java - j2me中如何监听textfield或textbox中值的变化？

Question

我想存储用户输入的每个字符。当用户按下键时，该键应存储在任何变量中。当用户按下其他键时，它必须用j2me中文本框中的新字符替换变量的值

Answer 1

是的，您需要监听事件 ItemStateListener 然后您可以在 itemStateChanged(..) 中处理它这是完整的代码

/*
 * 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 Jigar
 */
public class KeyEventListener extends MIDlet implements ItemStateListener{

    private boolean midletPaused = false;

    //<editor-fold defaultstate="collapsed" desc=" Generated Fields ">
    private Form form;
    private TextField textField;
    //</editor-fold>

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

    //<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 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("form", new Item[] { getTextField() });
            form.setItemStateListener(this);
        }
        return form;
    }
    //</editor-fold>

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

        }
        return textField;
    }
    //</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) {
    }

    public void itemStateChanged(Item item) {
        if(item.equals(getTextField())){
            System.out.println("KeyPressed :) ");
        }

    }

}