I have this JPanel (a) with BoxLayout.
When I add another JPanel (b) to it, with setPreferredSize() and setBackground(), it gets drawn nicely on (a). However, if I setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS) on (b), it doesn't get drawn at all. Or added, I cannot be sure.
If I use other layout manager (e.g. BorderLayout), it appears again.
Anybody care to explain?
I seemes that other components (with null layout) added to same parent got in the way. Setting a layout different from null to all the children of parent component fixes the issue, and keeps the layout to look as if they were all null layout...
Related
I am adding a JTextArea to my JPanel and setting it to a specific place but for some reason it does not move at all.
I have used both setBounds() and setLocation(), but to no avail. Here is what I stopped on:
JTextArea name_field=new JTextArea(1,10);
name_field.setBackground(color);
name_field.setBounds(100,100,600,420);
name_field.setLineWrap(true);
add(name_field);
It keeps creating the text field at the same spot: at the top of the screen in the middle. The only thing I managed to do is change it's width by adding name_field.setLineWrap(true) which only confused me even further. If this for some reason isn't supposed to work, is there another way of moving and possible resizing my JTextArea?
default layout of a jpanel is flowlayout .in order to work setBounds() it should be null layout.but it's highly discourage to use null layout[no layout].you should use layouts there are lot of layouts flow,grid,box,..etc.you first decide appropriate layout for your panel and then use it.
if you set layout to null then your code should work .[but dooont!]
setLayout(null); //change jpanel layout to null
JTextArea name_field=new JTextArea(1,10);
name_field.setBackground(color);
name_field.setBounds(100,100,600,420);
name_field.setLineWrap(true);
add(name_field);
I am adding lots of components (JPanels, JLabels etc.) into a JScrollPane programagically at the start of my program based on some stuff from a database.
It seems that this procedure is too fast for the GUI(?), so the JScrollPane does not always update correctly, i.e the scroll bars are not visible even though the inner JPanel is bigger than the visible area.
Resizing the Window (JFrame) fixes the problem, as I assume Java is re-printing the components when they are resized.
As a test, I have added a debug-button that I can click after the startup of the program has finished. I am trying to force the JScrollPane to "refresh" itself.
I have tried doing:
scrollpane.repaint();
scrollpane.validate();
scrollpane.revalidate();
None of them seems to work. However, if I change the border (or any other layout related to the JScrollPane), it refreshes correctly.
scrollpane.setBorder(new LineBorder(Color.RED));
So I basically have 2 questions.
What is the command for forcing the scrollpane to "refresh"? Obviously it is doing some kind of "repaint" thing when I am adding the border. How can I run that only?
Is there a way of "pausing" the printing of components as they are added and resume it again after I added all the wanted components? As it is now, I basically "see" the components being added on the screen (even though it is really fast). It would be better if I can add all the components I want and THEN tell the program to print it to the screen/JFrame.
The basic code for adding components to a visible panel is:
panel.add(...);
panel.add(...);
panel.revalidate();
panel.repaint();
Adding a component does nothing because the component still has a zero size so there is nothing to paint. When you invoke the revalidate() method the layout manager gets invoked so components will now have a location/size. The repaint() will then paint the components. The revalidate() will also cause the scrollbars to show when required. This of course assumes you are using layout managers.
The components are added to the panel so you invoke the methods on the panel, not the scrollpane.
In my case only
frame.pack();
helped to get the scrollbars on the JScrollPane, when the enclosed JPanel was resized dynamically.
I am trying to create a JScrollPane within one of the tabs to my JTabbedPane. I tried what I though would work which was this:
pane.add("Main", mainGame);// These are my other tabs
pane.add("Upgrades", upgradeScreen); //the JTabbedPane
pane.add("Credits", creditsTab);
upgradeScreen.setLayout(null); //The null layout
lblMoney2.setBounds(10, 11, 277, 22);
upgradeScreen.add(lblMoney2); // A simple JLabel
scrollPane.add(upgradeScreen); //my JScrollPane
Where pane is my JTabbedPane and scrollPane is my JScrollPane. This simply got rid of my upgradesScreen tab. I kind of expected this but I did not know what else to do. If more code is needed for you to figure it out, tell me and i'll put it in, otherwise, thanks for the help!
Don't us JScrollPane#add, instead you want to use JScrollPane#setViewportView
Check out How to use ScrollPane more details.
Advise- Don't use null layouts, they limit the ability for your application to run on multiple platforms. Instead take the time to learn how layout managers work
This simply got rid of my upgradesScreen tab.'
yes, because no component can have two parents at once. You added upgradeScreen to JTabbedPane first and then again added it to a JScrollPane. The Component's add(component) function will eventually call the addImpl(component) function: which will remove the component from it's old parent and add it to the new parent.
However:
You need to add the JScrollPane to the JTabbedPane instance.
The component which you wish to scroll set it as a view to JScrollPane using the setViewportView(component) function. for your context it is the upgradeScreen
I found three ways to fill my JFrame frame = new JFrame("...")
createContentPanel returns a JPanel and createToolBar returns a ToolBar.
frame.add(this.createToolBar(), BorderLayout.PAGE_START); //this works and puts the ToolBar above and the ContentPanel under it<br>
frame.add(this.createContentPanel(), BorderLayout.CENTER);
frame.setContentPane(this.createContentPanel()); //this lets the JToolBar hover over the ContentPanel
frame.getContentPane().add(this.createToolBar());
frame.getContentPane().add(this.createContentPanel()); //this only puts the last one into the JFrame
frame.getContentPane().add(this.createToolBar());
And now I am wondering why should i use the getContentPane()/setContentPane() method if i could just use a simple frame.add(...) to fill my frame.
You are right that it doesn't matter which you use (JFrame#add(...) vs. JFrame#getContentPane().add(...)) since they both essentially call the same code, however there will be times in the future when you'll need access to the contentPane itself, such as if you want to change its border, set its background color or determine its dimensions, and so you'll likely use getContentPane() at some point, and thus getting to know it and be familiar with it would be helpful.
//this only puts the last one into the JFrame
You need to understand how layout managers work. The default content pane is a JPanel that uses a BorderLayout. When you add a component and don't specify a constraint, then it defaults to the CENTER. However you can only has a single component in the center so the layout manager only knows about the last one added. When the layout manager is invoked it sets the size() and location() of that component. The other component has a size of 0, so it is never painted.
In Java 1.6, you can just use the add method of JFrame:
http://download.oracle.com/javase/6/docs/api/javax/swing/JFrame.html
(It will be delegated to the contentPane.)
http://download.oracle.com/javase/1.4.2/docs/api/javax/swing/JFrame.html
Which says:
The JFrame class is slightly
incompatible with Frame. Like all
other JFC/Swing top-level containers,
a JFrame contains a JRootPane as its
only child. The content pane provided
by the root pane should, as a rule,
contain all the non-menu components
displayed by the JFrame. This is
different from the AWT Frame case. For
example, to add a child to an AWT
frame you'd write:
frame.add(child);
However using JFrame you need to add the child
to the JFrame's content pane instead:
frame.getContentPane().add(child);
The same is true for setting layout
managers, removing components, listing
children, and so on. All these methods
should normally be sent to the content
pane instead of the JFrame itself. The
content pane will always be non-null.
Attempting to set it to null will
cause the JFrame to throw an
exception. The default content pane
will have a BorderLayout manager set
on it.
I'm having this strange issue with Swing. I have a main JPanel to which I am adding a JTabbedPane. Inside of this JTabbedPane I am adding another panel:
myTabbedPane.add(innerPanel, "Title", 0);
outerPanel.add(myTabbedPane);
Now, I no longer want myTabbedPane to be JTabbedPane, I want it to be a JPanel. When I change its type (and remove the extra params from its add() method), nothing within the outerPanel is visible anymore. (I am using setBounds() and I set the layouts to null).
Why does it work when using a tabbed pane but suddenly stop when switching to a JPanel? I know that this can be done differently (such as adding the innerPanel directly to the outerPanel), but please don't just tell me to do it differently. I'd just like to know why it suddenly doesn't work when using a JPanel instead. Is there an issue with adding a JPanel to a JPanel? Thanks!
Stop using null layout. Use BorderLayout and then use add inner panel to the center.
Tabbed pane used it own layered layout - that is why it worked before.