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 Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `activate(IIOParam param)`
  Activates the controller.

- ## Method Details

  - ### 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.