在Android中处理下载监听器

Question

你好我是Android Studio新手，我正在处理我的webView中的DownloadListener，以便下载已经上传到网页上的文件，基本上你可以说一个文件在pdf格式，但我想我的水平最好找错误，但未能发现错误one.The在于我们点击网页上的一些下载链接此刻却显示错误，是这样说：

02-05 22:47:29.425 3531-3531/myapp.hp.com.abhivyakti E/AndroidRuntime: FATAL EXCEPTION: main 
    Process: myapp.hp.com.abhivyakti, PID: 3531 
    java.lang.SecurityException: No permission to write to /storage/emulated/0/Download/download: Neither user 10059 nor current process has android.permission.WRITE_EXTERNAL_STORAGE. 
     at android.os.Parcel.readException(Parcel.java:1599) 
     at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:183) 
     at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135) 
     at android.content.ContentProviderProxy.insert(ContentProviderNative.java:476) 
     at android.content.ContentResolver.insert(ContentResolver.java:1231) 
     at android.app.DownloadManager.enqueue(DownloadManager.java:946) 
     at myapp.hp.com.abhivyakti.Notification.NotifyFragment$3.onDownloadStart(NotifyFragment.java:95) 
     at com.android.webview.chromium.WebViewContentsClientAdapter.onDownloadStart(WebViewContentsClientAdapter.java:884) 
     at com.android.org.chromium.android_webview.AwContentsClientCallbackHelper$MyHandler.handleMessage(AwContentsClientCallbackHelper.java:112) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:148) 
     at android.app.ActivityThread.main(ActivityThread.java:5417) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

我的活动代码如下：

public class NotifyFragment extends Fragment { 

    public NotifyFragment() { 
     // Required empty public constructor 
    } 

    private WebView webView; 
    private ProgressBar pb; 
    private ConnectivityManager cManager; 
    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 
     View view = inflater.inflate(R.layout.fragment_notify, container, false); 
     webView = (WebView)view.findViewById(R.id.notifywebView); 
     pb = (ProgressBar)view.findViewById(R.id.notifyprogressBar); 

     cManager = (ConnectivityManager) getActivity().getSystemService(getActivity().CONNECTIVITY_SERVICE); 
     NetworkInfo nInfo = cManager.getActiveNetworkInfo(); 
     if (nInfo == null) { 
      AlertDialog.Builder builder = new AlertDialog.Builder(getActivity()); 
      builder.setMessage("No Internet Connection") 
        .setTitle("Oops!!") 
        .setIcon(R.drawable.caution); 
      builder.setCancelable(false); 
      builder.setPositiveButton("Try Again", new DialogInterface.OnClickListener() { 
       @Override 
       public void onClick(DialogInterface dialog, int which) { 
        webView.loadUrl("https://docs.google.com/document/d/12u6jzoY8zB11valB2FwMyrf0HcWDnOvCkokzggNu1bA/edit?usp=sharing"); 
       } 
      }); 
      AlertDialog alert = builder.create(); 
      alert.show(); 
     }else { 
      webView.loadUrl("https://docs.google.com/document/d/12u6jzoY8zB11valB2FwMyrf0HcWDnOvCkokzggNu1bA/edit?usp=sharing"); 
     } 
     //getActivity().getWindow().requestFeature(Window.FEATURE_PROGRESS); 
     getActivity().getWindow().setFeatureInt(Window.FEATURE_PROGRESS, Window.PROGRESS_VISIBILITY_ON); 
     webView.setWebChromeClient(new WebChromeClient() { 
      public void onProgressChanged(WebView view, int progress) { 
       //Make the bar disappear after URL is loaded, and changes string to Loading... 
       pb.setProgress(progress * 100); //Make the bar disappear after URL is loaded 

       // Return the app name after finish loading 
       if (progress == 100) { 
        pb.setVisibility(View.GONE); 
       } else { 
        pb.setVisibility(View.VISIBLE); 
       } 
      } 
     }); 
     webView.setWebViewClient(new mywebClient()); 
     webView.getSettings().setJavaScriptEnabled(true); 
     webView.loadUrl("https://docs.google.com/document/d/12u6jzoY8zB11valB2FwMyrf0HcWDnOvCkokzggNu1bA/edit?usp=sharing"); 
     webView.setDownloadListener(new DownloadListener() { 
      public void onDownloadStart(String url, String userAgent, 
             String contentDisposition, String mimetype, 
             long contentLength) { 
       DownloadManager.Request request = new DownloadManager.Request(
         Uri.parse(url)); 
       request.allowScanningByMediaScanner(); 
       request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED); 
       request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "download"); 
       DownloadManager dm = (DownloadManager) getActivity().getSystemService(getActivity().DOWNLOAD_SERVICE); 
       dm.enqueue(request); 
       Toast.makeText(getActivity(), "Downloading File", Toast.LENGTH_SHORT).show(); 
      } 
     }); 
     return view; 
    } 

    public class mywebClient extends WebViewClient { 

     @Override 
     public boolean shouldOverrideUrlLoading(WebView view, String url) { 
      view.loadUrl(url); 
      return true; 
     } 
    } 
    public boolean onKeyDown(int keyCode, KeyEvent event){ 
     if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack()) { 
      webView.goBack(); 
      return true; 
     } 
     return onKeyDown(keyCode, event); 
    } 
} 

I w不好意思，因为它会帮助我向前发展并给予免费的应用程序。谢谢。

Answer 1

两个问题：

A）您是否在您的清单中添加了以下权限？ B）如果您确实仍然无法使用，那么您的Android设备是什么版本？