The program seems to crash when trying to open or save file JavaFX

[ShinRyu Kazuto]

I honestly don't know why the program crash every time I tried to open or save a file using this program.
Can anyone point out the problem?
Thank you!

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Orientation;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.ScrollBar;
import javafx.scene.control.TextArea;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.stage.FileChooser;
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
import javafx.scene.control.MenuItem;


public class IO extends Application 
{
    public static void main(String[] args) 
    {
     launch(args);
     }

    @Override
    public void start(Stage primaryStage) throws Exception
    {
     //AnchorPane for textArea
        AnchorPane root = new AnchorPane();
        final TextArea textArea = new TextArea();
        AnchorPane.setTopAnchor(textArea, 0.0);
        AnchorPane.setLeftAnchor(textArea, 0.0);
        AnchorPane.setRightAnchor(textArea, 0.0);
        AnchorPane.setBottomAnchor(textArea, 0.0);
        
      //adding menu
        MenuBar mainMenu = new MenuBar();
        final Menu file = new Menu("File");
        mainMenu.setUseSystemMenuBar(true);
        mainMenu.getMenus().addAll(file);        
        root.getChildren().add(textArea);
        root.getChildren().addAll(mainMenu);
        MenuItem open = new MenuItem("Open");
        MenuItem save = new MenuItem("Save");
        file.getItems().addAll(open,save);
        mainMenu.setUseSystemMenuBar(true);
        
        open.setOnAction(new EventHandler <ActionEvent >() {
         @Override
         public void handle(ActionEvent actionEvent) 
         {
          FileChooser fc = new FileChooser();
             File file = fc.showOpenDialog(primaryStage);
             if (file != null) 
             {
              try {
               Scanner fin = new Scanner(file);
               while (fin.hasNext()) {
                   // read from the file, appending text to a control or other object
                }
               fin.close();
               }
              catch (IOException e) { }
              }
             }
         }); 
        save.setOnAction(new EventHandler <ActionEvent >() 
        {
         @Override
         public void handle(ActionEvent actionEvent) 
         {
          FileChooser fc = new FileChooser();
             File file = fc.showSaveDialog(primaryStage);
             if (file != null) {
              }
             }
         }); 
        
        //Set up stage and scene
        primaryStage.setScene(new Scene( root, 400, 300));
        primaryStage.setTitle("Text Area"); // Set the stage title
        primaryStage.show();
        ScrollBar scrollBar = lookupVerticalScrollBar(textArea);
        scrollBar.setOpacity(0.0);
        scrollBar.visibleProperty().addListener(new ChangeListener<Boolean>() 
        {
         @Override
            public void changed(ObservableValue<? extends Boolean> source,
                                Boolean wasVisible,
                                Boolean isVisible) 
         {
          if (isVisible) 
          {
           textArea.setPrefRowCount(textArea.getPrefRowCount() + 1);
                    textArea.requestLayout();
                    textArea.setWrapText(true);
                    }
          }
         });
        }
    
    private ScrollBar lookupVerticalScrollBar(Node node) 
    {
     if (node instanceof ScrollBar && ((ScrollBar)node).getOrientation() == Orientation.VERTICAL) 
     {
      return (ScrollBar) node;
      }
     if (node instanceof Parent) 
     {
      ObservableList<Node> children = ((Parent) node).getChildrenUnmodifiable();
      for (Node child : children) 
      {
       ScrollBar scrollBar = lookupVerticalScrollBar(child);
       if (scrollBar != null) 
       {
        return scrollBar;
        }
       }
      }
     return null;
     }
    }

[Knute Snortum]

When you say the program's crashing, do you mean it's hanging?  

When opening, you have this code:

               Scanner fin = new Scanner(file);
               while (fin.hasNext()) {
                   // read from the file, appending text to a control or other object
                }

When will this loop terminate?

[Daniel Demesmaecker]

I especially have a problem with the readability of your code.
Don't just put everything in your startmethod, JavaFx uses controllers for a reasson.

It's also unclear to me, why you're opening a file in three different locations.

This is an exampe of a program that let's you open, edit and save a textfile.
For this example I maded the file and the list containing the files static, in production you would find a cleaner solution for that:


MainClass:

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
        primaryStage.setTitle("FileHandler");
        primaryStage.setScene(new Scene(root, 800, 600));
        primaryStage.show();
    }


    public static void main(String[] args) {
        launch(args);
    }
}

The BaseController:

package sample;

import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.control.Alert;
import javafx.scene.layout.BorderPane;
import javafx.stage.FileChooser;
import javafx.stage.Stage;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class Controller {
    @FXML
    private BorderPane bPane;
    static File file;
    static List<File> files = new ArrayList<>();
    private Alert alert = new Alert(Alert.AlertType.INFORMATION);

    @FXML
    private void openFile() {
        FileChooser fileChooser = new FileChooser();
        fileChooser.setTitle("Choose a textFile!");
        fileChooser.setInitialDirectory(new File(System.getProperty("user.home")));
        file = fileChooser.showOpenDialog(new Stage());

    }

    @FXML
    private void edit(){
        try {
            bPane.setCenter(FXMLLoader.load(getClass().getResource("center.fxml")));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @FXML
    private void save() {
        if (file != null) {
            files.add(file);
            alert.setContentText("File has bin saved");
            alert.showAndWait();
        } else {
            alert.setAlertType(Alert.AlertType.ERROR);
            alert.setContentText("No File Selected!");
            alert.showAndWait();
        }
    }



    @FXML
    private void delete() {
    }
}

The EditController:

package sample;

import javafx.fxml.FXML;
import javafx.scene.control.Alert;
import javafx.scene.control.TextArea;

import java.io.*;

public class Edit {
    @FXML
    private TextArea tArea;
    private Alert alert = new Alert(Alert.AlertType.NONE);

    @FXML
    public void initialize() throws IOException {
        BufferedReader br = null;
        try {
            br = new BufferedReader(new FileReader(Controller.file));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        if (br != null) {
            String st;
            while ((st = br.readLine()) != null)
                tArea.appendText(st + "\n");
        }
    }

    @FXML
    private void saveEdit() {
        try {
            PrintWriter writer = new PrintWriter(Controller.file);
            writer.write(tArea.getText());
            writer.close();
            Controller.files.add(Controller.file);
            alert.setAlertType(Alert.AlertType.INFORMATION);
            alert.setContentText("The file has bin successful edited and saved.");
            alert.showAndWait();
            tArea.setText("");
        } catch (FileNotFoundException e) {
            alert.setAlertType(Alert.AlertType.ERROR);
            alert.setContentText("Unable to write to file");
            alert.showAndWait();
        }
    }
}

sample.fxml:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.BorderPane?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <BorderPane fx:id="bPane">
      <top>
          <MenuBar BorderPane.alignment="CENTER">
              <Menu mnemonicParsing="false" text="File">
                  <MenuItem mnemonicParsing="false" onAction="#openFile" text="Open" />
                  <MenuItem mnemonicParsing="false" onAction="#edit" text="Edit" />
                  <MenuItem mnemonicParsing="false" onAction="#save" text="Save" />
                  <MenuItem mnemonicParsing="false" onAction="#delete" text="Delete" />
              </Menu>
          </MenuBar>
      </top>
   </BorderPane>
</AnchorPane>

center.fxml:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TextArea?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.VBox?>

<AnchorPane prefHeight="600.0" prefWidth="800.0" xmlns="http://javafx.com/javafx/8.0.121"
            xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Edit">
    <VBox alignment="CENTER" layoutX="-1.0">
        <TextArea fx:id="tArea" prefHeight="532.0" prefWidth="800.0"/>
        <Button alignment="CENTER" contentDisplay="CENTER" mnemonicParsing="false" onAction="#saveEdit"
                text="Save Edit"/>
    </VBox>
</AnchorPane>

As you can see, when you try to edit a file an textarea is loaded in the center of the borderpane containing the text of the file.
After editing the file is overwritten.
For this example you can only edit the file you last loaded, Ideally you would have a way to choose which file you want to edit.

A final tip. I myself am a big fan of seperating the desing of your fxml file from your businesslogic, ergo your fxmlfile should contain all your design.
If you don't know how to edit a fxmlfile, use scenebuilder, which you can download here or most idea's (like netbeans, intelij and eclipse) have build in plugin's.
Removing the desing from your controller (or in your case your startmethod) will greatly improve your readability.

[ShinRyu Kazuto]

So when I tried to run the program you shown me, it gave me this error message:
java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)

what does it mean? Does it mean that it could not load the .fxml file?

Sorry for the beginner question. I haven't got into learning much about JavaFX design.

[Daniel Demesmaecker]

ShinRyu Kazuto wrote:So when I tried to run the program you shown me, it gave me this error message:

You shouldn't get any errors when running my code as you can see on this demo:

[Daniel Demesmaecker]

I've put my source code on git for you.
Keep in mind that it's not productioncode, it's ment to be a quick example, but it should help you get started.

[Norm Radder]

the program crash every time

Please copy the full text of the error message and paste it here.

[Manuel Prochnow]

Hello ShinRyu Kazuto,

Please take a look at this code it´s more easier but dont crashed and you can read a text-file and show it (I think it ...)

import java.io.File;
import java.io.IOException;
import java.util.Scanner;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.MenuItem;
import javafx.scene.control.TextArea;
import javafx.scene.layout.BorderPane;
import javafx.stage.FileChooser;
import javafx.stage.Stage;

public class IO extends Application {
	public static void main(String[] args) {
		launch(args);
	}

	@Override
	public void start(Stage primaryStage) throws Exception {
		
		double width = 480;
		double height = 300;
		
		// BorderPane for Menu in Top-Area and text in Center-Area
		BorderPane root = new BorderPane();
		final TextArea textArea = new TextArea();
		textArea.setWrapText(true);

		// adding menu
		MenuBar mainMenu = new MenuBar();
		Menu menu= new Menu("File");		
		MenuItem open = new MenuItem("Open");
		MenuItem save = new MenuItem("Save");
		menu.getItems().addAll(open, save);

		mainMenu.getMenus().addAll(menu);

		root.setTop(mainMenu);
		root.setCenter(textArea);
		root.setBottom(new Label("manuel"));
		
		open.setOnAction(x -> {
			FileChooser fc = new FileChooser();
			File file = fc.showOpenDialog(primaryStage);
			if (file != null) {
				try {
					Scanner fin = new Scanner(file);
					while (fin.hasNext()) {
						// read from the file, appending text to a control or other object
						textArea.setText(textArea.getText() + fin.nextLine() + "\n");
					}
					fin.close();
				} catch (IOException e) {
					System.out.println(e);
				}
			}
		});
		
		save.setOnAction(x -> {
			FileChooser fc = new FileChooser();
			File file = fc.showSaveDialog(primaryStage);
			if (file != null) {
				// here seve the data to file
			}
		});
		
		// Set up stage and scene
		Scene scene = new Scene(root, width, height);
		primaryStage.setScene(scene);
		primaryStage.setTitle("Text Area");
		primaryStage.show();

	}
}