import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Image;
import java.awt.Insets;
import java.io.File;
import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class ThumbnailPanel extends JPanel {

    private File PraFile;               //根目录
    private String[] SubFile;           //根目录下文件名
    private String[] ImgPath;           //根目录下能识别图像
    private ImageIcon[] Img;            //图片文件
    private Image[] Thumbnail;          //缩略图
    private int ImgCount;               //图片数目
    private JPanel[] JpThum;            //用于装载缩略图+文件名
    private JPanel[] JpPic;             //用于装载缩略图
    private JLabel[] Pic;
    private JPanel[] JpTex;
    private JLabel[] Name;

    ThumbnailPanel(String PraPath) {
        ImgPath = new String[1000];
        Img = new ImageIcon[1000];
        Thumbnail = new Image[1000];
        ImgCount = 0;

        JpThum = new JPanel[1000];
        Pic = new JLabel[1000];
        Name = new JLabel[1000];
        JpPic = new JPanel[1000];
        JpTex = new JPanel[1000];

        loadImg(PraPath);
        paintPanel();

    }

    public Image getThumbnail(ImageIcon Img) {                  //根据图片宽和高的比例选择缩放
        Image img;
        if (Img.getIconHeight() > Img.getIconWidth()) {
            img = Img.getImage().getScaledInstance(-100, 100, 1);
        } else {
            img = Img.getImage().getScaledInstance(100, -100, 1);
        }
        return img;
    }

    public void loadImg(String PraPath) {                       //将根目录下图片格式的文件读入图片数组

        //装载目录下图片文件名
        PraFile = new File(PraPath);
        SubFile = PraFile.list();
        for (int i = 0; i < SubFile.length; ++i) {
            if (SubFile[i].contains(".jpeg") || SubFile[i].contains(".png") || SubFile[i].contains(".jpg") || SubFile[i].contains(".gif")) {
                ImgPath[ImgCount++] = "D:/javapic/" + SubFile[i];
            }
        }
        //装载图片和缩略图
        for (int i = 0; i < ImgCount; ++i) {
            Img[i] = new ImageIcon(ImgPath[i]);
            Thumbnail[i] = getThumbnail(Img[i]);
        }
    }

    public void paintPanel() {                                  //载入到缩略图面板

        for (int i = 0; i < ImgCount; ++i) {
            Pic[i] = new JLabel(new ImageIcon(Thumbnail[i]));
            Name[i] = new JLabel(ImgPath[i].replace("D:/javapic/", ""), JLabel.CENTER);
            Name[i].setBorder(BorderFactory.createEmptyBorder());

            JpThum[i] = new JPanel();

            JpPic[i] = new JPanel(new BorderLayout());
            JpPic[i].add(Pic[i], "South");
            JpPic[i].setPreferredSize(new Dimension(100, 100));

            JpTex[i] = new JPanel(new BorderLayout());
            JpTex[i].add(Name[i], "North");
            JpTex[i].setPreferredSize(new Dimension(100, 35));

            Dimension a = new Dimension(100, 135);
            JpThum[i].setPreferredSize(a);
            JpThum[i].add(JpPic[i], "North");
            JpThum[i].add(JpTex[i], "South");
        }
        
        GridBagLayout gridbag = new GridBagLayout();
        GridBagConstraints c = new GridBagConstraints(0,0,1,1,0,0,GridBagConstraints.EAST,GridBagConstraints.NONE,new Insets(150,150,150,150),100,100);
       
       
         for (int i = 0; i < ImgCount; ++i) {
            gridbag.setConstraints(JpThum[i], c);//结果表明用了跟直接add是一样的
            add(JpThum[i]);
        }
        
    }

    public static void main(String[] args) {
        ThumbnailPanel tp = new ThumbnailPanel("D:/javapic/");
        JFrame jf = new JFrame();
        jf.add(tp);
        jf.pack();
        jf.setSize(600, 600);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setVisible(true);
    }
}