如何爲JFrame添加新元素並將其顯示出來

Question

我有一個帶滾動窗格的GUI。滾動窗格通過JPanels的JPanel滾動。我希望能夠再添加一個到subJPanels的列表，並有JFrame更新來做到這一點。我現在有數組更新，但不是JFrame。

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package SSCCE; 

import java.awt.BorderLayout; 
import java.awt.Dimension; 
import java.awt.FlowLayout; 
import java.awt.GridLayout; 
import java.awt.Toolkit; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.io.IOException; 
import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.JTextField; 

public class Add extends JFrame{ 
    private JPanel[] branches; 
    private JPanel pane; //Pane that stores accounts 
    private JScrollPane scroller; 
    private JButton newBranch; 

    public static void main(String[] args) { 
     JFrame frame = new Add(); 
    } 

    public Add(){ 
     this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     this.setSize(500, 500); 
     this.setTitle("How Do I add?"); 

     this.setLayout(new BorderLayout()); 

     this.add(statusBar(), BorderLayout.NORTH); 

     populateBranches(); 

     pane = new JPanel(); 
     pane.setLayout(new GridLayout(branches.length,1)); 
     for (int i = 0; i < branches.length; i++){ 
      pane.add(branches[i]); 
     } 

     scroller = new JScrollPane(pane); 
     scroller.createVerticalScrollBar(); 
     this.add(scroller,BorderLayout.CENTER); 

     this.setVisible(true); 
    } 

    private JPanel statusBar(){ 
     JPanel statusBar = new JPanel(); 
     statusBar.setLayout(new FlowLayout()); 

     newBranch = new JButton("New Branch"); 
       newBranch.addActionListener(new ButtonEventHandler()); 

     statusBar.add(newBranch); 
     return statusBar; 
    } 

    private void populateBranches(){ 
     branches = new JPanel[2]; 

     for (int i = 0; i < branches.length; i++){ 
      branches[i] = new JPanel(); 
      branches[i].setLayout(new FlowLayout()); 
      branches[i].add(new JTextField(20)); 
     } 
    } 

    private void newBranch(){ 
     JPanel[] tempBranches = new JPanel[branches.length + 1]; 
       System.out.println(tempBranches.length); 

     for (int i = 0; i < branches.length; i++){ 
      tempBranches[i] = branches[i]; 
     } 

     tempBranches[branches.length] = new JPanel(); 
     tempBranches[branches.length].setLayout(new FlowLayout()); 
     tempBranches[branches.length].add(new JTextField(20)); 
     branches = tempBranches; 

     pane = new JPanel(); 
     pane.setLayout(new GridLayout(branches.length, 1)); 
     for (int i = 0; i < branches.length; i++){ 
      pane.add(branches[i]); 
     } 
       pane.repaint(); 
       pane.validate(); 

     scroller = new JScrollPane(pane); 
     this.add(scroller, BorderLayout.CENTER); 

     this.repaint(); 
     this.validate(); 
    } 

    private class ButtonEventHandler implements ActionListener { 
     @Override 
     public void actionPerformed(ActionEvent event) { 
      String btnClkd = event.getActionCommand(); 
      if (btnClkd.equals("New Branch")){ 
       newBranch(); 
      } 
     } 
    } 
} 

Answer 1

如果允許GridLayout的成長，你可以更簡單的組件添加到它：

// 0 means new rows are added as needed 
pane.setLayout(new GridLayout(0, 1)); 

// ... 

private void newBranch(){ 
    // Create the component 
    JPanel branch = new JPanel(); 
    branch.add(new JTextField(20)); 
    // + any additional subcomponents 

    // and just add it where the others already are 
    pane.add(branch); 
    pane.revalidate(); 
}