无法从Firebase存储获取下载URL(所需的引用处没有对象.) [英] Failing to get a download URL from firebase storage(No object exists at the desired reference.)

问题描述

我一直在尝试获取Firebase存储中图像的下载URL，因此可以将其添加到列表视图构建器"NetworkCatched Images"中.对于列表中每个项目，您都可以从下面的代码中看到，我首先在有状态类的开头声明了一个变量，称为"URL".所以我可以通过使其值等于我从Firebase存储获得的下载URL来更改值，但似乎我正在使用的异步函数甚至没有运行，因为我确保它在打印完后会打印出下载URL的值它已经完成了，但是我在调​​试控制台中什么也没看到，这里哪里出了问题?

我不断收到此错误所需的引用处没有对象.

顺便说一句，我的代码中的"thesnapshot.data()['image']" 等于图像文件的名称，例如 books.jpg 是文件的确切名称，它位于一个名为category的文件夹中，如下所示，非常感谢您的启发

  class Home扩展State< HomeScreen>{var url;ListView.builder(shrinkWrap:true，填充:EdgeInsets.all(0)，物理:NeverScrollableScrollPhysics()，itemCount:snapshot.data.documents.length，itemBuilder:(BuildContext context，int index){DocumentSnapshot thesnapshot = snapshot.data.docs [index];current_category = thesnapshot.data()['category'];printUrl()异步{参考ref = FirebaseStorage.instance.ref().child("category/" + thesnapshot.data()['image'].toString());var togo =(await ref.getDownloadURL()).toString();setState((){url =多哥;打印(URL);});}printUrl(); 

解决方案

我认为您的引用中包含的.ref()和thesnapshot.data()['image'].toString().

尝试这样的事情

  Future< void>downloadURLExample()异步{字符串downloadURL =等待firebase_storage.FirebaseStorage.instance.ref('users/123/avatar.jpg').getDownloadURL(); 

从文档中提取

i have been trying to get the download URL for my images in firebase storage so I can add it to my listview builders "NetworkCatched Images" for each of my items in the list, as you can see from my code below, I first declared a variable at the beginning of my stateful class called "URL" so I could change the value by making it equal to the download URL i get from firebase storage, but it seems like the async function I'm using doesn't even run because i made sure it prints out the value of the downloaded URL after it is done, but i see nothing in my debug console, where am going wrong here?

i keep getting this error No object exists at the desired reference.

by the way, the "thesnapshot.data()['image']" in my code is equal to the name of the image file e.g books.jpg which is the exact name of the file and it is in a folder called category as you can see below, would really appreciate some enlightenment on this, thanks

class Home extends State<HomeScreen> {
  var url;
  ListView.builder(shrinkWrap: true, padding: EdgeInsets.all(0), physics: NeverScrollableScrollPhysics(), itemCount: snapshot.data.documents.length, itemBuilder: (BuildContext context, int index) 
    {
        DocumentSnapshot thesnapshot = snapshot.data.docs[index];
        current_category = thesnapshot.data()['category'];
        printUrl() async {
            Reference ref = FirebaseStorage.instance.ref().child("category/" + thesnapshot.data()['image'].toString());
            var togo = (await ref.getDownloadURL()).toString();
            setState(() {
            url =  togo;
            print(url);
        });
    
}

printUrl();

                                                          

解决方案

I think that the .ref() included in your reference doesn't go thereas well as the thesnapshot.data()['image'].toString().

Try something like this

Future<void> downloadURLExample() async {
  String downloadURL = await firebase_storage.FirebaseStorage.instance
      .ref('users/123/avatar.jpg')
      .getDownloadURL();

Extracted from the documentation

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