JexerImageViewer.java

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.imageio.ImageIO;

import jexer.TAction;
import jexer.TApplication;
import jexer.TDesktop;
import jexer.TDirectoryList;
import jexer.TImage;
import jexer.backend.SwingTerminal;
import jexer.bits.CellAttributes;
import jexer.bits.GraphicsChars;
import jexer.event.TKeypressEvent;
import jexer.event.TResizeEvent;
import jexer.menu.TMenu;
import jexer.ttree.TDirectoryTreeItem;
import jexer.ttree.TTreeItem;
import jexer.ttree.TTreeViewWidget;
import static jexer.TKeypress.*;

/**
 * Implements a simple image thumbnail file viewer.  Much of this code was
 * stripped down from TFileOpenBox.
 */
public class JexerImageViewer extends TApplication {

    /**
     * Main entry point.
     */
    public static void main(String [] args) throws Exception {
        JexerImageViewer app = new JexerImageViewer();
        (new Thread(app)).start();
    }

    /**
     * Public constructor chooses the ECMA-48 / Xterm backend.
     */
    public JexerImageViewer() throws Exception {
        super(BackendType.XTERM);

        // The stock tool menu has items for redrawing the screen, opening
        // images, and (when using the Swing backend) setting the font.
        addToolMenu();

        // We will have one menu containing a mix of new and stock commands
        TMenu fileMenu = addMenu("&File");

        // Stock commands: a new shell, exit program.
        fileMenu.addDefaultItem(TMenu.MID_SHELL);
        fileMenu.addSeparator();
        fileMenu.addDefaultItem(TMenu.MID_EXIT);

        // Filter the files list to support image suffixes only.
        List<String> filters = new ArrayList<String>();
        filters.add("^.*\\.[Jj][Pp][Gg]$");
        filters.add("^.*\\.[Jj][Pp][Ee][Gg]$");
        filters.add("^.*\\.[Pp][Nn][Gg]$");
        filters.add("^.*\\.[Gg][Ii][Ff]$");
        filters.add("^.*\\.[Bb][Mm][Pp]$");
        setDesktop(new ImageViewerDesktop(this, ".", filters));
    }

}

/**
 * The desktop contains a tree view on the left, list of files on the top
 * right, and image view on the bottom right.
 */
class ImageViewerDesktop extends TDesktop {

    /**
     * The left-side tree view pane.
     */
    private TTreeViewWidget treeView;

    /**
     * The data behind treeView.
     */
    private TDirectoryTreeItem treeViewRoot;

    /**
     * The top-right-side directory list pane.
     */
    private TDirectoryList directoryList;

    /**
     * The bottom-right-side image pane.
     */
    private TImage imageWidget;

    /**
     * Public constructor.
     *
     * @param application the TApplication that manages this window
     * @param path path of selected file
     * @param filters a list of strings that files must match to be displayed
     * @throws IOException of a java.io operation throws
     */
    public ImageViewerDesktop(final TApplication application, final String path,
        final List<String> filters) throws IOException {

        super(application);
        setActive(true);

        // Add directory treeView
        treeView = addTreeViewWidget(0, 0, getWidth() / 2, getHeight(),
            new TAction() {
                public void DO() {
                    TTreeItem item = treeView.getSelected();
                    File selectedDir = ((TDirectoryTreeItem) item).getFile();
                    try {
                        directoryList.setPath(selectedDir.getCanonicalPath());
                        if (directoryList.getList().size() > 0) {
                            setThumbnail(directoryList.getPath());
                        } else {
                            if (imageWidget != null) {
                                getChildren().remove(imageWidget);
                            }
                            imageWidget = null;
                        }
                        activate(treeView);
                    } catch (IOException e) {
                        // If the backend is Swing, we can emit the stack
                        // trace to stderr.  Otherwise, just squash it.
                        if (getScreen() instanceof SwingTerminal) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        );
        treeViewRoot = new TDirectoryTreeItem(treeView, path, true);

        // Add directory files list
        directoryList = addDirectoryList(path, getWidth() / 2 + 1, 0,
            getWidth() / 2 - 1, getHeight() / 2,

            new TAction() {
                public void DO() {
                    setThumbnail(directoryList.getPath());
                }
            },
            new TAction() {

                public void DO() {
                    setThumbnail(directoryList.getPath());
                }
            },
            filters);

        if (directoryList.getList().size() > 0) {
            activate(directoryList);
            setThumbnail(directoryList.getPath());
        } else {
            activate(treeView);
        }
    }

    /**
     * Handle window/screen resize events.
     *
     * @param event resize event
     */
    @Override
    public void onResize(final TResizeEvent event) {

        // Resize the tree and list
        treeView.setY(1);
        treeView.setWidth(getWidth() / 2);
        treeView.setHeight(getHeight() - 1);
        treeView.onResize(new TResizeEvent(event.getBackend(),
                TResizeEvent.Type.WIDGET,
                treeView.getWidth(),
                treeView.getHeight()));
        treeView.getTreeView().onResize(new TResizeEvent(event.getBackend(),
                TResizeEvent.Type.WIDGET,
                treeView.getWidth() - 1,
                treeView.getHeight() - 1));
        directoryList.setX(getWidth() / 2 + 1);
        directoryList.setY(1);
        directoryList.setWidth(getWidth() / 2 - 1);
        directoryList.setHeight(getHeight() / 2 - 1);
        directoryList.onResize(new TResizeEvent(event.getBackend(),
                TResizeEvent.Type.WIDGET,
                directoryList.getWidth(),
                directoryList.getHeight()));

        // Recreate the image
        if (imageWidget != null) {
            getChildren().remove(imageWidget);
        }
        imageWidget = null;
        if (directoryList.getList().size() > 0) {
            activate(directoryList);
            setThumbnail(directoryList.getPath());
        } else {
            activate(treeView);
        }
    }

    /**
     * Handle keystrokes.
     *
     * @param keypress keystroke event
     */
    @Override
    public void onKeypress(final TKeypressEvent keypress) {

        if (treeView.isActive() || directoryList.isActive()) {
            if ((keypress.equals(kbEnter))
                || (keypress.equals(kbUp))
                || (keypress.equals(kbDown))
                || (keypress.equals(kbPgUp))
                || (keypress.equals(kbPgDn))
                || (keypress.equals(kbHome))
                || (keypress.equals(kbEnd))
            ) {
                // Tree view will be changing, update the directory list.
                super.onKeypress(keypress);

                // This is the same action as treeView's enter.
                TTreeItem item = treeView.getSelected();
                File selectedDir = ((TDirectoryTreeItem) item).getFile();
                try {
                    if (treeView.isActive()) {
                        directoryList.setPath(selectedDir.getCanonicalPath());
                    }
                    if (directoryList.getList().size() > 0) {
                        activate(directoryList);
                        setThumbnail(directoryList.getPath());
                    } else {
                        if (imageWidget != null) {
                            getChildren().remove(imageWidget);
                        }
                        imageWidget = null;
                        activate(treeView);
                    }
                } catch (IOException e) {
                    // If the backend is Swing, we can emit the stack trace
                    // to stderr.  Otherwise, just squash it.
                    if (getScreen() instanceof SwingTerminal) {
                        e.printStackTrace();
                    }
                }
                return;
            }
        }

        // Pass to my parent
        super.onKeypress(keypress);
    }

    /**
     * Draw me on screen.
     */
    @Override
    public void draw() {
        CellAttributes background = getTheme().getColor("tdesktop.background");
        putAll(' ', background);

        vLineXY(getWidth() / 2, 0, getHeight(),
            GraphicsChars.WINDOW_SIDE, getBackground());

        hLineXY(getWidth() / 2, getHeight() / 2, (getWidth() + 1) / 2,
            GraphicsChars.WINDOW_TOP, getBackground());

        putCharXY(getWidth() / 2, getHeight() / 2,
            GraphicsChars.WINDOW_LEFT_TEE, getBackground());
    }

    /**
     * Set the image thumbnail.
     *
     * @param file the image file
     */
    private void setThumbnail(final File file) {
        if (file == null) {
            return;
        }
        if (!file.exists() || !file.isFile()) {
            return;
        }

        BufferedImage image = null;
        try {
            image = ImageIO.read(file);
        } catch (IOException e) {
            // If the backend is Swing, we can emit the stack trace to
            // stderr.  Otherwise, just squash it.
            if (getScreen() instanceof SwingTerminal) {
                e.printStackTrace();
            }
            return;
        }

        if (imageWidget != null) {
            getChildren().remove(imageWidget);
        }
        int width = getWidth() / 2 - 1;
        int height = getHeight() / 2 - 1;

        imageWidget = new TImage(this, getWidth() - width,
            getHeight() - height, width, height, image, 0, 0, null);

        // Resize the image to fit within the pane.
        imageWidget.setScaleType(TImage.Scale.SCALE);

        imageWidget.setActive(false);
        activate(directoryList);
    }

}