All,
I am running into an issue using JTextArea and JScrollPane. For some reason the scroll pane appears to not recognize the last line in the document, and will only scroll down to the line before it. The scroll bar does not even change to a state where I can slide it until the lines in the document are two greater than the number of lines the textArea shows (it should happen as soon as it is one greater).
Has anyone run into this before? What would be a good solution (I want to avoid having to add an extra 'blank' line to the end of the document, which I would have to remove every time I add a new line)?
Here is how I instantiate the TextArea and ScrollPane:
JFrame frame = new JFrame("Java Chat Program");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container pane = frame.getContentPane();
if (!(pane.getLayout() instanceof BorderLayout)) {
System.err.println("Error: UI Container does not implement BorderLayout.");
System.exit(-1);
}
textArea = new JTextArea();
textArea.setPreferredSize(new Dimension(500, 100));
textArea.setEditable(false);
textArea.setLineWrap(true);
textArea.setWrapStyleWord(true);
JScrollPane scroller = new JScrollPane(textArea);
scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
pane.add(scroller, BorderLayout.CENTER);
Here is the method I use to add a new line to textArea:
public void println(String a)
{
textArea.append(" "+a+"\n");
textArea.setCaretPosition(textArea.getDocument().getLength());
}
Thanks for your help,
Jonathan
EDIT: Also, as a side note, with the current code I have to manually scroll down. I assumed that setCaretPosition(doc.getLength()) in the println(line) method would automatically set the page to the bottom after a line is entered... Should that be the case, or do I need to do something differently?
The problem is textArea.setPreferredSize(new Dimension(500, 100));
Remove that. Set the perferredSize of the scrollpane or the size of your frame instead
Is this a solution? I didn't test it, so please don't kill me.
scroller.getVerticalScrollBar().setValue(pane.getVerticalScrollBar().getMaximum());
Related
So I've been troubleshooting this as much as possible, but I just wanted to create a function that would take in a buffered stream and then display the contents of that buffered stream in a scrollable pane. However every time I've run it the window doesn't show up at all. I'd like to know what I've done wrong here.
void show(BufferedOutputStream showFileContent)
{
String fileContent = showFileContent.toString();
JTextArea content = new JTextArea(fileContent);
JScrollPane scrollableScreen = new JScrollPane(content);
JPanel makeScreenAppear = new JPanel(new BorderLayout());
scrollableScreen.setViewportView(makeScreenAppear);
scrollableScreen.setVisible(true);
scrollableScreen.setSize(500,400);
}
Thank you for your help.
You are replacing the JTextArea with an empty JPanel as the viewport of the JScrollPane in this line of your code:
scrollableScreen.setViewportView(makeScreenAppear);
That's why you don't see the text. No need for the JPanel. Simple add the JScrollPane to the top-level window - which I assume is JFrame or JDialog.
the jscrollpane that I am adding doesnt appearin my textarea
textArea = new JTextArea();
scroll = new JScrollPane(textArea);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
this.add(textArea);
this.add(scroll);
this.setSize(1000, 600);
this.setLayout(new BorderLayout());
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
textArea = new JTextArea();
scroll = new JScrollPane(textArea);
//this.add(textArea); // get rid of this
this.add(scroll);
You create the scrollpane with the text area, but then the next statement removes the text area from the scrollpane because a component can only have a single parent.
Get rid of that statement and just add the scrollpane to the frame.
Then scrollbars will appear automatically as you add data to the text area.
Also you should create the text area using something like:
textArea = new JTextArea(5, 20);
to give a suggestion on how big to make the text area.
I did what you said but still nothing happens
Another problem is that you need to set the layout manager BEFORE you start adding components to the frame (or panel).
Remove this.add(textArea); and add scroll.setSize( 100, 100 ); will also work for you.
I have two files that I need to display in a program. I need to use JTabbedPane and each file should be displayed in its own tab. I can make the text appear in the tab, but the scroll bar won't appear, so I can't see all of the information in the file. How do I add the scroll bar to the text area?
I made one method that creates a panel with the text in it (this is for one file). Then, I made another method that has JTabbedPane and I added the panel to a tab.
Panel method:
private void makeTextPanel() throws IOException
{
textPanel = new JPanel();
textArea = new JTextArea();
textArea.setEditable(false);
//width: 770 height: 1000
textAreaDimensions = new Dimension(TEXT_AREA_WIDTH, TEXT_AREA_HEIGHT);
textArea.setPreferredSize(textAreaDimensions);
BufferedReader inputFile = new BufferedReader(new FileReader(FILE_ONE));
String lineOfText = inputFile.readLine();
while(lineOfText != null)
{
textArea.append("\n" + lineOfText);
lineOfText = inputFile.readLine();
}
// Add a scroll bar
scrollPane = new JScrollPane(textArea);
// Add the text area and scroll bar to the panel
textPanel.add(textArea);
textPanel.add(scrollPane);
}
Tabbed pane method:
private void makeTabbedPane() throws IOException
{
frame = new JFrame("Project");
tabbedPane = new JTabbedPane();
frame.add(tabbedPane, BorderLayout.PAGE_START);
// add panel to the tab
makeTextPanel();
tabbedPane.addTab("Tab 1", textPanel);
// dimensions
frameDimensions = new Dimension(FRAME_WIDTH, FRAME_HEIGHT);
frame.setPreferredSize(frameDimensions);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
To reiterate:
How do I make the scroll bar visible?
I set the height of the text area to 1000. Will the scroll bar be able to scroll through everything? If not, how do I set the height of the text area to fit everything in the file?
The component you want scroll bars for should always a child of the JScrollPane. Adding the textArea and then the scrollPane to that tabbedPane probably isn't doing what you think it is. Make sure that textArea is the child of scrollPane, and add just the scrollPane to the tabbedPane, ensuring you've specified a layout that dictates how the scrollPane is to take up the space you want within tabbedPane.
The scrollpane will automatically add scrollbars only when it decides the textArea is bigger than it can render in the space it's been given.
Question 1) The JScrollPane methods setVerticalScrollBarPolicy() and setHorizontalScrollBarPolicy() will allow you to force the scrollbars to be always visible.
Question 2) The "preferred" height of the textArea is what your scrollPane will use to determine the scrollbar behaviour (see this example). It's all taken care of for you. If not, you'd be forced yourself to consider font rendering height, how much text you put in the textArea etc.
Generally speaking, just throwing a JTextArea into a JScrollPane will see the desired behaviour you're seeking without you having to do anything "special" with JTextArea size.
I have a JScrollPane on a panel (which has many panels inside of it) and when I open the frame with the scroll pane on it, the fame is scrolled to the bottom. Is there anyway I can avoid this?
Here are some facts:
The panel the scroller is on contains multiple panels. Some of these panels have text fields. I have tried to set the carat of the text fields to 0 and this did not work.
I know there should be actual code, but when I tried to make a mock pane (as the one I am using is intertwined with a lot of code) it is not replicating the issue.
The panel that is being scrolled is being generated using a loop that generates a series of questions... so a text box, a said amount of buttons/answers, and a text box and label that shows the amount of points for each question.
The last elements of my panel that is being scrolled are a JTextArea and a JLabel.
Below is the code to declare those.
Is there anyone out there that could at least throw out an idea of what would be making the scroll pane automatically go to the bottom?
Here is the declaration of the pane and the panels inside/outside of it
JPanel newPanel = new JPanel(new BorderLayout(0, 0));
JPanel showPanel = new JPanel();
BoxLayout layout = new BoxLayout(showQuizPanel, BoxLayout.Y_AXIS);
showQuizPanel.setLayout(layout);
buttonPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
buttonPanel.setBackground(Color.white);
newPanel.setBackground(Color.white);
showPanel.setBackground(Color.white);
populateButtonPanel();
populateShowPanel(showPanel, buttonPanel);
populateQuestions(showPanel);
JScrollPane scrollPane = new JScrollPane(showPanel, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scrollPane.getViewport().setBackground(Color.WHITE);
scrollPane.setAlignmentX(JScrollPane.CENTER_ALIGNMENT);
scrollPane.getVerticalScrollBar().setUnitIncrement(16);
scrollPane.getVerticalScrollBar().setValue(0);
scrollPane.getViewport().setViewPosition(new Point(0,0));
newPanel.add(scrollPane, BorderLayout.CENTER);
return newPanel;
code to declare last elements on page
JPanel pPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
pPanel.setBackground(Color.WHITE);
pPanel.add(qValue);
pPanel.add(new JLabel("Points"));
qArea.add(pPanel);
qArea.add(Box.createVerticalStrut(50));
qValue.setCaretPosition(0);
Thanks!
I believe that when you add text to a text area when building the GUI, the scroll pane will scroll to make the text area visible.
So basically you need to reset the scroll pane to the top.
You can use code like the following after adding all components to the scroll pane:
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
scrollPane.getViewport().setViewPosition( new Point(0, 0) );
}
});
The invokeLater() adds the code to the end of the Event Dispatch Thread (EDT) so that it gets executed after the GUI is visible.
Of course this code assumes that you are creating the rest of the GUI properly on the EDT.
INTRO:
I created a java application using JFrame. I have a JMenuBar at the top and under that I'd like to display rows of text.
PURPOSE:
When I have 50 rows and only 20 are displayable at once, I'd like to be able to scroll down and back up again.
PROBLEM:
Of course, my theory doesn't wanna work as it should. My problem is that I don't know how to add a vertical scroll properly.
QUESTION:
How should I change this code to reach my goal?
public void display(){
Container content = this.window.getContentPane();
content.setLayout(new BorderLayout());
Border border = LineBorder.createGrayLineBorder();
//this is just a sample
for(int i = 0;i<50;i++){
JLabel lab = new JLabel("lonyaladek");
lab.setSize(570, 20);
lab.setBorder(border);
lab.setLocation(10, 20+(i*25));
content.add(lab);
}
//scroll
JScrollBar sb = new JScrollBar(JScrollBar.VERTICAL, 0, 0, 0, 0);
content.add(sb);
}
First you need to start with a layout manager that allows you to add multiple components to the container. Maybe a GridLayout is the best place to start.
Then you add this container to the scrollPane and then you add the scrollpane to the window.
So the basic code would be:
JPanel panel = new JPanel( new GridLayout(0, 1) );
panel.add(...);
panel.add(...);
JScrollPane scrollPane = new JScrollPane( panel );
window.add(scrollPane, BorderLayout.CENTER);
I suggest you read the section from the Swing tutorial on How to Use Scroll Panes for more info.