如何使用 JFileChooser 保存文件？

Question

I have a method in my application called "Save as" which Saves the image of my application on computer my into a file. I used the JFileChooser to let the users choose their desired location for saving the file. The problem is unless user explicitly types in the file format, it saves the file with no extension. How can I have formats like jpg, png in the File Type drop down menu.

and, how can i get extension from the File Type drop menu for saving my image file.

 ImageIO.write(image,extension,file);

Answer 1

Finally, I solved my own problem:

JFileChooser fc = new JFileChooser("C:/");
fc.addChoosableFileFilter(new JPGSaveFilter());
fc.addChoosableFileFilter(new JPEGSaveFilter());
fc.addChoosableFileFilter(new PNGSaveFilter());
fc.addChoosableFileFilter(new GIFSaveFilter());
fc.addChoosableFileFilter(new BMPSaveFilter());
fc.addChoosableFileFilter(new WBMPSaveFilter()); 

int retrieval = fc.showSaveDialog(null);

if (retrieval == JFileChooser.APPROVE_OPTION) {
  String ext = "";

  String extension = fc.getFileFilter().getDescription();

  if (extension.equals("*.jpg,*.JPG")) {
    ext = ".jpg";
  } else if (extension.equals("*.png,*.PNG")) {
    ext = ".png";
  } else if (extension.equals("*.gif,*.GIF")) {
    ext = ".gif";
  } else if (extension.equals("*.wbmp,*.WBMP")) {
    ext = ".wbmp";
  } else if (extension.equals("*.jpeg,*.JPEG")) {
    ext = ".jpeg";
  } else if (extension.equals("*.bmp,*.BMP")) {
    ext = ".bmp";
  }
}

Example Filter:

package example

import java.io.File;
import javax.swing.filechooser.FileFilter;

class JPGSaveFilter extends FileFilter {
  @Override
  public boolean accept(File f) {
    if (f.isDirectory()) {
      return false;
    }

    String s = f.getName().toLowerCase();

    return s.endsWith(".jpg");
  }

  @Override
  public String getDescription() {
    return "*.jpg,*.JPG";
  }
}

Answer 2

Prepare the file chooser filters:

    jFileChooser.addChoosableFileFilter(new FileNameExtensionFilter("File X (.xxx)", "xxx"));
    jFileChooser.addChoosableFileFilter(new FileNameExtensionFilter("File Y (.yyy)", "yyy"));
    jFileChooser.addChoosableFileFilter(new FileNameExtensionFilter("File Z (.zzz)", "zzz"));

    // set default type
    jFileChooser.setFileFilter(jFileChooser.getChoosableFileFilters()[0]);

    // set default file
    jFileChooser().setSelectedFile(defaultFile);

After approve validation

//Add extension to Selected file 
File file = new File(jFileChooser().getSelectedFile().getCanonicalPath() + "." + ((FileNameExtensionFilter) jFileChooser().getFileFilter()).getExtensions()[0]);

Could be a good idea validate if the selected file come with extension.

Answer 3

使用 JFileChoose.SetFileFilter 示例： http : //www.java2s.com/Code/JavaAPI/javax.swing/JFileChoosersetFileFilterFileFilterfilter.htm

Answer 4

I think I got better solution. Will explain it with sample code fragments.

This is how I set file filter:
jFileChooser.setFileFilter(new FileNameExtensionFilter(".txt", "txt")); .

After this the main saving line:
textArea1.write(new BufferedWriter(new FileWriter(jFileChooser.getSelectedFile().getAbsolutePath() + jFileChooser.getFileFilter().getDescription().replace("All Files", "")))); .

Of course the most important is this fragment: jFileChooser.getSelectedFile().getAbsolutePath() + jFileChooser.getFileFilter().getDescription().replace("All Files", "") .

The only thing I don't like is, that I could not find any method like 'getExtension' which means that You cannot have any nice description without unnecessary troubles with strings.

---

Ok, got it. You can do something like that: jFileChooser.getFileFilter().toString().replaceFirst(".*extensions=\\\\[(.*)]]", ".$1").replaceFirst(".*AcceptAllFileFilter.*", "") .

Unfortunately it's not so beautiful, but seems to work like a charm.