I want my JTextArea to resize itself (expand vertically) when the last line (that the text area's height can offer) is reached and the user wants to start a new line. You know, like the textbox in MSWord.
I have an idea to use getLineCount() and determine (if necessary) the new height of the JTextArea. Do you have, or know of better approaches for implementing this?
Actually, the JTextArea always has the correct size so all lines of text are visible. What you experience is probably that you wrapped the text area in a JScrollPane. Just omit the scroll pane and make the text area a direct child of the container.
Another solution is to listen to resize events of the text area and size the scroll pane accordingly. This way, you can grow to a certain size and then start to display scroll bars (for example, when someone pastes 500KB of text into the text area).
I had the same problem. From my tests, I do not believe that the JTextArea sets its size dynamically. Instead, its size seems to be limited by its container (a JPanel in my case). However, the JTextArea does change its preferred size based on the text it contains. From the documentation:
java.awt.TextArea has two properties rows and columns that are used to determine the preferred size. JTextArea uses these properties to indicate the preferred size of the viewport when placed inside a JScrollPane to match the functionality provided by java.awt.TextArea. JTextArea has a preferred size of what is needed to display all of the text, so that it functions properly inside of a JScrollPane. If the value for rows or columns is equal to zero, the preferred size along that axis is used for the viewport preferred size along the same axis.
Go to JTextArea "Properties" - checklist "lineWrap".
I had the same problem，I put the JTextArea into a JScrollPane and set the preferred size of JTextArea, and I believe that's the cause of the problem.
So the right solution is to put the JTextArea into a JScrollPane, and don't touch the preferred size of JTextArea, set JScrollPane's instead.
Related
I am setting a JLabel for the error messages in my program, so initially the label is empty label.setText(""), but when there is an error it should change to something like label.setText("Error, you have entered invalid data...").
If I use setSize(x,y) on the label, it forces other components to displace when error message takes place. But using setPreferredSize(Dimension(x,y))doesn't impact them.
Q1. Why is that?
Q2. What is the difference between setSize(x,y) and setPreferredSize(Dimension(x,y))
Q3. Does it have to do anything with layout?
Thank you in advance for explanation!
P.S. I am using GridBagLayout for positioning my components on the JPanel.
Don’t use the setSize method.
setSize is called by LayoutManagers, like GridBagLayout, to lay out child components. When you call setSize explicitly, you are fighting with the GridBagLayout. Eventually, GridBagLayout will undo your setSize call, when it calls setSize for its own purposes.
In other words, any call to setSize eventually will be wiped out by the parent layout.
setPreferredSize will not be wiped out. Most LayoutManagers, including GridBagLayout, do their best to respect a component’s preferred size.
However, you should not be calling setPreferredSize. Components already have a preferred size by default, and it is almost certainly better than any numbers you can come up with. For instance, a JLabel’s default preferred size is the size which is just large enough to accommodate its text, icon, and borders.
Computing a preferred size is harder than you might think. How many pixels does text use? How many pixels high is a 12 point font? 12 points is not 12 pixels. 12 points is 12⁄72 inch. How many pixels is that? It depends on the user’s monitor and graphics resolution. All of this is known to the Swing rendering system, and JLabel uses all of that information to determine its default preferred size. You should not try to reinvent all of that work, and you should not try to replace that work with something simpler, as it will be inadequate.
If you just let the JLabel keep its preferred size, GridBagLayout will do its best to accommodate that. If the window itself does not have room to display the JLabel’s new text, you probably should call the window’s pack() method after changing the text.
Update: This appears to be an XY problem—you really want a message that you can show and hide.
You want your layout to be big enough to accommodate your message text as soon as you create it. This is typically done with a CardLayout, which lets you place several components on top of each other, with only one of them visible at any given moment. Since you want to show no text at all, initially, you would add an empty JLabel as the first component in the CardLayout, so it is shown by default:
JLabel label = new JLabel("Error, you have entered invalid data...");
CardLayout messageLayout = new CardLayout();
JPanel messagePane = new JPanel(messageLayout);
messagePane.add(new JLabel(), "blank");
messagePane.add(label, "message");
// Do not add label directly to your user interface.
// Add messagePane instead.
mainWindow.add(messagePane);
// ...
// Show message
messageLayout.show(messagePane, "message");
// ...
// Hide message
messageLayout.show(messagePane, "blank");
"message" and "blank" are never seen by the user. They are just unique identifiers for each component (“card”) in the CardLayout. You can make them anything you want.
The setSize() function sets the size not based on any LayoutManager. Thats why you should always use setPrefferedSize() when working with a LayoutManager. setPrefferedSize() firstly tries to be conform with the LayoutManagers dimensions if then possible Java tries to set the size of the Label according to your setPrefferedSize() input.
So yes, it does have anything to do with layout. If possible, you should only use setPrefferedSize() as you are working with layout managers.
I have a problem with Java Swing JLabel.
The text i want to display on the JLabel exceeds the bounds of the JLabel. I want to display it via a Marqueeeffect. I already implemented the effect but when there is a string that exceeds the bounds of the JLabel it gets cut off and the rest gets replaced with "...".
My question is, if there is any opportunity to set the textlength for a JLabel individually, not depending on the bounds, that it doesnt get cut off?
Hope somebody got an answer for me.
I dont use any LayoutManagers and i dont want the JLabel to get resized, it should only can contain text longer than the bounds of it.
I want to display it via a Marqueeeffect.
Check out the Marquee Panel.
In this LayoutTest, you can see how the label's UI delegate uses layoutCompoundLabel() to elide the text when label's size falls below the preferred size.
In this MarqueeTest, MarqueePanel has a default FlowLayout, which adopts the display label's preferred size.
The Swing JLabel was not designed to do marquee scrolling.
Here's the source code for JLabel. You can modify the text handling routines to do a marquee scroll rather than compressing the text with an ellipsis.
Oh, you'd better use a layout manager. Your marquee JLabel won't layout correctly without a layout manager.
I have a JTextPane with HTML text.
I used GroupLayout (using WindowBuilder).
I've set the minimum size of my JFrame to 800x600 so the user cannot make it smaller than that.
The app has a big scrolling JPanel the size of the entire window. The top part of the panel is taken up by a JTextPane wrapped in JScrollPane. I have disabled the scroll bars and sized the JScrollPane to make the entire text visible.
In group layout the JScrollPane is set to stay constant vertically, but size horizontally.
My issue is that when the user makes the window larger the JScrollPane also expands, but now there is a big white space left at the bottom of the text pane. Is there a way that I can make JTextPane shrink to fit its contents.
Also if you suggest a different layout, I would be willing to try it.
I used this TextPanePerfectSize example from #camickr to solve a similar problem. The example uses validate() and pack() to adjust to the preferred size. You might be able to adapt it to your situation.
Take a look at SpringLayout. It gives you far more control over the positioning of components. Look at the SpringLayout tutorial if you get stuck.
The trick in your case is to bind the bottom (south) of your JScrollPane to the top (north) of the screen.
I'm trying to build a simple interface for an assignment, in which multi-line word-wrapped input boxes can be stacked vertically in a single, fixed-width column. then the whole stack (if tall enough) has to scroll vertically inside of a scroll pane with the same fixed width and a fixed height.
The active box has to change height dynamically to fit the amount of text as it is being typed/deleted. This means the y position of all subsequent inputs in the column should change accordingly. A layout manager's job, right?
I started reading about the swing layouts, and it seemed like only the GridBagLayout could do this. Since this is my app's only interface window, it seemed like a clunky layout to achieve something simple.
So, which swing layout should I use, along with which text input class for word-wrapping and auto height adjustment? Thanks.
A BoxLayout might be what you are after for this use-case.
I have a JTextArea of a fixed size (300 x 33) with line wrapping enabled that I have added inside of a JPanel. Whenever one types inside it and goes past the last visible row (in this case the second one), the text continues outside of the text area's view, and is hidden.
Is there anyway to limit the text entered inside of a JTextArea to the size of the text area rather than to the number of characters that it contains (making it dependent to the different space that each character of different fonts occupies)?
Edit:
I forgot to mention that not fixing the size of the JTextArea and providing row and column numbers in the constructor would result in the text area to stretch and fill the JPanel holding it. I believe this is due to the fact that the panel's layout is a BoxLayout.
You shouldn't fix the size of a JTextArea. Rather initialize it by calling its constructor with decent column and row number parameters, and put it in a JScrollPane so if the text increases, you'll not lose the text.