Question

我知道在Java中的事件驱动程序中可以找出导致事件的对象（例如JRadioButton被选中），因此将发生某个动作。我的问题是，如果你在一个buttongroup中有两个JRadioButtons，两个都添加了动作监听器，并且你继续从一个选择到另一个，是否有可能找出之前选择的JRadioButton ？换句话说，如果我选择了另一个JRadioButton，是否可以在选择当前JRadioButton之前编写确定先前选择了JRadioButton的代码？

public class Drinks extends JPanel implements ActionListener{
double drinksPrice = 2.10;
double noDrinks = 0;
static  String selectedDrink;
JRadioButton btnPepsi = new JRadioButton("Pepsi"); //add a button to choose different drinks

JRadioButton btnMtDew = new JRadioButton("Mt Dew"); 

JRadioButton btnDietPepsi= new JRadioButton("Diet Pepsi");

JRadioButton btnCoffee = new JRadioButton("Coffee");

JRadioButton btnTea = new JRadioButton("Tea");

JRadioButton btnNone = new JRadioButton("None");
JLabel lblDrinksHeading = new JLabel("Choose a drink (each drink is $2.10):");
ButtonGroup drinksButtonGroup = new ButtonGroup();



private static final long serialVersionUID = 1L;

public Drinks(){

    setLayout(new FlowLayout());    //Using GridLayout  

    btnPepsi.setActionCommand(btnPepsi.getText());    //set the ActionCommand to getText so I can retrieve the name for the receipt

    btnMtDew.setActionCommand(btnMtDew.getText());

    btnDietPepsi.setActionCommand(btnDietPepsi.getText());

    btnCoffee.setActionCommand(btnCoffee.getText());

    btnTea.setActionCommand(btnTea.getText());

    btnNone.setActionCommand(btnNone.getText());

    drinksButtonGroup.add(btnPepsi);
    drinksButtonGroup.add(btnMtDew);
    drinksButtonGroup.add(btnDietPepsi);
    drinksButtonGroup.add(btnCoffee);
    drinksButtonGroup.add(btnTea);
    drinksButtonGroup.add(btnNone);
    btnNone.setSelected(true); //set default to "none"

    btnPepsi.addActionListener(this);
    btnMtDew.addActionListener(this);
    btnDietPepsi.addActionListener(this);
    btnCoffee.addActionListener(this);
    btnTea.addActionListener(this);
    btnNone.addActionListener(this);

    add(lblDrinksHeading);

    add(btnPepsi);

    add(btnDietPepsi);

    add(btnMtDew);

    add(btnCoffee);

    add(btnTea);

    add(btnNone);


    repaint();
    revalidate();

    selectedDrink = drinksButtonGroup.getSelection().getActionCommand();
//add the drink price to totalPrice, it is adding it every time though, even if its none
/*if(drinksButtonGroup.getSelection() == btnNone){
    MenuFrame.totalPrice += 0;
    }
    else{
        MenuFrame.totalPrice += drinksPrice;
        }
*/


//      buttonGroup1.getSelection().getActionCommand()

//String selectedDrink = drinksButtonGroup.getSelection().toString();
//class 

}

@Override
public void actionPerformed(ActionEvent e) {

    Object source = e.getSource();

    if(source == btnNone) {

        MenuFrame.totalPrice += 0;
        TaxAndGratuityFrame.subtotalTextField.setText("$" + MenuFrame.totalPrice);
        TaxAndGratuityFrame.subtotalVariable = MenuFrame.totalPrice;
        TaxAndGratuityFrame.taxVariable = TaxAndGratuityFrame.subtotalVariable * TaxAndGratuityFrame.TAX_RATE;
        TaxAndGratuityFrame.taxTextField.setText("$" + TaxAndGratuityFrame.taxVariable);
        Receipt.receiptTotal.setText("Total: $" + (MenuFrame.totalPrice));
        Receipt.receiptsubtotal.setText("Subtotal: " + (TaxAndGratuityFrame.subtotalVariable));

    }

    else {

        MenuFrame.totalPrice += drinksPrice;
        TaxAndGratuityFrame.subtotalTextField.setText("$" + MenuFrame.totalPrice);
        TaxAndGratuityFrame.subtotalVariable = MenuFrame.totalPrice;
        TaxAndGratuityFrame.taxVariable = TaxAndGratuityFrame.subtotalVariable * TaxAndGratuityFrame.TAX_RATE;
        TaxAndGratuityFrame.taxTextField.setText("$" + TaxAndGratuityFrame.taxVariable);
        Receipt.receiptTotal.setText("Total: $" + (MenuFrame.totalPrice));
        Receipt.receiptsubtotal.setText("Subtotal: " + (TaxAndGratuityFrame.subtotalVariable));

    }

}

编辑：我会更具体。我正在创建一个“虚构的”餐厅计划。在其中，我列出了几种价格相同的饮料（例如百事可乐：2.10美元，Mountain Due：2.10美元等）。这些列出的饮料是JRadioButtons。一旦客户点击其中一个按钮“订购饮料”，2.10美元将被添加到“总”变量中。但是，当用户想要更改饮料时会出现问题，因为如果他们点击不同的JRadioButton，仍然会将$ 2.10添加到“total”变量中。我想做到这一点，他们可以改变那里饮料，而不是每次都给订单增加2.10美元。

Answer 1

我认为问题出在这一行：

MenuFrame.totalPrice += drinksPrice;

因为“+ =”将值增加另一个值而不是简单地添加两个值。

因此，每当用户点击其中一个单选按钮时，它将不断向您的总价值添加2.10，而如果您只是说：

MenuFrame.totalPrice = MenuFrame.totalPrice + drinksPrice;

它会将您的总价格设置为当前总价格加上饮料价格，而不是每次按下按钮时将总价格加上2.10。

Answer 2

也许我误解了这个问题，但我正在考虑创建一个公共变量，然后在动作监听器中使用刚刚选中的单选按钮更新变量。当所选事件触发时，您可以查看变量以查看上次选择了哪个单选按钮，执行您想要的操作，然后使用新的单选按钮进行更新。

Java确定选择了哪个JRadioButton

2 个答案: