单击时如何使数字增加1

8cdiaqws  于 2021-08-20  发布在  Java
关注(0)|答案(1)|浏览(333)

此问题已在此处找到答案：

什么是nullpointerexception，如何修复它(（12个答案）
6天前关门。

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.Color;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JTextField;
import javax.swing.JTextPane;

@SuppressWarnings({ "serial", "unused" })
public class jframe extends JFrame {

    private JPanel contentPane;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    jframe frame = new jframe();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public jframe() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBackground(Color.WHITE);
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);

        JLabel lblNewLabel = new JLabel("        PRESS THE BUTTON TO GET CLICKS");
        lblNewLabel.setFont(new Font("Sitka Small", Font.PLAIN, 15));
        lblNewLabel.setBounds(29, 71, 382, 34);
        contentPane.add(lblNewLabel);

        JButton btnNewButton = new JButton("CLICK ME");
        btnNewButton.setFont(new Font("Tahoma", Font.PLAIN, 14));
        btnNewButton.setForeground(Color.DARK_GRAY);
        btnNewButton.setBackground(Color.CYAN);
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) { 
                myMethod();
            }
        });
        btnNewButton.setBounds(153, 139, 116, 42);
        contentPane.add(btnNewButton);

        JTextPane txtpnClicks = new JTextPane();
        txtpnClicks.setForeground(Color.GRAY);
        txtpnClicks.setText("                        CLICKS:"+x);
        txtpnClicks.setFont(new Font("Sylfaen", Font.PLAIN, 15));
        txtpnClicks.setBounds(86, 189, 275, 28);
        contentPane.add(txtpnClicks);
    }
    static int x = 1;
    @SuppressWarnings("null")
    static void add1() {

        x++;
        textpnClicks.setText("CLICKS"+x);
}   

}
I have tried looking for the answer online. When I run the code this error comes up in the console :

线程“awt-eventqueue-0”java.lang.nullpointerexception中的异常：无法调用“javax.swing.jlabel.settext（string）”，因为jframe$2处的jframe.mymethod（jframe.java:77）处的“txtpnclicks”为空。java.desktop/javax.swing.abstractbutton.fireactionperformed（abstractbutton.java:1967）处的actionperformed（jframe.java:59）为空java.desktop/javax.swing.abstractbutton$handler.actionperformed（abstractbutton.java:2308）位于java.desktop/javax.swing.defaultbuttonmodel.fireactionperformed（defaultbuttonmodel.java:405）位于位于java.desktop/java.awt.component.processmouseevent（component.java:6379）的java.desktop/java.awt.component.processmouseevent（component.java:6614）的java.desktop/javax.swing.jcomponent.processmouseevent（jcomponent.java:3342）的java.desktop/java.awt.component.component.processevent（component.java:6379）的javajava.desktop/java.awt.container.processevent（container.java:2263）在java.desktop/java.awt.component.dispatcheventimpl（component.java:4990）在java.desktop/java.awt.container.dispatcheventimpl（container.java:2321）在java.desktop/java.awt.component.dispatchevent（component.java:4822）在java.desktop/java.awt.lightweightdispatcher.RetargetMouseeEvent（container.java:4919）在java.desktop/java.awt.lightweightdispatcher.ProcessMouseeEvent（container.java:4548）在java.desktop/java.awt.container.DispatcheEventImpl（container.java:2307）在java.desktop/java.awt.window.dispatcheventimpl（window.java:2769）在java.desktop/java.awt.component.dispatchevent（component.java:4822）在java.desktop/java.awt.eventqueue.dispatcheventimpl（eventqueue.java:772）在java.desktop/java.awt.eventqueue$4.run（eventqueue.java:721）在java.desktop/java.awt.awt.eventqueue$4.run（eventqueue.java:715）在java.base/java.security.accesscontroller.doprivileged（accesscontroller.java:391）位于java.base/java.security.protectiondomain$javasecurityaccessimpl.dointersectionprivilege（protectiondomain.java:85）位于java.base/java.security.protectiondomain$javasecurityaccessimpl.dointersectionprivilege（protectiondomain.java:95）位于java.desktop/java.awt.eventqueue$5.run（eventqueue.java:745）在java.desktop/java.awt.eventqueue$5.run（eventqueue.java:743）在java.base/java.security.accesscontroller.doprivileged（accesscontroller.java:391）在java.base/java.security.protectiondomain$javasecurityaccessimpl.dointersectionprivilege（protection.java:85）在位于java.desktop/java.awt.eventqueue.dispatchevent（eventqueue.java:742）的java.desktop/java.awt.eventdispatchthread.PumponeeEventForFilters（eventdispatchthread.java:203）的java.desktop/java.awt.eventdispatchthread.pumpeventsforfilter（eventdispatchthread.java:124）位于java.desktop/java.awt.eventdispatchthread.PumpeEventsforHierarchy（eventdispatchthread.java:113）位于java.desktop/java.awt.eventdispatchthread.PumpeEvents（eventdispatchthread.java:109）位于java.desktop/java.awt.eventdispatchthread.run（eventdispatchthread.java:101）位于java.desktop/java.awt.java:90线程“awt-eventqueue-0”java.lang.nullpointerexception中的异常：无法调用“javax.swing.jlabel.settext（string）”，因为jframe$2处的jframe.mymethod（jframe.java:79）处的“txtpnclicks”为空。java.desktop/javax.swing.abstractbutton.fireactionperformed（abstractbutton.java:1967）处的actionperformed（jframe.java:60）为空java.desktop/javax.swing.abstractbutton$handler.actionperformed（abstractbutton.java:2308）位于java.desktop/javax.swing.defaultbuttonmodel.fireactionperformed（defaultbuttonmodel.java:405）位于位于java.desktop/java.awt.component.processmouseevent（component.java:6379）的java.desktop/java.awt.component.processmouseevent（component.java:6614）的java.desktop/javax.swing.jcomponent.processmouseevent（jcomponent.java:3342）的java.desktop/java.awt.component.component.processevent（component.java:6379）的javajava.desktop/java.awt.container.processevent（container.java:2263）在java.desktop/java.awt.component.dispatcheventimpl（component.java:4990）在java.desktop/java.awt.container.dispatcheventimpl（container.java:2321）在java.desktop/java.awt.component.dispatchevent（component.java:4822）在java.desktop/java.awt.lightweightdispatcher.RetargetMouseeEvent（container.java:4919）在java.desktop/java.awt.lightweightdispatcher.ProcessMouseeEvent（container.java:4548）在java.desktop/java.awt.container.DispatcheEventImpl（container.java:2307）在java.desktop/java.awt.window.dispatcheventimpl（window.java:2769）在java.desktop/java.awt.component.dispatchevent（component.java:4822）在java.desktop/java.awt.eventqueue.dispatcheventimpl（eventqueue.java:772）在java.desktop/java.awt.eventqueue$4.run（eventqueue.java:721）在java.desktop/java.awt.awt.eventqueue$4.run（eventqueue.java:715）在java.base/java.security.accesscontroller.doprivileged（accesscontroller.java:391）位于java.base/java.security.protectiondomain$javasecurityaccessimpl.dointersectionprivilege（protectiondomain.java:85）位于java.base/java.security.protectiondomain$javasecurityaccessimpl.dointersectionprivilege（protectiondomain.java:95）位于java.desktop/java.awt.eventqueue$5.run（eventqueue.java:745）在java.desktop/java.awt.eventqueue$5.run（eventqueue.java:743）在java.base/java.security.accesscontroller.doprivileged（accesscontroller.java:391）在java.base/java.security.protectiondomain$javasecurityaccessimpl.dointersectionprivilege（protection.java:85）在位于java.desktop/java.awt.eventqueue.dispatchevent（eventqueue.java:742）的java.desktop/java.awt.eventdispatchthread.PumponeeEventForFilters（eventdispatchthread.java:203）的java.desktop/java.awt.eventdispatchthread.pumpeventsforfilter（eventdispatchthread.java:124）位于java.desktop/java.awt.eventdispatchthread.PumpeEventsforHierarchy（eventdispatchthread.java:113）位于java.desktop/java.awt.eventdispatchthread.PumpeEvents（eventdispatchthread.java:109）位于java.desktop/java.awt.eventdispatchthread.run（eventdispatchthread.java:101）位于java.desktop/java.awt.java:90

JavaIntegerButton

1条答案

按热度按时间
s5a0g9ez

s5a0g9ez1#

功能 add1() 不知道任何关于 JTextPane 类别- txtpnClicks ，因此无法调用方法settext（）。错误日志中写得很清楚
线程“awt-eventqueue-0”java.lang.nullpointerexception中的异常：无法调用“javax.swing.jlabel.settext（string）”，因为jframe.mymethod（jframe.java:77）中的“txtpnclicks”为空
您需要将其传递给函数

static void add1(JTextPane txtpnClicks) {
    x++;
    txtpnClicks.setText("CLICKS:" + x);
}

此外 txtpnClicks 必须在之前创建 btnNewButton ，否则 btnNewButton.addActionListener(e -> add1(txtpnClicks)); 我不明白是什么 txtpnClicks 工作代码：

import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.awt.*;
@SuppressWarnings({"serial", "unused"})
public class jframe extends JFrame {
private JPanel contentPane;

public static void main(String[] args) {
    EventQueue.invokeLater(() -> {
        try {
            jframe frame = new jframe();
            frame.setVisible(true);
        } catch (Exception e) {
            e.printStackTrace();
        }
    });
}

public jframe() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 450, 300);
    contentPane = new JPanel();
    contentPane.setBackground(Color.WHITE);
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    contentPane.setLayout(null);

    JLabel lblNewLabel = new JLabel("PRESS THE BUTTON TO GET CLICKS");
    lblNewLabel.setFont(new Font("Sitka Small", Font.PLAIN, 15));
    lblNewLabel.setBounds(29, 71, 382, 34);
    contentPane.add(lblNewLabel);

    JTextPane txtpnClicks = new JTextPane();
    txtpnClicks.setForeground(Color.GRAY);
    txtpnClicks.setText("CLICKS:" + x);
    txtpnClicks.setFont(new Font("Sylfaen", Font.PLAIN, 15));
    txtpnClicks.setBounds(86, 189, 275, 28);
    contentPane.add(txtpnClicks);

    JButton btnNewButton = new JButton("CLICK ME");
    btnNewButton.setFont(new Font("Tahoma", Font.PLAIN, 14));
    btnNewButton.setForeground(Color.DARK_GRAY);
    btnNewButton.setBackground(Color.CYAN);
    btnNewButton.addActionListener(e -> add1(txtpnClicks));
    btnNewButton.setBounds(153, 139, 116, 42);
    contentPane.add(btnNewButton);
}

static int x = 1;

@SuppressWarnings("null")
static void add1(JTextPane txtpnClicks) {
    x++;
    txtpnClicks.setText("CLICKS:" + x);
}
}
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