使用循环中的按钮调用方法

Question

I have created a gridPane called gPaneCenter which is designed to create a table. When I add an item to the grid it will call the mehtod addRow(), please see below:

public static void addRow() {
    System.out.println("Test");
    Label prodDes = new Label(String.valueOf(Controller.shoppingCart.getOrder(i).getProduct().getDescription()));
    Label prodPrice = new Label(String.valueOf(Controller.shoppingCart.getOrder(i).getProduct().getUnitPrice()));
    Label prodQuant = new Label(String.valueOf(Controller.shoppingCart.getOrder(i).getQuantity()));
    Label prodCost = new Label(String.valueOf(Controller.shoppingCart.getOrder(i).getCost()));

    HBox quantityChanger = new HBox();
    Button decreaseQuantBut = new Button("-");
    Button increaseQuantBut = new Button("+");


    decreaseQuantBut.setOnAction(e -> Controller.shoppingCart.getOrder(i).decreaseQuantity());
    increaseQuantBut.setOnAction(e -> Controller.shoppingCart.getOrder(i).increaseQuantity());

    quantityChanger.getChildren().addAll(decreaseQuantBut,prodQuant,increaseQuantBut);

    View.gPaneCenter.addRow(l, prodDes,prodPrice,quantityChanger,prodCost);
    l++;
    i++;
}

'i' and 'l' are declared at the start:

static int i = 0;
static int l = 1;

Which produces the following GUI when an item is added:

When I click the "-" button or "+" button I would like to decrease the quantity and increase the quantity respectively however I get the following error when I click either button:

Exception in thread "JavaFX Application Thread" java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at model.Cart.getOrder(Cart.java:59)

Which suggests it cannot find order however it can successfully find the order to print the following: prodDes, prodPrice and prodQuant.

Method of called the order in class Cart, this is also (Cart.java.59):

    public Order getOrder(int i) {
    return contents.get(i);
}

Method of increasing and decreasing the quantity in class Order:

    public void increaseQuantity() {
    quantity++;
}

public void decreaseQuantity() {
    quantity--;
}

The methods for used for getting the prodQuant and prodCost (prodDes and prodUnitPrice are through getProduct() ):

    public int getCost() {
    return quantity * item.getUnitPrice();
}

public Product getProduct() {
    return item;
}

public int getQuantity() {
    return quantity;
}

Answer 1

You use i to identify a certain row, but the value of i changes when you add more rows.

public static void addRow() {   
    int rowNum = i; //solution: a local variable to keep current i value  
     .....
    decreaseQuantBut.setOnAction(e -> Controller.shoppingCart.getOrder(rowNum).decreaseQuantity());
    increaseQuantBut.setOnAction(e -> Controller.shoppingCart.getOrder(rowNum).increaseQuantity());
    .....
}