如何知道是否选中了Jcheckbox？ [英] How do i know if a Jcheckbox is checked?with GUI

问题描述

你能告诉我详细信息我怎么知道一个jcheckbox是否被选中？方法isSelected不能与我一起工作，它在运行时给我一个异常

can you tell me in details how do i know if a jcheckbox is checked or not? method isSelected didn't work with me it gives me an exception while running

{
    Sandwich = new JButton("Tall");
    contentPane.add(Tall);
    Sandwitch.setBounds(350, 110, 90,40);   //in main
    Sandwitch.addActionListener(this);
}
.....

public void actionPerformed(ActionEvent event) {
    JButton clickedButton = (JButton) event.getSource();

    String  buttonText = clickedButton.getText();
    ..........
    if(clickedButton.getText()=="Sandwitch"){
        if(Ketchup.getState()&&!Garlic.getState()){//

        itm=new Item(""+m+clickedButton.getText(),3.0);
        xyz.addItem(itm);
        textArea.append(" "+clickedButton.getText()+",");
        textArea.append(" "+itm.getPrice()+"\n");
    }
    else if(!Ketchup.isSelected()&&Garlic.isSelected()){//

        ....................
    }

正在运行：
此处

您可以帮助我解决这个问题？

can you please help me with this problem?

Boann问我的代码

推荐答案

这里有问题：

JCheckBox Ketchup = new JCheckBox();
Ketchup.setText("Ketchup");
Ketchup.setSize(50,25);
contentPane.add(Ketchup);
Ketchup.setBounds(175, 100, 175,25);

JCheckBox Garlic = new JCheckBox();
Garlic.setText("Garlic");
Garlic.setSize(50,25);
contentPane.add(Garlic);
Garlic.setBounds(175, 120, 175,25);

由于赋值前的JCheckBox，这段代码声明了局部变量叫做番茄酱大蒜。

Because of the "JCheckBox" in front of the assignments, this code is declaring local variables called Ketchup and Garlic. Outside the method, those variables don't exist any more.

同时，ClassName（ProjectInterface？）的私有字段具有相同的名称，但在其他方面不相关。

Meanwhile, the private fields of ClassName (ProjectInterface?) have the same names but are otherwise unrelated. They are left null.

将上述代码移到ClassName构造函数中，并删除赋值前面的JCheckBox。所以你会有：

Move the above code into the ClassName constructor, and remove the "JCheckBox" in front of the assignments. So you'll have:

private JCheckBox Ketchup;
private JCheckBox Garlic;

public ClassName() {
    Ketchup = new JCheckBox();
    Ketchup.setText("Ketchup");
    Ketchup.setSize(50,25);
    add(Ketchup);
    Ketchup.setBounds(175, 100, 175,25);

    Garlic = new JCheckBox();
    Garlic.setText("Garlic");
    Garlic.setSize(50,25);
    add(Garlic);
    Garlic.setBounds(175, 120, 175,25);
}

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