[Chapter 18] 18.53 java.awt.ScrollPane (JDK 1.1)

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| Chapter 18 The java.awt Package |

## 18.53 java.awt.ScrollPane (JDK 1.1)

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This `Container` class creates horizontal and vertical scrollbars surrounding a "viewport" and allows a single child component to be displayed and scrolled within this viewport. Typically the child of the `ScrollPane` is larger than the `ScrollPane` itself, so scrollbars allow the user to select the currently visible portion.

When you call the `ScrollPane()` constructor, you may optionally specify a scrollbar display policy, which should be one of the three constants defined by this class. If you do not specify a policy, `ScrollPane` uses the `SCROLLBARS_AS_NEEDED` policy.

A program can programmatically scroll the child within the viewport by calling `setScrollPosition()`. `getHAdjustable()` and `getVAdjustable()` return the horizontal and vertical `Adjustable` objects that control scrolling (typically these are not actually instances of `Scrollbar`). You can use these `Adjustable` objects to specify the unit and block increment values for the scrollbars. You can also directly set the `Adjustable` value, as an alternative to `setScrollPosition()`, but should not set other values of the `Adjustable` objects.

Use `setSize()` to set the size of the `ScrollPane` container. You may want to take the size of the scrollbars into account when computing the overall container size--use `getHScrollbarHeight()` and `getVScrollbarWidth()` to obtain these values.

`ScrollPane` overrides the `printComponents()` method of `Container` so that when a `ScrollPane` is printed, the entire child component is printed, rather than only the currently visible portion.

    public class ScrollPane extends Container {
        // Public Constructors
                public ScrollPane();
                public ScrollPane(int scrollbarDisplayPolicy);
        // Constants
                public static final int SCROLLBARS_ALWAYS;
                public static final int SCROLLBARS_AS_NEEDED;
                public static final int SCROLLBARS_NEVER;
        // Public Instance Methods
                public void addNotify();  // Overrides Container
                public void doLayout();  // Overrides Container
                public Adjustable getHAdjustable();
                public int getHScrollbarHeight();
                public Point getScrollPosition();
                public int getScrollbarDisplayPolicy();
                public Adjustable getVAdjustable();
                public int getVScrollbarWidth();
                public Dimension getViewportSize();
            #   public void layout();  // Overrides Container
                public String paramString();  // Overrides Container
                public void printComponents(Graphics g);  // Overrides Container
                public final void setLayout(LayoutManager mgr);  // Overrides Container
                public void setScrollPosition(int x, int y);
                public void setScrollPosition(Point p);
        // Protected Instance Methods
                protected final void addImpl(Component comp, Object constraints, int index);  // Overrides Container
    }

### Hierarchy:

`Object->Component(ImageObserver, MenuContainer, Serializable)->Container->ScrollPane`

### Passed To:

`Toolkit.createScrollPane()`

java.awt.Rectangle (JDK 1.0) |  | java.awt.Scrollbar (JDK 1.0)