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javaswingjtablejscrollpane

JTable and JScrollPane not shown as they should

Why doesn't this work (doesn't show up in GUI)

JTable table=new JTable(20,20);
table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

JScrollPane tableScrollPane=new JScrollPane(table);
tableScrollPane.setBounds(10,70,540,280);
tableScrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
tableScrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
add(tableScrollPane);

Whereas this does(does show up in GUI).

JTable table=new JTable(20,20);
table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

JScrollPane tableScrollPane=new JScrollPane();
tableScrollPane.setBounds(10,70,540,280);
tableScrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
tableScrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
tableScrollPane.add(table);
add(tableScrollPane);

Why is this the case, shouldn't they both do the same thing?

Solution

  • Why is this the case, shouldn't they both do the same thing?

    No.

    A JScrollPane contains many components including the scrollbars and a viewport and uses its own internal layout manager to set the location of each component. You can't just "add" a component to the scroll pane because the layout manager doesn't support this.

    Read the section from the Swing tutorial on How a Scroll Pane Works for more information.

    The component (in this case, JTable) needs to be added to the "viewport" of the scroll pane.

    You can use:

    JScrollPane scrollPane = new JScrollPane( table );

    or

    JScrollPane scrollPane = new JScrollPane( );    
scrollPanwe.setViewportView( table );