Java 实现可折叠Panel

1.原理

        原理非常简单：就是一个JLabel和JPanel。Jlabel显示标题文字以及标明控件当前是处于展开还是折叠状态的图片；而JPanel主要就一个作用——承载控件的容器。JLabel通过响应鼠标事件来控制JPanel是否显示。这样就可以达到折叠或展开的效果。

2.代码

public class JShrinkablePanel extends JPanel {

private JLabellabel;

private Stringtitle ="";

private JPanelcontentPanel =null;

private boolean isExpanded =true;

private JListlist =new JList();

private IconiconExpand =null;

private IconiconCollapse =null;

public JShrinkablePanel(String title, JPanel contentPanel) {

super();

this.title = title;

this.contentPanel = contentPanel;

initComponents();

initComponentsStatus();

initLayout();

initResources();

unRegisterEvents();

registerEvents();

}

private void initComponents() {

this.label =new JLabel();

}

private void initComponentsStatus() {

this.label.setHorizontalAlignment(JLabel.LEFT);

this.label.setVerticalAlignment(JLabel.CENTER);

this.label.setVerticalTextPosition(JLabel.CENTER);

this.label.setBackground(this.list.getSelectionBackground());

this.iconExpand =new ImageIcon("src/Resources/Expand.png");

this.iconCollapse =new ImageIcon("src/Resources/Collapse.png");

}

private void initLayout() {

this.setLayout(new GridBagLayout());

this.add(this.label,new GridBagConstraints(0,0,1,1,1,0, GridBagConstraints.WEST, GridBagConstraints.HORIZONTAL,new Insets(0,0,0,0),0,0));

this.add(this.contentPanel,new GridBagConstraints(0,1,1,1,1,0, GridBagConstraints.WEST, GridBagConstraints.HORIZONTAL,new Insets(0,0,0,0),0,0));

}

private void initResources() {

this.label.setIcon(this.iconExpand);

this.label.setText(this.title);

}

private void unRegisterEvents() {

this.label.removeMouseListener(this.mouseListener);

}

private void registerEvents() {

this.label.addMouseListener(this.mouseListener);

}

private MouseListenermouseListener =new MouseAdapter() {

@Override

public void mouseClicked(MouseEvent e) {

isExpanded = !isExpanded;

panelVisible();

}

@Override

public void mouseEntered(MouseEvent e) {

label.setOpaque(true);

label.repaint();

}

@Override

public void mouseExited(MouseEvent e) {

label.setOpaque(false);

label.repaint();

}

};

private void panelVisible() {

this.contentPanel.setVisible(this.isExpanded);

this.label.setIcon(this.isExpanded ?this.iconExpand :this.iconCollapse);

}

public static void main(String[] args) {

JFrame jf =new JFrame("JShrinkablePanel");

jf.setBounds(400,200,400,300);

jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JPanel panel=new JPanel();

panel.add(new JButton("Just for show"));

panel.setBorder(BorderFactory.createTitledBorder("Border"));

JShrinkablePanel scrollPane=new JShrinkablePanel("TestJShrinkablePanel",panel);

jf.add(scrollPane);

jf.setVisible(true);

}

}

3.效果

panel展开鼠标在标题Label上

panel展开鼠标没在标题Label上

panel折叠鼠标在标题Label上

panel折叠鼠标没在标题Label上