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Java JViewport

The JViewport class is used to implement scrolling. JViewport is designed to support both logical scrolling and pixel-based scrolling. The viewport's child, called the view, is scrolled by calling the JViewport.setViewPosition() method.

Nested Classes

Modifier and Type Class Description
protected class JViewport.AccessibleJViewport This class implements accessibility support for the Jviewport class.
protected class JViewport.ViewListener A listener for the view.

Fields

Modifier and Type Field Description
static int BACKINGSTORE_SCROLL_MODE It draws viewport contents into an offscreen image.
protected Image backingStoreImage The view image used for a backing store.
static int BLIT_SCROLL_MODE It uses graphics.copyArea to implement scrolling.
protected boolean isViewSizeSet True when the viewport dimensions have been determined.
protected Point lastPaintPosition The last viewPosition that we've painted, so we know how much of the backing store image is valid.
protected boolean scrollUnderway The scrollUnderway flag is used for components like JList.
static int SIMPLE_SCROLL_MODE This mode uses the very simple method of redrawing the entire contents of the scrollpane each time it is scrolled.

Constructor

Constructor Description
JViewport() Creates a JViewport.

Methods

Modifier and Type Method Description
void addChangeListener(ChangeListener l) It adds a ChangeListener to the list that is notified each time the view's size, position, or the viewport's extent size has changed.
protected LayoutManager createLayoutManager() Subclassers can override this to install a different layout manager (or null) in the constructor.
protected Jviewport.ViewListener createViewListener() It creates a listener for the view.
int getScrollMode() It returns the current scrolling mode.
Component getView() It returns the JViewport's one child or null.
Point getViewPosition() It returns the view coordinates that appear in the upper left hand corner of the viewport, or 0,0 if there's no view.
Dimension getViewSize() If the view's size hasn't been explicitly set, return the preferred size, otherwise return the view's current size.
void setExtentSize(Dimension newExtent) It sets the size of the visible part of the view using view coordinates.
void setScrollMode(int mode) It used to control the method of scrolling the viewport contents.
void setViewSize(Dimension newSize) It sets the size of the view.

JViewport Example

Output:

Java Jviewport
Next TopicJava JFrame




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