Recently do a project need to download pictures from the server to the local sdcard, the Internet to find some examples, the following is more appropriate, the original content is as follows:
we often need to download files from the server in development, the content of the download may have Exchange information, cached pictures, program update package and so on. We use URLConnection to implement downloads. Let's look at a few lines of code:String urldownload = ""; urldownload = "Http://www.baidu.com/img/baidu_sylogo1.gif"; URL url = new URL (urldownload); Open connection URLConnection con = url.openconnection ();//input stream InputStream is = Con.getinputstream ();
as shown in the code above, specify a download target link, we specify a picture address above. It then constructs a URL object that invokes the object's OpenConnection method to establish a data path (connection). The last line of code uses Con.getinputstream to get an input stream object, through which we can read the contents of this file. The next thing to do is to read the stream and write the stream to our local file. But before we do that, we're going to say this way:<span xmlns= "http://www.w3.org/1999/xhtml" >//get the length of the file int contentlength = Con.getcontentlength (); System.out.println ("Length:" +contentlength) </span>
method to get the file length. ContentLength is not very familiar. It is one of the description attributes in the HTTP protocol that describes the header (head) section. Actually here is sent an HTTP request that analyzes the contents of the data returned (response).
we often download files to the phone's memory card, so we also use the method of obtaining the memory card path:<span xmlns= "http://www.w3.org/1999/xhtml" >//gets the memory card path, which forms the destination path of the saved file string dirName = "";d irname = Environment.getexternalstoragedirectory () + "/mydownload/"; File F = new file (dirName), if (!f.exists ()) {F.mkdir ();} </span>
The environment.getexternalstoragedirectory () method returns a string that indicates the path of the memory card. We stitch strings out of a folder to prepare the downloaded files. and first determine if the folder is present, or if it does not exist, create a new folder.
after finishing the above preparation, the basic will be able to achieve the download. Let's look at the main complete code.
Pre-Download preparation work:File path to download string urldownload = "";//urldownload = "Http://192.168.3.39/text.txt"; urldownload = "http://www.baidu.com/ Img/baidu_sylogo1.gif ";//Gets the memory card path that forms the destination path of the saved file string dirName =" ";d irname = Environment.getexternalstoragedirectory () + "/mydownload/"; File F = new file (dirName), if (!f.exists ()) {F.mkdir ();}
Download the operation: //ready to splice the new file name (the file name saved on the memory card) String NewFileName = _urlstr.substring (_urlstr.lastindexof ("/") +1); NewFileName = _ DirName + newfilename; File File = new file (newfilename);//If the destination file already exists, delete it. Produces an effect that overwrites the old file if (file.exists ()) { File.delete ();} Try { //construct URL url url = new URL (_urlstr); //Open connection urlconnection con = ur L.openconnection (); //Get the length of the file int contentlength = CON.G Etcontentlength (); &NBSP;SYSTEM.OUT.PRINTLN ("Length:" +contentlength); //input stream inputstream is = Con.getinputstream (); //1K data buffer byte[] bs = new byte[1024 ]; //Length of data read int Len; //output file stream outputstream OS = NE W FileOutputStream (NewFileName); //start reading while (len = Is.read ( BS))! =-1) { os.write (BS, 0, Len); } //complete, close all links o S.close (); is.close (); } catch (Exception e) {& nbsp e.printstacktrace ();} Transfer from:http://www.itivy.com/android/archive/2011/6/28/android-file-download.html
The section of my code is as follows: Download pictures from server to local private void Getphotofromserver (list<advert> adverts) { //Read server IP address String ServerIP = Networkutil.getdns (); Direct read server IP address //string ServerURL = serverurlall.substring (Serverurlall.indexof (":") +3, Serverurlall.lastindexof (":")); It is best to read the IP address directly from the database or elsewhere LOG.D (TAG, "Server IP is" + ServerIP); //integrated into the full advertising image storage directory &NBSP ; String urldownload = "/http" + ServerIP + ": 8080/propicrecord/"; //advertising image local SD card storage directory String Dirnam E = "/sdcard/advert/"; //Determine if the directory where the local ad image is stored, does not exist, creates a new folder file F = new file (dirName); if ( !f.exists ()) { f.mkdir (); } //server advertising image full path name for download String Urldownloadall = ""; //Ready to splice New file name (file name saved on memory card) for (int i=0; Adverts!=null && i<adverts.size (); i++) { advert advert = aDverts.get (i); //download path add AD image name Urldownlo Adall = Urldownload + advert.geturl (); LOG.D (TAG, "The whole server download URL is "+ Urldownloadall); //Get the name of the ad image Word, actually using advert.geturl () can also String newfilename = urldownloadall.substring (Urldownloadall.lastindexof ("/") + 1); //The full path of the local broadcast ad image NewFileName = dirName + newfilename; LOG.D (TAG, "the is "+ newfilename); File File = new file (newfilename); //If the destination file already exists, then delete, resulting in an effect that overwrites the old file (This can be extended later to the already existing picture no longer re-download feature) if (file.exists ()) { file.delete (); } try{ //structuring url url URL = new URL (Urldownloadall); //Open connection urlconnection con = url.openconnection (); //Get the length of the file //int contentlength = Con.getcontentlength () ; &NBSP;//SYSTEM.OUT.PRINTLN ("Length:" +contentlength); & nbsp;//input stream inputstream is = Con.getinputstream (); &NBSP ; //1k data buffering byte[] bs = new byte[1024]; &NBS p;//read data length int len; //output file stream &NBSP ; outputstream OS = new FileOutputStream (newfilename); // Start reading while ((len = Is.read (BS))! =-1) { os.write (BS, 0, Len); } //complete, close all links &N Bsp os.close (); is.close (); }catch (Exception e) {& nbsp E.printstacktrace (); } } }
