使用SwingWorker更新JTextArea

Question

I'm trying use the SwinWorker to update one TextArea with the status of the execution of one button actionPerform method.

I get various samples from internet and nothing work form me. Anybody can help me?

bellow my button method:

private void buttonActionPerformed(java.awt.event.ActionEvent evt) {                                                
        atualizaTextArea("", true);
        button.setEnabled(false);

        SearchDataBase cd = new SearchDataBase();
        textAreaField.setForeground(Color.BLUE);
        try {
            refreshTextArea("......Process Started......\n\n", true);
            cd.search();
            String textt = textAreaField.getText();
            refreshTextArea("Finish\n\n", false);
        } catch (Exception e) {
            button.setEnabled(true);
            StringWriter errors = new StringWriter();
            e.printStackTrace(new PrintWriter(errors));

            textAreaField.setText("Error - Contact the developer");
            textAreaField.setForeground(Color.red);
        }

        if (comboBoxSearchType.getSelectedIndex() == 1) {
            try {
                refreshTextArea("......History search started (too slow!!)......\n\n", false);
                cd.searchHistoryTable(dateChoserPesquisa.getDate().getTime());
                refreshTextArea("Finish\n\n", false);
            } catch (Exception e) {
                button.setEnabled(true);
                StringWriter errors = new StringWriter();
                e.printStackTrace(new PrintWriter(errors));

                textAreaField.setText("Error - Contact the developer");
                textAreaField.setForeground(Color.red);
            }
        }
        refreshTextArea("...............Finish..............", false);
        button.setEnabled(true);
    }

TextAreaAviso is the JtextArea that I'm trying to update.

refreshTextArea(String, boolean) is the method that I have created to update the JTextArea

  private void refreshTextArea(String text, boolean rep) {
        this.texttt = text;
        this.replace = rep;


        // define a SwingWorker to run in background  
        SwingWorker<String, String> worker = new SwingWorker<String, String>() {
            @Override
            public String doInBackground() {
                String t = textAreaField.getText();
                if (replace) {
                    publish(texttt);
                    t = texttt;
                } else {
                    publish(t + texttt);
                    t+= texttt;
                }
                System.out.println(texttt);

                return "";
            }

            @Override
            protected void process(final List<String> chunks) {
                for (String text : chunks) {
                    TextAreaAviso.setText(texttt);
                    System.out.println("HERE!!!!");
                }
            }

        };
        worker.execute();

       // (new AtualizaTextArea(TextAreaAviso, texto, replace)).execute();
    }

In this case I have created all process in the method scope, but I was tried using a separated class, as bellow:

private void refreshTextArea(String text, boolean rep) {
       (new RefreshTextArea(TextAreaAviso, texto, replace)).execute();
 }

class RefreshTextArea extends SwingWorker<Integer, String> {

    private JTextArea textArea;
    private String texto;
    private boolean replace;

    public RefreshTextArea(JTextArea textArea, String texto, boolean replace) {
        this.textArea = textArea;
        this.texttt = texto;
        this.replace = replace;
    }

    @Override
    protected Integer doInBackground() throws Exception {

        int i = 0;
        String t = "";
        if (!replace) {
            t = texttt + textArea.getText();
        } else {
            t = texttt;
        }

        System.out.println(t);
        publish(t);

        return i;
    }

    @Override
    protected void process(final List<String> chunks) {
        for (String text : chunks) {
            textArea.setText(texttt);
        }
    }
}

In both implementations I have tried using with and without execution of revalidate method of textarea. In both implementations I have tried update the textarea value in doBackground method and/or process method.

Answer 1

Your SwingWorker should not access or update the JTextArea in your implementation of doInBackground() . Instead publish() intermediate results and update the JTextArea only in process() . Moreover, setText() will have the effect of replacing the existing text; you may want append() instead. A complete example is shown here . Note that BackgroundTask has access to the JTextArea in the enclosing scope, but you can also pass it as a parameter to the SwingWorker .