嘿伙计我已经做了一个连接到我的数据库的小型登录应用程序，但是我有一个小问题，我不知道如何将框架居中，我的意思是当我启动应用程序使其正确进入屏幕中间。 我尝试过这个：
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize()
但我不确定在哪里放置它并且它不完整。 提前谢谢。
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package mysqltryouts;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Scanner;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
/**
*
* @author ExtremeSwat
*/
public class login_panel extends javax.swing.JFrame {
private Connection connect = null;
private Statement statement = null;
private PreparedStatement preparedStatement = null;
private ResultSet resultSet = null;
public void readDataBase() throws Exception
{
String username = jTextField1.getText();
String password = jPasswordField1.getText();
// System.out.println(username);
// System.out.println(password);
// System.out.println("test");
//---------------------
// String databaseUsername = "";
// String databasePassword = "";
try {
// this will load the MySQL driver, each DB has its own driver
Class.forName("com.mysql.jdbc.Driver");
// setup the connection with the DB.
connect = DriverManager
.getConnection("jdbc:mysql://localhost/cards?"
+ "user=root&password=password");
//String sqlQuery = "select count(*) > 0 as match_found FROM username WHERE username = ? and password = MD5(?)";
String sqlQuery = "SELECT * FROM username WHERE username = ? and password = MD5(?)";
// String sqlQuery = "select count(*) > 0 as cnt FROM username WHERE username = ? and password = MD5(?)";
PreparedStatement pst = connect.prepareStatement( sqlQuery );
pst.setString( 1, username );
pst.setString( 2, password );
ResultSet rs = pst.executeQuery();
if( rs.next() ) {
System.out.println("You did it!");
}
else
System.out.println("Bad PW");
} catch (Exception e) {
throw e;
} finally {
close();
}
}
private void close() {
close(resultSet);
close(statement);
close(connect);
}
private void close(AutoCloseable c) throws UnsupportedOperationException {
try {
if (c != null) {
c.close();
}
} catch (Exception e) {
// don't throw now as it might leave following closables in undefined state
}
}
/**
* Creates new form login_panel
*/
public login_panel() {
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jTextField1 = new javax.swing.JTextField();
jPasswordField1 = new javax.swing.JPasswordField();
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
jButton1 = new javax.swing.JButton();
jButton2 = new javax.swing.JButton();
jLabel3 = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jTextField1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jTextField1ActionPerformed(evt);
}
});
jPasswordField1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jPasswordField1ActionPerformed(evt);
}
});
jLabel1.setText("Username");
jLabel2.setText("Password");
jButton1.setText("Login");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
jButton2.setText("eXIT");
jButton2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton2ActionPerformed(evt);
}
});
jLabel3.setFont(new java.awt.Font("Old English Text MT", 1, 36)); // NOI18N
jLabel3.setText("Login B0$$");
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(66, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jButton2)
.addContainerGap())
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jLabel3)
.addGap(53, 53, 53))))
.addGroup(layout.createSequentialGroup()
.addGap(20, 20, 20)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jLabel1)
.addComponent(jLabel2))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 92, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addComponent(jButton1))
.addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, 92, javax.swing.GroupLayout.PREFERRED_SIZE))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel3)
.addGap(38, 38, 38)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel1)
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton1))
.addGap(4, 4, 4)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel2)
.addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 63, Short.MAX_VALUE)
.addComponent(jButton2))
);
pack();
}// </editor-fold>
private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}
private void jPasswordField1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
try{
// login_panel dao = new login_panel();
//
//
// dao.readDataBase();
this.readDataBase();
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
}
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
int dialogButton = JOptionPane.YES_NO_OPTION;
int dialogResult = JOptionPane.showConfirmDialog(null, "Exit? ", "Information",dialogButton);
if(dialogResult == JOptionPane.YES_OPTION)
{
JOptionPane.showMessageDialog(null, "Thanks for the stay","Confirm",JOptionPane.INFORMATION_MESSAGE);
System.exit(0);
}else
{
JOptionPane.showMessageDialog(null, "Remaining...","Remaining....",JOptionPane.INFORMATION_MESSAGE);
}
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(login_panel.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(login_panel.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(login_panel.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(login_panel.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new login_panel().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JPasswordField jPasswordField1;
private javax.swing.JTextField jTextField1;
// End of variables declaration
}
答案 0 :(得分：3)
如果您使用的是Java 1.4或更高版本，则可以在对话框，框架或窗口上使用简单方法setLocationRelativeTo（null）来居中它。
答案 1 :(得分：3)
//new login_panel().setVisible(true); <-- get rid of this
login_panel frame = new login_panel();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
在run()
备注：遵循Java命名约定。类名使用大写字母，使用驼峰套管。 login_panel→LoginPanel
答案 2 :(得分：1)
这样做
imension dim = Toolkit.getDefaultToolkit().getScreenSize();
frame.setLocation(dim.width/2-this.getSize().width/2, dim.height/2-this.getSize().height/2);