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package javax.imageio;


An interface to be implemented by objects that can determine the
settings of an IIOParam object, either by putting up a
GUI to obtain values from a user, or by other means.  This
interface merely specifies a generic activate method
that invokes the controller, without regard for how the controller
obtains values (i.e., whether the controller puts up a GUI
or merely computes a set of values is irrelevant to this
interface).

 Within the activate method, a controller obtains
initial values by querying the IIOParam object's
get methods, modifies values by whatever means, then
invokes the IIOParam object's set methods
to modify the appropriate settings.  Normally, these
set methods will be invoked all at once at a final
commit in order that a cancel operation not disturb existing
values.  In general, applications may expect that when the
activate method returns true, the
IIOParam object is ready for use in a read or write
operation.

 Vendors may choose to provide GUIs for the
IIOParam subclasses they define for a particular
plug-in.  These can be set up as default controllers in the
corresponding IIOParam subclasses.

 Applications may override any default GUIs and provide their
own controllers embedded in their own framework.  All that is
required is that theactivate method behave modally
(not returning until either cancelled or committed), though it need
not put up an explicitly modal dialog.  Such a non-modal GUI
component would be coded roughly as follows:



class MyGUI extends SomeComponent implements IIOParamController {
   public MyGUI() {
       // ...
       setEnabled(false);
   }
   public boolean activate(IIOParam param) {
       // disable other components if desired
       setEnabled(true);
       // go to sleep until either cancelled or committed
       boolean ret = false;
       if (!cancelled) {
           // set values on param
           ret = true;
       }
       setEnabled(false);
       // enable any components disabled above
       return ret;
   }



 Alternatively, an algorithmic process such as a database lookup
or the parsing of a command line could be used as a controller, in
which case the activate method would simply look up or
compute the settings, call the IIOParam.setXXX
methods, and return true.

See Also:
/**
 * An interface to be implemented by objects that can determine the
 * settings of an <code>IIOParam</code> object, either by putting up a
 * GUI to obtain values from a user, or by other means.  This
 * interface merely specifies a generic <code>activate</code> method
 * that invokes the controller, without regard for how the controller
 * obtains values (<i>i.e.</i>, whether the controller puts up a GUI
 * or merely computes a set of values is irrelevant to this
 * interface).
 *
 * <p> Within the <code>activate</code> method, a controller obtains
 * initial values by querying the <code>IIOParam</code> object's
 * <code>get</code> methods, modifies values by whatever means, then
 * invokes the <code>IIOParam</code> object's <code>set</code> methods
 * to modify the appropriate settings.  Normally, these
 * <code>set</code> methods will be invoked all at once at a final
 * commit in order that a cancel operation not disturb existing
 * values.  In general, applications may expect that when the
 * <code>activate</code> method returns <code>true</code>, the
 * <code>IIOParam</code> object is ready for use in a read or write
 * operation.
 *
 * <p> Vendors may choose to provide GUIs for the
 * <code>IIOParam</code> subclasses they define for a particular
 * plug-in.  These can be set up as default controllers in the
 * corresponding <code>IIOParam</code> subclasses.
 *
 * <p> Applications may override any default GUIs and provide their
 * own controllers embedded in their own framework.  All that is
 * required is that the<code>activate</code> method behave modally
 * (not returning until either cancelled or committed), though it need
 * not put up an explicitly modal dialog.  Such a non-modal GUI
 * component would be coded roughly as follows:
 *
 * <br>
 * <pre>
 * class MyGUI extends SomeComponent implements IIOParamController {
 *
 *    public MyGUI() {
 *        // ...
 *        setEnabled(false);
 *    }
 *
 *    public boolean activate(IIOParam param) {
 *        // disable other components if desired
 *        setEnabled(true);
 *        // go to sleep until either cancelled or committed
 *        boolean ret = false;
 *        if (!cancelled) {
 *            // set values on param
 *            ret = true;
 *        }
 *        setEnabled(false);
 *        // enable any components disabled above
 *        return ret;
 *    }
 * </pre>
 *
 * <p> Alternatively, an algorithmic process such as a database lookup
 * or the parsing of a command line could be used as a controller, in
 * which case the <code>activate</code> method would simply look up or
 * compute the settings, call the <code>IIOParam.setXXX</code>
 * methods, and return <code>true</code>.
 *
 * @see IIOParam#setController
 * @see IIOParam#getController
 * @see IIOParam#getDefaultController
 * @see IIOParam#hasController
 * @see IIOParam#activateController
 *
 */
public interface IIOParamController {

    
Activates the controller.  If true is returned,
all settings in the IIOParam object should be
ready for use in a read or write operation.  If
false is returned, no settings in the
IIOParam object will be disturbed (i.e.,
the user canceled the operation).

Params:
  • param – the IIOParam object to be modified.
Throws:
Returns:true if the IIOParam has been
modified, false otherwise.
/**
     * Activates the controller.  If <code>true</code> is returned,
     * all settings in the <code>IIOParam</code> object should be
     * ready for use in a read or write operation.  If
     * <code>false</code> is returned, no settings in the
     * <code>IIOParam</code> object will be disturbed (<i>i.e.</i>,
     * the user canceled the operation).
     *
     * @param param the <code>IIOParam</code> object to be modified.
     *
     * @return <code>true</code> if the <code>IIOParam</code> has been
     * modified, <code>false</code> otherwise.
     *
     * @exception IllegalArgumentException if <code>param</code> is
     * <code>null</code> or is not an instance of the correct class.
     */
    boolean activate(IIOParam param);
}