Java Code Examples for javax.swing.JScrollBar#getMinimum()

void scrollByBlock(JScrollBar scrollbar, int direction) {
    // This method is called from BasicScrollPaneUI to implement wheel
    // scrolling, and also from scrollByBlock().
    int oldValue = scrollbar.getValue();
    int blockIncrement = scrollbar.getBlockIncrement(direction);
    int delta = blockIncrement * ((direction > 0) ? +1 : -1);
    int newValue = oldValue + delta;

    // Check for overflow.
    if (delta > 0 && newValue < oldValue) {
        newValue = scrollbar.getMaximum();
    } else if (delta < 0 && newValue > oldValue) {
        newValue = scrollbar.getMinimum();
    }

    scrollbar.setValue(newValue);
}
 

private void mouseWheelMovedSmooth( MouseWheelEvent e ) {
		// return if there is no viewport
		JViewport viewport = scrollpane.getViewport();
		if( viewport == null )
			return;

		// find scrollbar to scroll
		JScrollBar scrollbar = scrollpane.getVerticalScrollBar();
		if( scrollbar == null || !scrollbar.isVisible() || e.isShiftDown() ) {
			scrollbar = scrollpane.getHorizontalScrollBar();
			if( scrollbar == null || !scrollbar.isVisible() )
				return;
		}

		// consume event
		e.consume();

		// get precise wheel rotation
		double rotation = e.getPreciseWheelRotation();

		// get unit and block increment
		int unitIncrement;
		int blockIncrement;
		int orientation = scrollbar.getOrientation();
		Component view = viewport.getView();
		if( view instanceof Scrollable ) {
			Scrollable scrollable = (Scrollable) view;

			// Use (0, 0) view position to obtain constant unit increment of first item
			// (which might otherwise be variable on smaller-than-unit scrolling).
			Rectangle visibleRect = new Rectangle( viewport.getViewSize() );
			unitIncrement = scrollable.getScrollableUnitIncrement( visibleRect, orientation, 1 );
			blockIncrement = scrollable.getScrollableBlockIncrement( visibleRect, orientation, 1 );

			if( unitIncrement > 0 ) {
				// For the case that the first item (e.g. in a list) is larger
				// than the other items, get the unit increment of the second item
				// and use the smaller one.
				if( orientation == SwingConstants.VERTICAL ) {
					visibleRect.y += unitIncrement;
					visibleRect.height -= unitIncrement;
				} else {
					visibleRect.x += unitIncrement;
					visibleRect.width -= unitIncrement;
				}
				int unitIncrement2 = scrollable.getScrollableUnitIncrement( visibleRect, orientation, 1 );
				if( unitIncrement2 > 0 )
					unitIncrement = Math.min( unitIncrement, unitIncrement2 );
			}
		} else {
			int direction = rotation < 0 ? -1 : 1;
			unitIncrement = scrollbar.getUnitIncrement( direction );
			blockIncrement = scrollbar.getBlockIncrement( direction );
		}

		// limit scroll amount (number of units to scroll) for small viewports
		// (e.g. vertical scrolling in file chooser)
		int scrollAmount = e.getScrollAmount();
		int viewportWH = (orientation == SwingConstants.VERTICAL)
			? viewport.getHeight()
			: viewport.getWidth();
		if( unitIncrement * scrollAmount > viewportWH )
			scrollAmount = Math.max( viewportWH / unitIncrement, 1 );

		// compute relative delta
		double delta = rotation * scrollAmount * unitIncrement;
		boolean adjustDelta = Math.abs( rotation ) < (1.0 + EPSILON);
		double adjustedDelta = adjustDelta
			? Math.max( -blockIncrement, Math.min( delta, blockIncrement ) )
			: delta;

		// compute new value
		int value = scrollbar.getValue();
		double minDelta = scrollbar.getMinimum() - value;
		double maxDelta = scrollbar.getMaximum() - scrollbar.getModel().getExtent() - value;
		double boundedDelta = Math.max( minDelta, Math.min( adjustedDelta, maxDelta ) );
		int newValue = value + (int) Math.round( boundedDelta );

		// set new value
		if( newValue != value )
			scrollbar.setValue( newValue );

/*debug
		System.out.println( String.format( "%4d  %9f / %4d %4d / %12f %5s %12f / %4d %4d %4d / %12f %12f %12f / %4d",
			e.getWheelRotation(),
			e.getPreciseWheelRotation(),
			unitIncrement,
			blockIncrement,
			delta,
			adjustDelta,
			adjustedDelta,
			value,
			scrollbar.getMinimum(),
			scrollbar.getMaximum(),
			minDelta,
			maxDelta,
			boundedDelta,
			newValue ) );
*/
	}