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package javax.imageio.metadata;

An interface to be implemented by objects that can determine the settings of an IIOMetadata 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 IIOMetadata object's settings, either using the XML DOM tree or a plug-in specific interface, modifies values by whatever means, then modifies the IIOMetadata object's settings, using either the setFromTree or mergeTree methods, or a plug-in specific interface. In general, applications may expect that when the activate method returns true, the IIOMetadata object is ready for use in a write operation.

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

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 methods on IIOMetadata to set its state, and return true.

See Also:
/** * An interface to be implemented by objects that can determine the * settings of an <code>IIOMetadata</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>IIOMetadata</code> object's * settings, either using the XML DOM tree or a plug-in specific * interface, modifies values by whatever means, then modifies the * <code>IIOMetadata</code> object's settings, using either the * <code>setFromTree</code> or <code>mergeTree</code> methods, or a * plug-in specific interface. In general, applications may expect * that when the <code>activate</code> method returns * <code>true</code>, the <code>IIOMetadata</code> object is ready for * use in a write operation. * * <p> Vendors may choose to provide GUIs for the * <code>IIOMetadata</code> subclasses they define for a particular * plug-in. These can be set up as default controllers in the * corresponding <code>IIOMetadata</code> subclasses. * * <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 methods on <code>IIOMetadata</code> to * set its state, and return <code>true</code>. * * @see IIOMetadata#setController * @see IIOMetadata#getController * @see IIOMetadata#getDefaultController * @see IIOMetadata#hasController * @see IIOMetadata#activateController * */
public interface IIOMetadataController {
Activates the controller. If true is returned, all settings in the IIOMetadata object should be ready for use in a write operation. If false is returned, no settings in the IIOMetadata object will be disturbed (i.e., the user canceled the operation).
Params:
  • metadata – the IIOMetadata object to be modified.
Throws:
Returns:true if the IIOMetadata has been modified, false otherwise.
/** * Activates the controller. If <code>true</code> is returned, * all settings in the <code>IIOMetadata</code> object should be * ready for use in a write operation. If <code>false</code> is * returned, no settings in the <code>IIOMetadata</code> object * will be disturbed (<i>i.e.</i>, the user canceled the * operation). * * @param metadata the <code>IIOMetadata</code> object to be modified. * * @return <code>true</code> if the <code>IIOMetadata</code> has been * modified, <code>false</code> otherwise. * * @exception IllegalArgumentException if <code>metadata</code> is * <code>null</code> or is not an instance of the correct class. */
boolean activate(IIOMetadata metadata); }