JTextPane appending a new string

Question

In an every article the answer to a question "How to append a string to a JEditorPane?" is something like

jep.setText(jep.getText + "new string");

I have tried this:

jep.setText("<b>Termination time : </b>" + 
                        CriterionFunction.estimateIndividual_top(individual) + " </br>");
jep.setText(jep.getText() + "Processes' distribution: </br>");

And as a result I got "Termination time : 1000" without "Processes' distribution:"

Why did this happen???

Moonfaced

Answer 1

I doubt that is the recommended approach for appending text. This means every time you change some text you need to reparse the entire document. The reason people may do this is because the don't understand how to use a JEditorPane. That includes me.

I much prefer using a JTextPane and then using attributes. A simple example might be something like:

JTextPane textPane = new JTextPane();
textPane.setText( "original text" );
StyledDocument doc = textPane.getStyledDocument();

//  Define a keyword attribute

SimpleAttributeSet keyWord = new SimpleAttributeSet();
StyleConstants.setForeground(keyWord, Color.RED);
StyleConstants.setBackground(keyWord, Color.YELLOW);
StyleConstants.setBold(keyWord, true);

//  Add some text

try
{
    doc.insertString(0, "Start of text\n", null );
    doc.insertString(doc.getLength(), "\nEnd of text", keyWord );
}
catch(Exception e) { System.out.println(e); }

Reflector

That would recreate the Document and lose all the custom attributes you added previously. – Reflector

@Moonfaced Combining setText + getText to append is probably considered sloppy programming. (I personally use it for simple testing.) For instance, if I was going to maintain a log file with that method, a new String would have to be built every time a log entry is appended (which is a very bad idea given that Strings are immutable.) This will likely eventually lead to a noticeable memory footprint. – Timetable

Good example, but doesn't answer the question of appending text to a JEditorPane. – Invalidate

one might wana use HTMLDocument instead of StyledDocument in order to keep HTML-formatting, if used. – Solomonsolon

Answer 2

A JEditorPane, just a like a JTextPane has a Document that you can use for inserting strings.

What you'll want to do to append text into a JEditorPane is this snippet:

JEditorPane pane = new JEditorPane();
/* ... Other stuff ... */
public void append(String s) {
   try {
      Document doc = pane.getDocument();
      doc.insertString(doc.getLength(), s, null);
   } catch(BadLocationException exc) {
      exc.printStackTrace();
   }
}

I tested this and it worked fine for me. The doc.getLength() is where you want to insert the string, obviously with this line you would be adding it to the end of the text.

Essen

I can't answer for sure, I haven't played around with JEditorPane at all, just JTextPane mostly. I'd have to play around and research it before I could answer that. – Essen

I think the issue is just that setText doesn't actually cause the component to update itself, for whatever reason it only works before the component is displayed. – Invalidate

@sh1ftst0rm I've never had issues with it before, but then again when I wrote a console emulator I didn't depend on setText I went with document manipulation for control. – Essen

@Moonfaced Actually setText(getText() + newText) works, but its use is limited to no styled text. For styled text it will lose the previous style, and normally you don't want it. Besides, I found and submitted a bug of JTextPane getText() till Java 9, so I will not rely on it. – Stella

Answer 3

setText is to set all text in a textpane. Use the StyledDocument interface to append, remove, ans so on text.

txtPane.getStyledDocument().insertString(
  offsetWhereYouWant, "text you want", attributesYouHope);

Maestricht