React Native JSX：设置状态导致应用程序崩溃

Question

我正在使用 React Native 来构建我的应用程序。下面是我用来显示 'tags' 列表的代码。所以代码是用来隐藏除前2个标签外的所有标签，会出现一个'load more' link。单击加载更多 link 应该会显示其余标签。但是代码在我身上崩溃了。

this.state = {
  visibleCount: 2,
};

<TextLink onPress={() => {
    this.setState({visibleCount: mealTags.length});
  }}
</TextLink>

我正在使用更改状态来显示标签。谁能告诉我出了什么问题以及如何更新它？

export function MealTagsSection(props: MealTagsProps) {
  let {mealTags} = props;
  let loadMoreLink;

  if (mealTags.length > 2) {
    loadMoreLink = (
      //THIS CAUSES THE APP TO CRASH
      <TextLink onPress={() => {
        this.setState({visibleCount: mealTags.length});
      }}
      >
        load more...
      </TextLink>
    );
  } else {
    loadMoreLink = null;
  }

  this.state = {
    visibleCount: 2,
  };

  return (
    <View style={styles.mealTagsContainer}>
      {
        mealTags.slice(0, this.state.visibleCount).map((mealTag) => {
          let tagStyle = '';
          if (mealTag.category === 1) {
            tagStyle = styles.tag_healthy;
          } else {
            tagStyle = styles.tag_improve;
          }
          return (
            <View style={tagStyle}>
              <Text style={styles.tagText}>{mealTag.description}</Text>
            </View>
          );
        })
      }
      {loadMoreLink}
    </View>
  );
}

我得到的错误是： *** 由于未捕获的异常 'RCTFatalException：未处理的 JS 异常：t.setState 不是函数而终止应用程序。（在 't.setState({visibleCount:n.length})' 中，'t.setState' 未定义）', reason: 'Unhandled JS Exception: t.setState is not a function. (在't.setState({visi..., stack: onPress@439:2034

Answer 1

您的 MealTagsSection 是功能组件。 React 功能组件不必包含本地状态。如果想拥有本地状态，则应将其设为 class 组件。

export class MealTagsSection extends Component {
  constructor() {
    super();
    this.state = { visibleCount: 2 };
  }

  render() {
    let { mealTags } = this.props;
    let loadMoreLink;

    if (mealTags.length > 2) {
      loadMoreLink =
        (
          <TextLink
            onPress={() => {
              this.setState({ visibleCount: mealTags.length });
            }}
          >
            load more...
          </TextLink>
        );
    } else {
      loadMoreLink = null;
    }

    return (
      <View style={styles.mealTagsContainer}>
        {mealTags.slice(0, this.state.visibleCount).map(mealTag => {
          let tagStyle = "";
          if (mealTag.category === 1) {
            tagStyle = styles.tag_healthy;
          } else {
            tagStyle = styles.tag_improve;
          }
          return (
            <View style={tagStyle}>
              <Text style={styles.tagText}>{mealTag.description}</Text>
            </View>
          );
        })}
        {loadMoreLink}
      </View>
    );
  }
}

React Native JSX：设置状态导致应用程序崩溃

React Native JSX: Setting state causes app to crash

state

reactjs

react-jsx

react-native