文件下載通過http請求失敗

Question

在我的android應用程序我有一個歌曲列表。用戶可以從它下載任何歌曲。 但我的問題是，當我使用http請求下載文件時，它返回內容長度= 0或-1，所以我無法下載文件。 當我在瀏覽器中使用相同的網址，然後完全下載歌曲。 我的代碼，下載一首歌曲文件 -

URL url = new URL(mUrl); 
       HttpURLConnection connection = (HttpURLConnection) url.openConnection(); 
       connection.setRequestMethod("GET"); 
       connection.setDoOutput(true); 
       connection.setConnectTimeout(TimeOut); 
       connection.setReadTimeout(TimeOut); 
       connection.connect(); 
       int lenghtOfFile = connection.getContentLength(); 

和文件長度爲0或-1。 我的代碼中存在什麼問題。

在此先感謝。

Answer 1

運行一個HTTP請求wheter下載或上傳是爲了從你的UI拆分下載任務使用AsycTask的最佳方式，

嘗試把這個代碼的方法來下載你的文件，並調用它如果您使用的AsyncTask您可以從下面給出代碼

添加進度和更新它的進展更新進度取消註釋

updateProgress(downloadedSize,totalSize); 

    try { 
     //set the download URL, a url that points to a file on the internet 
     //this is the file to be downloaded 
     URL url = new URL("File Url"); 

     //create the new connection 
     HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); 

     //set up some things on the connection 
     urlConnection.setRequestMethod("GET"); 
     urlConnection.setDoOutput(true); 

     //connect! 
     urlConnection.connect(); 

     //set the path where we want to save the file 
     //in this case, going to save it on the root directory of the 
     //sd card. 
     File SDCardRoot = Environment.getExternalStorageDirectory(); 
     //create a new file, specifying the path, and the filename 
     //which we want to save the file as. 
     File file = new File(SDCardRoot,"song.extension"); 

     //this will be used to write the downloaded data into the file we created 
     FileOutputStream fileOutput = new FileOutputStream(file); 

     //this will be used in reading the data from the internet 
     InputStream inputStream = urlConnection.getInputStream(); 

     //this is the total size of the file 
     int totalSize = urlConnection.getContentLength(); 
     //variable to store total downloaded bytes 
     int downloadedSize = 0; 

     //create a buffer... 
     byte[] buffer = new byte[1024]; 
     int bufferLength = 0; //used to store a temporary size of the buffer 

     //now, read through the input buffer and write the contents to the file 
     while ((bufferLength = inputStream.read(buffer)) > 0) { 
       //add the data in the buffer to the file in the file output stream (the file on the sd card 
       fileOutput.write(buffer, 0, bufferLength); 
       //add up the size so we know how much is downloaded 
       downloadedSize += bufferLength; 
       //this is where you would do something to report the prgress, like this maybe 
       //updateProgress(downloadedSize, totalSize); if your run this code from AsyncTask 

     } 
     //close the output stream when done 
     fileOutput.close(); 

//catch some possible errors... 
} catch (MalformedURLException e) { 
     e.printStackTrace(); 
} catch (IOException e) { 
     e.printStackTrace(); 
}