libjava/java/beans/PropertyEditor.java

   1 /* java.beans.PropertyEditor
   2    Copyright (C) 1998 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.beans;
  40
  41 /**
  42  ** PropertyEditors are custom GUI editors for specific types of values.
  43  **
  44  ** A PropertyEditor can be used, for example, if you are editing a type of value
  45  ** that can be more easily represented graphically, such as a Point, or one that
  46  ** can be more easily represented by a list, such as a boolean (true/false).<P>
  47  **
  48  ** A PropertyEditor must be able to display its contents when asked to and
  49  ** be able to allow the user to change its underlying field value.  However, it
  50  ** is not the PropertyEditor's responsibility to make the change to the
  51  ** underlying Object; in fact, the PropertyEditor does not even know about the
  52  ** Object it is actually editing--only about the property it is currently
  53  ** editing.  When a change is made to the property, the PropertyEditor must
  54  ** simply fire a PropertyChangeEvent and allow the RAD tool to actually set
  55  ** the property in the underlying Bean.<P>
  56  **
  57  ** PropertyEditors should not change the Objects they are given by setValue().
  58  ** These Objects may or may not be the actual Objects which are properties of
  59  ** the Bean being edited.  Instead, PropertyEditors should create a new Object
  60  ** and fire a PropertyChangeEvent with the old and new values.<P>
  61  **
  62  ** PropertyEditors also must support the ability to return a Java
  63  ** initialization string.  See the getJavaInitializationString() method for
  64  ** details.<P>
  65  **
  66  ** There are several different ways a PropertyEditor may display and control
  67  ** editing of its value.  When multiple types of input and display are
  68  ** given by a single PropertyEditor, the RAD tool may decide which of the call
  69  ** to support.  Some RAD tools may even be text-only, so even if you support
  70  ** a graphical set and get, it may choose the text set and get whenever it can.
  71  ** <OL>
  72  **   <LI>Every PropertyEditor must support getValue() and setValue().  For
  73  **       setValue(), the component must only support it when the argument is
  74  **       the same type that the PropertyEditor supports.</LI>
  75  **   <LI>Every PropertyEditor must support getJavaInitializationString().</LI>
  76  **   <LI>You may support painting the value yourself if you wish.  To do this,
  77  **       have isPaintable() return true and implement the paintValue() method.
  78  **       This method does not determine in any way how the value is edited;
  79  **       merely how it is displayed.</LI>
  80  **   <LU>Let the caller of the PropertyEditor give the user a text input.  Do
  81  **       this by returning a non-null String from getAsText().  If you support
  82  **       text input, you *must* support setAsText().</LI>
  83  **   <LI>Give the caller a set of possible values, such as "true"/"false", that
  84  **       the user must select from.  To do this, return the list of Strings
  85  **       from the getTags() method.  The RAD tool may choose to implement the
  86  **       user input any way it wishes, and only guarantees that setAsText() will
  87  **       only be called with one of the Strings returned from getTags().</LI>
  88  **   <LI>You may support a whole custom editing control by supporting
  89  **       getCustomEditor().  To do this, return true from supportsCustomEditor()
  90  **       and return a Component that does the job.  It is the component's job,
  91  **       or the PropertyEditor's job, to make sure that when the editor changes
  92  **       its value, the PropertyChangeEvent is thrown.</LI>
  93  ** </OL>
  94  **
  95  ** The PropertyEditor for a particular Bean can be found using the
  96  ** PropertyEditorManager class, which goes through a series of different
  97  ** checks to find the appropriate class.<P>
  98  **
  99  ** A PropertyChangeEvent should be thrown from the PropertyEditor whenever a
 100  ** bound  property (a property PropertyDescriptor.isBound() set to true)
 101  ** changes.  When this happens, the editor itself should *not* change the value
 102  ** itself, but rather allow the RAD tool to call setValue() or setAsText().
 103  **
 104  ** @author John Keiser
 105  ** @since JDK1.1
 106  ** @version 1.1.0, 30 June 1998
 107  ** @see java.beans.PropertyEditorManager
 108  ** @see java.beans.PropertyEditorSupport
 109  **/
 110
 111 public interface PropertyEditor {
 112         /** Called by the RAD tool to set the value of this property for the PropertyEditor.
 113          ** If the property type is native, it should be wrapped in the appropriate
 114          ** wrapper type.
 115          ** @param value the value to set this property to.
 116          **/
 117         void setValue(Object value);
 118
 119         /** Accessor method to get the current value the PropertyEditor is working with.
 120          ** If the property type is native, it will be wrapped in the appropriate
 121          ** wrapper type.
 122          ** @return the current value of the PropertyEditor.
 123          **/
 124         Object getValue();
 125
 126
 127         /** Set the value of this property using a String.
 128          ** Whether or not this PropertyEditor is editing a String type, this converts
 129          ** the String into the type of the PropertyEditor.
 130          ** @param text the text to set it to.
 131          ** @exception IllegalArgumentException if the String is in the wrong format or setAsText() is not supported.
 132          **/
 133         void setAsText(String text) throws IllegalArgumentException;
 134
 135         /** Get the value of this property in String format.
 136          ** Many times this can simply use Object.toString().<P>
 137          ** Return null if you do not support getAsText()/setAsText().
 138          ** <code>setAsText(getAsText())</code> should be valid; i.e. the stuff you spit out in
 139          ** getAsText() should be able to go into setAsText().
 140          ** @return the value of this property in String format.
 141          **/
 142         String getAsText();
 143
 144         /** Get a list of possible Strings which this property type can have.
 145          ** The value of these will be used by the RAD tool to construct some sort
 146          ** of list box or to check text box input, and the resulting String passed
 147          ** to setAsText() should be one of these.  Note, however, that like most things
 148          ** with this mammoth, unwieldy interface, this is not guaranteed.  Thus, you
 149          ** must check the value in setAsText() anyway.
 150          ** @return the list of possible String values for this property type.
 151          **/
 152         String[] getTags();
 153
 154
 155         /** The RAD tool calls this to find out whether the PropertyEditor can paint itself.
 156          ** @return true if it can paint itself graphically, false if it cannot.
 157          **/
 158         boolean isPaintable();
 159
 160         /** The RAD tool calls this to paint the actual value of the property.
 161          ** The Graphics context will have the same current font, color, etc. as the
 162          ** parent Container.  You may safely change the font, color, etc. and not
 163          ** change them back.<P>
 164          ** This method should do a silent no-op if isPaintable() is false.
 165          ** @param g the Graphics context to paint on
 166          ** @param bounds the rectangle you have reserved to work in
 167          **/
 168         void paintValue(java.awt.Graphics g, java.awt.Rectangle bounds);
 169
 170
 171         /** The RAD tool calls this to find out whether the PropertyEditor supports a custom component to edit and display itself.
 172          ** @return true if getCustomEditor() will return a component, false if not.
 173          **/
 174         boolean supportsCustomEditor();
 175
 176         /** The RAD tool calls this to grab the component that can edit this type.
 177          ** The component may be painted anywhere the RAD tool wants to paint it--
 178          ** even in its own window.<P>
 179          ** The component must hook up with the PropertyEditor and, whenever a
 180          ** change to the value is made, fire a PropertyChangeEvent to the source.<P>
 181          ** @return the custom editor for this property type.
 182          **/
 183         java.awt.Component getCustomEditor();
 184
 185
 186         /** Adds a property change listener to this PropertyEditor.
 187          ** @param listener the listener to add
 188          **/
 189         void addPropertyChangeListener(PropertyChangeListener listener);
 190
 191         /** Removes a property change listener from this PropertyEditor.
 192          ** @param listener the listener to remove
 193          **/
 194         void removePropertyChangeListener(PropertyChangeListener listener);
 195
 196         /** Get a Java language-specific String which could be used to create an Object
 197          ** of the specified type.  Every PropertyEditor must support this.<P>
 198          ** The reason for this is that while most RAD tools will serialize the Beans
 199          ** and deserialize them at runtime, some RAD tools will generate code that
 200          ** creates the Beans.  Examples of Java initialization strings would be:<P>
 201          ** <OL>
 202          **     <LI><CODE>2</CODE></LI>
 203          **     <LI><CODE>"I am a String"</CODE></LI>
 204          **     <LI><CODE>new MyObject(2, "String", new StringBuffer())</CODE></LI>
 205          ** </OL>
 206          ** @return the initialization string for this object in Java.
 207          **/
 208         String getJavaInitializationString();
 209 }