import java.io.*;
import java.nio.file.*;

import javafx.application.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.control.Alert.*;
import javafx.scene.image.*;
import javafx.scene.layout.*;
import javafx.stage.*;
import javafx.stage.FileChooser.*;

/**
 * A program for viewing images.
 * @version 1.40 2017-12-10
 * @author Cay Horstmann
 */
public class ImageViewer extends Application
{
   private static final int MIN_SIZE = 400;

   public void start(Stage stage) throws IOException
   {
      BorderPane pane = new BorderPane();
      MenuBar bar = new MenuBar();
      pane.setTop(bar);
      Menu fileMenu = new Menu("File");
      bar.getMenus().add(fileMenu);
      MenuItem openItem = new MenuItem("Open");
      openItem.setOnAction(event -> load(stage, pane));
      MenuItem exitItem = new MenuItem("Exit");
      exitItem.setOnAction(event -> System.exit(0));
      fileMenu.getItems().addAll(openItem, exitItem);
      stage.setScene(new Scene(pane, MIN_SIZE, MIN_SIZE));
      stage.setTitle("ImageViewer");
      stage.show();
   }

   /**
    * Loads an image.
    * @param stage the stage above which to place the file chooser
    * @param pane the pane into which to place the image view
    */
   public void load(Stage stage, BorderPane pane)
   {
      FileChooser fileChooser = new FileChooser();
      fileChooser.getExtensionFilters().addAll(
            new ExtensionFilter("Image Files", "*.png", "*.jpg", "*.gif"),
            new ExtensionFilter("All Files", "*.*"));
      File file = fileChooser.showOpenDialog(stage);
      if (file != null)
      {
         try
         {
            Path path = file.toPath();
            Image image = new Image(Files.newInputStream(path));
            pane.setCenter(new ImageView(image));
         }
         catch (IOException e)
         {
            Alert alert = new Alert(AlertType.ERROR,
               "Cannot open file.");
            alert.showAndWait();
         }
      }
   }
}