java-me - 如何在J2ME 中添加按钮？

Question

我想知道，如何在表单中添加按钮？

下面是我的代码

        form = new Form("ePolicia Transgressor Accuse");
        tb = new TextField("Complaint Id: ", "", 30, TextField.ANY);
        form.append(tb);
        ticker = new Ticker("Creating Safer City for You");
        form.addCommand(submitCommand);
        form.addCommand(exitCommand);
        form.setCommandListener(this);
        form.setTicker(ticker);
        display.setCurrent(form);

现在，我想在表单中添加一个我可以使用的按钮。

注意:我不是在询问退出、提交等软按钮。我想添加自己的按钮。

Answer 1

我使用 Netbeans 和 Visual Midlet 为您创建了以下演示代码，希望它对您的代码有所帮助，

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package hello;

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

/**
 * @author 
 */
public class HelloMIDlet extends MIDlet implements CommandListener, ItemCommandListener {

    private boolean midletPaused = false;

    //<editor-fold defaultstate="collapsed" desc=" Generated Fields ">                      
    private Command exitCommand;
    private Command okCommand;
    private Command exitCommand1;
    private Form form;
    private StringItem lblUserName;
    private TextField txtUserName;
    private StringItem lblPassword;
    private TextField txtPassword;
    private StringItem lblBlankSpace;
    private StringItem cmdOK;
    private StringItem stringItem;
    //</editor-fold>                    

    /**
     * The HelloMIDlet constructor.
     */
    public HelloMIDlet() {
    }

    //<editor-fold defaultstate="collapsed" desc=" Generated Methods ">                       
    //</editor-fold>                     

    //<editor-fold defaultstate="collapsed" desc=" Generated Method: initialize ">                                           
    /**
     * Initilizes the application.
     * It is called only once when the MIDlet is started. The method is called before the <code>startMIDlet</code> method.
     */
    private void initialize() {                                         
        // write pre-initialize user code here

        // write post-initialize user code here
    }                            
    //</editor-fold>                          

    //<editor-fold defaultstate="collapsed" desc=" Generated Method: startMIDlet ">                                        
    /**
     * Performs an action assigned to the Mobile Device - MIDlet Started point.
     */
    public void startMIDlet() {                                      
        // write pre-action user code here
        switchDisplayable(null, getForm());                                        
        // write post-action user code here
    }                             
    //</editor-fold>                           

    //<editor-fold defaultstate="collapsed" desc=" Generated Method: resumeMIDlet ">                                         
    /**
     * Performs an action assigned to the Mobile Device - MIDlet Resumed point.
     */
    public void resumeMIDlet() {                                       
        // write pre-action user code here

        // write post-action user code here
    }                              
    //</editor-fold>                            

    //<editor-fold defaultstate="collapsed" desc=" Generated Method: switchDisplayable ">                                              
    /**
     * Switches a current displayable in a display. The <code>display</code> instance is taken from <code>getDisplay</code> method. This method is used by all actions in the design for switching displayable.
     * @param alert the Alert which is temporarily set to the display; if <code>null</code>, then <code>nextDisplayable</code> is set immediately
     * @param nextDisplayable the Displayable to be set
     */
    public void switchDisplayable(Alert alert, Displayable nextDisplayable) {                                            
        // write pre-switch user code here
        Display display = getDisplay();                                               
        if (alert == null) {
            display.setCurrent(nextDisplayable);
        } else {
            display.setCurrent(alert, nextDisplayable);
        }                                             
        // write post-switch user code here
    }                                   
    //</editor-fold>                                 

    //<editor-fold defaultstate="collapsed" desc=" Generated Method: commandAction for Displayables ">                                                 
    /**
     * Called by a system to indicated that a command has been invoked on a particular displayable.
     * @param command the Command that was invoked
     * @param displayable the Displayable where the command was invoked
     */
    public void commandAction(Command command, Displayable displayable) {                                               
        // write pre-action user code here
        if (displayable == form) {                                           
            if (command == exitCommand) {                                         
                // write pre-action user code here
                exitMIDlet();                                           
                // write post-action user code here
            }                                                  
        }                                                
        // write post-action user code here
    }                               
    //</editor-fold>                             

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: exitCommand ">                                   
    /**
     * Returns an initiliazed instance of exitCommand component.
     * @return the initialized component instance
     */
    public Command getExitCommand() {
        if (exitCommand == null) {                                 
            // write pre-init user code here
            exitCommand = new Command("Exit", Command.EXIT, 0);                                   
            // write post-init user code here
        }                         
        return exitCommand;
    }
    //</editor-fold>                       

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: form ">                                   
    /**
     * Returns an initiliazed instance of form component.
     * @return the initialized component instance
     */
    public Form getForm() {
        if (form == null) {                                 
            // write pre-init user code here
            form = new Form("Welcome", new Item[] { getLblUserName(), getTxtUserName(), getLblPassword(), getTxtPassword(), getLblBlankSpace(), getCmdOK(), getStringItem() });                                    
            form.addCommand(getExitCommand());
            form.setCommandListener(this);                                  
            // write post-init user code here
        }                         
        return form;
    }
    //</editor-fold>                       
    //</editor-fold>



    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: lblUserName ">                                   
    /**
     * Returns an initiliazed instance of lblUserName component.
     * @return the initialized component instance
     */
    public StringItem getLblUserName() {
        if (lblUserName == null) {                                 
            // write pre-init user code here
            lblUserName = new StringItem("User Name :", "");                                    
            lblUserName.setLayout(ImageItem.LAYOUT_CENTER);                                  
            // write post-init user code here
        }                         
        return lblUserName;
    }
    //</editor-fold>                       

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: txtUserName ">                                   
    /**
     * Returns an initiliazed instance of txtUserName component.
     * @return the initialized component instance
     */
    public TextField getTxtUserName() {
        if (txtUserName == null) {                                 
            // write pre-init user code here
            txtUserName = new TextField("", "", 32, TextField.ANY);                                    
            txtUserName.setLayout(ImageItem.LAYOUT_CENTER | ImageItem.LAYOUT_NEWLINE_AFTER);                                  
            // write post-init user code here
        }                         
        return txtUserName;
    }
    //</editor-fold>                       

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: lblPassword ">                                   
    /**
     * Returns an initiliazed instance of lblPassword component.
     * @return the initialized component instance
     */
    public StringItem getLblPassword() {
        if (lblPassword == null) {                                 
            // write pre-init user code here
            lblPassword = new StringItem("Password :", "");                                    
            lblPassword.setLayout(ImageItem.LAYOUT_CENTER | ImageItem.LAYOUT_NEWLINE_AFTER);                                  
            // write post-init user code here
        }                         
        return lblPassword;
    }
    //</editor-fold>                       

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: txtPassword ">                                   
    /**
     * Returns an initiliazed instance of txtPassword component.
     * @return the initialized component instance
     */
    public TextField getTxtPassword() {
        if (txtPassword == null) {                                 
            // write pre-init user code here
            txtPassword = new TextField("", "", 32, TextField.ANY);                                    
            txtPassword.setLayout(ImageItem.LAYOUT_CENTER | ImageItem.LAYOUT_NEWLINE_AFTER);                                  
            // write post-init user code here
        }                         
        return txtPassword;
    }
    //</editor-fold>                       
    //</editor-fold>

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: lblBlankSpace ">                                   
    /**
     * Returns an initiliazed instance of lblBlankSpace component.
     * @return the initialized component instance
     */
    public StringItem getLblBlankSpace() {
        if (lblBlankSpace == null) {                                 
            // write pre-init user code here
            lblBlankSpace = new StringItem("", "");                                   
            // write post-init user code here
        }                         
        return lblBlankSpace;
    }
    //</editor-fold>                       

    //<editor-fold defaultstate="collapsed" desc=" Generated Method: commandAction for Items ">                                                           
    /**
     * Called by a system to indicated that a command has been invoked on a particular item.
     * @param command the Command that was invoked
     * @param displayable the Item where the command was invoked
     */
    public void commandAction(Command command, Item item) {                                                         
        // write pre-action user code here
        if (item == cmdOK) {                                                
            if (command == okCommand) {                                              
                // write pre-action user code here

                // write post-action user code here
            }                                                
        } else if (item == stringItem) {
            if (command == exitCommand1) {                                              
                // write pre-action user code here
                exitMIDlet();                                                
                // write post-action user code here
            }                                                            
        }                                                          
        // write post-action user code here
    }                                    
    //</editor-fold>                                  

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: okCommand ">                                   
    /**
     * Returns an initiliazed instance of okCommand component.
     * @return the initialized component instance
     */
    public Command getOkCommand() {
        if (okCommand == null) {                                 
            // write pre-init user code here
            okCommand = new Command("Ok", Command.OK, 0);                                   
            // write post-init user code here
        }                         
        return okCommand;
    }
    //</editor-fold>                       

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: cmdOK ">                                   
    /**
     * Returns an initiliazed instance of cmdOK component.
     * @return the initialized component instance
     */
    public StringItem getCmdOK() {
        if (cmdOK == null) {                                 
            // write pre-init user code here
            cmdOK = new StringItem("Login", "", Item.BUTTON);                                    
            cmdOK.addCommand(getOkCommand());
            cmdOK.setItemCommandListener(this);                                  
            // write post-init user code here
        }                         
        return cmdOK;
    }
    //</editor-fold>                       

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: stringItem ">                                   
    /**
     * Returns an initiliazed instance of stringItem component.
     * @return the initialized component instance
     */
    public StringItem getStringItem() {
        if (stringItem == null) {                                 
            // write pre-init user code here
            stringItem = new StringItem("Cancel", "", Item.BUTTON);                                    
            stringItem.addCommand(getExitCommand1());
            stringItem.setItemCommandListener(this);                                  
            // write post-init user code here
        }                         
        return stringItem;
    }
    //</editor-fold>                       

    //<editor-fold defaultstate="collapsed" desc=" Generated Getter: exitCommand1 ">                                   
    /**
     * Returns an initiliazed instance of exitCommand1 component.
     * @return the initialized component instance
     */
    public Command getExitCommand1() {
        if (exitCommand1 == null) {                                 
            // write pre-init user code here
            exitCommand1 = new Command("Exit", Command.EXIT, 0);                                   
            // write post-init user code here
        }                         
        return exitCommand1;
    }
    //</editor-fold>                       

    /**
     * Returns a display instance.
     * @return the display instance.
     */
    public Display getDisplay () {
        return Display.getDisplay(this);
    }

    /**
     * Exits MIDlet.
     */
    public void exitMIDlet() {
        switchDisplayable (null, null);
        destroyApp(true);
        notifyDestroyed();
    }

    /**
     * Called when MIDlet is started.
     * Checks whether the MIDlet have been already started and initialize/starts or resumes the MIDlet.
     */
    public void startApp() {
        if (midletPaused) {
            resumeMIDlet ();
        } else {
            initialize ();
            startMIDlet ();
        }
        midletPaused = false;
    }

    /**
     * Called when MIDlet is paused.
     */
    public void pauseApp() {
        midletPaused = true;
    }

    /**
     * Called to signal the MIDlet to terminate.
     * @param unconditional if true, then the MIDlet has to be unconditionally terminated and all resources has to be released.
     */
    public void destroyApp(boolean unconditional) {
    }

}

这是输出