将文件从 Firebase 存储下载到颤振

Question

我已经看到了几个关于在 firebase 存储中上传文档的示例，但是没有从 firebase 存储中下载文件列表到 Flutter 的文档。 在 Firebase 文档上，有很多关于 Android、iOS、web、c++ 等的 firebase 存储的文档，但没有 Flutter。 特别是如果我谈论视频的

VideoPlayerController videoPlayerController;
  @override
  void initState() {

    videoPlayerController = VideoPlayerController.network('/* Download Url*/');
    super.initState();
  }

视频在app初始化时需要Url

Answer 1

要查找从 Flutter 上传和下载文件到 Cloud Storage 的示例，请查看 FlutterFire 库 firebase_storage 的 example application。

该过程主要包括获取下载 URL，它使您可以只读访问文件：

final String url = await ref.getDownloadURL();

然后从该 URL 加载数据：

final http.Response downloadData = await http.get(url);

查看_downloadFile method 获取完整示例。

Answer 2

class UploadMultipleImageDemo extends StatefulWidget {
  UploadMultipleImageDemo() : super();

  final String title = 'Firebase Storage';

  @override
  UploadMultipleImageDemoState createState() => UploadMultipleImageDemoState();
}

class UploadMultipleImageDemoState extends State<UploadMultipleImageDemo> {

  String _path;
  Map<String, String> _paths;
  String _extension;
  FileType _pickType = FileType.video;
  bool _multiPick = false;
  GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey();
  List<StorageUploadTask> _tasks = <StorageUploadTask>[];

  void openFileExplorer() async {
    try {
      _path = null;
      if (_multiPick) {
        _paths = await FilePicker.getMultiFilePath(
          type: FileType.video,  );
      } else {
        _path = await FilePicker.getFilePath(
          type: FileType.video, );
      }

      uploadToFirebase();
    } on PlatformException catch (e) {
      print("Unsupported operation" + e.toString());
    }
    if (!mounted) return;

  }

  uploadToFirebase() {
    if (_multiPick) {
      _paths.forEach((fileName, filePath) => {upload(fileName, filePath)});
    } else {
      String fileName = _path.split('/').last;
      String filePath = _path;
      upload(fileName, filePath);
    }
  }

  upload(fileName, filePath) {
    _extension = fileName.toString().split('.').last;
    StorageReference storageRef =
    FirebaseStorage.instance.ref().child(fileName);
    final StorageUploadTask uploadTask = storageRef.putFile(
      File(filePath),
      StorageMetadata(
        contentType: '$_pickType/$_extension',
      ),
    );
    setState(() {
      _tasks.add(uploadTask);
    });
  }
  String _bytesTransferred(StorageTaskSnapshot snapshot) {
    return '${snapshot.bytesTransferred}/${snapshot.totalByteCount}';
  }

  @override
  Widget build(BuildContext context) {
    final List<Widget> children = <Widget>[];
    _tasks.forEach((StorageUploadTask task) {
      final Widget tile = UploadTaskList(
        task: task,
        onDismissed: () => setState(() => _tasks.remove(task)),
        onDownload: () => downloadFile(task.lastSnapshot.ref),
      );
      children.add(tile);
    });

    return  MaterialApp(
      home: new Scaffold(
        key: _scaffoldKey,
        appBar: new AppBar(
          title: Text(widget.title),
        ),
        body: new Container(
          padding: EdgeInsets.all(20.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            mainAxisAlignment: MainAxisAlignment.start,
            children: <Widget>[
              OutlineButton(
                onPressed: () => openFileExplorer(),
                child: new Text("Open file picker"),
              ),
              SizedBox(
                height: 20.0,
              ),


              Flexible(
                child: ListView(
                  children: children,
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Future<void> downloadFile(StorageReference ref) async {
    final String url = await ref.getDownloadURL();
    final http.Response downloadData = await http.get(url);
    final Directory systemTempDir = Directory.systemTemp;
    final File tempFile = File('${systemTempDir.path}/tmp.jpg');
    if (tempFile.existsSync()) {
      await tempFile.delete();
    }
    await tempFile.create();
    final StorageFileDownloadTask task = ref.writeToFile(tempFile);
    final int byteCount = (await task.future).totalByteCount;
    var bodyBytes = downloadData.bodyBytes;
    final String name = await ref.getName();
    final String path = await ref.getPath();
    print(url);
    _scaffoldKey.currentState.showSnackBar(
      SnackBar(
        backgroundColor: Colors.white,
        content: Image.memory(
          bodyBytes,
          fit: BoxFit.fill,
        ),
      ),
    );
  }
}

class UploadTaskList extends StatelessWidget {
  const UploadTaskList(
      {Key key, this.task, this.onDismissed, this.onDownload})
      : super(key: key);

  final StorageUploadTask task;
  final VoidCallback onDismissed;
  final VoidCallback onDownload;

  String get status {
    String result;
    if (task.isComplete) {
      if (task.isSuccessful) {
        result = 'Complete';
      } else if (task.isCanceled) {
        result = 'Canceled';
      } else {
        result = 'Failed ERROR: ${task.lastSnapshot.error}';
      }
    } else if (task.isInProgress) {
      result = 'Uploading';
    } else if (task.isPaused) {
      result = 'Paused';
    }
    return result;
  }

  String _bytesTransferred(StorageTaskSnapshot snapshot) {
    return '${snapshot.bytesTransferred}/${snapshot.totalByteCount}';

  }

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<StorageTaskEvent>(
      stream: task.events,
      builder: (BuildContext context,
          AsyncSnapshot<StorageTaskEvent> asyncSnapshot) {
        Widget subtitle;
        Widget prog;
        Widget progtext;
        if (asyncSnapshot.hasData) {
          final StorageTaskEvent event = asyncSnapshot.data;
          final StorageTaskSnapshot snapshot = event.snapshot;
          subtitle = Text('$status: ${_bytesTransferred(snapshot)}');
          double _progress = event.snapshot.bytesTransferred.toDouble() / event.snapshot.totalByteCount.toDouble();
          prog = LinearProgressIndicator(
            value: _progress,
            backgroundColor: Colors.red,
          );
          progtext = Text('${(_progress * 100).toStringAsFixed(2)} %');



        } else {
          subtitle = const Text('Starting...');
        }
        return Dismissible(
          key: Key(task.hashCode.toString()),
          onDismissed: (_) => onDismissed(),
          child: ListTile(
            title: subtitle,
            // Text('Upload Task #${task.hashCode}'),

            subtitle: prog,
            trailing: Row(
              mainAxisSize: MainAxisSize.min,
              children: <Widget>[
                Offstage(
                  offstage: !task.isInProgress,
                  child: IconButton(
                    icon: const Icon(Icons.pause),
                    onPressed: () => task.pause(),
                  ),
                ),
                Offstage(
                  offstage: !task.isPaused,
                  child: IconButton(
                    icon: const Icon(Icons.file_upload),
                    onPressed: () => task.resume(),
                  ),
                ),
                Offstage(
                  offstage: task.isComplete,
                  child: IconButton(
                    icon: const Icon(Icons.cancel),
                    onPressed: () => task.cancel(),
                  ),
                ),
                Offstage(
                  offstage: !(task.isComplete && task.isSuccessful),
                  child: IconButton(
                    icon: const Icon(Icons.file_download),
                    onPressed: onDownload,
                  ),
                ),

              ],


            ),
          ),
        );
      },
    );
  }
}