PropertyEditor.java revision 10444:f08705540498 
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25
26package java.beans;
27
28/**
29 * A PropertyEditor class provides support for GUIs that want to
30 * allow users to edit a property value of a given type.
31 * <p>
32 * PropertyEditor supports a variety of different kinds of ways of
33 * displaying and updating property values.  Most PropertyEditors will
34 * only need to support a subset of the different options available in
35 * this API.
36 * <P>
37 * Simple PropertyEditors may only support the getAsText and setAsText
38 * methods and need not support (say) paintValue or getCustomEditor.  More
39 * complex types may be unable to support getAsText and setAsText but will
40 * instead support paintValue and getCustomEditor.
41 * <p>
42 * Every propertyEditor must support one or more of the three simple
43 * display styles.  Thus it can either (1) support isPaintable or (2)
44 * both return a non-null String[] from getTags() and return a non-null
45 * value from getAsText or (3) simply return a non-null String from
46 * getAsText().
47 * <p>
48 * Every property editor must support a call on setValue when the argument
49 * object is of the type for which this is the corresponding propertyEditor.
50 * In addition, each property editor must either support a custom editor,
51 * or support setAsText.
52 * <p>
53 * Each PropertyEditor should have a null constructor.
54 *
55 * @since 1.1
56 */
57
58public interface PropertyEditor {
59
60    /**
61     * Set (or change) the object that is to be edited.  Primitive types such
62     * as "int" must be wrapped as the corresponding object type such as
63     * "java.lang.Integer".
64     *
65     * @param value The new target object to be edited.  Note that this
66     *     object should not be modified by the PropertyEditor, rather
67     *     the PropertyEditor should create a new object to hold any
68     *     modified value.
69     */
70    void setValue(Object value);
71
72    /**
73     * Gets the property value.
74     *
75     * @return The value of the property.  Primitive types such as "int" will
76     * be wrapped as the corresponding object type such as "java.lang.Integer".
77     */
78
79    Object getValue();
80
81    //----------------------------------------------------------------------
82
83    /**
84     * Determines whether this property editor is paintable.
85     *
86     * @return  True if the class will honor the paintValue method.
87     */
88
89    boolean isPaintable();
90
91    /**
92     * Paint a representation of the value into a given area of screen
93     * real estate.  Note that the propertyEditor is responsible for doing
94     * its own clipping so that it fits into the given rectangle.
95     * <p>
96     * If the PropertyEditor doesn't honor paint requests (see isPaintable)
97     * this method should be a silent noop.
98     * <p>
99     * The given Graphics object will have the default font, color, etc of
100     * the parent container.  The PropertyEditor may change graphics attributes
101     * such as font and color and doesn't need to restore the old values.
102     *
103     * @param gfx  Graphics object to paint into.
104     * @param box  Rectangle within graphics object into which we should paint.
105     */
106    void paintValue(java.awt.Graphics gfx, java.awt.Rectangle box);
107
108    //----------------------------------------------------------------------
109
110    /**
111     * Returns a fragment of Java code that can be used to set a property
112     * to match the editors current state. This method is intended
113     * for use when generating Java code to reflect changes made through the
114     * property editor.
115     * <p>
116     * The code fragment should be context free and must be a legal Java
117     * expression as specified by the JLS.
118     * <p>
119     * Specifically, if the expression represents a computation then all
120     * classes and static members should be fully qualified. This rule
121     * applies to constructors, static methods and non primitive arguments.
122     * <p>
123     * Caution should be used when evaluating the expression as it may throw
124     * exceptions. In particular, code generators must ensure that generated
125     * code will compile in the presence of an expression that can throw
126     * checked exceptions.
127     * <p>
128     * Example results are:
129     * <ul>
130     * <li>Primitive expresssion: <code>2</code>
131     * <li>Class constructor: <code>new java.awt.Color(127,127,34)</code>
132     * <li>Static field: <code>java.awt.Color.orange</code>
133     * <li>Static method: <code>javax.swing.Box.createRigidArea(new
134     *                                   java.awt.Dimension(0, 5))</code>
135     * </ul>
136     *
137     * @return a fragment of Java code representing an initializer for the
138     *         current value. It should not contain a semi-colon
139     *         ('<code>;</code>') to end the expression.
140     */
141    String getJavaInitializationString();
142
143    //----------------------------------------------------------------------
144
145    /**
146     * Gets the property value as text.
147     *
148     * @return The property value as a human editable string.
149     * <p>   Returns null if the value can't be expressed as an editable string.
150     * <p>   If a non-null value is returned, then the PropertyEditor should
151     *       be prepared to parse that string back in setAsText().
152     */
153    String getAsText();
154
155    /**
156     * Set the property value by parsing a given String.  May raise
157     * java.lang.IllegalArgumentException if either the String is
158     * badly formatted or if this kind of property can't be expressed
159     * as text.
160     * @param text  The string to be parsed.
161     */
162    void setAsText(String text) throws java.lang.IllegalArgumentException;
163
164    //----------------------------------------------------------------------
165
166    /**
167     * If the property value must be one of a set of known tagged values,
168     * then this method should return an array of the tags.  This can
169     * be used to represent (for example) enum values.  If a PropertyEditor
170     * supports tags, then it should support the use of setAsText with
171     * a tag value as a way of setting the value and the use of getAsText
172     * to identify the current value.
173     *
174     * @return The tag values for this property.  May be null if this
175     *   property cannot be represented as a tagged value.
176     *
177     */
178    String[] getTags();
179
180    //----------------------------------------------------------------------
181
182    /**
183     * A PropertyEditor may choose to make available a full custom Component
184     * that edits its property value.  It is the responsibility of the
185     * PropertyEditor to hook itself up to its editor Component itself and
186     * to report property value changes by firing a PropertyChange event.
187     * <P>
188     * The higher-level code that calls getCustomEditor may either embed
189     * the Component in some larger property sheet, or it may put it in
190     * its own individual dialog, or ...
191     *
192     * @return A java.awt.Component that will allow a human to directly
193     *      edit the current property value.  May be null if this is
194     *      not supported.
195     */
196
197    java.awt.Component getCustomEditor();
198
199    /**
200     * Determines whether this property editor supports a custom editor.
201     *
202     * @return  True if the propertyEditor can provide a custom editor.
203     */
204    boolean supportsCustomEditor();
205
206    //----------------------------------------------------------------------
207
208    /**
209     * Adds a listener for the value change.
210     * When the property editor changes its value
211     * it should fire a {@link PropertyChangeEvent}
212     * on all registered {@link PropertyChangeListener}s,
213     * specifying the {@code null} value for the property name
214     * and itself as the source.
215     *
216     * @param listener  the {@link PropertyChangeListener} to add
217     */
218    void addPropertyChangeListener(PropertyChangeListener listener);
219
220    /**
221     * Removes a listener for the value change.
222     *
223     * @param listener  the {@link PropertyChangeListener} to remove
224     */
225    void removePropertyChangeListener(PropertyChangeListener listener);
226
227}
228