java - 画出不断变化的画面

Question

我正在尝试对老虎机进行编程。所以，我做了一个JPanel，在其中我覆盖了该paintComponent()方法。

public void paintComponent(Graphics g)
{
    Graphics2D g2 = (Graphics2D)g;

    g2.drawImage(backImage, 0, 0, this.getWidth(), this.getHeight(),null); // Background
    if(slot1On) //Slot Machine
    {
        g2.drawImage(getSlot1(masterCount), 26, 50,slotSizeW,slotSizeH, null);
    }
    else
    {
        g2.drawImage(getSlot1(slot1Pos), 26, 50,slotSizeW,slotSizeH, null);
    }
    g2.setColor(Color.WHITE); // Text
    g2.setFont(new Font(lblAction.getFont().getName(),Font.BOLD,16));
    g2.drawString("Press Space to stop the wheel!", 32, 25);
    int i,j;
    for(i=0;i<3;i++) // Lines on the slot machine
    {
        g2.setColor(new Color(0,0,0,0.9f));
        g2.fillRect(27+ 12 * i + slotSizeW * i, 50 + slotSizeH/2-1, slotSizeW, 3);
        g2.fillRect(28+ 12 * i + slotSizeW * i, 50 +slotSizeH/2-4, 3,9);
        g2.fillRect(22+ 12 * i + slotSizeW * (i +1) , 50 +slotSizeH/2-4, 3, 9);
        for(j=0;j<8;j++)
        {
            if(j < 4)
            {
                g2.setColor(new Color(0,0,0,0.9f - j * 0.1f));
                g2.fillRect(26 + 12 * i + slotSizeW * i, 50 + j * 4, slotSizeW, 4); 
            }
            else
            {
                g2.setColor(new Color(0,0,0,0.9f - (8 - j) * 0.1f));
                g2.fillRect(26+ 12 * i + slotSizeW * i, 50 + slotSizeH - (8 - j) * 4,    slotSizeW, 4); 
            }
        }
    }  
}

但是，只要老虎机轮子移动，我在老虎机后尝试绘制的所有内容都不会显示，如图所示：

那么，为什么它们不能正确显示呢？

Answer 1

试试这个：

public void paintComponent(Graphics g)
{
super.paintComponent(g);
//the rest of your painting here
}