Getting text value from a jButton

问题

So I need to simply check whether a clicked button's text is "X" or "O" (making tic tac toe) This code doesn't work:

if (jButton1.getText()=="X")

However the following code does work:

String jButText = jButton1.getText();
if (jButText=="X")

Why doesn't the first bit of code work when the second does? Does it need to be something more like if (jButton1.getText().toString=="X")? By the way, I don't think toString exists in Java. That is just somewhat the equivalent in Visual Basic, which is what I normally use to create GUIs.

回答1:

This behavior is not reproducible in java 1.7.0_45 or 1.7.0_25, it might be a weird occurrence of String interning for your java version.

In order for your code to work properly on all java versions you have to use equals()

== compares objects meanwhile .equals() compares the content of the string objects.

jButton1.getText().equals("X")

回答2:

This was also driving me nuts when using AWT Button class... Here's the answer: There is no .getText() method for a Button... you need to use .getLabel()

Now, the story for JButtons: Depending on your version of java, getLabel() was deprecated, and finally replaced by getText... Aren't namespaces wonderful?

回答3:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class MyFrame extends JFrame{
    JButton equalsButton;
    JLabel ansLabel;
    JLabel addLabel;
    JTextField text1;
    JTextField text2;

    MyFrame (){
        setSize(300,300); 
        setDefaultCloseOperation(3);
        setLayout(new FlowLayout());
        text1=new JTextField(10);
        add(text1);
        addLabel=new JLabel("+");
        add(addLabel);
        text2=new JTextField(10);
        add(text2);     
        equalsButton=new JButton("=");
        equalsButton.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent evt){
                int num1=Integer.parseInt(text1.getText());
                int num2=Integer.parseInt(text2.getText());
                int tot=num1+num2;
                ansLabel.setText(Integer.toString(tot));
            }
        });
        add(equalsButton);
        ansLabel=new JLabel("    "); 
        add(ansLabel);
        pack();
        setVisible(true);
    }
}

class Demo{
    public static void main(String args[]){
        MyFrame f1=new MyFrame();

    }
}

回答4:

in java when you compare strings using == , you're comparing their memory addresses, to check if two strings contains same text you should call .equals()

if ("X".equals(jButton1.getText()))

来源：https://stackoverflow.com/questions/20082051/getting-text-value-from-a-jbutton

标签

java

swing

user-interface

jbutton