退出屏幕时撤消重新渲染

Question

在我的代码中，我将电子邮件作为输入并运行 graphql 查询。使用 graphql 查询结果，我使用我的showUsersfunction 来渲染一些组件。当我点击cancel 并转到上一个屏幕（切换）时，渲染的对象（查询结果）应该会消失。当我回到屏幕上时，我仍然看到它们。退出时如何重置它们？

目前这就是我在回归时所做的事情

{showUsers(userData, Number(numberOfUsers))}

我的代码概览：

export const Page: React.FunctionComponent<PageProps> = ({
  toggleShowPage,
  showAddFriendEmailPage,
}) => {

  const [userData, setUserData] = useState<UsersLazyQueryHookResult>('');
  const [numberOfUsers, setNumberOfUsers] = useState('');

  const validationSchema = emailValidationSchema;

   const showUsers = React.useCallback(
     (data: UsersLazyQueryHookResult, numberOfUsers: Number) => {
       for (var i = 0; i < numberOfUsers; i++) {
         const userId = data.users.nodes[i].id;
         const userName = data.users.nodes[i].firstName
           .concat(' ')
           .concat(data.users.nodes[i].lastName);
         return (
           <View style={styles.friends}>
             <View style={styles.item}>              
               <Text style={styles.userName}>{userName}</Text>
               <View style={styles.addButtonContainer}>
               <Button  rounded style={styles.addButton}
               //onPress={() => addFriend(Number(data.users.nodes[i].id))}
               >
               </Button>
               </View>
             </View>
           </View>
         );
       }
     },
     [createUserRelationMutation],
   );

  const addFriend = React.useCallback(
    (id: Number) => {
      console.log('Whats the Id', id);
      createUserRelationMutation({
        variables: {
          input: { relatedUserId: id, type: RelationType.Friend, userId: 7 },
        },
      });
    },
    [createUserRelationMutation],
  );

  const getFriendId = React.useCallback(
    (data: UsersLazyQueryHookResult) => {
      if (data) {
        if (data.users.nodes.length == 0) {
          Alert.alert('User Not Found');
        } else {
          setUserData(data);
          setNumberOfUsers(data.users.nodes.length);
        }
      }
    },
    [addFriend],
  );



  const [loadUsers] = useUsersLazyQuery({
    onCompleted: getFriendId,
    onError: _onLoadUserError,
  });

  const handleSubmitForm = React.useCallback(

    (values: FormValues, helpers: FormikHelpers<FormValues>) => {

      console.log('Submitted');
      loadUsers({
        variables: {
          where: { email: values.email },
        },
      });
      values.email = '';
    },
    [loadUsers],
  );

  return (
    <Modal
      visible={showAddFriendEmailPage}
      animationType="slide"
      transparent={true}>
      <SafeAreaView>
        <View style={styles.container}>
          <View style={styles.searchTopContainer}>
            <View style={styles.searchTopTextContainer}>
              <Text
                style={styles.searchCancelDoneText}
                onPress={toggleShowPage}>
                Cancel
              </Text>
              <Text style={styles.searchTopMiddleText}>
                Add Friend by Email
              </Text>
              <Text style={styles.searchCancelDoneText}>Done</Text>
            </View>
            <View>
              <Formik
                initialValues={initialValues}
                onSubmit={handleSubmitForm}
                validationSchema={validationSchema}>
                {({ handleChange, handleBlur, handleSubmit, values }) => (
                  <View style={styles.searchFieldContainer}>
                    <View style={styles.form}>
                      <FieldInput
                        handleChange={handleChange}
                        handleBlur={handleBlur}
                        value={values.email}
                        fieldType="email"
                      />
                      <ErrorMessage
                        name="email"
                        render={msg => (
                          <Text style={styles.errorText}>{msg}</Text>
                        )}
                      />
                    </View>
                    <View style={styles.buttonContainer}>
                      <Button
                        rounded
                        style={styles.button}
                        onPress={handleSubmit}>
                        <Text style={styles.text}>Search </Text>
                      </Button>
                    </View>
                  </View>
                )}
              </Formik>
            </View>
            {showUsers(userData, Number(numberOfUsers))}            
          </View>
        </View>
      </SafeAreaView>
    </Modal>
  );
};

Answer 1

这对我有用：

 const [isSubmitted, setIsSubmitted] = useState(false);

  const handleSubmitForm = React.useCallback(    
    (values: FormValues, helpers: FormikHelpers<FormValues>) => {
      setIsSubmitted(true);
      ...
    },
    [loadUsers],
  );

 {isSubmitted && showUsers(userData, Number(numberOfUsers))}

取消后，我们可以将IsSubmitted设置为false。