Programming Tutorials

(追記) (追記ここまで)

Download a file over a network in J2ME midlet

By: Eriq Tan in J2ME Tutorials on 2006年12月12日 [フレーム]

This sample code can be used to download and view a file over a network in a TextBox component Through an httpConnection,

Important Points:

1) One benefit of using an HttpConnection (as compared to InputStream or StreamConnection) is the availability of a method to check for the length of the remote data. The data can then be read in one fell-swoop, in contrast to reading one character/byte at a time.

2) Before leaving the viewFile() method, check to the status of the input stream and the httpConnection, and close if necessary.

3) This example is written for version 1.0.3 of MIDP and CLDC

Java Code:

/*--------------------------------------------------
* FileViewer.java
*
* Download and view a file over a network 
*-------------------------------------------------*/
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;
import java.io.*;
public class FileViewer extends MIDlet implements CommandListener
{
 private Display display;	 // Reference to Display object
 private TextBox tbViewer; // View file contents in a textbox
 private Command cmView; // Command to view file
 private Command cmExit; // Command to exit
 private String url = "http://www.corej2me.com/midpbook_v1e1/scratch/fileViewer.hlp"; 
 public FileViewer()
 { 
 display = Display.getDisplay(this);
 
 // Define commands
 cmView = new Command("View", Command.SCREEN, 2);
 cmExit = new Command("Exit", Command.EXIT, 1);
 tbViewer = new TextBox("Viewer", "", 250, TextField.ANY);
 tbViewer.addCommand(cmView);
 tbViewer.addCommand(cmExit);
 tbViewer.setCommandListener(this); 
 }
 public void startApp()
 {
 display.setCurrent(tbViewer);
 } 
 private void viewFile() throws IOException
 {
 HttpConnection http = null;
 InputStream iStrm = null;
 
 try
 {
 // Create the connection
 http = (HttpConnection) Connector.open(url);
 
 //----------------
 // Client Request
 //----------------
 // 1) Send request method
 http.setRequestMethod(HttpConnection.GET);
 
 // 2) Send header information (this header is optional)
 http.setRequestProperty("User-Agent", "Profile/MIDP-1.0 Configuration/CLDC-1.0");
 
 // 3) Send body/data - No data for this request
 
 //----------------
 // Server Response
 //----------------
 // 1) Get status Line
 System.out.println("Msg: " + http.getResponseMessage()); 
 System.out.println("Code: " + http.getResponseCode()); 
 
 // 2) Get header information 
 if (http.getResponseCode() == HttpConnection.HTTP_OK)
 {
 // 3) Get data (show the file contents)
 iStrm = http.openInputStream();
 int length = (int) http.getLength();
 if (length > 0)
 {
 byte serverData[] = new byte[length];
 iStrm.read(serverData);
 tbViewer.setString(new String(serverData));
 }
 }
 }
 finally
 {
 // Clean up
 if (iStrm != null)
 iStrm.close();
 if (http != null)
 http.close();
 }
 }
 public void pauseApp()
 { }
 public void destroyApp(boolean unconditional)
 { }
 public void commandAction(Command c, Displayable s)
 {
 if (c == cmView)
 {
 try
 {
 viewFile();
 }
 catch (Exception e)
 {
 System.out.println(e.toString());
 }
 }
 else if (c == cmExit)
 {
 destroyApp(false);
 notifyDestroyed();
 }	
 }
}

Previous
<< What is J2ME?

Next
How to load J2ME applications to the IDEN handsets>>

(追記) (追記ここまで)