I have created JTextpane and inserted components inside textpane (components like Jtextarea). (vertical scrollbar of )Jscrollpane of JTextpane is automatically set to bottom when I insert new components in that JTextpane. I want to keep it to be set to the top position. How can I do this
Thanks Sunil Kumar Sahoo
Here's a utility class I use. It can be used to scroll to the top, bottom, left, right or horizonatal / vertical center of a JScrollPane
.
public final class ScrollUtil {
public static final int NONE = 0, TOP = 1, VCENTER = 2, BOTTOM = 4, LEFT = 8, HCENTER = 16, RIGHT = 32;
private static final int OFFSET = 100; // Required for hack (see below).
private ScrollUtil() {
}
/**
* Scroll to specified location. e.g. <tt>scroll(component, BOTTOM);</tt>.
*
* @param c JComponent to scroll.
* @param part Location to scroll to. Should be a bit-wise OR of one or moe of the values:
* NONE, TOP, VCENTER, BOTTOM, LEFT, HCENTER, RIGHT.
*/
public static void scroll(JComponent c, int part) {
scroll(c, part & (LEFT|HCENTER|RIGHT), part & (TOP|VCENTER|BOTTOM));
}
/**
* Scroll to specified location. e.g. <tt>scroll(component, LEFT, BOTTOM);</tt>.
*
* @param c JComponent to scroll.
* @param horizontal Horizontal location. Should take the value: LEFT, HCENTER or RIGHT.
* @param vertical Vertical location. Should take the value: TOP, VCENTER or BOTTOM.
*/
public static void scroll(JComponent c, int horizontal, int vertical) {
Rectangle visible = c.getVisibleRect();
Rectangle bounds = c.getBounds();
switch (vertical) {
case TOP: visible.y = 0; break;
case VCENTER: visible.y = (bounds.height - visible.height) / 2; break;
case BOTTOM: visible.y = bounds.height - visible.height + OFFSET; break;
}
switch (horizontal) {
case LEFT: visible.x = 0; break;
case HCENTER: visible.x = (bounds.width - visible.width) / 2; break;
case RIGHT: visible.x = bounds.width - visible.width + OFFSET; break;
}
// When scrolling to bottom or right of viewport, add an OFFSET value.
// This is because without this certain components (e.g. JTable) would
// not scroll right to the bottom (presumably the bounds calculation
// doesn't take the table header into account. It doesn't matter if
// OFFSET is a huge value (e.g. 10000) - the scrollRectToVisible method
// still works correctly.
c.scrollRectToVisible(visible);
}
}
I have found that the easiest way to do this is the following:
public void scroll(int vertical) {
switch (vertical) {
case SwingConstants.TOP:
getVerticalScrollBar().setValue(0);
break;
case SwingConstants.CENTER:
getVerticalScrollBar().setValue(getVerticalScrollBar().getMaximum());
getVerticalScrollBar().setValue(getVerticalScrollBar().getValue() / 2);
break;
case SwingConstants.BOTTOM:
getVerticalScrollBar().setValue(getVerticalScrollBar().getMaximum());
break;
}
}
I placed this in an object which extended JScrollPane but you could also add the name of your JScrollPane before all the getVertivalScrollBar()
. There is two setValue()
s for CENTER because getMaximum()
returns the bottom of the JScrollBar
, not the lowest value it goes to. This also works for Horizontal Scrolling using getHorizontalScrollBar()
in place of getverticalScrollBar()
.
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