將JPanel添加到JFrame後未顯示

Question

我必須設置基本的JAVA應用程序，包括基於swing的GUI。 我的想法是創建一個JFrame和不同的JPanels，並基於用戶輸入來更改顯示的JPanel。 運行我的應用程序後，將顯示JFrame，但不顯示JPanel的內容。 我認爲在這裏它應該是海峽前進......但它看起來不是。希望你能給我一個提示:)

這裏是我的主：

public class Client { 
    public static void main(String[] args) { 
     MainWindow window = new MainWindow(); 
     window.setVisible(true); 

     LoginView pane = new LoginView(); 
     window.getContentPane().add(pane); 

     window.invalidate(); 
     window.repaint(); 
    } 
} 

我的主窗口：

package client; 

public class MainWindow extends javax.swing.JFrame { 
    public MainWindow() { 
     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") 
    private void initComponents() { 
     setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); 
     org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane()); 
     getContentPane().setLayout(layout); 
     layout.setHorizontalGroup(
      layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING) 
      .add(0, 352, Short.MAX_VALUE) 
     ); 
     layout.setVerticalGroup(
      layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING) 
      .add(0, 250, Short.MAX_VALUE) 
     ); 
     pack(); 
    } 
} 

我LoginView：

package client.views; 

public class LoginView extends javax.swing.JPanel { 
    public LoginView() { 
     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") 
    private void initComponents() { 
     jLabel1 = new javax.swing.JLabel(); 
     jLabel1.setText("Login"); 
     org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(this); 
     this.setLayout(layout); 
     layout.setHorizontalGroup(
      layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING) 
      .add(layout.createSequentialGroup() 
       .addContainerGap() 
       .add(jLabel1) 
       .addContainerGap(345, Short.MAX_VALUE)) 
     ); 
     layout.setVerticalGroup(
      layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING) 
      .add(layout.createSequentialGroup() 
       .addContainerGap() 
       .add(jLabel1) 
       .addContainerGap(264, Short.MAX_VALUE)) 
     ); 
    } 
    private javax.swing.JLabel jLabel1; 
} 

Answer 1

你知道其他的事情，比打電話revalidate()和repaint()，我會做的是，而不是調用add()到當前內容窗格只需設置一個新的窗格。

我認爲你的問題涉及到向當前內容窗格添加組件的不正確方法。我認爲這是這種情況，因此，使用setContentPane()方法。

Answer 2

作爲替代方案，請使用CardLayout更改面板。

import java.awt.BorderLayout; 
import java.awt.CardLayout; 
import java.awt.event.ActionEvent; 
import javax.swing.AbstractAction; 
import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 

public class Client { 

    public static void main(String[] args) { 
     JFrame window = new JFrame(); 
     window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     final CardLayout cl = new CardLayout(); 
     final JPanel cards = new JPanel(cl); 
     cards.add(new LoginView(), "Login"); 
     cards.add(new MainView(), "Main"); 
     window.add(cards); 
     JPanel control = new JPanel(); 
     control.add(new JButton(new AbstractAction("Login") { 

      @Override 
      public void actionPerformed(ActionEvent e) { 
       cl.show(cards, "Main"); 
      } 
     })); 
     window.add(control, BorderLayout.SOUTH); 
     window.pack(); 
     window.setLocationRelativeTo(null); 
     window.setVisible(true); 
    } 
} 

class MainView extends javax.swing.JPanel { 

    public MainView() { 
     initComponents(); 
    } 
    ... 
} 

class LoginView extends javax.swing.JPanel { 

    public LoginView() { 
     initComponents(); 
    } 
    ... 
}