netclientmidlet.java

Sun公司的J2ME官方例程若干

/*
 * Copyright (c) 2000-2001 Sun Microsystems, Inc. All Rights Reserved.
 */

package examples.netclient;

import java.lang.*;
import java.io.*;
import java.util.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;

/**
 * A simple network client.
 *
 * This MIDlet shows a simple use of the HTTP
 * networking interface. It opens a HTTP POST
 * connection to a server, authenticates using
 * HTTP Basic Authentication and writes a string
 * to the connection. It then reads the
 * connection and displays the results.
 */
public class NetClientMIDlet extends MIDlet
    implements CommandListener {

    private Display display;  // handle to the display
    private Form mainScr;     // main screen
    private Command cmdOK;    // OK command
    private Command cmdExit;  // EXIT command
    private Form dataScr;     // for display of results

    /**
     * Constructor.
     *
     * Create main screen and commands. Main
     * screen shows simple instructions.
     */
    public NetClientMIDlet() {
        display = Display.getDisplay(this);
        mainScr = new Form("NetClient");
        mainScr.append("Hit OK to make network connection");
        mainScr.append(" ");
        mainScr.append("Hit EXIT to quit");
        cmdOK = new Command("OK", Command.OK, 1);
        cmdExit = new Command("Exit", Command.EXIT, 1);
        mainScr.addCommand(cmdOK);
        mainScr.addCommand(cmdExit);
        mainScr.setCommandListener(this);
    }

    /**
     * Called by the system to start our MIDlet.
     * Set main screen to be displayed.
     */
    protected void startApp() {
        display.setCurrent(mainScr);
    }

    /**
     * Called by the system to pause our MIDlet.
     * No actions required by our MIDLet.
     */
    protected void pauseApp() {}

    /**
     * Called by the system to end our MIDlet.
     * No actions required by our MIDLet.
     */
    protected void destroyApp(boolean unconditional) {}

    /**
     * Gets data from server.
     *
     * Open a connection to the server, set a
     * user and password to use, send data, then
     * read the data from the server.
     */
    private void genDataScr() {
        ConnectionManager h = new ConnectionManager();

        // Set message to send, user, password
        h.setMsg("Esse quam videri");
        h.setUser("book");
        h.setPassword("bkpasswd");
        byte[] data = h.Process();

        // create data screen
        dataScr = new Form("Data Screen");
        dataScr.addCommand(cmdOK);
        dataScr.addCommand(cmdExit);
        dataScr.setCommandListener(this);
        if (data == null || data.length == 0) {
            // tell user no data was returned
            dataScr.append("No Data Returned!");
        } else {
            // loop trough data and extract strings
            // (delimited by '\n' characters
            StringBuffer sb = new StringBuffer();
            for (int i = 0; i < data.length; i++) {
                if (data[i] == (byte)'\n') {
                    dataScr.append(sb.toString());
                    sb.setLength(0);
                } else {
                    sb.append((char)data[i]);
                }
            }
        }
        display.setCurrent(dataScr);
    }

    /**
     * This method implements a state machine that drives
     * the MIDlet from one state (screen) to the next.
     */
    public void commandAction(Command c,
                              Displayable d) {
        if (c == cmdOK) {
            if (d == mainScr) {
                genDataScr();
            } else {
                display.setCurrent(mainScr);
            }
        } else if (c == cmdExit) {
            destroyApp(false);
            notifyDestroyed();
        }
    }
}