React Native ListView - not all visible items are rendered

Question

As a first React-Native project, I'm just trying to create a simple animation. It's a ListView filled with squares that are animating their opacity. For that I've created a ListView that contains Square which is a 50X50 square painted with one of 3 colors.

 class Square extends Component {
       constructor(props) {
         super(props);
        _defaultTransition  = 500;
         this.state = {
        _rowOpacity : new Animated.Value(0),
           targetOpacity: 0
         };
         setInterval(() => {
          this.state.targetOpcacity = this.state.targetOpcacity == 0 ? 1 : 0;
          this.animate(this.state.targetOpcacity);
        }, Math.random() * 1000);
       }

       animate(to) {
        Animated.timing(          
            this.state._rowOpacity,   
            {toValue: to, duration : 500}
            ).start();
       }
       componentDidMount() {
         this.animate(1);
       }

       render() {
        var rand = Math.random();
        var color =  rand < 0.3 ? 'powderblue' : rand > 0.6 ? 'skyblue' : 'steelblue';
        return (
            <Animated.View 
            style={{height:50, width: 50, backgroundColor: color, opacity: this.state._rowOpacity}}>
         {this.props.children}
        </Animated.View>
        );
      }
    }

    class ReactFirst extends Component {
      constructor(props) {
        super(props);
        var array = Array.apply(null, {length: 1000}).map(Number.call, Number);
        const ds = new ListView.DataSource({rowHasChanged: (r1, r2) => r1 !== r2});
        this.state = {
          dataSource: ds.cloneWithRows(array)
        };
      }
      render() {
        return (
            <ListView contentContainerStyle={styles.list}
              dataSource={this.state.dataSource}
              renderRow={(rowData) => <Square></Square>}
            />

        );
      }
    }

    var styles = StyleSheet.create({
        list: {
            flexDirection: 'row',
            flexWrap: 'wrap'
        }
    });

The result is that only 11 squares are animating themselves on the screen, although the array has 1000 cells. this means, one and a half lines are rendered and the rest of the screen is blank.

I would like to have the entire screen filled with animating squares.

Thanks a lot for the help, Giora.

Answer 1

Ok, after trying some things and going back to the docs, I've found the: initialListSize prop which allows to set the initial number of rendered rows.

<ListView contentContainerStyle={styles.list}
          dataSource={this.state.dataSource}
      initialListSize={size}
          renderRow={(rowData) => <Square></Square>}
        />

And it worked.