Java Tutorial/J2ME/Command
Содержание
Add Command to MIDlet
<source lang="java">
import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.TextBox; import javax.microedition.lcdui.TextField; import javax.microedition.lcdui.Ticker; import javax.microedition.midlet.MIDlet; public class TextBoxMIDlet extends MIDlet implements CommandListener {
private static final int MAX_TEXT_SIZE = 64;
protected TextBox textBox;
protected Display display;
private static final Command EXIT_COMMAND = new Command("Exit", Command.EXIT,0);
private static final Command OK_COMMAND = new Command("OK", Command.OK, 0);
private static final Command CLEAR_COMMAND = new Command("Clear",Command.SCREEN, 1);
private static final Command REVERSE_COMMAND = new Command("Reverse",Command.SCREEN, 1);
protected void startApp() {
String str = null;
try {
InputStream is = getClass().getResourceAsStream("resources/text.txt");
InputStreamReader r = new InputStreamReader(is);
char[] buffer = new char[32];
StringBuffer sb = new StringBuffer();
int count;
while ((count = r.read(buffer, 0, buffer.length)) > -1) {
sb.append(buffer, 0, count);
}
str = sb.toString();
} catch (IOException ex) {
str = "Failed to load text";
}
textBox = new TextBox("TextBox Example", str, MAX_TEXT_SIZE, TextField.ANY);
Ticker ticker = new Ticker("This is a ticker...");
textBox.setTicker(ticker);
textBox.addCommand(OK_COMMAND);
textBox.addCommand(EXIT_COMMAND);
textBox.addCommand(CLEAR_COMMAND);
textBox.addCommand(REVERSE_COMMAND);
textBox.setCommandListener(this);
display = Display.getDisplay(this);
display.setCurrent(textBox);
}
protected void pauseApp() {
}
protected void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable d) {
if (c == EXIT_COMMAND) {
destroyApp(true);
notifyDestroyed();
} else if (c == OK_COMMAND) {
System.out.println("OK pressed");
} else if (c == CLEAR_COMMAND) {
textBox.setString(null);
} else if (c == REVERSE_COMMAND) {
String str = textBox.getString();
if (str != null) {
StringBuffer sb = new StringBuffer(str);
textBox.setString(sb.reverse().toString());
}
}
}
}</source>
A MIDlet with simple text and a few commands.
<source lang="java">
import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.TextBox; import javax.microedition.midlet.MIDlet; public class FewCommandsMIDlet extends MIDlet implements CommandListener {
private Command exitCommand = new Command("A", Command.SCREEN, 1);
private Command infoCommand = new Command("B", Command.SCREEN, 2);
private Command aboutCommand = new Command("C", Command.SCREEN, 2);
private Display display;
public FewCommandsMIDlet() {
display = Display.getDisplay(this);
}
public void startApp() {
TextBox t = new TextBox("sdf", "Welcome to MIDP Programming", 256, 0);
t.addCommand(infoCommand);
t.addCommand(exitCommand);
t.addCommand(aboutCommand);
t.setCommandListener(this);
display.setCurrent(t);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable s) {
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();
}
}
}</source>
Exit Command
<source lang="java">
import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.TextField; import javax.microedition.midlet.MIDlet; public class TextFieldMIDlet extends MIDlet implements CommandListener {
private Command exitCommand = new Command("Exit", Command.EXIT, 1);
private TextField aTextField = new TextField("Label", "Content", 4, TextField.ANY);
private Display display = Display.getDisplay(this);
public TextFieldMIDlet() {
}
public void startApp() {
Form aForm = new Form("TextField");
aForm.append(aTextField);
aForm.addCommand(exitCommand);
aForm.setCommandListener(this);
display.setCurrent(aForm);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable s) {
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();
}
}
}</source>
Get command label and type
<source lang="java">
import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.TextBox; import javax.microedition.midlet.MIDlet; public class J2MECommandGetter extends MIDlet implements CommandListener {
private Command exitCommand = new Command("EXIT", Command.EXIT, 1);
private Command infoCommand = new Command("info", Command.SCREEN, 1);
TextBox t= new TextBox("Hello MIDP", "Welcome to MIDP Programming", 256, 0);
private Display display;
public J2MECommandGetter() {
display = Display.getDisplay(this);
}
public void startApp() {
t.addCommand(exitCommand);
t.addCommand(infoCommand);
t.setCommandListener(this);
display.setCurrent(t);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable s) {
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();
}
if (c == infoCommand) {
((TextBox) s).setString(infoCommand.getLabel() + " " + infoCommand.getCommandType()
+ infoCommand.getPriority());
}
}
}</source>
Help command
<source lang="java">
import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.TextBox; import javax.microedition.midlet.MIDlet; public class J2MEOnlineHelp extends MIDlet implements CommandListener {
private Display display;
private Command back = new Command("Back", Command.BACK, 2);
private Command exit = new Command("Exit", Command.EXIT, 1);
private Command help = new Command("Help", Command.HELP, 3);
private Form form = new Form("Online Help Example");
private TextBox helpMesg;
public J2MEOnlineHelp() {
display = Display.getDisplay(this);
helpMesg = new TextBox("Online Help","Press Back to return .",81, 0);
helpMesg.addCommand(back);
form.addCommand(exit);
form.addCommand(help);
form.setCommandListener(this);
helpMesg.setCommandListener(this);
}
public void startApp() {
display.setCurrent(form);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command command, Displayable displayable) {
if (command == back) {
display.setCurrent(form);
} else if (command == exit) {
destroyApp(false);
notifyDestroyed();
} else if (command == help) {
display.setCurrent(helpMesg);
}
}
}</source>
Start the MIDlet by creating a list of items and associating the exit command with it
<source lang="java">
/* License
*
* Copyright 1994-2004 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistribution of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* * Redistribution in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
* AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
* AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
* REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
* INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
* OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
* EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed, licensed or intended
* for use in the design, construction, operation or maintenance of any
* nuclear facility.
*/
import javax.microedition.lcdui.Choice; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.List; import javax.microedition.lcdui.TextBox; import javax.microedition.lcdui.TextField; import javax.microedition.midlet.MIDlet; import javax.microedition.midlet.MIDletStateChangeException; public class EventEx1 extends MIDlet implements CommandListener {
// display manager
Display display = null;
// a menu with items
List menu = null; // main menu
// textbox
TextBox input = null;
// command
static final Command backCommand = new Command("Back", Command.BACK, 0);
static final Command mainMenuCommand = new Command("Main", Command.SCREEN, 1);
static final Command exitCommand = new Command("Exit", Command.STOP, 2);
String currentMenu = null;
// constructor.
public EventEx1() {
}
/**
* Start the MIDlet by creating a list of items and associating the exit
* command with it.
*/
public void startApp() throws MIDletStateChangeException {
display = Display.getDisplay(this);
menu = new List("Menu Items", Choice.IMPLICIT);
menu.append("Item1", null);
menu.append("Item2", null);
menu.append("Item3", null);
menu.append("Item4", null);
menu.addCommand(exitCommand);
menu.setCommandListener(this);
mainMenu();
}
public void pauseApp() {
display = null;
menu = null;
input = null;
}
public void destroyApp(boolean unconditional) {
notifyDestroyed();
}
// main menu
void mainMenu() {
display.setCurrent(menu);
currentMenu = "Main";
}
/**
* a generic method that will be called when selected any of the items on the
* list.
*/
public void prepare() {
input = new TextBox("Enter some text: ", "", 5, TextField.ANY);
input.addCommand(backCommand);
input.setCommandListener(this);
input.setString("");
display.setCurrent(input);
}
/**
* Test item1.
*/
public void testItem1() {
prepare();
currentMenu = "item1";
}
/**
* Test item2.
*/
public void testItem2() {
prepare();
currentMenu = "item2";
}
/**
* Test item3.
*/
public void testItem3() {
prepare();
currentMenu = "item3";
}
/**
* Test item4.
*/
public void testItem4() {
prepare();
currentMenu = "item4";
}
/**
* Handle events.
*/
public void commandAction(Command c, Displayable d) {
String label = c.getLabel();
if (label.equals("Exit")) {
destroyApp(true);
} else if (label.equals("Back")) {
if (currentMenu.equals("item1") || currentMenu.equals("item2")
|| currentMenu.equals("item3") || currentMenu.equals("item4")) {
// go back to menu
mainMenu();
}
} else {
List down = (List) display.getCurrent();
switch (down.getSelectedIndex()) {
case 0:
testItem1();
break;
case 1:
testItem2();
break;
case 2:
testItem3();
break;
case 3:
testItem4();
break;
}
}
}
}</source>
