softkeybar.java

j2me下的1套UI框架.包含j2me开发中会应用的各种低级组件

package com.jmobilecore.ui.core;

import javax.microedition.lcdui.Graphics;

/**
 * The <code>SoftKeyBar</code> is special <code>Component</code> which represents
 * bottom line of the phone screen with names of soft keys.
 * This class contains set of methods that supports insertion/delition of soft keys
 * and execution of associated actions when softkey is pressed
 *
 * @author Greg Gridin
 */
public class SoftKeyBar extends Component {

    /**
     * The left positioned softkey
     */
    protected SoftKey leftSoftKey;

    /**
     * The center positioned softkey
     */
    protected SoftKey centerSoftKey;

    /**
     * The right positioned softkey
     */
    protected SoftKey rightSoftKey;

    /**
     * Constructs a new softkey bar
     */
    public SoftKeyBar() {

        foreground = Style.SOFTKEYBAR_TEXT_COLOR;
        background = Style.SOFTKEYBAR_BACKGROUND_COLOR;
        setFont(Style.SOFTKEY_FONT);
    }

    /**
     * Sets softkey to the softkey bar
     * If new soft key is <code>null</code> then action is equivalent to <code>removeSoftKey</code>
     * from specified position
     * @param softKey new soft key
     * @param position the position of the key,
     * @see com.jmobilecore.ui.core.SoftKey
     * @see #removeSoftKey(int)
     */
    public void setSoftKey(SoftKey softKey, int position) {

        if (position == SoftKey.LEFT) {
            leftSoftKey = softKey;
        } else if (position == SoftKey.CENTER) {
            centerSoftKey = softKey;
        } else if (position == SoftKey.RIGHT) {
            rightSoftKey = softKey;
        }
    }

    /**
     * Removes softkey from the softkey bar
     * @param position the position of the key,
     * if there is no key in specified position then does nothing
     * @see com.jmobilecore.ui.core.SoftKey
     */
    public void removeSoftKey(int position) {
        if (position == SoftKey.LEFT) {
            leftSoftKey = null;
        } else if (position == SoftKey.CENTER) {
            centerSoftKey = null;
        } else if (position == SoftKey.RIGHT) {
            rightSoftKey = null;
        }
    }

    /**
     * Paints the cursor for this component
     * @param g Graphics object
     */
    public void paint(Graphics g) {

        g.setColor(background);
        g.fillRect(0, ScreenCanvas.HEIGHT - this.height, ScreenCanvas.WIDTH, this.height);

        g.setColor(foreground);

        g.setFont(font);
        if (leftSoftKey != null) {
            g.drawString(leftSoftKey.label, Style.H_GAP, ScreenCanvas.HEIGHT,
                    Graphics.BOTTOM | Graphics.LEFT);
        }
        if (centerSoftKey != null) {
            g.drawString(centerSoftKey.label, ScreenCanvas.WIDTH / 2, ScreenCanvas.HEIGHT,
                    Graphics.BOTTOM | Graphics.HCENTER);
        }
        if (rightSoftKey != null) {
            g.drawString(rightSoftKey.label, ScreenCanvas.WIDTH - Style.H_GAP, ScreenCanvas.HEIGHT,
                    Graphics.BOTTOM | Graphics.RIGHT);
        }
    }

    /**
     * Responds to a key press.
     * @param keyCode The code for the key that was pressed.
     * @return <code>true</code> if the key was successfully processed, <code>false</code> otherwise
     */
    protected boolean keyPressed(int keyCode) {

        if (keyCode == SoftKey.LEFT && leftSoftKey != null) {
            leftSoftKey.performAction();
            return true;
        } else if (keyCode == SoftKey.CENTER && centerSoftKey != null) {
            centerSoftKey.performAction();
            return true;
        } else if (keyCode == SoftKey.RIGHT && rightSoftKey != null) {
            rightSoftKey.performAction();
            return true;
        }
        return false;
    }

    /**
     * Default destructor. Helps VM to perform garbage collection
     */
    public void destructor() {

        leftSoftKey = centerSoftKey = rightSoftKey = null;
    }
} // class SoftKeyBar