height : 25, | |
width : windowDims.width, | |
backgroundColor : 'rgba(0,0,0,.8)' | |
} | |
}); | |
class Placeholder extends Component { | |
// Initial state | |
state = { | |
data : [] // empty data array | |
}; | |
// Step #4 (Self-bound function) | |
// We will update the state of the application so that images can render | |
onAfterLoad = (data) => { | |
this.setState({ | |
data : data.data | |
}); | |
}; | |
// Step #1 & #2 | |
// Here we’ll fetch JSON for images to be displayed | |
componentWillMount() { | |
// The URL below has an 'r' parameter that is used as a 'cache buster' and is only intended for demonstration purposes | |
let url = 'http://api.giphy.com/v1/gifs/search?q=javascript&api_key=dc6zaTOxFJmzC&limit=30&r=' + Math.random(); | |
console.log('Loading data') | |
// Initiate query, parse, then update view via callback | |
fetch(url) | |
.then(function(r) { | |
return r.json(); | |
}) | |
.then(this.onAfterLoad) // Success callback registration | |
.catch(function(e) { // Failure callback registartion | |
alert('Failure fetching data'); | |
console.log(e) | |
}); | |
} | |
// This will be responsible for rendering the image components | |
buildImages(data) { | |
let images = [], | |
length = data.length, | |
i = 0, | |
randVal = '?r=' + Math.random(), // Cache busting for testing only can be removed | |
source, | |
item; | |
// Empty array? | |
if (data.length == 0) { | |
// This console.log() call can be removed. | |
console.log('Rendering placeholders'); | |
// Fill the array with 10 undefines | |
data.length = length = 10; | |
} | |
else { | |
// This else branch is here just for debugging and can be removed. | |
console.log(`Got data. Rendering ${length} images.`); | |
} | |
for (; i < length; i++) { | |
item = data[i]; | |
// For when we actually have data | |
if (item) { | |
source = { | |
uri : item.images.original_still.url + randVal, | |
width : itemSize, | |
height : itemSize | |
} | |
} | |
images.push( | |
<Image style={styles.child} | |
source={source} | |
defaultSource={placeholder} | |
key={'img' + i}/> | |
) | |
} | |
return images; | |
} | |
render() { | |
let state = this.state, | |
data = state.data, | |
images = this.buildImages(data); | |
return ( | |
<View style={{flex:1}}> | |
<ScrollView contentContainerStyle={styles.container} | |
style={{backgroundColor: '#F5FCFF'}}> | |
{images} | |
</ScrollView> | |
<View style={styles.topBar}/> | |
</View> | |
); | |
} | |
} | |
AppRegistry.registerComponent('Placeholder', () => Placeholder); |
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