jTextArea追加无法正常工作

Question

I have a scrollpane in a panel and a jtextarea under the scrollpane. jtextarea append is not working

I am using this for logging purpose.

JPanel panel_1 = new JPanel();
tabbedPane.addTab("Logs", null, panel_1, null);
panel_1.setLayout(null);

JScrollPane scrollPane_1 = new JScrollPane();
scrollPane_1.setBounds(0, 0, 672, 303);
panel_1.add(scrollPane_1);

JTextArea jTextArea = new JTextArea(100,200);
jTextArea.setEditable(false);
jTextArea.setVisible(true);
scrollPane_1.add(jTextArea);
jTextArea.append("Hello");

Answer 1

scrollPane_1.add(jTextArea);

Don't add components to a scrollpane. The component needs to be added to the viewport of the scrollpane.

The easiest way to do this is to use:

JTextArea jTextArea = new JTextArea(100,200);
jTextArea.setEditable(false);
jTextArea.setVisible(true);
//scrollPane_1.add(jTextArea);
jTextArea.append("Hello");

JScrollPane scrollPane_1 = new JScrollPane(jTextArea);
scrollPane_1.setBounds(0, 0, 672, 303);
panel_1.add(scrollPane_1);

The other way to do this is to use:

JScrollPane scrollPane_1 = new JScrollPane();
scrollPane_1.setViewportView( jTextArea );

Also you should note when you create a text area the parameters are row/columns, not pixels so your values are too large. I would suggest something like:

//JTextArea jTextArea = new JTextArea(100,200);
JTextArea jTextArea = new JTextArea(30,10);

Finally you should not be setting the bounds of the scrollpane. Swing was designed to be used with layout managers. The layout manager will determine the size of the scrollpane based on the size of the text area:

//scrollPane_1.setBounds(0, 0, 672, 303);