Java paint（）仅从paintAll（）调用一次

Question

I have the following code being called:

    while(true){
        view.onTick();

        trySleep(55);
    }

The onTick() method is described as such:

    public void onTick() {
    mainFrame.paintAll(mainFrame.getGraphics());
}

Here is where I set up my JFrame and JPanels etc (mainFrame is a JFrame):

    private void runProgramSetup(){
    JPanel canvas = new JPanel();
    canvas.setLayout(new BoxLayout(canvas, BoxLayout.Y_AXIS));
    mainFrame.getContentPane().add(canvas);

    //create the main game panel
    mapPanel = new MapPanel(model, this);
    mapPanel.setPreferredSize(new Dimension(TOTAL_FRAME_WIDTH, MAP_PANEL_HEIGHT));
    mapPanel.setBackground(Color.cyan);

    //create the menu panel
    menuPanel = new MenuPanel(model, this);
    menuPanel.setLayout(new BoxLayout(menuPanel, 0));
    menuPanel.setPreferredSize(new Dimension(TOTAL_FRAME_WIDTH, MENUS_PANEL_HEIGHT));

    //add the panels to the window
    canvas.add(mapPanel);
    canvas.add(menuPanel);

    //make both panels visible
    mapPanel.setVisible(true);
    menuPanel.setVisible(true);
}

Now here is my problem. Everything repaints when repaintAll() is called EXCEPT mapPanel's overridden paint(Graphics g) method:

    @Override
public void paint(Graphics g) {
    transformedImages.transformAndStoreImages(model);
    paintGrid(g);
    paintScenery(g);
    paintElements(g);
    paintDraggedElement(g);
    paintUIOverlay(g);
}

It is only called once. That is it. However, every other component continues to repaint. It is only mapPanel that paints once. Here is what is even more strange. I am running on Ubuntu and get this problem. The rest of my team is running on Macs and they do not have this problem. The only way I have been able to solve this is to replace onTick() with two paint calls:

    public void onTick() {
    mainFrame.repaint();
    mainFrame.paintAll(mainFrame.getGraphics());
}

This is all that has worked for me. I need both calls. Neither works alone. I don't like doing this though obviously because of inefficiency.. :/ Any ideas?

Thanks!

Answer 1

you should be overriding JPanel's

paintComponent(Graphics g)

not paint

Answer 2

The reason mainFrame.repaint() forces the map to refresh is because repaint() calls repaint(0, 0, 0, width, height) , which marks the entire mainFrame 's area to be marked as "dirty" for the RepaintManager . This is designed this way on purpose, because you usually do not want to repaint every pixel in the JFrame just to update a component. So, in onTick() , when mainFrame.paintAll() is being called, my guess is that the mapPanel 's area has not been marked dirty, so the RepaintManager skips it, to save processing time. If you are very sure that you want to repaint the whole mapPanel every time onTick() is called, the simplest way would be to call mapPanel.repaint() inside of your onTick() method. This will mark the whole mapPanel as dirty so it will be redrawn asap. Also, if your menuPanel is just using regular swing JComponents, you don't need to manually cause them to repaint, they will be repainted when their values change, if you are using the API correctly.

I know this is a kind of old question, but I figured I'd answer in case anyone else runs into something similar.