Flutter 颤振Dio包：如何收听下载进度从另一个类？

我有一个

downloadservice

类，它使用

dio

包处理文件下载。我想听听我的

ViewModel

类的下载进度，该类在

DownloadService

类中实现了

downloadsfile

方法。我该怎么做

以下是我的

下载服务

类的代码片段：

class DownloadsService {
   final String urlOfFileToDownload = 'http://justadummyurl.com/'; //in my actual app, this is user input
   final String filename = 'dummyfile.jpg';
   final String dir = 'downloads/$filename'; //i'll have it saved inside internal storage downloads directory

   void downloadFile() {
     Dio dio = Dio();
     dio.download(urlOfFileToDownload, '$dir/$filename', onReceiveProgress(received, total) {
        int percentage = ((received / total) * 100).floor(); //this is what I want to listen to from my ViewModel class
     });
   }
}

class ViewModel {
   DownloadsService _dlService = DownloadsService(); //note: I'm using get_it package for my services class to make a singleton instance. I just wrote it this way here for simplicity..

      void implementDownload() {

       if(Permission.storage.request().isGranted) { //so I can save the file in my internal storage
          _dlService.downloadFile();

        /*
         now this is where I'm stuck.. My ViewModel class is connected to my View - which displays
         the progress of my download in a LinearProgressIndicator. I need to listen to the changes in
         percentage inside this class.. Note: my View class has no access to DownloadsService class. 
       */

      }        
   }
}

这是我的

ViewModel

课程：

class DownloadsService {
   final String urlOfFileToDownload = 'http://justadummyurl.com/'; //in my actual app, this is user input
   final String filename = 'dummyfile.jpg';
   final String dir = 'downloads/$filename'; //i'll have it saved inside internal storage downloads directory

   void downloadFile() {
     Dio dio = Dio();
     dio.download(urlOfFileToDownload, '$dir/$filename', onReceiveProgress(received, total) {
        int percentage = ((received / total) * 100).floor(); //this is what I want to listen to from my ViewModel class
     });
   }
}

class ViewModel {
   DownloadsService _dlService = DownloadsService(); //note: I'm using get_it package for my services class to make a singleton instance. I just wrote it this way here for simplicity..

      void implementDownload() {

       if(Permission.storage.request().isGranted) { //so I can save the file in my internal storage
          _dlService.downloadFile();

        /*
         now this is where I'm stuck.. My ViewModel class is connected to my View - which displays
         the progress of my download in a LinearProgressIndicator. I need to listen to the changes in
         percentage inside this class.. Note: my View class has no access to DownloadsService class. 
       */

      }        
   }
}

---

Dio文档提供了如何将响应类型转换为流/字节的示例。。但它没有给出任何下载文件时如何执行的示例。有人能给我指个正确的方向吗？我现在真的被困住了。。多谢各位

如果视图创建了视图模型，则必须在视图类中定义变量，然后将其传递给视图模型，并将其作为参数传递给下载服务

像这样：

class ViewModel {
       PublishSubject publishSubject;
       ViewModel(this.publishSubject);
       DownloadsService _dlService = DownloadsService();   
          void implementDownload() { 
           if(Permission.storage.request().isGranted) {  
              _dlService.downloadFile(publishSubject); 
          }        
       }
    }

因此，视图侦听在下载文件方法之前将发生的更改，该方法依次发送更改

像这样：

void downloadFile(PublishSubject publishSubject) {
     Dio dio = Dio();
     dio.download(urlOfFileToDownload, '$dir/$filename', 
        onReceiveProgress(received,total) {
        int percentage = ((received / total) * 100).floor(); 
        publishSubject.add(percentage);
     });
   }

class View {
  PublishSubject publishSubject = PublishSubject();
  ViewModel viewModel;
  View(){
    publishSubject.listen((value) {
      // the value is percentage.
      //can you refresh view or do anything
    });
   viewModel = ViewModel(publishSubject);
  }  
}

因此，接口将侦听以前发生的更改

像这样：

void downloadFile(PublishSubject publishSubject) {
     Dio dio = Dio();
     dio.download(urlOfFileToDownload, '$dir/$filename', 
        onReceiveProgress(received,total) {
        int percentage = ((received / total) * 100).floor(); 
        publishSubject.add(percentage);
     });
   }

class View {
  PublishSubject publishSubject = PublishSubject();
  ViewModel viewModel;
  View(){
    publishSubject.listen((value) {
      // the value is percentage.
      //can you refresh view or do anything
    });
   viewModel = ViewModel(publishSubject);
  }  
}

---

嘿，伙计，谢谢你的回复。我的视图类实际上只是我的UI代码。严格来说，我不想在视图类中放入任何业务逻辑。我想做的是，我的ViewModel类将侦听DownloadsService类，然后将当前值传递给View类。因此，我的View类所做的唯一一件事就是在UI中显示数据。不客气，我知道您真正想要的是什么，您可以在“ViewModel”中定义“publishSubject”变量并收听“DownloadsService”