我上週處理類似的問題，並最終使用AsyncTask與進步因爲可能需要一段時間才能下載文件，因此顯示條形圖。這樣做的一種方式是有以下嵌套在您的Activity類，只是把它，你需要簡單地是這樣的：
new DownloadManager().execute("here be URL", "here be filename");
或者該類不位於一個活動中，並從一個活動叫..
new DownloadManager(this).execute("URL", "filename");
這通過活性，所以我們有機會獲得方法getSystemService（）;
這是實際的代碼做所有的骯髒的工作。您可能需要修改它以滿足您的需求。
private class DownloadManager extends AsyncTask<String, Integer, Drawable>
{
private Drawable d;
private HttpURLConnection conn;
private InputStream stream; //to read
private ByteArrayOutputStream out; //to write
private Context mCtx;
private double fileSize;
private double downloaded; // number of bytes downloaded
private int status = DOWNLOADING; //status of current process
private ProgressDialog progressDialog;
private static final int MAX_BUFFER_SIZE = 1024; //1kb
private static final int DOWNLOADING = 0;
private static final int COMPLETE = 1;
public DownloadManager(Context ctx)
{
d = null;
conn = null;
fileSize = 0;
downloaded = 0;
status = DOWNLOADING;
mCtx = ctx;
}
public boolean isOnline()
{
try
{
ConnectivityManager cm = (ConnectivityManager)mCtx.getSystemService(Context.CONNECTIVITY_SERVICE);
return cm.getActiveNetworkInfo().isConnectedOrConnecting();
}
catch (Exception e)
{
return false;
}
}
@Override
protected Drawable doInBackground(String... url)
{
try
{
String filename = url[1];
if (isOnline())
{
conn = (HttpURLConnection) new URL(url[0]).openConnection();
fileSize = conn.getContentLength();
out = new ByteArrayOutputStream((int)fileSize);
conn.connect();
stream = conn.getInputStream();
// loop with step
while (status == DOWNLOADING)
{
byte buffer[];
if (fileSize - downloaded > MAX_BUFFER_SIZE)
{
buffer = new byte[MAX_BUFFER_SIZE];
}
else
{
buffer = new byte[(int) (fileSize - downloaded)];
}
int read = stream.read(buffer);
if (read == -1)
{
publishProgress(100);
break;
}
// writing to buffer
out.write(buffer, 0, read);
downloaded += read;
// update progress bar
publishProgress((int) ((downloaded/fileSize) * 100));
} // end of while
if (status == DOWNLOADING)
{
status = COMPLETE;
}
try
{
FileOutputStream fos = new FileOutputStream(filename);
fos.write(out.toByteArray());
fos.close();
}
catch (IOException e)
{
e.printStackTrace();
return null;
}
d = Drawable.createFromStream((InputStream) new ByteArrayInputStream(out.toByteArray()), "filename");
return d;
} // end of if isOnline
else
{
return null;
}
}
catch (Exception e)
{
e.printStackTrace();
return null;
}// end of catch
} // end of class DownloadManager()
@Override
protected void onProgressUpdate(Integer... changed)
{
progressDialog.setProgress(changed[0]);
}
@Override
protected void onPreExecute()
{
progressDialog = new ProgressDialog(/*ShowContent.this*/); // your activity
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Downloading ...");
progressDialog.setCancelable(false);
progressDialog.show();
}
@Override
protected void onPostExecute(Drawable result)
{
progressDialog.dismiss();
// do something
}
}