Wait until any button is pressed?

Question

I am writing a TicTacToe game in JavaFX. I've decided to make a board as 9 (3x3) buttons with changing text: "" (if empty) or "X" or "O". Everything is going ok beside one thing... I got stuck here:

public void game() {

        while(keepPlaying) {
            if(computerTurn) {;
                computerMove();
            }else {
                while(waitForUser) {
                    //wait until any of 9 buttons is pushed!
                }
            }

            if (checkResult()) {
                keepPlaying = false;
            }
            computerTurn = !computerTurn;
        }
    }

How to wait for user pushing any of those 9 buttons and then continue with computer turn??

I need something like waiting for scanner input in console application, but this input must be one of 9 buttons...

I know that there are few "possible duplicates", but in fact those problems were solved using methods I can't use here, for example timer. Correct me if I am wrong.

Answer 1

Blocking the application thread in JavaFX should not be done since it freezes the UI. For this reason a loop like this is not well suited for a JavaFX application. Instead you should react to user input:

public void game() {
    if (keepPlaying && computerTurn) {
        computerMove();
        if (checkResult()) {
            keepPlaying = false;
        }
        computerTurn = false;
    }
}

// button event handler
private void button(ActionEvent event) {
    if (keepPlaying) {
        Button source = (Button) event.getSource();

        // probably the following 2 coordinates are computed from GridPane indices
        int x = getX(source);
        int y = getY(source);

        // TODO: update state according to button pressed

        if (checkResult()) {
            keepPlaying = false;
        } else {
            computerMove();
            if (checkResult()) {
                keepPlaying = false;
            }
        }
    }

}

---

Starting with javafx 9 there is a public API for "pausing" on the application thread however:

private static class GridCoordinates {
    int x,y;
    GridCoordinates (int x, int y) {
        this.x = x;
        this.y = y;
    }
}

private final Object loopKey = new Object();

public void game() {
    while(keepPlaying) {
        if(computerTurn) {
            computerMove();
        } else {
            // wait for call of Platform.exitNestedEventLoop​(loopKey, *)
            GridCoordinates coord = (GridCoordinates)  Platform.enterNestedEventLoop​(loopKey);

            // TODO: update state
        }

        if (checkResult()) {
            keepPlaying = false;
        }
        computerTurn = !computerTurn;
    }
}

private void button(ActionEvent event) {
    if (keepPlaying) {
        Button source = (Button) event.getSource();

        // probably the following 2 coordinates are computed from GridPane indices
        int x = getX(source);
        int y = getY(source);

        Platform.exitNestedEventLoop​(loopKey, new GridCoordinates(x, y));
    }
}