I am trying to set preferred width for jscrollpane in borderlayout(WEST).but it is not working
Please look into my sample code
JTree tree=new JTree(root);
JScrollPane jsp=newJScrollPane(tree);
jsp.setBounds(0,0,200,100);
Jframe.add(jsp,BorderLayout.WEST);
but it is showing default width.
Alternatively I tried to set preferred size for JTree , it is working fine but jscrollpane is not working properly.Please help me in this.
It is the layout manager who determines the position of the component, based on the sizes of the component (minimum/maximum/preferred). So your call to setBounds will be ignored and instead the BorderLayout will determine where it places your component.
Normally this mechanism works just fine. The problem with a JScrollPane is that its size hints might not be in sync with what you want as behavior (due to the fact the scroll pane can have scroll bars, so it can determine its own size).
Solution: just call setPreferredSize on the JScrollPane before adding it. This is also done in the official tutorial and about the only time I can think of that it is acceptable to call this method.
Related
Before I start, I'm aware that its a bad idea to not use a Layout Manager and usually I do use one, however, I also have all my components automatically re-size and relocate based on the size of the window. In addition the program I'm working on is only intended to run on 1 machine throughout its entire lifetime. Please don't downvote me just because of lack of layout manager, I found it to be what I need for this particular program.
To my issue, I found a similar post on stackoverflow but a solution was never achieved.
I'm adding a dynamic amount of JLabels to my JPanel, I've noticed that when not using a layout manager, the scroller doesn't work.
This is a simplified version of my initialization code.
JPanel mypanel = new JPanel();
mypanel.setLayout(null);
mypanel.setSize(800,450);
mypanel.setForeground(Color.WHITE);
mypanel.setBackground(Color.BLACK);
scrollablePanel = new JScrollPane(mypanel);
scrollablePanel.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollablePanel.setPreferredSize(new Dimension(800,300));
scrollablePanel.setSize(800,300);
scrollablePanel.setLocation(250,156);
myContainer.add(scrollablePanel);
where myContainer would be the container (also without a layout manager). The JLabels are added later on to the JPanel with:
enter code heremypanel.add(label1);
after some basic settings are set for the labels such as setForeground and setBackground.
Unfortunately when run, the scrollbar appears as if its not required (see image)
http://i.imgur.com/zp0QKGG.png
The table text seen in the image is made up of multiple JLabels.
If it's not possible to resolve the issue without using a Layout Manager I will switch to BoxLayout, I was just hoping there would be a solution.
The problem is JScrollPanel needs the preferred size of the view component to determine when the view exceeds the scroll pane's viewable area.
The preferred size of a component is normally determined via the layout manager. While you can use setPreferredSize, it is typically discouraged and you will simply run into the same problem as the content exceeds what ever value you decide to set.
A better solution would be to use a LayoutManager or compound layout (using multiple layout managers over multiple containers) to achieve the result you desired...or write your own...
Unfortunately, I have seen this question multiple times but unfortunately I do not know what I am doing well enough to be able to interpret what I have to implement in my own code.
I have used the GUI editor in netbeans to create a JScrollPane and a JPanel on top of this. I am aware I can create these components at runtime along with everything else but this proved problematic and simply adding the scroll pane and panel in the editor and adding components to them during runtime has worked for me thus far.
So far, creating components and adding them to the panel is no problem. The problem I face is that the scroll pane will not update itself to enable the user to scroll further down to view the created components at the bottom. I have been generating ‘entries’ each time a button is pressed, that currently creates a JTextField and adds this component to the panel, more components are going to be added later but for now this is just experimentation.
Once the ‘list’ of ‘entries’ exceeds the limit of the window, the window has to be resized in order to view components at the bottom but after a certain number of entries (around 25-30) the components are no longer viewable as the scroll bar does not scroll down the panel.
This is how I am adding components at runtime...
JTextField txtName1 = new JTextField();
txtName1.setLocation(10, 90);
txtName1.setSize(135, 25);
pnlContainer.add(txtName1);
The 'pnlContainer' is attached on top of the 'jspContainer' which is my JScrollPane and I am using the 'repaint()' method to get the components visible on the panel.
So far, adding components at runtime has worked, all of the components are visible and interact-able.
I am fairly new to programming in general with only a few years experience, any documentation that may help, tutorials or anything else is greatly appreciated. Documentation is always welcome as I still have a lot to learn.
JTextField txtName1 = new JTextField();
txtName1.setLocation(10, 90);
txtName1.setSize(135, 25);
pnlContainer.add(txtName1);
So far, adding components at runtime has worked, all of the components are visible and interact-able.
In you above code example you are setting the size/location of each component which implies you are using a null layout. Don't use a null layout!!!
Swing was designed to be used with layout managers and scrolling will work properly when you use panels with a layout manager.
The layout manager is responsible for determining the "preferred size" of the panel. The panel will then display scrollbars automatically when the preferred size of the panel is greater than the size of the scroll panel.
When you use a null layout the preferred size of the panel is 0, so the scrollbars will never appear.
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.
How does a JLabel or JButton notify a JScrollPane that the view size has changed (for example when an icon has been set) so it can determine whether showing scrollbars are necessary?
How could I implement similar behaviour to display an image with a simple JPanel without resorting to the aforementionned components?
P.S: I've looked through the source code and so far all I see is that a Component is referred to as "view" and is passed on to a JView or JViewport which registers some listeners. From there on things seem unclear.
As noted in the JScrollPane API, unless you change the policy, "both horizontal and vertical scrollbars appear whenever the component's contents are larger than the view." Once pack() has sized the Window "to fit the preferred size and layouts of its subcomponents," any subsequent changes are seen by the scroll pane when the container is validated and repainted. See Painting in AWT and Swing for more.
Guys, I need to put some buttons in a jscrollpanel, but the JScrollPane won't create a scroll vertically. I'm using a JPanel inside the JScrollPane which is using the simple FlowLayout layout. How can I make the JScrollPanel to scroll only in the vertical??
Problem:
Desired Solution:
Check out the Wrap Layout
The fact you use a JScrollPane changes quite a few things concerning the internal FlowLayout. indeed, when the FlowLayout tries to layout contained JButtons, it use for that the available space. In your case, you don't have limits to the space in the "scrollable client" of your JScrollPane. As a consequence, considering your FlowLayout has infinite space, it uses this space to display items according to it.
So the solution would be to change your scrollable client in order to limit its viewable area to the same than your JScrollPane's JViewport.
However, you would not even in this case have your line returns, as FlowLayout don't really well handle this case.
Were I to be you, I would of course choose an other layout. As GridLayout don't really well handles borders, i think the only reasonible standard layout you can use is GridBagLayout, althgough I fear your dynamic content constraints may require you something even more customizable.
JTextArea c = new JTextArea();
c.setLineWrap(true);
c.setWrapStyleWord(false);
This will wrap anything in a text area to the next line without creating a Horizontal Scroll.
Use the modified Flow Layout that I posted in this answer: How can I let JToolBars wrap to the next line (FlowLayout) without them being hidden ty the JPanel below them?
It will wrap to the next line and your scrollbar should scroll vertically.
scrollbar = new Scrollbar(Scrollbar.VERTICAL);
Or you could use a JList.
See this site for more info: http://docs.oracle.com/javase/tutorial/uiswing/components/list.html
the example class: ListDialog uses only a vertical scrollbar, when the window is resized or the elements don't fit the view.