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File preview and checking in file choosers



It is possible to add a preview in a Java JFileChooser to throw an eye at the files during the selection.

chooser = new JFileChooser(Settings.getProperty("heterofor.species.path", PathManager.getInstallDir()));
new FileAccessory(chooser);

The preview (here on the right side) tries to shows the file content

Checking file format in the file chooser: method 1 - simple

If the file is to be read with a file loader (i.e. jeeb.lib.util RecordSet or FileLoader), it is possible to pass the file loader class to a CheckingFileChooser. All the listed files will be evaluated with the file loader to evaluate their compatibility.

The compatible files will be associated to a green mark, the others to a red mark.

Note: this process only checks the format of the file, there may still be errors at effective load time if the read values are not correct.

// fc-8.11.2017 CheckingFileChooser tells user which files are supposed
// to be correct
JFileChooser chooser = CheckingFileChooser.getInstance(
		Settings.getProperty("heterofor.samsaraLightPath", PathManager.getDir("data") + File.separator
				+ "heterofor"), SLSettingsLoader.class);
int returnVal = chooser.showDialog(this, null); // null: approveButton text was already set
if (returnVal == JFileChooser.APPROVE_OPTION && chooser.getSelectedFile().exists())


It is also possible to use the CheckingFileChooser instead of the JFileChooser to check during selection which files will be loaded without error. The process relies on a method to be redefined called check (File f). When the file given to this method is correct, the method must return true.

The result is a green check mark associated to each correct file, and a red mark for those which will not load correctly.

The Preview is always shown in the CheckingFileChooser, it will show the mark for the selected file.

Warning: some Java look and feels do not show the icon for each file during selection (e.g. GTK+ under Linux). In this case, the mark can still be seen in the FileAccessory preview.

// fc-4.12.2017 A file chooser showing which files can be loaded
JFileChooser chooser = new CheckingFileChooser(Settings.getProperty("capsis.inventory.path",
		PathManager.getDir("data"))) {
	public boolean check(File f) {
		String fileName = f.getAbsolutePath();
		try {
			// Use fake objects to avoid side effects
			Samsa2Model modelFake = new Samsa2Model();
			Samsa2InitialParameters ipFake = modelFake.getSettings();
			// Check if the file can be loaded
			ipFake.vParamMS.virtualStand = false;
			ipFake.fileName = fileName;
			// Seems ok
			return true;
		} catch (Throwable e) {
			// Seems problematic
			return false;

The green and red marks in Windows' Look & FeelA green mark shows which file will be loaded correctlyUnder GTK+ L&F, the mark can be seen in the file preview

Fast checking

This is a proposal of a simple check () implementation for the CheckingFileChooser when the file is to be loaded by a RecordSet / FileLoader.

It will check the file format interpretation by the loader but will not go further: an error might still happen later during effective file loading, when interpreting the content of the fields and lines.

Note: jeeb.lib.util.RecordSet is a tool to build text file loaders quickly, by specifying the expected line formats in objects extending the Record class. Giving a fileName to the tool, it will use introspection to check if the lines match the given Records and turn the file into a List of Records, easying their interpretation in a load () method called after.

See also jeeb.lib.util.fileloader.FileLoader for a variant.

String path = inventoryFileName.getText();
JFileChooser chooser = new CheckingFileChooser(path) {
	public boolean check(File file) {
		try {
			// Just checks if the loader loads, do not check until Plot creation
			new Lub2InventoryLoader(file.getAbsolutePath());
			return true;
		} catch (Exception e) {
			return false;

The files with a green mark are supposed to be loaded correctly if selected

file_preview_and_checking_in_file_chooser.1512748619.txt ยท Last modified: 2017/12/08 15:56 by coligny