在我的Swing小代码中需要帮助纠正绘画

public void paint(Graphics g)
    {
        super.paint(g);
        Graphics2D g2=(Graphics2D)g;
        LinearGradientPaint p=new LinearGradientPaint(0,0,0,height,new float[]{0f,1f},new Color[]{new Color(0.2498f,0.2498f,0.2498f,0.3f),new Color(0.1598f,0.1598f,0.1598f,0.8f)});
        g2.setPaint(p);
        g2.fillRect(0, 0, width,height);
    }

When you are painting with paint() function you are painting with graphics instance g after your child component panel is painted. Go to the source of the super.paint(g) function and you will see that three subsequent function is being called:

• protected void paintComponent(Graphics g): this one paint your component, e,g.:background
• protected void paintBorder(Graphics g): this one paints the border of the component
• protected void paintChildren(Graphics g): This one paints the children of the component in it

So after this super.paint(g) call, anything you draw will appear above all the painting made with these three above function: hence above the children components, for your context the panel with blue background.

Now, a solution would be:

 public void paint(Graphics g)
{

            Graphics2D g2 = (Graphics2D)g.create();
                 // note, we are creating a graphics object here for safe painting
            LinearGradientPaint p=new LinearGradientPaint(0,0,0,height,new float[]{0f,1f},new Color[]{new Color(0.2498f,0.2498f,0.2498f,0.3f),new Color(0.1598f,0.1598f,0.1598f,0.8f)});
            g2.setPaint(p);
            g2.fillRect(0, 0, width,height);
            g2.dispose(); // disposing the object which we created 

            super.paint(g);

    }

但是，您可以使用诸如之类的类而不是这样做，MyCanvas extends JComponent并覆盖其paintComponent(Graphics)功能并在其内部进行绘制。然后，您可以将实例设置MyCanvas为JFrame使用该setContentPane(component)函数的内容窗格。

看看 A Closer Look at the Paint Mechanism

编辑您的用例的一个小型演示实现：

class AMyContainer extends JComponent
{

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g); 

        Graphics2D g2 = (Graphics2D)g.create();
                 // note, we are creating a graphics object here for safe painting
            LinearGradientPaint p=new LinearGradientPaint(0, 0, 0, getHeight(),new float[]{0f,1f},new Color[]{new Color(0.2498f,0.2498f,0.2498f,0.3f),new Color(0.1598f,0.1598f,0.1598f,0.8f)});
            g2.setPaint(p);
            g2.fillRect(0, 0, getWidth(), getHeight());
            g2.dispose(); // disposing the object which we created 
    }

}

class Home extends JFrame
{
    int width=GraphicsEnvironment.getLocalGraphicsEnvironment().getMaximumWindowBounds().width;
    int height=GraphicsEnvironment.getLocalGraphicsEnvironment().getMaximumWindowBounds().height;
    public Home()
    {
        super("WiND");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setUndecorated(true);
        setSize(width,height);
        setBackground(new Color(0,0,0,0));
        setUndecorated(true);

        JComponent container = new AMyContainer();
        container.setLayout(new FlowLayout());
        add(container);

        JPanel p=new JPanel();
        p.setBackground(new Color(0x0D70E8));
        p.setPreferredSize(new Dimension(width,height/10));
        container.add(p);
    }



    public static void main(String[] args)
    {
        new Home().setVisible(true);

    }
}