propertyeditorsupport.java

来自「《移动Agent技术》一书的所有章节源代码。」· Java 代码 · 共 247 行

/*
 * @(#)PropertyEditorSupport.java	1.6 96/12/16  
 * 
 * Copyright (c) 1996 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 * 
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 * 
 * CopyrightVersion bdk_beta
 * 
 */

package java.beans;

/**
 * This is a support class to help build property editors.
 * <p>
 * It can be used either as a base class or as a delagatee.
 */

import java.beans.*;

public class PropertyEditorSupport implements PropertyEditor {

    /**
     * Constructor for use by derived PropertyEditor classes.
     */

    protected PropertyEditorSupport() {
	source = this;
    }

    /**
     * Constructor for use when a PropertyEditor is delegating to us.
     * @param source  The source to use for any events we fire.
     */

    protected PropertyEditorSupport(Object source) {
	this.source = source;
    }

    /**
     * Set (or change) the object that is to be edited.
     * @param value The new target object to be edited.  Note that this
     *     object should not be modified by the PropertyEditor, rather 
     *     the PropertyEditor should create a new object to hold any
     *     modified value.
     */
    public void setValue(Object value) {
	this.value = value;
	firePropertyChange();
    }

    /**
     * @return The value of the property.
     */

    public Object getValue() {
	return value;
    }

    //----------------------------------------------------------------------

    /**
     * @return  True if the class will honor the paintValue method.
     */

    public boolean isPaintable() {
	return false;
    }

    /**
     * Paint a representation of the value into a given area of screen
     * real estate.  Note that the propertyEditor is responsible for doing
     * its own clipping so that it fits into the given rectangle.
     * <p>
     * If the PropertyEditor doesn't honor paint requests (see isPaintable)
     * this method should be a silent noop.
     *
     * @param gfx  Graphics object to paint into.
     * @param box  Rectangle within graphics object into which we should paint.
     */
    public void paintValue(java.awt.Graphics gfx, java.awt.Rectangle box) {
    }

    //----------------------------------------------------------------------

    /**
     * This method is intended for use when generating Java code to set
     * the value of the property.  It should return a fragment of Java code
     * that can be used to initialize a variable with the current property
     * value.
     * <p>
     * Example results are "2", "new Color(127,127,34)", "Color.orange", etc.
     *
     * @return A fragment of Java code representing an initializer for the
     *   	current value.
     */
    public String getJavaInitializationString() {
	return "???";
    }

    //----------------------------------------------------------------------

    /**
     * @return The property value as a string suitable for presentation
     *       to a human to edit.
     * <p>   Returns "null" is the value can't be expressed as a string.
     * <p>   If a non-null value is returned, then the PropertyEditor should
     *	     be prepared to parse that string back in setAsText().
     */
    public String getAsText() {
	if (value instanceof String) {
	    return (String)value;
	}
	return ("" + value);
    }

    /**
     * Set the property value by parsing a given String.  May raise
     * java.lang.IllegalArgumentException if either the String is
     * badly formatted or if this kind of property can't be expressed
     * as text.
     * @param text  The string to be parsed.
     */
    public void setAsText(String text) throws java.lang.IllegalArgumentException {
	if (value instanceof String) {
	    setValue(text);
	    return;
	}
	throw new java.lang.IllegalArgumentException(text);
    }

    //----------------------------------------------------------------------

    /**
     * If the property value must be one of a set of known tagged values, 
     * then this method should return an array of the tag values.  This can
     * be used to represent (for example) enum values.  If a PropertyEditor
     * supports tags, then it should support the use of setAsText with
     * a tag value as a way of setting the value.
     *
     * @return The tag values for this property.  May be null if this 
     *   property cannot be represented as a tagged value.
     *	
     */
    public String[] getTags() {
	return null;
    }

    //----------------------------------------------------------------------

    /**
     * A PropertyEditor may chose to make available a full custom Component
     * that edits its property value.  It is the responsibility of the
     * PropertyEditor to hook itself up to its editor Component itself and
     * to report property value changes by firing a PropertyChange event.
     * <P>
     * The higher-level code that calls getCustomEditor may either embed
     * the Component in some larger property sheet, or it may put it in
     * its own individual dialog, or ...
     *
     * @return A java.awt.Component that will allow a human to directly
     *      edit the current property value.  May be null if this is
     *	    not supported.
     */

    public java.awt.Component getCustomEditor() {
	return null;
    }

    /**
     * @return  True if the propertyEditor can provide a custom editor.
     */
    public boolean supportsCustomEditor() {
	return false;
    }
  
    //----------------------------------------------------------------------

    /**
     * Register a listener for the PropertyChange event.  The class will
     * fire a PropertyChange value whenever the value is updated.
     *
     * @param listener  An object to be invoked when a PropertyChange
     *		event is fired.
     */
    public synchronized void addPropertyChangeListener(
				PropertyChangeListener listener) {
	if (listeners == null) {
	    listeners = new java.util.Vector();
	}
	listeners.addElement(listener);
    }

    /**
     * Remove a listener for the PropertyChange event.
     *
     * @param listener  The PropertyChange listener to be removed.
     */
    public synchronized void removePropertyChangeListener(
				PropertyChangeListener listener) {
	if (listeners == null) {
	    return;
	}
	listeners.removeElement(listener);
    }

    /**
     * Report that we have been modified to any interested listeners.
     *
     * @param source  The PropertyEditor that caused the event.
     */
    public void firePropertyChange() {
	java.util.Vector targets;
	synchronized (this) {
	    if (listeners == null) {
	    	return;
	    }
	    targets = (java.util.Vector) listeners.clone();
	}
	// Tell our listeners that "everything" has changed.
        PropertyChangeEvent evt = new PropertyChangeEvent(source, null, null, null);

	for (int i = 0; i < targets.size(); i++) {
	    PropertyChangeListener target = (PropertyChangeListener)targets.elementAt(i);
	    target.propertyChange(evt);
	}
    }

    //----------------------------------------------------------------------

    private Object value;
    private Object source;
    private java.util.Vector listeners;
}