I really do my best to not ask for help here unless i am desperate to the point of school assignment failure, being a new coder. That being said, i have spent the last 3 days trying to figure out the issue with threading. I am trying to instantiate a javafx class thats in a separate package, and keep running into the dreaded "java.lang.IllegalStateException: This operation is permitted on the event thread only; currentThread = main" exception.
I have tried calling theGamePreBoard.start(new Stage()), which doesnt work, and i have also tried calling its start method during construction of that object with a new Stage() passed in during construction. Please help!!!
How can i instantiate this PreBoard() class and get it's start method to run without throwing this?
main class:
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package battleship.model;
import battleship.viewcon.*;
import javafx.stage.Stage;
/**
*
* #author foolishklown
*/
public class MainApp {
Player player1;
Player player2;
Board board1;
Board board2;
BattleshipGame theGame;
PreBoard theGamePreBoard;
public void go() {
theGame = new BattleshipGame();
theGamePreBoard = new PreBoard();
theGamePreBoard.start(new Stage());
System.out.println(theGamePreBoard);
theGamePreBoard.setBattleshipGame(theGame);
}
public static void main(String[] args) {
MainApp app = new MainApp();
app.go();
}
}
PreBoard class:
/*
* PreBoard object. This is the starter class for the different JavaFX stages (different windows - username screen,
* and each players window)
* After first username input, this class hides and calls on a new P1Board object
*/
package battleship.viewcon;
import battleship.model.*;
import javafx.geometry.Insets;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.GridPane;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
/**
*
*
* #author c-dub
*/
public class PreBoard extends Application {
private boolean turn; // field to determine which players name to put into which board
private String player;
private Button hideBtn;
private Button showBtn;
private TextField userText;
private ViewCon controller;
private P1Board p1B;
private P2Board p2B;
private BattleshipGame game;
private Stage theStage;
#Override
public void start(Stage primaryStage) {
turn = false;
p1B = new P1Board();
p2B = new P2Board();
controller = new ViewCon();
controller.setp1(p1B);
controller.setp2(p2B);
controller.setPreB(this);
this.game = controller.getBattleshipGame();
primaryStage.setTitle("Battleship setup"); //Main stage (window container)
//Gridpane for using rows/columns for child node placement
GridPane grid = new GridPane();
grid.setAlignment(Pos.CENTER_LEFT);
grid.setHgap(10);
grid.setVgap(5);
grid.setPadding(new Insets(100, 25, 25, 25));
// label in window
Text sceneTitle = new Text("Setup");
sceneTitle.setId("setup-text");
grid.add(sceneTitle, 0, 0, 2, 1);
// label and textfield
Label userName = new Label("Enter UserName:");
userName.setId("user-name");
grid.add(userName, 0, 1);
TextField userTextField = new TextField();
userTextField.setId("text-field");
grid.add(userTextField, 0, 2);
// button for setup, with actionListener to save player name or default if its left blank
Button setupBtn = new Button("Setup Board");
HBox hbBtn = new HBox(10);
hbBtn.setAlignment(Pos.BOTTOM_LEFT);
hbBtn.getChildren().add(setupBtn);
grid.add(hbBtn, 0, 3);
setupBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
// determine which player name to use to pass into which player board
if(turn == false) {
String temp1 = userTextField.getText();
if(temp1.equals("")) {
player = "Player1";
} else {
player = temp1;
}
controller.setPlayer1(player);
game.setPlayer1(player);
turn = true;
Stage stage = new Stage();
p1B.start(stage);
grid.getChildren().remove(userTextField);
userText = new TextField();
userText.setId("text-field2");
grid.add(userText, 0, 2);
hideBtn.fire();
} else {
String temp2 = userText.getText();
if(temp2.equals("")) {
player = "Player2";
} else {
player = temp2;
}
controller.setPlayer2(player);
game.setPlayer2(player);
Stage stage2 = new Stage();
p2B.start(stage2);
hideBtn.fire();
}
}
});
hideBtn = new Button();
hideBtn.setId("hideBtn");
hideBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
primaryStage.hide();
}
});
showBtn = new Button();
showBtn.setId("showBtn");
showBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
primaryStage.show();
}
});
controller.setPreShowBtn(showBtn);
controller.setPreHideBtn(hideBtn);
// Add the entire scene into the main window(stage) after setting the scene dimensions
Scene scene = new Scene(grid, 580, 200);
primaryStage.setScene(scene);
// Attach css stylesheet
scene.getStylesheets().add(PreBoard.class.getResource("styles/PreBoardStyle.css").toExternalForm());
// Show this window(stage) upon instantiation
primaryStage.show();
}
public void setLink(ViewCon v) {
this.controller = v;
}
public static void main(String[] args) {
Application.launch(args);
}
public void setBattleshipGame(BattleshipGame b) {
this.game = b;
}
}
I don't think this has anything at all to do with threading: I don't see any reason why you would ever create another thread in this application. The part you seem to be missing is the actual life-cycle of a JavaFX application. (There's a little you could need to know about how JavaFX manages threading, but it is a bit incidental here.)
The Application class represents an entire application. Your application should typically have just one Application subclass, and one instance of that class. The instance is created for you by JavaFX when you call the static Application.launch() method (or when you execute your Application subclass from the command line, which effectively calls launch for you).
When launch is invoked, the JavaFX toolkit (including the FX Application Thread) is started. An instance of theApplication subclass is created for you, and then start(...) is invoked on that instance on the FX Application Thread.
So what that means is that the start(...) method is the entry point (startup) for your JavaFX application. Since the most common thing to do here is to display something in a window, a window (Stage) is passed into this method for your convenience: however you can ignore it and just create your own if you like.
A typical start(...) method should be quite short, and will usually just create some UI (maybe defined in another class or in an FXML file), put that UI in a scene, and display the scene in a stage. In a more complex application, you will create an instance of your model class here, create some views and controllers, give the controllers references to the model, and assemble the views.
For a simple structural example, see my answer to Java: How do I start a standalone application from the current one when both are in the same package? (which is a similar question, I think).
Related
I am creating a game in which I am checking for collisions between two ImageView objects, but when I use the intersects method it doesn't quite work the way I want it to. Score in checkCollision() method is counted to huge size and even though first image is not touching second collision is already happening and I don't know why - my program should add a +1 whenever one object touches another.
Here code sample after improvemets based on minimal reproducible example:
import javafx.animation.PathTransition;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.Pane;
import javafx.scene.shape.CubicCurveTo;
import javafx.scene.shape.MoveTo;
import javafx.scene.shape.Path;
import javafx.stage.Stage;
import javafx.util.Duration;
import java.util.ArrayList;
public class TestCollision extends Application {
private Thread collisionThread;
private Scene scene;
private Pane pane;
private ImageView wolfIv;
private ArrayList<ImageView> eggsList;
private int score;
#Override
public void start(Stage primaryStage) throws Exception {
pane = new Pane();
scene = new Scene(pane,800, 600);
Image wolf = new Image("/images/wolf.png");
wolfIv = new ImageView(wolf);
eggsList = new ArrayList<>();
eggsList.add(new ImageView(new Image(getClass().getResourceAsStream("/images/egg.png"))));
eggsList.get(0).setFitHeight(45);
eggsList.get(0).setFitWidth(35);
pane.getChildren().add(eggsList.get(0));
MoveTo moveToEgg = new MoveTo();
moveToEgg.setX(60.0f);
moveToEgg.setY(95.0f);
Path eggPath = new Path();
eggPath.getElements().add(moveToEgg);
eggPath.getElements().add(new CubicCurveTo(190,200,190, 200,190,480));
PathTransition pathTransition = new PathTransition();
pathTransition.setDuration(Duration.millis(4000));
pathTransition.setNode(eggsList.get(0));
pathTransition.setPath(eggPath);
pathTransition.setCycleCount(PathTransition.INDEFINITE);
pathTransition.setAutoReverse(false);
pathTransition.play();
wolfIv.setFitWidth(200);
wolfIv.setFitHeight(250);
wolfIv.setX(140);
wolfIv.setY(218);
pane.getChildren().addAll(wolfIv);
primaryStage.setResizable(false);
primaryStage.setScene(scene);
primaryStage.show();
collisionCheckThread();
}
public void checkCollision(ImageView imageView, ImageView imageView2){
if(imageView.getBoundsInParent().intersects(imageView2.getBoundsInParent())){
score++;
System.out.println(score);
System.out.println("Boom");
}
}
public void collisionCheckThread()
{
collisionThread = new Thread(){
#Override
public void run(){
while(scene.getWindow().isShowing() == true){
checkCollision(wolfIv,eggsList.get(0));
}
}
};
collisionThread.start();
}
public static void main(String[] args) {
launch(args);
}
}
The reason the score "becomes huge" is that the background thread is repeatedly checking for collisions as fast and as often as it can. Any time it checks and the bounds intersect, it adds one to the score.
The reason you see incorrect results sometimes, such as a collision being detected immediately when none should happen, is more complex. This occurs because values (in particular the boundsInParent of the two image views) are being changed on one thread (the FX Application thread) and observed on another thread (your background thread) without proper synchronization. JavaFX, like most UI toolkits, is designed as a single-threaded toolkit, and so there is no way to add synchronization to this.
What actually happens here is due to something called "hoisting". The code in your background thread is essentially
public void run(){
while(scene.getWindow().isShowing() == true){
if(imageView.getBoundsInParent().intersects(imageView2.getBoundsInParent())){
score++;
System.out.println(score);
System.out.println("Boom");
}
}
}
It is legal, per the Java Language Specification, for a JVM to optimize code in certain ways. For variables that are not declared volatile, and without synchronization, the JVM is allowed to reorder code assuming that each thread is independent of each other. Under this assumption, since there are no changes to the boundsInParent made in this thread, the code can be treated as being equivalent to
public void run(){
if(imageView.getBoundsInParent().intersects(imageView2.getBoundsInParent())){
while(scene.getWindow().isShowing() == true){
score++;
System.out.println(score);
System.out.println("Boom");
}
}
}
Furthermore, this optimization may be made at an arbitrary time (when the JVM decides it may be beneficial), so if you are accessing the boundsInParent from a thread other than the FX Application Thread, the behavior of this code becomes essentially non-deterministic.
For more information, I recommend reading the relevant items in Joshua Bloch's book Effective Java. (No one who has spent more than an hour programming in Java should be without this book.)
Using a background thread here is completely the wrong approach anyway.
What you actually want to do, I assume, is add one to the score (and perhaps perform other actions) when the state of the images changes from "not intersecting" to "intersecting". You can do this by creating a BooleanBinding with the correct value, and which is bound to the two boundsInParent properties. Then register a listener with that binding and react when it changes from false to true:
BooleanBinding collision = Bindings.createBooleanBinding(
() -> wolfIv.getBoundsInParent().intersects(eggsList.get(0).getBoundsInParent()),
wolfIv.boundsInParentProperty(),
eggsList.get(0).boundsInParentProperty()
);
collision.addListener((obs, wasCollision, isNowCollision) -> {
if (isNowCollision) {
score++;
System.out.println(score);
System.out.println("Boom");
}
});
Here's a complete runnable example which demonstrates this:
import java.util.ArrayList;
import javafx.animation.PathTransition;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.binding.Bindings;
import javafx.beans.binding.BooleanBinding;
import javafx.scene.Scene;
import javafx.scene.image.ImageView;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.CubicCurveTo;
import javafx.scene.shape.MoveTo;
import javafx.scene.shape.Path;
import javafx.stage.Stage;
import javafx.util.Duration;
public class TestCollision extends Application {
private Scene scene;
private Pane pane;
private ImageView wolfIv;
private ArrayList<ImageView> eggsList;
private int score;
#Override
public void start(Stage primaryStage) throws Exception {
pane = new Pane();
scene = new Scene(pane,800, 600);
WritableImage wolf = new WritableImage(1, 1);
wolf.getPixelWriter().setColor(0, 0, Color.RED);
wolfIv = new ImageView(wolf);
eggsList = new ArrayList<>();
WritableImage egg = new WritableImage(1, 1);
egg.getPixelWriter().setColor(0, 0, Color.YELLOW);
eggsList.add(new ImageView(egg));
BooleanBinding collision = Bindings.createBooleanBinding(
() -> wolfIv.getBoundsInParent().intersects(eggsList.get(0).getBoundsInParent()),
wolfIv.boundsInParentProperty(),
eggsList.get(0).boundsInParentProperty()
);
collision.addListener((obs, wasCollision, isNowCollision) -> {
if (isNowCollision) {
score++;
System.out.println(score);
System.out.println("Boom");
}
});
eggsList.get(0).setFitHeight(45);
eggsList.get(0).setFitWidth(35);
pane.getChildren().add(eggsList.get(0));
MoveTo moveToEgg = new MoveTo();
moveToEgg.setX(60.0f);
moveToEgg.setY(95.0f);
Path eggPath = new Path();
eggPath.getElements().add(moveToEgg);
eggPath.getElements().add(new CubicCurveTo(190,200,190, 200,190,480));
PathTransition pathTransition = new PathTransition();
pathTransition.setDuration(Duration.millis(4000));
pathTransition.setNode(eggsList.get(0));
pathTransition.setPath(eggPath);
pathTransition.setCycleCount(PathTransition.INDEFINITE);
pathTransition.setAutoReverse(false);
pathTransition.play();
wolfIv.setFitWidth(200);
wolfIv.setFitHeight(250);
wolfIv.setX(140);
wolfIv.setY(218);
pane.getChildren().addAll(wolfIv);
primaryStage.setResizable(false);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
I have a class tasks, which handles multiple tasks using a menu layout, class tasks check the application flow by setting up the stage, with the menu scene to list all individual task. I want to run some task from the available list using there own classes, something like this:
Tasks.java:
package tasks;
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.VBox;
import javafx.scene.control.Button;
public class Tasks extends Application
{
private Stage window;
private Scene menuScene;
private Task1 task1;
public Tasks()
{
this.window=null;
this.menuScene=null;
this.task1=null;
}
private void setMenu()
{
VBox menu=new VBox();
Button newTask1Button=new Button("New Task 1");
newTask1Button.setOnAction(clickEvent -> this.startNewTask1());
menu.getChildren().add(newTask1Button);
//More buttons
this.menuScene=new Scene(menu,400,600);
this.window.setScene(this.menuScene);
}
private void startNewTask1()
{
this.task1=new Task1(this.window);
this.launchTask1();
}
private void launchTask1()
{
if(this.task1!=null)
{
int task1State=1;
//while(task1State==1) //To re-run for pause state
//{
task1State=this.task1.runTask1();
System.out.println("Task1 is in state "+task1State); //In no way part of program, just for debugging. Always give state=-1
//If 1-Paused, then display pause Menu for task1, by calling this.task1.paused(); and then again based on user input re-run runTask1
//If 0-Exit, then change the scene back to menuScene and quit the function
//}
}
}
#Override
public void start(Stage primaryStage)
{
this.window=primaryStage;
this.window.setTitle("Tasks");
this.setMenu();
this.window.show();
}
public static void main(String[] args)
{
Application.launch(args);
}
}
Task1.java:
package tasks;
import javafx.stage.Stage;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.HBox;
import javafx.scene.control.Button;
class Task1
{
private Stage window;
private Scene task1Scene;
private boolean intialised;
private int state;
public Task1()
{
}
public Task1(Stage _window)
{
this.window=_window;
this.task1Scene=null; //Will be set later
this.intialised=false;
this.state=-1;
}
private Scene createScene()
{
//Creates some GUI to interact
//Buttons in End, to control exit
HBox menu=new HBox();
Button pauseButton=new Button("Pause");
pauseButton.setOnAction(clickEvent -> this.state=1);
menu.getChildren().add(pauseButton);
Button exitButton=new Button("Exit");
exitButton.setOnAction(clickEvent -> this.state=0);
menu.getChildren().add(exitButton);
Scene scene=new Scene(menu,400,600);
return scene;
}
private void setupControls()
{
//To assign event handlers to interact with GUI
}
public int runTask1()
{
if(!this.intialised)
this.task1Scene=this.createScene();
this.window.setScene(this.task1Scene);
this.setupControls();
//while(this.state==-1);
return this.state;
}
}
The problem with this I face is, function runTask1() is always instantly returning, even though operation assigned using event handlers for Task1 are still running and no event for exit has been generated.
I tried to solve this by setting an instance variable named state and setting it to -1, and putting a while loop till this state variable is not modified. But that completely stops the GUI.
I realised its reason later by Googling, but couldn't determine which way to solve this.
At places, it was suggested to use Threads (not sure how, I don't want multiple processes running in the program) and at places, it was also suggested to set another Event Handler (but, they were running the different process in the start() function (inherited from Application) itself and it was more of transferring the flow rather than returning backwards).
How should I code to keep running only runTask1() till it is not finished, and return to launchTask1() sequentially?
The infinite while loop in method runTask1() in class Task1 is freezing the JavaFX application thread. Just remove it.
Basically your Task1 class is another Scene so when you click on button newTask1Button in class Tasks you simply want to set a new Scene.
Here is class Task1 with the required change.
package tasks;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.HBox;
import javafx.scene.control.Button;
public class Task1 {
private Stage window;
private Scene task1Scene;
private boolean intialised;
private int state;
public Task1() {
}
public Task1(Stage _window) {
this.window = _window;
this.task1Scene = null; // Will be set later
this.intialised = false;
this.state = -1;
}
private Scene createScene() {
// Creates some GUI to interact
// Buttons in End, to control exit
HBox menu = new HBox();
Button pauseButton = new Button("Pause");
pauseButton.setOnAction(clickEvent -> this.state = 1);
menu.getChildren().add(pauseButton);
Button exitButton = new Button("Exit");
exitButton.setOnAction(clickEvent -> this.state = 0);
menu.getChildren().add(exitButton);
Scene scene = new Scene(menu, 400, 600);
return scene;
}
private void setupControls() {
// To assign event handlers to interact with GUI
}
public int runTask1() {
if (!this.intialised)
this.task1Scene = this.createScene();
this.window.setScene(this.task1Scene);
this.setupControls();
// while (this.state == -1)
// ;
return this.state;
}
}
As you can see, I simply commented out the while loop. The JavaFX application thread contains a loop that waits for user actions to occur such as moving the mouse or typing a key on the keyboard. You don't have to handle that in your code.
EDIT
As a result of the typo in the code in your question, that you mentioned in your comment to my answer and that you corrected in your question in a subsequent edit, I am editing my answer.
The way a JavaFX application works is that it reacts to user actions. You want class Tasks to be notified when the "state", in class Task1, is changed and the "state" is changed when the user clicks on either pauseButton or exitButton in class Task1. According to the code you posted, you could callback to class Tasks from the event handler of pauseButton.
Class Task1.
(Note comment CHANGE HERE and extra parameter in constructor.)
package tasks;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.HBox;
import javafx.scene.control.Button;
public class Task1 {
private Tasks tasks;
private Stage window;
private Scene task1Scene;
private boolean intialised;
private int state;
public Task1(Stage _window, Tasks tasks) {
this.tasks = tasks;
this.window = _window;
this.task1Scene = null; // Will be set later
this.intialised = false;
this.state = -1;
}
private Scene createScene() {
HBox menu = new HBox();
Button pauseButton = new Button("Pause");
pauseButton.setOnAction(clickEvent -> tasks.setState(this.state = 1)); // CHANGE HERE
menu.getChildren().add(pauseButton);
Button exitButton = new Button("Exit");
exitButton.setOnAction(clickEvent -> this.state = 0);
menu.getChildren().add(exitButton);
Scene scene = new Scene(menu, 400, 600);
return scene;
}
private void setupControls() {
// To assign event handlers to interact with GUI
}
public int runTask1() {
if (!this.intialised) {
this.task1Scene = this.createScene();
}
this.window.setScene(this.task1Scene);
this.setupControls();
return this.state;
}
}
Class Tasks
(Added method setState(int).)
package tasks;
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.VBox;
import javafx.scene.control.Button;
public class Tasks extends Application {
private Stage window;
private Scene menuScene;
private Task1 task1;
public Tasks() {
this.window = null;
this.menuScene = null;
this.task1 = null;
}
private void setMenu() {
VBox menu = new VBox();
Button newTask1Button = new Button("New Task 1");
newTask1Button.setOnAction(clickEvent -> this.startNewTask1());
menu.getChildren().add(newTask1Button);
this.menuScene = new Scene(menu, 400, 600);
this.window.setScene(this.menuScene);
}
private void startNewTask1() {
this.task1 = new Task1(this.window, this);
this.launchTask1();
}
private void launchTask1() {
if (this.task1 != null) {
this.task1.runTask1();
}
}
#Override
public void start(Stage primaryStage) {
this.window = primaryStage;
this.window.setTitle("Tasks");
this.setMenu();
this.window.show();
}
public static void main(String[] args) {
Application.launch(args);
}
public void setState(int task1State) {
System.out.println("Task1 is in state " + task1State); // In no way part of program,
// just for debugging.
}
}
This question already has answers here:
Reading a plain text file in Java
(31 answers)
Closed 5 years ago.
I have a program called "AddUser" that allows the user to type in their username and password, which will add this info to user.txt file. I also have a program called "Login" that takes the information the user inputs, username and password, and verifies the input against the user.txt file.
However, I cannot figure out how to validate the input for the Login program. I have found several other posts here, but not from validating from a text file. Any help or guidance would be GREATLY appreciated.
Program Add User
import javax.swing.JOptionPane;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.geometry.HPos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import java.io.*;
public class AddUser extends Application {
private TextField tfUsername = new TextField();
private TextField tfPassword = new TextField();
private Button btAddUser = new Button("Add User");
private Button btClear = new Button("Clear");
#Override // Override the start method in the Application class
public void start(Stage primaryStage) {
// Create UI
GridPane gridPane = new GridPane();
gridPane.setHgap(5);
gridPane.setVgap(5);
gridPane.add(new Label("Username:"), 0, 0);
gridPane.add(tfUsername, 1, 0);
gridPane.add(new Label("Password:"), 0, 1);
gridPane.add(tfPassword, 1, 1);
gridPane.add(btAddUser, 1, 3);
gridPane.add(btClear, 1, 3);
// Set properties for UI
gridPane.setAlignment(Pos.CENTER);
tfUsername.setAlignment(Pos.BOTTOM_RIGHT);
tfPassword.setAlignment(Pos.BOTTOM_RIGHT);
GridPane.setHalignment(btAddUser, HPos.LEFT);
GridPane.setHalignment(btClear, HPos.RIGHT);
// Process events
btAddUser.setOnAction(e -> writeNewUser());
btClear.setOnAction(e -> {
tfUsername.clear();
tfPassword.clear();
});
// Create a scene and place it in the stage
Scene scene = new Scene(gridPane, 300, 150);
primaryStage.setTitle("Add User"); // Set title
primaryStage.setScene(scene); // Place the scene in the stage
primaryStage.show(); // Display the stage
}
public void writeNewUser() {
try (BufferedWriter bw = new BufferedWriter(new FileWriter("users.txt", true))) {
bw.write(tfUsername.getText());
bw.newLine();
bw.write(tfPassword.getText());
bw.newLine();
}
catch (IOException e){
e.printStackTrace();
}
}
/**
* The main method is only needed for the IDE with limited
* JavaFX support. Not needed for running from the command line.
*/
public static void main(String[] args) {
launch(args);
}
}
Program Login
import javax.swing.JOptionPane;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.geometry.HPos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import java.io.*;
public class Login extends Application {
private TextField tfUsername = new TextField();
private TextField tfPassword = new TextField();
private Button btAddUser = new Button("Login");
private Button btClear = new Button("Clear");
#Override // Override the start method in the Application class
public void start(Stage primaryStage) {
// Create UI
GridPane gridPane = new GridPane();
gridPane.setHgap(5);
gridPane.setVgap(5);
gridPane.add(new Label("Username:"), 0, 0);
gridPane.add(tfUsername, 1, 0);
gridPane.add(new Label("Password:"), 0, 1);
gridPane.add(tfPassword, 1, 1);
gridPane.add(btAddUser, 1, 3);
gridPane.add(btClear, 1, 3);
// Set properties for UI
gridPane.setAlignment(Pos.CENTER);
tfUsername.setAlignment(Pos.BOTTOM_RIGHT);
tfPassword.setAlignment(Pos.BOTTOM_RIGHT);
GridPane.setHalignment(btAddUser, HPos.LEFT);
GridPane.setHalignment(btClear, HPos.RIGHT);
// Process events
btClear.setOnAction(e -> {
tfUsername.clear();
tfPassword.clear();
});
// Create a scene and place it in the stage
Scene scene = new Scene(gridPane, 300, 150);
primaryStage.setTitle("Login"); // Set title
primaryStage.setScene(scene); // Place the scene in the stage
primaryStage.show(); // Display the stage
}
/**
* The main method is only needed for the IDE with limited
* JavaFX support. Not needed for running from the command line.
*/
public static void main(String[] args) {
launch(args);
}
}
Consider this Example (Explanation in Comments):
// create boolean variable for final decision
boolean grantAccess = false;
// get the user name and password when user press on login button
// you already know how to use action listener
// (i.e wrap the following code with action listener block of login button)
String userName = tfUsername.getText();
String password = tfPassword.getText();
File f = new File("users.txt");
try {
Scanner read = new Scanner(f);
int noOfLines=0; // count how many lines in the file
while(read.hasNextLine()){
noOfLines++;
}
//loop through every line in the file and check against the user name & password (as I noticed you saved inputs in pairs of lines)
for(int i=0; i<noOfLines; i++){
if(read.nextLine().equals(userName)){ // if the same user name
i++;
if(read.nextLine().equals(password)){ // check password
grantAccess=true; // if also same, change boolean to true
break; // and break the for-loop
}
}
}
if(grantAccess){
// let the user continue
// and do other stuff, for example: move to next window ..etc
}
else{
// return Alert message to notify the deny
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
I have 2 sides of the MVC. on the model side, is where i have my main class for the entire battleship program. It instantiates the view/controller side of things, which consists of 3 different windows(classes that extend Application): a PreBoard, which gets both players names, and then one player board each (P1Board, P2Board). In all 3 of these separate classes, they extend Application, and all have a start(Stage primaryStage) method.
Since ive been reading about javaFX threading for the last 48 hours i am still barely understanding where the javaFX application thread starts. Does the javaFX Application thread start the very first time that Application.launch() is called, even if you have 3 seperate classes that extend Application and have their own start methods?
My original intentions were to have a window where players can enter their names, then a separate window with their own board, and i have failed MISERABLY because im getting more and more exceptions the longer the whole program runs.
So the question is, where the hell does the javaFX Application thread start?
Main class, on the model side
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package battleship.model;
import battleship.viewcon.*;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.stage.Stage;
/**
*
* #author foolishklown
*/
public class MainApp {
Player player1;
Player player2;
BattleshipGame theGame;
PreBoard theGamePreBoard;
ViewCon viewConnector;
public void go() {
theGamePreBoard = new PreBoard();
theGamePreBoard.setMainAppConnection(this);
viewConnector = theGamePreBoard.getVcon();
}
public void startBsGame(String[] names) {
theGame = new BattleshipGame(names[0], names[1]);
viewConnector.setGame(theGame);
}
public BattleshipGame getGame() {
return theGame;
}
public void setConnection(ViewCon vc) {
this.viewConnector = vc;
}
public static void main(String[] args) {
MainApp app = new MainApp();
app.go();
}
}
PreBoard code, which instantiates 2 other classes that extend Application and have their own start methods......
package battleship.viewcon;
import battleship.model.*;
import javafx.geometry.Insets;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.GridPane;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
/**
* PreBoard class, used for getting user input for players names
* #author Chris Wilson
* #author Bob McHenry
* #author Mario Rodriguez De la Raza en la casa!
* #author Jessy Bernoudi
*/
public class PreBoard extends Application {
private boolean turn; // field to determine which players name to put into which board
private String player;
private Button hideBtn;
private Button showBtn;
private TextField userText;
private ViewCon controller;
private P1Board p1B;
private P2Board p2B;
private BattleshipGame game;
private String[] playerNames;
private MainApp mainApp;
/**
* Application class override method, where javaFX stage starts
* #param primaryStage
*/
#Override
public void start(Stage primaryStage) {
playerNames = new String[2];
turn = false;
p1B = new P1Board();
p2B = new P2Board();
controller = new ViewCon();
controller.setPreB(this);
controller.setp1(p1B);
controller.setp2(p2B);
controller.setMain();
primaryStage.setTitle("Battleship setup"); //Main stage (window container)
//Gridpane for using rows/columns for child node placement
GridPane grid = new GridPane();
grid.setAlignment(Pos.CENTER_LEFT);
grid.setHgap(10);
grid.setVgap(5);
grid.setPadding(new Insets(100, 25, 25, 25));
// label in window
Text sceneTitle = new Text("Setup");
sceneTitle.setId("setup-text");
grid.add(sceneTitle, 0, 0, 2, 1);
// label and textfield
Label userName = new Label("Enter Player1 UserName:");
userName.setId("user-name");
grid.add(userName, 0, 1);
TextField userTextField = new TextField();
userTextField.setId("text-field");
grid.add(userTextField, 0, 2);
// button for setup, with actionListener to save player name or default if its left blank
Button setupBtn = new Button("Setup Board");
HBox hbBtn = new HBox(10);
hbBtn.setAlignment(Pos.BOTTOM_LEFT);
hbBtn.getChildren().add(setupBtn);
grid.add(hbBtn, 0, 3);
setupBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
// determine which player name to use to pass into which player board
if(turn == false) {
String temp1 = userTextField.getText();
if(temp1.equals("")) {
player = "Player1";
} else {
player = temp1;
}
playerNames[0] = player;
controller.setPlayer1(player);
turn = true;
p1B.start(new Stage());
grid.getChildren().remove(userTextField);
userText = new TextField();
userText.setId("text-field");
grid.add(userText, 0, 2);
userName.setText("Enter Player2 username:");
} else {
String temp2 = userText.getText();
if(temp2.equals("")) {
player = "Player2";
} else {
player = temp2;
}
playerNames[1] = player;
controller.startGame(playerNames);
controller.setPlayer2(player);
p2B.start(new Stage());
p1B.primeShow();
}
}
});
hideBtn = new Button();
hideBtn.setId("hideBtn");
hideBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
primaryStage.hide();
}
});
showBtn = new Button();
showBtn.setId("showBtn");
showBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
primaryStage.show();
}
});
controller.setPreShowBtn(showBtn);
controller.setPreHideBtn(hideBtn);
// Add the entire scene into the main window(stage) after setting the scene dimensions
Scene scene = new Scene(grid, 580, 200);
primaryStage.setScene(scene);
// Attach css stylesheet
scene.getStylesheets().add(PreBoard.class.getResource("styles/PreBoardStyle.css").toExternalForm());
// Show this window(stage) upon instantiation
primaryStage.show();
}
/**
*
* #param v
*/
public void setLink(ViewCon v) {
this.controller = v;
}
/**
*
* #param b
*/
public void setBattleshipGame(BattleshipGame b) {
this.game = b;
}
/**
*
* #param main
*/
public void setMainAppConnection(MainApp main) {
this.mainApp = main;
}
/**
*
* #return
*/
public MainApp getMainConnection() {
return mainApp;
}
/**
*
* #return
*/
public ViewCon getVcon() {
return controller;
}
public void exitPre() {
Platform.exit();
}
public static void main(String[] args) {
Application.launch(args);
}
}
I'm working with Javafx and threads simultaneously and I constanly run into this problem where I make a button and then when the button is clicked (using event handlers) I make a for loop that changes the button to 1,2,3,4,5 and then delays for a second in the middle of each. Like a count down!
But what happens is it delays for 5 seconds and changes the text of button to 5.
The problem is I want to see it change between 1 and 5 but all I see is 5 at the end of a 5 second delay. I would assume that it changing the button text but I don't see it. I might have to to do with the .show() method in the Javafx class.
public class HewoWorld extends Application implements EventHandler<ActionEvent>
{
Thread t = new Thread();
Button butt;
boolean buttWasClicked = false;
Circle circ1 = new Circle(40, 40, 30, Color.RED);
Circle circ2 = new Circle(100, 100, 30, Color.BLUE);
Group root;
Scene scene;
Stage disStage = new Stage();
int i = 1;
public static void main(String[] args)
{
launch(args);
}
public void start(Stage stage) throws Exception
{
disStage.setTitle("tests stuffs");
Screen screen = Screen.getPrimary();
Rectangle2D bounds = screen.getVisualBounds();
double windh = bounds.getHeight()/2+150;//sets height of screen
double windw = bounds.getWidth()/3;//sets width of screen
Pane layout = new Pane();
butt = new Button();
butt.setText("Hello world");
root = new Group(circ1, circ2, butt);
scene = new Scene(root, 800, 400);
disStage.setWidth(windw);
disStage.setHeight(windh);
butt.setLayoutX(200);
butt.setLayoutY(200);
butt.setOnAction(this);
disStage.setScene(scene);
disStage.show();
}
public void handle(ActionEvent event)
{
if (event.getSource() == butt && buttWasClicked == false)
{
try
{
butt.setText(i+"");
t.sleep(1000);
i++;
}
catch(Exception q)
{
}
circ1 = new Circle(40, 40, 30, Color.BLACK);
circ2 = new Circle(100, 100, 30, Color.RED);
}
}
}
Why your code doesn't work
The reason your code doesn't work is that you are blocking the FX Application Thread.
Like (almost?) all UI toolkits, JavaFX is a single-threaded UI toolkit. This means that all event handlers, and all the rendering of the UI, are performed on a single thread (called the FX Application Thread).
In your code, you have an event handler that takes more than a second to run, because it pauses for a second via a call to Thread.sleep(...). While that event handler is running, the UI cannot be redrawn (because a single thread cannot do two things at once). So while the value of the button's text has changed immediately, the new value won't actually be rendered on the screen until the handle(...) method has finished running. If you had a for loop in the handle method, nothing would be rendered until the entire loop (and anything else in the method) had completed.
How to fix it
The simplest way to do what you want in JavaFX is to use a Timeline to handle the pause. The Timeline manages the threading appropriately for you:
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.util.Duration;
public class CountingButton extends Application {
#Override
public void start(Stage primaryStage) {
Button button = new Button("Count");
Timeline timeline = new Timeline();
for (int count = 0; count <= 5 ; count++) {
final String text = Integer.toString(count);
KeyFrame frame = new KeyFrame(Duration.seconds(count), event ->
button.setText(text));
timeline.getKeyFrames().add(frame);
}
button.setOnAction(e -> timeline.play());
primaryStage.setScene(new Scene(new StackPane(button), 120, 75));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
In general, for changing the appearance of the user interface at specific time points, the JavaFX Animation API (see also the tutorial) can be useful, especially Timeline and PauseTransition.
A "lower-level" way to do this would be to create a Thread yourself and pause in that thread. This is much more advanced: you need to be careful to update the UI on the FX Application Thread, not on the thread you created. You can do this with a call to Platform.runLater(...):
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
public class CountingButton extends Application {
#Override
public void start(Stage primaryStage) {
Button button = new Button("Start");
button.setOnAction(e -> {
Thread thread = new Thread(() -> {
for (int i = 0; i <= 5 ; i++) {
final String text = "Count: "+i ;
Platform.runLater(() -> button.setText(text));
try {
Thread.sleep(1000);
} catch (InterruptedException exc) {
exc.printStackTrace();
}
}
});
thread.start();
});
primaryStage.setScene(new Scene(new StackPane(button), 120, 75));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
For more general information on threading in JavaFX, have a look at this post: Using threads to make database requests
What you have to do is to replace the thread use by the following method :
scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(
new Runnable(){
#Override
public void run() {
Platform.runLater(new Runnable() {
#Override
public void run() {
//Here your code to change the number by for example incrementig the value of the button
}
});
}
},
1000,
80,
TimeUnit.MILLISECONDS);
+1 if it helps :D
In this case you need a timer to run every second and increment a counter on every hit. To my knowledge, the best way to make a timer in javafx is to use a timeline. https://stackoverflow.com/a/9966213/4683264.
int i = 0;// class field
// ....
Timeline fiveSecondsWonder = new Timeline(new KeyFrame(Duration.seconds(1), event ->
button.setText(++i)));
fiveSecondsWonder.setCycleCount(5);// repeat five times
fiveSecondsWonder.play();