JPanel image Background

在这里找到的。
http://topic.csdn.net/u/20090326/21/a4ca9989-631e-42d1-8f4e-7d6cd6efa14f.html

原来核心是重载paintComponent绘制方法。原来的代码给我改过了。先看原代码会好点，他的注释很详细！

import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;

import javax.swing.JPanel;

public class JImagePanel extends JPanel
{
	public static final int TENSILE = 1; // 拉伸
	public static final int CENTRE = 2; // 居中
	public static final int TILED = 3; // 平铺

	private Image backGround = null;
	private int displayMode = 2;

	public JImagePanel(String image, int displayMode)
	{
		this(Toolkit.getDefaultToolkit().getImage(image), displayMode);
	}

	public JImagePanel(Image image, int displayMode)
	{
		super();
		this.displayMode = displayMode;
		backGround = image;
	}

	protected void paintComponent(Graphics g)
	{
		super.paintComponent(g);
		if (backGround != null)
		{
			int width = getWidth();
			int height = getHeight();
			int imageWidth = backGround.getWidth(this);
			int imageHeight = backGround.getHeight(this);

			switch (displayMode)
			{
				case CENTRE:
				{
					int x = (width - imageWidth) / 2;
					int y = (height - imageHeight) / 2;
					g.drawImage(backGround, x, y, this);
					break;
				}
				case TILED:
				{
					for (int ix = 0; ix < width; ix += imageWidth)
					{
						for (int iy = 0; iy < height; iy += imageHeight)
						{
							g.drawImage(backGround, ix, iy, this);
						}
					}
					break;
				}
				case TENSILE:
				{
					g.drawImage(backGround, 0, 0, width, height, this);
					break;
				}
			}
		}
	}
}