Swing/AWT/SWT :: How To Use Container Order Focus Traversal Policy
Feb 1, 2014
the focus traversal policy (hereafter "tab order") in forms and panels doesn't follow the order in which controls were inserted into the container, but is derived from the position of the components on the form or panel. This is very neat (and probably allows sloppy coders and GUI builders to exist without actually ever thinking about the tab order), except when it isn't. As when you actually want to specify a different component order, for example.
In the following example, I've created a form with two columns of buttons. I want the tab order to go through the first column of buttons, followed by second column of buttons (ie. a column-by-column schema). The default tab order is row-by-row, however, and can be obtained for reference by commenting out the setupFocus() call in the constructor.
I had hoped that the ContainerOrderFocusTraversalPolicy would do the job, but there is a couple of problems (which I've addressed in the setupFocus() method). Firstly, the container itself is part of the focus chain. This at least is easily remediable by calling setFocusable(false), but I don't have to do that with the initial focus traversal policy, so I wonder why I have to do it with this one. The other problem is more pressing, though - the ContainerOrderFocusTraversalPolicy lets me (un)hapilly tab through JLabels. Again, I've fixed this, but the initial policy knows all by itself that it's not a good idea to focus a JLabel. Moreover, I'm afraid there might be other components that do not receive focus with the original policy, but ContainerOrderFocusTraversalPolicy might plod though them.
isn't there some focus traversal policy implementation that I could just set and it would tab through exactly the same components as the original policy, except it would order them according to their order in the container?
I'm facing a problem in controlling the focus traversal mechanism inside a jframe...as i want the focus to travel from top to bottom by pressing tab key regularly , but it travels left to right and then top to bottom through the textfields... The form looks like textfield1 textfield4
textfield2 textfield5
textfield3
The focus travels from 1 to 4 , 2 to 5 and then rests at 3. but i want it to be like from 1 to 2 to 3 and then 4 and 5....
We are working with LinkedBinarySearchTrees. One of specs on my assignment is to "Using a level-order traversal, create a 2-D display of your trees, using the forward and back slashes as the branch lines. The tree nodes should be spaced proportionally to show the structure of the tree neatly."
I have a JPanel with vertical BoxLayout. It contains four components. I set the JPanel to LEFT_ALIGNMENT, which has no effect on its components. I set the first component to LEFT_ALIGNMENT, which has no effect. Only after I have set all four components to LEFT_ALIGNMENT do any of them align properly.
This suggests that it is impossible to have varying alignments in a container. They must all be the same alignment.
I accept that this is just the way things are: "Java works in mysterious ways." And I'm sure that it is possible to work around this limitation by stacking boxes that themselves have different internal alignments.
But I still wonder what in the world was going on in the minds of the Java developers. Is there a rational reason for this oddity?
This raises my most serious criticism of Swing: the hidden gotcha. Swing is a tangled mess of cross-connecting requirements that are impossible to divine by simple inspection of the documentation. If you want to use, say, a JRadioButton, it's not enough to study the documentation on JRadioButtons; you must also consult lots of documents for which there is no obvious connection to JRadioButton other than it being part of Swing.
I have a program with a main panel JPanel that implements KeyListener. I added a JTextArea to which I added as the KeyListener: this, meaning the main panel. I made the JTextArea fill the entire main panel because I want to catch a key press anywhere in the main panel.I catch the key presses and the program does what I want it to.
I added a JToolBar to the program; it is working just fine.Now that I have two components on the main panel - toolbar and panel with textarea -, the textarea must have the focus before it will send the KeyEvent and call keyPressed(). I don't want to expect the user to click on the main window to get the program to start or after each time they use the toolbar.
I have tried calling both requestFocus() and requestFocusInWindow() on the textarea; neither call worked. I put the toolbar at PAGE_END instead of PAGE_START; this worked to allow the program to start but I don't want to have the toolbar at the bottom and once I clicked on a toolbar button, the textarea lost the focus.
I need to be able to give the textarea the focus when the program starts and after the user uses a toolbar button. (I suspect that if I solve the problem when the program starts, I can use the same method after handling a button press.)
I'm having issues with providing focus to keyboard buttons when a JInternalFrame with keyboard buttons is called in my program. So for example when the program is started the attachment called signinscn.png is called.
This screen is a JDesktopPane which calls JPanel for its components.
From here a JInternalFrame containing the buttons ESC and F1 to F4 as seen in the attachment called signinscn.png is called.
I would like the buttons in my JInternalFrame to have focus such that when a user engages the equivalent keyboard button i.e. ESC or F1 to F4 WITHOUT clicking on the JInternalFrame the respective button's action listener kicks in. At the moment only after the user clicks on the JInternalFrame do the equivalent keyboard buttons respond.
Here's the constructor of my JInternalFrame and you can see how I handle the ESC keyboard button in the constructor of the JInternalFrame (but as I mentioned only after the user has engaged the JInternalFrame):
How would you set a column in a JTable to make it unable to gain focus i.e. select the next column on the same row or ignore the command completely when selecting a column that should not be able to be gained focus on?
I'm working with AffineTransforms, and am confused by one aspect of their behavior. It appears that the order in which two sequential concatenations are executed effects the final result. Here's a fragment of code to illustrate the concept:
public void draw() { radius *= 1.1; if (radius>800) { radius = 10;
[Code].....
This code has dramatically different results if the two concatenations are reversed in order. I want to understand what's going on. Is it really true that the order of concatenations affects the final result? From my understanding of matrix multiplication, it shouldn't. Have I missed something here?
This method uses BFS traversal on a vertex and displays the values. I have worked this out on paper and 2 out of 3 the results from my code match my work on paper. I believe the error is that it prints out 3's adjacent child before 3 itself. I have attached the results I did by hand. Here's the graph and results from my code:
One of the random number generators in Java extract the higher-order bits of the random number in order to get a longer period.
I'm not sure if I understand how this is done. Suppose that the random number r = 0000 1100 1000 1101. If we extract the 16 most significant bits from r; is the new number r = 0000 1100 or r = 0000 1100 0000 0000?
I want to implement a kind of "container" in which to store objects (instances) of different types. Then with an iterator I'd call common methods. This is what I have in mind:
Where translate(x, y, z) is a method common for objects in Positionables which objects are of different types (Sphere, Box etc.).
Now I was thinking Positionables could be a List<Positionable> and Positionable is an abstract class and Sphere and Box extends from it. But I don't know how to propagate the call of translate() to the subclasses.
What are the best approaches for this matter? It would be perfect if I could make it so I could somehow use the "with" construction like in the example above.
I am looking for a way to have a Servlet (my container is Tomcat) calling a JSP file and processing it in order to retrieve the generated HTML. The compete scenario:
I have virtual shop and whenever a purchase is being carried out, the customer is redirected to a Servlet that post-processes the purchase (list of the items, etc.)
Among all these, the Servlet is also supposed to send me an email about the new purchase. I would like to have nice designed HTML mail and not just a simple plain text notification. I thought of having a designated JSP as a view, and it will only be available from the Servlet container, for this purpose. One way is having the Servlet create an HTTPClient (or any other method of network communication) to my own host and ask for the JSP.
I wonder if there is a simpler way to ask my own container to process a JSP, since I am not really making a request to an outside web application. Something like getServletContext.processAndReturnJsp("mail.jsp")
BTW, if you think my approach is too cumbersome to fill an email with HTML code, it would be great to know of a simpler way.
I have configured form based JAAS in my app. Basically, in web.xml I have declared security constraints on certain jsp page, declared specific roles, login and error pages. So, my login form is:
I read JEE6 doc and confused with : Does container managed entity manager (injected by PersistenceContext annotation) is thread-safe in stateless session bean in multiple-thread env?
See code below, if there are 2 requests to stateless sesion bean in 2 concurrent threads , is it using same Entity Manager Instance or not?
@Stateless(name = "HRFacade", mappedName = "HR_FACES_EJB_JPA-HRFacade-HRFacade") public class HRFacadeBean implements HRFacade, HRFacadeLocal { @Resource SessionContext sessionContext;
How to do draw the original binary tree based on traversal results?
A binary tree has this pre-order traversal result: A,B,D,H,I,E,F,C,G,K,J (TreeNodes) And the same tree gives the following in-order traversal: B,H,I,D,A,C,F,E,K,G,J. Can you draw the tree structure?
I'm creating a simple login screen and I need to focus on the first field "login" after I click a submit button, so when the page return. I tryed using JS :
