[java] How do I make JScrollPane scroll to the top
Author
Easy question this one...
I've got a JScrollPane that contains a JTextArea object. The text area is larger than the scroll pane so vertical scroll bars appear. When I display the scroll pane it is defaulting to being scrolled to the bottom of the pane and not the top.
How do I get the pane to display scrolled to the top.
This is what I'm trying but its not working...
JScrollPane scrollPane = new JScrollPane(textArea);
scrollPane.getVerticalScrollBar().setValue(0); // this doesn't work
getContentPane().add(scrollPane, BorderLayout.CENTER);
scrollPane.getVerticalScrollBar().setValue(0); // this doesn't workThat line needs to be called after the JTextarea is filled with its text. Also all components will have to have been displayed.
After setting the value, you may also have to call repaint on the JScrollPane.
Author
It still doesn't seem to be working. Here's what I've got so far. Note that after the object has been created it's setVisible method is called from outside the class ie. scrollPane.setVisible().
class RulesView extends JFrame implements ActionListener{ // -- DATA MEMBERS -- private static final int DEFAULT_WIDTH = 500; private static final int DEFAULT_HEIGHT = 300; private JButton m_btnOk = new JButton("Ok"); // ok btn private JScrollPane m_ScrollPane; // -- CLASS METHODS -- // --------------------------------------------------------------------- // CONSTRUCTOR public RulesView() { super("Game Rules"); // set text area JTextArea textArea = new JTextArea(getText()); textArea.setLineWrap(true); // set text flow textArea.setWrapStyleWord(true); // wrap at word boundarys textArea.setEditable(false); // set to non editable textArea.setOpaque(false); // transparent bg setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT); // set dimensions setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); // dispose of child window on close getContentPane().setLayout(new BorderLayout(5,5)); // use border layout // display text in center m_ScrollPane = new JScrollPane(textArea); getContentPane().add(m_ScrollPane, BorderLayout.CENTER); // add action listener to ok button m_btnOk.addActionListener(this); // display button in south getContentPane().add(m_btnOk, BorderLayout.SOUTH); } // --------------------------------------------------------------------- // RETURNS: text for Rules private String getText() { return "Multiple lines of text....."; } // --------------------------------------------------------------------- // Actionlistener public void actionPerformed(ActionEvent e) { setVisible(false); } // --------------------------------------------------------------------- // Overrides set visible to allow scroll bars to be scrolled to top public void setVisible(boolean visible) { if (visible == true) { m_ScrollPane.getVerticalScrollBar().setValue(0); // scroll bar to top m_ScrollPane.repaint(); } super.setVisible(visible); }}Original post by Kristafariipublic void setVisible(boolean visible) { if (visible == true) { m_ScrollPane.getVerticalScrollBar().setValue(0); // scroll bar to top m_ScrollPane.repaint(); } super.setVisible(visible); }
This won't work. You are still trying to set the value to 0 before the JFrame is displayed.
Try:public void setVisible(boolean visible) { super.setVisible(visible); if (visible == true) { m_ScrollPane.getVerticalScrollBar().setValue(0); // scroll bar to top m_ScrollPane.repaint(); } }
I recall this should work:
Haven't tested it though...
m_ScrollPane.getViewport().setViewPosition( new Point(0, 0) );Haven't tested it though...
Author
thanks Anon
textArea.setSelectionStart(0);
textArea.setSelectionEnd(0);
in the constructor worked..
cheers
textArea.setSelectionStart(0);
textArea.setSelectionEnd(0);
in the constructor worked..
cheers
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