如何在 Flutter 中获取数据库中的图像下载 URL

Question

我想获取图片下载链接并将其存储在 Firestore 数据库中。下面是上传图片到 Firebase 存储的功能，如果功能错误，请解释原因并给我写一个功能？

File _image1;
Future uploadPic() async {
    StorageReference reference = storage.ref().child('image');
    StorageUploadTask uploadTask = reference.putFile(_image1);
    StorageTaskSnapshot taskSnapshot = await uploadTask.onComplete;
    String url = await taskSnapshot.ref.getDownloadURL();
    imageUrl1 = url;
  }

Answer 1

在函数中添加返回以检索输出（url）

File _image1;
Future uploadPic() async {
    StorageReference reference = storage.ref().child('image');
    StorageUploadTask uploadTask = reference.putFile(_image1);
    StorageTaskSnapshot taskSnapshot = await uploadTask.onComplete;
    String url = await taskSnapshot.ref.getDownloadURL();
    imageUrl1 = url;
    return url;
  }

从这里你可以调用then函数，

uploadPic().then((value)
            {
        DocumentReference docRef = 
        Firestore.instance.collection('collectionname').document(documentid);
             docRef.setData({'pic' : value},merge:true)
             });