Module java.desktop
Package javax.imageio

Interface IIOParamController

  • public interface IIOParamController
    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 the activate 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:
    IIOParam.setController(javax.imageio.IIOParamController), IIOParam.getController(), IIOParam.getDefaultController(), IIOParam.hasController(), IIOParam.activateController()

    • Method Detail

      • activate

        boolean activate​(IIOParam param)
        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).
        Parameters:
        param - the IIOParam object to be modified.
        Returns:
        true if the IIOParam has been modified, false otherwise.
        Throws:
        IllegalArgumentException - if param is null or is not an instance of the correct class.