Question

我正在制作一个Android应用程序从android下载pdf文件，然后将它们保存在内部或外部存储器的文件夹中。但有时由于糟糕的互联网连接下载停止没有finshing。像文件大小是1.1mb，它只下载到750KB。现在的问题是文件是否完全下载或我的应用程序显示为下载但实际上它不是。所以我想知道文件的确切大小和下载后，以便我可以找到文件是否完全下载。并希望重新启动下载。有谁能够帮我........ 我的代码

 String DownloadUrl = "http://www.example.com/books/"+book_name;
                            String fileName = book_name;


                            URL url = new URL(DownloadUrl);

//create the new connection





                            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

//set up some things on the connection

                            urlConnection.setRequestMethod("GET");

                            urlConnection.setDoOutput(true);

//and 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 = new File("/storage/emulated/0/documents/docx/stuff/");

                            File SDCardRoot = new File(Environment.getExternalStorageDirectory()+File.separator+"MybookStore/paper/paperStuff/documents/docx/other/stuff/");
//create a new file, specifying the path, and the filename

//which we want to save the file as.

                            File file = new File(SDCardRoot,fileName);

                            String file_size = Long.toString(file.length()/1024);

                            int size_file=Integer.parseInt(file_size);
//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;

                                int progress=(int)(downloadedSize*100/totalSize);

//this is where you would do something to report the prgress, like this maybe

//updateProgress(downloadedSize, totalSize);

                            }

我的代码

Answer 1

任何合理的服务器响应标头都会包含一个Content-Length密钥，它有望表示您尝试下载的资源的全长。

考虑到这一点，这是一个简单的例子：

HttpURLConnection connection = null;
InputStream input = null;
OutputStream output = null;

try {
  final URL url = new URL(resourceUrl);
  connection = (HttpURLConnection) url.openConnection();
  connection.connect();

  final int length = connection.getContentLength();
  int downloaded = 0;

  input = url.openStream();
  output = new FileOutputStream(targetFile);

  final byte[] buffer = new byte[BUFFER_SIZE];
  int read;
  while ((read = input.read(buffer)) != -1) {
    output.write(buffer, 0, read);
    downloaded += read;
  }

  if (downloaded == length) {
    // The file was successfully downloaded.
  } else {
    // The file was not fully downloaded.
  }
} catch (IOException e) {
  // Handle exception.
} finally {
  // Close resources.
}

如何在android下载之前和之后知道下载文件的大小

1 个答案: