Can I make dynamic styles in React Native?

Question

Say I have a component with a render like this:

<View style={jewelStyle}></View>

Where jewelStyle =

  {
    borderRadius: 10,
    backgroundColor: '#FFEFCC',
    width: 20,
    height: 20,
  },

How could I make the background colour dynamic and randomly assigned? I've tried

  {
    borderRadius: 10,
    backgroundColor: getRandomColor(),
    width: 20,
    height: 20,
  },

But this makes all instances of View have the same colour, I want each one to be unique.

Any tips?

Answer 1

Had some issue syntactically. This worked for me

<Text style={StyleSheet.flatten([styles.textStyle,{color: 'red'}])}> Hello </Text>

const styles = StyleSheet.create({
   textStyle :{
      textAlign: 'center',   
      fontFamily: 'Arial',
      fontSize: 16
  }
  });

Answer 2

The easiest is mine:

<TextInput
  style={[
    styles.default,
    this.props.singleSourceOfTruth ?
    { backgroundColor: 'black' } 
    : { backgroundColor: 'white' }
]}/>

Answer 3

I know there are several answers, but i think the best and most simple is using a state "To change" is the state purpose.

export default class App extends Component {
    constructor(props) {
      super(props);
      this.state = {
          style: {
              backgroundColor: "white"
          }
      };
    }
    onPress = function() {
      this.setState({style: {backgroundColor: "red"}});
    }
    render() {
       return (
          ...
          <View style={this.state.style}></View>
          ...
       )
    }

}

Answer 4

You'll want something like this:

var RandomBgApp = React.createClass({
    render: function() {

        var getRandomColor = function() {
            var letters = '0123456789ABCDEF'.split('');
            var color = '#';
            for (var i = 0; i < 6; i++ ) {
                color += letters[Math.floor(Math.random() * 16)];
            }
            return color;
        };

        var rows = [
            { name: 'row 1'},
            { name: 'row 2'},
            { name: 'row 3'}
        ];

        var rowNodes = rows.map(function(row) {
            return <Text style={{backgroundColor:getRandomColor()}}>{row.name}</Text>
        });

        return (
            <View>
                {rowNodes}
            </View>
        );

    }
});

In this example I take the rows array, containing the data for the rows in the component, and map it into an array of Text components. I use inline styles to call the getRandomColor function every time I create a new Text component.

The issue with your code is that you define the style once and therefore getRandomColor only gets called once - when you define the style.

Answer 5

You can bind state value directly to style object. Here is an example:

class Timer extends Component{
 constructor(props){
 super(props);
 this.state = {timer: 0, color: '#FF0000'};
 setInterval(() => {
   this.setState({timer: this.state.timer + 1, color: this.state.timer % 2 == 0 ? '#FF0000' : '#0000FF'});
 }, 1000);
}

render(){
 return (
   <View>

    <Text>Timer:</Text>
    <Text style={{backgroundColor: this.state.color}}>{this.state.timer}</Text>
  </View>
 );
 }
}

Answer 6

In case someone needs to apply conditions

 selectedMenuUI = function(value) {
       if(value==this.state.selectedMenu){
           return {
                flexDirection: 'row',
                alignItems: 'center',
                paddingHorizontal: 20,
                paddingVertical: 10,
                backgroundColor: 'rgba(255,255,255,0.3)', 
                borderRadius: 5
           }  
       } 
       return {
            flexDirection: 'row',
            alignItems: 'center',
            paddingHorizontal: 20,
            paddingVertical: 10
       }
    }