请问RN 用base64上传图片时提示 Creating an AV.File from a String is not yet supported.如何解决？

[CapSnake]

代码如下

const result = await ImagePicker.launchImageLibraryAsync({
mediaTypes: ImagePicker.MediaTypeOptions.All,
allowsEditing: true,
aspect: [4, 3],
base64: true
});
if (result.cancelled) {
return;
}

var data = {base64: result.base64}

var file = new AV.File("avatar.jpg", result.base64);
var fileId = "";
file
  .save({
    onprogress: progress => {
      console.log(progress);
      // {
      //   loaded:  1024,
      //   total:   2048,
      //   percent: 50
      // }
    }
  })