如何在Swing中顯示檔案選擇器以只選擇的影象？

下面的範例展示了如何在swing的應用程式中顯示「開啟檔案」對話方塊，以便僅選擇影象檔案。

使用以下API -

• JFileChooser - 建立檔案選擇器。
• JFileChooser.addChoosableFileFilter(ImageFilter) - 僅為影象新增自定義檔案過濾器。
• JFileChooser.setAcceptAllFileFilterUsed(true) - 禁用預設過濾器。

範例

package com.yiibai.swingdemo;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.filechooser.FileFilter;

public class SwingTester {
    public static void main(String[] args) {
        createWindow();
    }

    private static void createWindow() {
        JFrame frame = new JFrame("Swing檔案選擇(僅選圖片檔案)");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        createUI(frame);
        frame.setSize(560, 200);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private static void createUI(final JFrame frame) {
        JPanel panel = new JPanel();
        LayoutManager layout = new FlowLayout();
        panel.setLayout(layout);
        JButton button = new JButton("點選這裡開始~");
        final JLabel label = new JLabel();
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                JFileChooser fileChooser = new JFileChooser();
                fileChooser.addChoosableFileFilter(new ImageFilter());
                fileChooser.setAcceptAllFileFilterUsed(false);

                int option = fileChooser.showOpenDialog(frame);
                if (option == JFileChooser.APPROVE_OPTION) {
                    File file = fileChooser.getSelectedFile();
                    label.setText("選擇了以下圖片資訊: " + file.getName());
                } else {
                    label.setText("Open command canceled");
                }
            }
        });

        panel.add(button);
        panel.add(label);
        frame.getContentPane().add(panel, BorderLayout.CENTER);
    }
}

class ImageFilter extends FileFilter {
    public final static String JPEG = "jpeg";
    public final static String JPG = "jpg";
    public final static String GIF = "gif";
    public final static String TIFF = "tiff";
    public final static String TIF = "tif";
    public final static String PNG = "png";

    @Override
    public boolean accept(File f) {
        if (f.isDirectory()) {
            return true;
        }

        String extension = getExtension(f);
        if (extension != null) {
            if (extension.equals(TIFF) || extension.equals(TIF) || extension.equals(GIF) || extension.equals(JPEG)
                    || extension.equals(JPG) || extension.equals(PNG)) {
                return true;
            } else {
                return false;
            }
        }
        return false;
    }

    @Override
    public String getDescription() {
        return "Image Only";
    }

    String getExtension(File f) {
        String ext = null;
        String s = f.getName();
        int i = s.lastIndexOf('.');

        if (i > 0 && i < s.length() - 1) {
            ext = s.substring(i + 1).toLowerCase();
        }
        return ext;
    }
}

執行上面範例程式碼，得到以下結果：