javascript - 渲染没有返回任何内容。这通常意味着缺少 return 语句

Question

我使用React Native Camera来扫描条形码，现在我正在尝试在条形码与数据库中的项目进行检查时显示模态。

我收到的错误是:

Error: checkBarcode(...): Nothing was returned from render. This usually means a return statement is missing. Or, to render nothing, return null.

我应该怎么做才能让它正常工作。我做错了什么？

代码:

CheckBarcode(scanResult) {
  const product = DataBase.find((codeMetadata) => {
    return codeMetadata.id === scanResult.data;
  });

  if (this.barCodeRead) {
    if (product) {
      this.barCodeRead = false;
      this.setModalVisible(true);
      return (
        <View>
          <Text>{product.company}</Text>
          <Text>{product.name}</Text>
          <Text>{product.gluten}</Text>
          <Text>{product.ingredients}</Text>
          <Text>{product.id}</Text>
        </View>
      );
    } else {
      this.barCodeRead = true;
      return (
        <View>
          <Text>Produkten finns inte</Text>
        </View>
      );
    }
  }
}

模态:

<Modal
  animationType="fade"
  transparent={true}
  visible={modalVisible}
  onRequestClose={() => {
    this.setModalVisible(!modalVisible);
  }}
>
  <View
    style={{
      flex: 1,
      justifyContent: "center",
      alignItems: "center",
      backgroundColor: "rgba(0,0,0,0.8)",
    }}
  >
    <View
      style={{
        backgroundColor: "#fff",
        padding: 35,
        borderRadius: 10,
        width: "80%",
        height: "80%",
      }}
    >
      <View
        style={{
          borderTopWidth: 1,
          borderTopColor: "#000",
          marginBottom: 10,
        }}
      >
        <this.CheckBarcode />
      </View>
      <View>
        <TouchableOpacity
          style={{}}
          onPress={() => {
            this.setModalVisible(!modalVisible);
            this.barCodeRead = true;
          }}
        >
          <Text style={{ alignSelf: "center", color: "#FF0000" }}>Skanna</Text>
        </TouchableOpacity>
      </View>
    </View>
  </View>
</Modal>

Answer 1

您需要返回一些JSX来自组件中的渲染函数。如果您不想在 UI 上显示任何内容，可以返回 null。一个例子:

if (this.barCodeRead) {
  if (product) {
    return (
      <View>
        <Text>{product.company}</Text>
      </View>
    );
  } else {
    return (
      <View>
        <Text>Produkten finns inte</Text>
      </View>
    );
  }
 }
 return <div>No Data to show</div> // or null