使用react native和expo，我们希望用户能够发布视频或图像。
代码如下：

import * as ImagePicker from 'expo-image-picker';

const openImagePickerAsync = async() => {
    const permissionResult = await ImagePicker.requestMediaLibraryPermissionsAsync();

    if (permissionResult.granted === false) {
      setImage(null);
      setHasImage(false);
      alert('Permission to access camera roll is required!');
      return;
    }

    const pickerResult = await ImagePicker.launchImageLibraryAsync({
      mediaTypes: ImagePicker.MediaTypeOptions.All, <---------------- allowing photos and video
      allowsEditing: true,
    });

    try {
      if (pickerResult.cancelled === true) {
        setHasImage(false);
        console.log('pickerResult is cancelled');
        return;
      }

      if (pickerResult !== null) {
        setHasImage(true);
        setImage(pickerResult.uri);
        console.log(image);
      } else {
        setImage(null);
        setHasImage(false);
        console.log('pickerResult is null');
        return;
      }
    } catch (error) {
      console.log(error);
    }
  };

我们如何才能知道用户是否选择了照片或视频？是否在元数据中？