private void fileChanged() {
		if (listener != null) {
			String file = filenameTextField.getText();
			if (file.length() == 0) {
				listener.fileChanged(null);
			}
			else {
				listener.fileChanged(new File(file));
			}
		}
	}
Sets the file filter.
@param filter the new file filter
Ghidra/Framework/Docking/src/main/java/docking/widgets/filechooser/GhidraFileChooserPanel.java