Как прокручивать вертикальную полосу прокрутки на JScrollPane?

Question

Я использую Netbeans с Java/Swing, и у меня есть проблема с моей панелью прокрутки. Прежде всего у меня есть два компонента JPanel внутри моей панели прокрутки. Когда я запускаю все компоненты, я не вижу вторую панель. Я хотел, чтобы, когда я нажимаю кнопку, вторая панель отображается видимой (она работает), а вертикальная полоса прокрутки перемещается вниз, чтобы отобразить вторую панель.

Я использую этот код, когда я нажимаю на кнопку:

public void eventoAdd() { 
     miVista.getJpanelSegundo().setVisible(true); 
     miVista.getJScrollPane1().getVerticalScrollBar().setValue(280); 
} 

Вертикальная полоса прокрутки никогда не идет на дно, на первый щелчок, но при второй попытке казаться, что вертикальная полоса прокрутки идет ко дну. В чем проблема?

PS: Я вижу много вопросов, но ответов на этот конкретный вопрос нет.

/* 
* 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. 
*/ 

/** 
* 
* @author rober 
*/ 
public class View extends javax.swing.JFrame { 

    /** 
    * Creates new form View 
    */ 
    public View() { 
    initComponents(); 
    jPanelSecond.setVisible(false); 

    } 

    /** 
    * 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() { 

    jScrollPaneFirst = new javax.swing.JScrollPane(); 
    jPanelMain = new javax.swing.JPanel(); 
    jPanelFirst = new javax.swing.JPanel(); 
    jPanelSecond = new javax.swing.JPanel(); 
    jButton1 = new javax.swing.JButton(); 

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); 

    jScrollPaneFirst.setHorizontalScrollBarPolicy(javax.swing.ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER); 

    jPanelFirst.setBorder(javax.swing.BorderFactory.createTitledBorder("First")); 

    javax.swing.GroupLayout jPanelFirstLayout = new javax.swing.GroupLayout(jPanelFirst); 
    jPanelFirst.setLayout(jPanelFirstLayout); 
    jPanelFirstLayout.setHorizontalGroup(
     jPanelFirstLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addGap(0, 0, Short.MAX_VALUE) 
    ); 
    jPanelFirstLayout.setVerticalGroup(
     jPanelFirstLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addGap(0, 61, Short.MAX_VALUE) 
    ); 

    jPanelSecond.setBorder(javax.swing.BorderFactory.createTitledBorder("Second")); 

    javax.swing.GroupLayout jPanelSecondLayout = new javax.swing.GroupLayout(jPanelSecond); 
    jPanelSecond.setLayout(jPanelSecondLayout); 
    jPanelSecondLayout.setHorizontalGroup(
     jPanelSecondLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addGap(0, 294, Short.MAX_VALUE) 
    ); 
    jPanelSecondLayout.setVerticalGroup(
     jPanelSecondLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addGap(0, 63, Short.MAX_VALUE) 
    ); 

    javax.swing.GroupLayout jPanelMainLayout = new javax.swing.GroupLayout(jPanelMain); 
    jPanelMain.setLayout(jPanelMainLayout); 
    jPanelMainLayout.setHorizontalGroup(
     jPanelMainLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addComponent(jPanelFirst, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) 
     .addComponent(jPanelSecond, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) 
    ); 
    jPanelMainLayout.setVerticalGroup(
     jPanelMainLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addGroup(jPanelMainLayout.createSequentialGroup() 
      .addComponent(jPanelFirst, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) 
      .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) 
      .addComponent(jPanelSecond, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) 
      .addContainerGap()) 
    ); 

    jScrollPaneFirst.setViewportView(jPanelMain); 

    jButton1.setText("Add"); 
    jButton1.addActionListener(new java.awt.event.ActionListener() { 
     public void actionPerformed(java.awt.event.ActionEvent evt) { 
      jButton1ActionPerformed(evt); 
     } 
    }); 

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); 
    getContentPane().setLayout(layout); 
    layout.setHorizontalGroup(
     layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addGroup(layout.createSequentialGroup() 
      .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
       .addComponent(jScrollPaneFirst, javax.swing.GroupLayout.PREFERRED_SIZE, 280, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addGroup(layout.createSequentialGroup() 
        .addGap(98, 98, 98) 
        .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 58, 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() 
      .addComponent(jScrollPaneFirst, javax.swing.GroupLayout.PREFERRED_SIZE, 113, javax.swing.GroupLayout.PREFERRED_SIZE) 
      .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) 
      .addComponent(jButton1)) 
    ); 

    pack(); 
    }// </editor-fold>       

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {           
    jPanelSecond.setVisible(true); 
    jScrollPaneFirst.getVerticalScrollBar().setValue(280); 
    }           

    /** 
    * @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(View.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
    } catch (InstantiationException ex) { 
     java.util.logging.Logger.getLogger(View.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
    } catch (IllegalAccessException ex) { 
     java.util.logging.Logger.getLogger(View.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
    } catch (javax.swing.UnsupportedLookAndFeelException ex) { 
     java.util.logging.Logger.getLogger(View.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 View().setVisible(true); 
     } 
    }); 
    } 

    // Variables declaration - do not modify      
    private javax.swing.JButton jButton1; 
    private javax.swing.JPanel jPanelFirst; 
    private javax.swing.JPanel jPanelMain; 
    private javax.swing.JPanel jPanelSecond; 
    private javax.swing.JScrollPane jScrollPaneFirst; 
    // End of variables declaration     
} 

Answer 1

В личных предпочтений, я считаю scrollRectToVisible быть одним из самых надежных средств для достижения этой цели, но вы должны знать, как использовать его

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { 
    jPanelSecond.setVisible(true); 
    Rectangle viewBounds = jScrollPaneFirst.getViewportBorderBounds(); 
    Dimension size = jPanelMain.getPreferredSize(); 
    jPanelMain.scrollRectToVisible(new Rectangle(0, size.height, viewBounds.width, viewBounds.height)); 
    //jScrollPaneFirst.getVerticalScrollBar().setValue(280); 
}