firebase - 从 Firebase 数据库中提取值并在 React-Native-Chart-Kit 中呈现

Question

我正在尝试从我的 Firebase 实时数据库中提取值并将它们存储在基本 react-native-chart-kit 的数据部分中。我可以下拉值，但每次尝试将数据插入图表的数据参数时，都会出现错误。

我尝试将 data 参数设置为等于我的值数组，我也尝试一次只传递一个值（如变量'single'所见），但每次我得到一个错误。

这是我为下面显示的代码得到的错误。任何帮助将不胜感激

componentDidMount() {
    itemsRef.on('value', snapshot => {
      let data = snapshot.val();
      let items = Object.values(data);
      this.setState({ items: items });

      var i = 0;
      var total = [];
      for (i = 0; i < items.length; i++)
      {
        parseInt(items[i].name)
        total[i] = ''
        total[i] += items[i].name
      }

      this.setState({total})

      return total;
    });
  }

  render() {

    array = []
    array = this.state.total
    single = array[0]

    console.log(single)

    return (

      <React.Fragment>
      <View>

    <Text>Bezier Line Chart + {this.state.total}</Text>
  <LineChart
    data={{
      labels: ['January', 'February', 'March', 'April', 'May', 'June'],
      datasets: [
        {
          data: this.state.total,
        },
      ],
    }}

Answer 1

I also had this problem. To get rid of this error, I set the state to 0 for each data from firebase, eg:

    class MyComponent extends Component {
    constructor(props) {
        super(props);

        this.state = {
            total: 0,
            isLoading: false,
        };
    };