PropertyEditor.java

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package java.beans;

/**
 * A PropertyEditor class provides support for GUIs that want to
 * allow users to edit a property value of a given type.
 * <p>
 * PropertyEditor supports a variety of different kinds of ways of
 * displaying and updating property values.  Most PropertyEditors will
 * only need to support a subset of the different options available in
 * this API.
 * <P>
 * Simple PropertyEditors may only support the getAsText and setAsText
 * methods and need not support (say) paintValue or getCustomEditor.  More
 * complex types may be unable to support getAsText and setAsText but will
 * instead support paintValue and getCustomEditor.
 * <p>
 * Every propertyEditor must support one or more of the three simple
 * display styles.  Thus it can either (1) support isPaintable or (2)
 * both return a non-null String[] from getTags() and return a non-null
 * value from getAsText or (3) simply return a non-null String from
 * getAsText().
 * <p>
 * Every property editor must support a call on setValue when the argument
 * object is of the type for which this is the corresponding propertyEditor.
 * In addition, each property editor must either support a custom editor,
 * or support setAsText.
 * <p>
 * Each PropertyEditor should have a null constructor.
 */

public interface PropertyEditor {

    /**
     * Set (or change) the object that is to be edited.  Primitive types such
     * as "int" must be wrapped as the corresponding object type such as
     * "java.lang.Integer".
     *
     * @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.
     */
    void setValue(Object value);

    /**
     * Gets the property value.
     *
     * @return The value of the property.  Primitive types such as "int" will
     * be wrapped as the corresponding object type such as "java.lang.Integer".
     */

    Object getValue();

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

    /**
     * Determines whether this property editor is paintable.
     *
     * @return  True if the class will honor the paintValue method.
     */

    boolean isPaintable();

    /**
     * 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.
     * <p>
     * The given Graphics object will have the default font, color, etc of
     * the parent container.  The PropertyEditor may change graphics attributes
     * such as font and color and doesn't need to restore the old values.
     *
     * @param gfx  Graphics object to paint into.
     * @param box  Rectangle within graphics object into which we should paint.
     */
    void paintValue(java.awt.Graphics gfx, java.awt.Rectangle box);

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

    /**
     * Returns a fragment of Java code that can be used to set a property
     * to match the editors current state. This method is intended
     * for use when generating Java code to reflect changes made through the
     * property editor.
     * <p>
     * The code fragment should be context free and must be a legal Java
     * expression as specified by the JLS.
     * <p>
     * Specifically, if the expression represents a computation then all
     * classes and static members should be fully qualified. This rule
     * applies to constructors, static methods and non primitive arguments.
     * <p>
     * Caution should be used when evaluating the expression as it may throw
     * exceptions. In particular, code generators must ensure that generated
     * code will compile in the presence of an expression that can throw
     * checked exceptions.
     * <p>
     * Example results are:
     * <ul>
     * <li>Primitive expresssion: <code>2</code>
     * <li>Class constructor: <code>new java.awt.Color(127,127,34)</code>
     * <li>Static field: <code>java.awt.Color.orange</code>
     * <li>Static method: <code>javax.swing.Box.createRigidArea(new
     *                                   java.awt.Dimension(0, 5))</code>
     * </ul>
     *
     * @return a fragment of Java code representing an initializer for the
     *         current value. It should not contain a semi-colon
     *         ('<code>;</code>') to end the expression.
     */
    String getJavaInitializationString();

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

    /**
     * Gets the property value as text.
     *
     * @return The property value as a human editable string.
     * <p>   Returns null if the value can't be expressed as an editable string.
     * <p>   If a non-null value is returned, then the PropertyEditor should
     *       be prepared to parse that string back in setAsText().
     */
    String getAsText();

    /**
     * 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.
     */
    void setAsText(String text) throws java.lang.IllegalArgumentException;

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

    /**
     * If the property value must be one of a set of known tagged values,
     * then this method should return an array of the tags.  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 and the use of getAsText
     * to identify the current value.
     *
     * @return The tag values for this property.  May be null if this
     *   property cannot be represented as a tagged value.
     *
     */
    String[] getTags();

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

    /**
     * A PropertyEditor may choose 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.
     */

    java.awt.Component getCustomEditor();

    /**
     * Determines whether this property editor supports a custom editor.
     *
     * @return  True if the propertyEditor can provide a custom editor.
     */
    boolean supportsCustomEditor();

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

    /**
     * Adds a listener for the value change.
     * When the property editor changes its value
     * it should fire a {@link PropertyChangeEvent}
     * on all registered {@link PropertyChangeListener}s,
     * specifying the {@code null} value for the property name
     * and itself as the source.
     *
     * @param listener  the {@link PropertyChangeListener} to add
     */
    void addPropertyChangeListener(PropertyChangeListener listener);

    /**
     * Removes a listener for the value change.
     *
     * @param listener  the {@link PropertyChangeListener} to remove
     */
    void removePropertyChangeListener(PropertyChangeListener listener);

}