Model-View-Controller with JavaFx

Question

im trying to create a simple Minesweeper game with Modell-View-Controller and got this problem, here is my View Class

public class View extends VBox implements Observer {
     public Button [][] buttonarray;
     public int width;
     public int height;
     public Model model ;
     public TextArea textfeld;

     public View(int buttoncolumn, int buttonrow, Model model){
         this.model = model;
         this.width = buttoncolumn;
         this.height = buttonrow;

         GridPane buttonpanel = new GridPane();

         buttonpanel.setAlignment(Pos.CENTER);

         Button [][] buttonarray = new Button [buttoncolumn][buttonrow];

         textfeld = new TextArea();
         textfeld.setMaxSize( buttoncolumn*25,60);
         textfeld.setMinSize(buttoncolumn*25,60);

         for(int x=0; x < buttoncolumn; x++) {
             for (int y = 0; y < buttonrow; y++) {
                 buttonarray[x][y] = new Button();
                 buttonarray[x][y].setMinSize(25,25);
                 buttonarray[x][y].setMaxSize(25,25);
                 buttonpanel.add(buttonarray[x][y],x,y);
             }
         }

         this.getChildren().add(buttonpanel);
         this.getChildren().add(textfeld);

     }
     public Button [][] getButtonarray(){
         return buttonarray;
     }
     public Button getButton(int x, int y){
         return buttonarray[x][y];
     }
     public void update(Observable obs, Object o){


     }

 }

And in Controller Class i tried to implement this

public class Controller implements Observer {
public Model model;
public View view;

public Controller(Model a, View b){
    this.model = a;
    this.view = b;
    model.addObserver(this);
    for (int x=0;x<model.width;x++){
        for(int y=0;y<model.length;y++){
            int xvalue = x;
            int yvalue = y;

             /* HERE IS THE PROBLEM */
            view.getButtonarray()[x][y].setOnAction(event -> linksKlick(xvalue,yvalue));
        }

    }

    model.addObserver(this);

}

And things went horribly wrong, there are too many exceptions such as :

Exception in thread "main" 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$155(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:745)
 Caused by: java.lang.NullPointerException
at Uebung2.Controller.<init>(Controller.java:28)
at Uebung2.Main.start(Main.java:22)

I noticed that if i removed the row with .setOnAction everything will be fine, but not like i want to, can someone care enough to explain why ? Please note that for the sake of a short question i removed all the imports and irrelevant methods