[Chapter 20] 20.3 java.awt.event.AdjustmentEvent (JDK 1.1)

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| Chapter 20 The java.awt.event Package |

## 20.3 java.awt.event.AdjustmentEvent (JDK 1.1)

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An event of this type indicates that an adjustment has been made to an `Adjustable` object--usually, this means that the user has interacted with a `Scrollbar` component.

The `getValue()` method returns the new value of the `Adjustable` object. This is usually the most important piece of information stored in the event. `getAdjustable()` returns the `Adjustable` object that was the source of the event. It is a convenient alternative to the inherited `getSource()` method.

The `getID()` method returns the type of an `AdjustmentEvent`. The standard AWT components only generate adjustment events of type `AdjustmentEvent.ADJUSTMENT_VALUE_CHANGED`. There are several types of adjustments that can be made to an `Adjustable` object, however, and the `getAdjustmentType()` method returns one of five constants to indicate which type has occurred. `UNIT_INCREMENT` indicates that the `Adjustable` value has been incremented by one unit, as in a scroll-line-down operation. `UNIT_DECREMENT` indicates the opposite: scroll-line-up. `BLOCK_INCREMENT` and `BLOCK_DECREMENT` indicate that the `Adjustable` object has been incremented or decremented by multiple units, as in a scroll-page-down or scroll-page-up operation. Finally, the `TRACK` constant indicates that the `Adjustable` value has been set to an absolute value unrelated to its previous value, as when the user drags a scrollbar to a new position.

    public class AdjustmentEvent extends AWTEvent {
        // Public Constructor
                public AdjustmentEvent(Adjustable source, int id, int type, int value);
        // Constants
                public static final int ADJUSTMENT_FIRST;
                public static final int ADJUSTMENT_LAST;
                public static final int ADJUSTMENT_VALUE_CHANGED;
                public static final int BLOCK_DECREMENT;
                public static final int BLOCK_INCREMENT;
                public static final int TRACK;
                public static final int UNIT_DECREMENT;
                public static final int UNIT_INCREMENT;
        // Public Instance Methods
                public Adjustable getAdjustable();
                public int getAdjustmentType();
                public int getValue();
                public String paramString();  // Overrides AWTEvent
    }

### Hierarchy:

`Object->EventObject(Serializable)->AWTEvent->AdjustmentEvent`

### Passed To:

`AdjustmentListener.adjustmentValueChanged(), AWTEventMulticaster.adjustmentValueChanged(), Scrollbar.processAdjustmentEvent()`

java.awt.event.ActionListener (JDK 1.1) |  | java.awt.event.AdjustmentListener (JDK 1.1)