Develop Reference

JPane inside JScrolledPane. No vertical scrollbar when needed

ive got a JPane within a JScrolledPane. When i add content to JPane , JScrollPane doesnt show scrollbar. I tried repaint() and revalidate() but it didnt help.
static void ladowaniePaneli()
{
int b;
for(b=0;b<o;b++)
{
bgPanel[b] = new JBackgroundPanel();
nowyPanel[b] = new JPanel();
((FlowLayout)bgPanel[b].getLayout()).setVgap(0);
nowyPanel[b].setPreferredSize(new Dimension(790,518));
nowyPanel[b].setOpaque(false);
vertical[b] = new JScrollPane(nowyPanel[b]);
vertical[b].setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
vertical[b].setPreferredSize(new Dimension(789,517));
vertical[b].setOpaque(false);
vertical[b].getViewport().setOpaque(false);
bgPanel[b].add(vertical[b]);
}
}

It makes sense that scrollbars are never seen since you restrict the size of the contained component so that it's always trivially larger than the scrollopane's viewport:
nowyPanel[b].setPreferredSize(new Dimension(790,518));
Solution: don't do that.

if i dont use setPreferredSize method components wont warp to another line
You can try the Wrap Layout.
pairs should be warped to new line if they exceed JScrollPane width
Components are layed out individually. I you want a group of components to wrap then you would need to add the components to a separate panel first. Then add the panel to the panel using the WrapLayout.

Dynamically create list of jpanels swing/java

I am attempting to create panel, PluginListPanel (extending JPanel), which will show a list of plugin panels which will respect the preferred height of the plugin's panel, but will force the width. I have a solution, but it is slow and has a weird bug. In the screenshot, there are two such panels, one to the left and one to the right:
I don't know different layout manager systems very well, but I know that the TOP field in the BorderLayout does what I want. So, I came up with this 'recursive' solution:
public PluginListPanel(List<PanelContainer> items) {
JPanel body = this;
for (PanelContainer item : items) {
body.setLayout(new BorderLayout(0, 0));
JPanel panel = new PluginOnePanel(item);
body.add(panel, BorderLayout.NORTH);
JPanel newBody = new JPanel();
body.add(newBody, BorderLayout.CENTER);
body = newBody;
}
}
The problem I encounter is when I scroll, the system responds somewhat slowly, and the colour of the SamplePluginPanels is different (see picture below), even if the number of SamplePluginPanels is as low as 8.
The question is, how can I make this more elegant, not slow down the program and not miscolour the panels?
Any insights are highly appreciated.

I think a vertical Box is the answer (actually 2, on both columns):
Box leftBox = Box.createVerticalBox();
Box rightBox = Box.createVerticalBox();
/* put them together */
setLayout(new GridLayout(2,1));
add(leftBox);
add(rightBox);
Also make sure, that the content of the scroll pane implements Scrollable and returns true, to scrollableTracksViewportWidth(). This will force equal widths.

Java: Freezing components on a JFrame

Long time lurker, second time poster (it's got that desperate)
I have a frame that needs to display twelve components next to each other (as if each component is its own column). The first component is a list of attribute names, the second component shows the default attribute, and the next ten are all pulled in from a database. I would like for my Scroll Bar to effectively "freeze" the first two components (i.e. it always shows the first two components) and the scroll bar allows you to look through the rest of the entries. This is similar to Excel where we freeze columns, a la here.
I've looked into using tables, but the problem is that my components are not just text. They've got images and the like too.
Here's some of the code I'm using
JPanel info = new JPanel(); // this is the main component (holds the other 12)
info.setLayout(new GridBagLayout()); // GridBag Layoout
info.add(attNames); // add in the attribute names component
info.add(currentCase); // add in the default values
JPanel rets = new JPanel(); // add in the ten retrieved cases
rets.setLayout(new GridLayout(1,10));
for (int i=0;i<maxCases;i++)
{
rets.add(retCase[i]);
}
info.add(rets); // add the return cases to the info component
JScrollPane scrollBar2=new JScrollPane(rets,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); // surround the return cases with a scroll bar
info.add(scrollBar2); // add the scrollbar
//add the info comp to the content pane along with other necessary components
this.getContentPane().add(casesPanel, BorderLayout.NORTH);
this.getContentPane().add(info, BorderLayout.CENTER);
this.getContentPane().add(buttons, BorderLayout.SOUTH);
//finally, add the overall scrollbars and set the size
this.pack();
JScrollPane scrollBar=new JScrollPane(info,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
this.setSize(this.getWidth(), 750);
this.setResizable(true);
this.add(scrollBar);
The problem is that the scroll bar for the returned case doesn't think it's needed and I have to use the big scroll bar, meaning I can move away from the first two components.
Any help would be greatly appreciated!!
Here's the problem
Cheers,
K

Place the frozen section into the scroll panes row header. Check how to use scroll panes for more info and examples

Java : jscrollpane disable horizontal scrolling

I want to add a Jpanel on a jscrollpane; also I want to have only vertical scrolling. I want to set layout of my jPanel "flowLaout" and add several components to my jPanel in my code by jpanel.add(component) method. The result is that all components are placed in just one row that excide width of jpanel and are not shown. I have used this tricks and both failed:
jScrollPane1.setHorizontalScrollBar(null);
jScrollPane1.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

Wrap Layout should work for you.

I am unsure of the particulars for your current project, but i would recommend MigLayout. It has never served me wrong.
I am currently writing a touchscreen interface with nested MigLayout panels up to 4 or five layers deep, and have not had a single problem.

Please use the below policy to turn on vertical scrolling and turn off horizontal scrolling(Works with Java SE 7):
Panel graphicPanel = new Panel();
JScrollPane scrollbar = new JScrollPane(graphicPanel);
scrollbar.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
scrollbar.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
scrollbar.setPreferredSize(new Dimension(1300, 600));
scrollbar.setVisible(true);
add(scrollbar, BorderLayout.CENTER);

Swing Overlapping components

I have two AWT components in a Frame, Panel A and Panel B. I would like panel A to be sized to the height width of the frame (and maintain that size on frame resize), but I would like panel B to overlap A. B will be at a fixed position (0,0 to make it easier) with a fixed height and width. I'm not sure what kind of layout manager I would need to make this work. If I use a null layout, I think I would have to manage the resizing of panel A myself, but it would make the sizing of panel B relatively easy. Any thoughts on how to accomplish this?
thanks,
Jeff

Take a look at JLayeredPanes. Here is a tutorial.
edit:
If panelA is an AWT component, you will be hard pressed to get panelB to overlap. From Sun's article entitled Mixing Heavy and Light Components:
Do not mix lightweight (Swing) and heavyweight (AWT) components within a container where the lightweight component is expected to overlap the heavyweight one.
However, if you are looking to have panelA fill the Frame completely, why not add panelB as a component of panelA?
Edit2:
If you can make panelB a heavyweight component, then you can use the JLayeredPane.
Here is a quick mockup that shows how:
public static void main(String[] args){
new GUITest();
}
public GUITest() {
frame = new JFrame("test");
frame.setSize(300,300);
addStuffToFrame();
SwingUtilities.invokeLater(new Runnable(){
public void run() {
frame.setVisible(true);
}
});
}
private void addStuffToFrame() {
Panel awtPanel = new Panel();
awtPanel.setBackground(Color.blue);
//here you can fool around with the pane:
//first, you can see how the layered pane works by switching the
//DEFUALT_LAYER and PALLETTE_LAYER back and forth between the two panels
//and re-compiling to see the results
awtPanel.setSize(200,300);
frame.getLayeredPane().add(awtPanel, JLayeredPane.DEFAULT_LAYER);
//next you comment out the above two lines and
//uncomment the following line. this will give you the desired effect of
//awtPanel filling in the entire frame, even on a resize.
//frame.add(awtPanel);
Panel awtPanel2 = new Panel();
awtPanel2.setBackground(Color.red);
awtPanel2.setSize(300,200);
frame.getLayeredPane().add(awtPanel2,JLayeredPane.PALETTE_LAYER);
}

Your best bet is to have your own LayoutManager. The easiest way is probably to extend or proxy BorderLayout, and have a specific case to layout panel B.

Maybe I'm missing something. If B is fixed size and is at (0,0) and A runs the full width what's the use of having B overlap A? You will never see anything that is placed under B.
I can't think of any of the default layout managers, but Orielly has this one you can use:
relative layout manager (see source code link) with documentation. I haven't used it in a long while, but it should beat managing the layout yourself.