Question

直到今天，我从未想过要从Urls下载文件，需要在其Activity类上实现Interface Download Listener。我在Xamarin Android上有一个webview，但似乎无法下载文件。认为这是因为我尚未在我的课程上实现此接口Download Listener。.因此，我尝试了一下，但似乎无法将Interface实现方法与OnDwnloadStart方法连接起来，当我请求从以下位置下载时，我认为网页，则IDownloadListener方法不执行任何操作，因为它没有代码...。但是应该处理下载请求的代码在带有OnDownloadStart参数的url, ContentDisposition and mimetype方法中，任何调用该接口的帮助OnDownloadStart方法将不胜感激..这是我使用的代码...

class Internet : AppCompatActivity,IDownloadListener
    {
       protected override void OnCreate(Bundle savedInstanceState)
        {

            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            SetContentView(Resource.Layout.Browser);
           //Webview definition
         webview = this.FindViewById<WebView>(Resource.Id.webview1);
           //webview properties
            webview.SetWebViewClient(new WebViewClient());
            WebSettings webSettings = webview.Settings;
            webSettings.SetSupportMultipleWindows(true);
            webSettings.SetEnableSmoothTransition(true);
            webSettings.JavaScriptEnabled = true;
            webSettings.DomStorageEnabled = true;
            webSettings.AllowFileAccessFromFileURLs = true;
            // webSettings.JavaScriptEnabled.
            webview.SetDownloadListener(this);
      }
     //Interface Download Listener Method
       public interface IDownloadListener : Android.Runtime.IJavaObject, IDisposable
        {
         //I got nothing here and this is what i think needs to call OndownloadStart  
        }
      //implementing OnDownloadStart Method
       public void OnDownloadStart(string url, string userAgent, string contentDisposition, string mimetype, long contentLength)
        {
            DownloadManager.Request request = new DownloadManager.Request(Android.Net.Uri.Parse(url));
            String cookies = CookieManager.Instance.GetCookie(url);
            request.AddRequestHeader("cookie", cookies);
            request.AddRequestHeader("User-Agent", userAgent);
            request.SetDescription("Downloading file to crn folder...");
            request.SetTitle(URLUtil.GuessFileName(url, contentDisposition, mimetype));
            request.AllowScanningByMediaScanner();
            request.SetNotificationVisibility(Android.App.DownloadVisibility.VisibleNotifyCompleted);
            File dest = new File(Android.OS.Environment.RootDirectory + "download");
            if (!dest.Exists())
            {
                if (!dest.Mkdir())
                { Log.Debug("TravellerLog ::", "Problem creating Image folder"); }
            }
            request.SetDestinationInExternalFilesDir(Application.Context, "download", 
       URLUtil.GuessFileName(url, contentDisposition, mimetype));
            DownloadManager manager = 
       (DownloadManager)GetSystemService(Android.App.Application.DownloadService);
            manager.Enqueue(request);
            //Notify if success with BroadCast Receiver
        }
}

该代码的哪个部分运行错误？任何帮助表示赞赏。

Answer 1

您不需要创建新的IDownloadListener接口，IDownloadListener接口是IDownloadListener下的系统namespace Android.Webkit：

namespace Android.Webkit
{
    [Register("android/webkit/DownloadListener", "", "Android.Webkit.IDownloadListenerInvoker", ApiSince = 1)]
    public interface IDownloadListener : IJavaObject, IDisposable, IJavaPeerable
    {
        void OnDownloadStart(string url, string userAgent, string contentDisposition, string mimetype, long contentLength);
    }
}

实现IDownloadListener接口的任何类或结构都必须包含与该接口指定的OnDownloadStart相匹配的Equals方法的定义。

就是这样：

public class MainActivity : AppCompatActivity, IDownloadListener
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        Xamarin.Essentials.Platform.Init(this, savedInstanceState);
       SetContentView(Resource.Layout.activity_main);

    }

    public void OnDownloadStart(string url, string userAgent, string contentDisposition, string mimetype, long contentLength)
    {
        throw new NotImplementedException();
    }
}

在Xamarin Android上实现下载侦听器界面

1 个答案: