如何正确在框架/面板上绘画？

Question

I've tried many variations of everything at the bottom of this class and so far nothing works. Occasionally an edit will cause the print statement to work, but the window just always opens at a size that isn't even the one I set it up and stays blank. I don't know what's wrong with it. I'm trying to print 1024 rectangles on my window with a pause inbetween each print. The values are right, they're just not getting painted for some reason. Changing the method to paintComponent doesn't seem to do much either. The code is long, so here's a pastebin: http://pastebin.com/ridipz3X . The important stuff is at the end though:

JFrame frm = new TestEnvironment();
                        frm.setSize(1152, 1152);
                        frm.setVisible(true);
                        JPanel panel = new JPanel();
                        frm.add(panel);
                        t = 0;
                        i = 0;
                        while (t < x - 1) {

                                panel.repaint();

                                j++;
                                t++;
                                Thread.sleep(10000);
                        }

                } catch (Exception e) {
                        System.out.println(e);
                        e.printStackTrace();
                }
        }
public void paint(Graphics g) {
                g.setColor(Color.black);
                g.setColor(getBackground());
                g.fillRect(0, 0, getWidth(), getHeight());
                g.setColor(getForeground());
                try {
                        for (int h = 0; h < 1152; h++) {
                                g.drawRect(h, 0, (int) (((ampArray[h][j]) / maxFreq) * 1152),
                                                1);
                                g.fillRect(h, 0, (int) (((ampArray[h][j]) / maxFreq) * 1152),
                                                1);
                                System.out.println(ampArray[h][j]);
                        }
                } finally {
                        g.dispose();
                }
        }
}

Thanks

Answer 1

Painting is typically done from within the paintComponent method of a component that extends from JComponent , typically a JPanel , depending on your needs.

You should refrain from overriding paint of top level containers like JFrame for a number of reasons, including, they are not double buffered, you will end up painting under the window decorations, Swing windows contain a number of layered components which make up the viewable content of a window, meaning that you will either paint over or under this content, which just gets messy.

You should never dispose of Graphics context that you did not create yourself.

Swing is a single threaded environment, that is, anything that blocks the thread (such as Thread.sleep , will prevent it from process new repaint requests and events, making it look like you program has stopped.

Swing is also not thread safe. This means that you are required to ensure that all updates and interactions with the UI are done from within the context of the Event Dispatching Thread.

Animation is typically achieved through the use of a javax.swing.Timer or SwingWorker depending on the complexity of the animation. You can use a Thread , but it complicates the issues as you will be required to ensure that all updates to the UI (directly or otherwise) are done from within the context of the EDT manually.

Take a look at:

• Performing Custom Painting
• Painting in AWT and Swing
• Concurrency in Swing