Java JPanel，在JScrollPane中包含JComponents和自定义LayoutManager

我已经编写了JComponent的一个子类，它在paintComponent方法中绘制自己。在构造函数中，我使用setBounds设置边界。这个很好用。我将这个子类添加到JPanel中。此JPanel位于JScrollPane中。这个JPanel是JPanel的子类，实现了MouseInputListener和KeyListener。因此，每当用户单击JPanel时，每个JComponent的边界都会根据鼠标点进行检查。如果匹配，则焦点设置为该JComponent。如果焦点在JComponent上，并且用户拖动鼠标，则JComponent将在JPanel中移动。我想要实现的是，每当JPanel中的JComponent的位置发生变化并离开JScrollPane的视口时，滚动条就会可见，JPanel就会调整大小，这样用户就可以滚动到可视区域之外。为了实现这一点，我编写了一个定制的LayoutManager，它不以任何方式布局JComponents，而是绝对位置。但是，每当我在JPanel内部和可视区域外部移动JComponent时，滚动条都不会得到更新。我怎样才能做到这一点

下面是类子类JComponent：

public abstract class Gate extends JComponent {

/**
 * 
 */
private static final long serialVersionUID = 1L;

public Gate() {
    super();
    setBounds(new Rectangle(0, 0, 100, 100));
    setBorder(BorderFactory.createLineBorder(Color.black));
    setFocusable(true);
    setOpaque(false);
    setBackground(Color.white);
}

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    if(hasFocus()) {
        setBorder(BorderFactory.createLineBorder(Color.green));
    } else {
        setBorder(BorderFactory.createLineBorder(Color.black));
    }
    Graphics g2 = g.create();
    g2.setColor(getBackground());
    g2.fillRect(0, 0, getWidth(), getHeight());
    g2.dispose();
}
}

下面是JPanel的子类：

public class GatesPanel extends JPanel implements MouseInputListener, KeyListener {

/**
 * 
 */
private static final long serialVersionUID = 1L;

public GatesPanel() {
    super();
    setLayout(new GateLayout());
    addMouseListener(this);
    addMouseMotionListener(this);
    addKeyListener(this);
    setFocusable(true);
}

@Override
public void mouseClicked(MouseEvent e) {
    if(e.getButton() == MouseEvent.BUTTON1) {
        for(int i = 0; i < getComponentCount(); i++) {
            Component c = getComponent(i);
            if(c instanceof JComponent) {
                JComponent j = (JComponent)c;
                if(j.getBounds().contains(e.getPoint())) {
                    if(j.hasFocus()) {
                        grabFocus();
                    } else {
                        j.grabFocus();
                    }
                }
            }
        }
    }
}

@Override
public void mouseEntered(MouseEvent e) {

}

@Override
public void mouseExited(MouseEvent e) {

}

@Override
public void mousePressed(MouseEvent e) {

}

@Override
public void mouseReleased(MouseEvent e) {

}

@Override
public void mouseDragged(MouseEvent e) {

}

@Override
public void mouseMoved(MouseEvent e) {
    for(int i = 0; i < getComponentCount(); i++) {
        Component c = getComponent(i);
        if(c.hasFocus()) {
            c.setLocation(e.getPoint());
        }
    }
}

@Override
public void keyPressed(KeyEvent e) {

}

@Override
public void keyReleased(KeyEvent e) {

}

@Override
public void keyTyped(KeyEvent e) {

}
}

在此之后，我向GatesPanel添加了一个名为GateAND的Gate子类：

gatesPanel.add(new GateAND());

那么，当用户在滚动窗格包围的面板内移动组件时，滚动条没有更新，这是我做错了什么？欢迎任何帮助

格里兹

maxpa1n87

为了实现这一点，我编写了一个定制的LayoutManager，它不以任何方式布局JComponents，而是绝对位置。但是，每当我在JPanel内部和可视区域外部移动JComponent时，滚动条都不会得到更新

可能布局管理器没有正确设置首选大小。当首选大小大于滚动窗格的大小时，滚动条将自动显示

您还需要确保在完成拖动面板上调用的组件时，

revalidate（）

，以便调用布局管理器

查看为此目的而设计的

下面是一个简单的例子：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;

public class DragLayoutTest
{
    public static void main( String[] args )
    {
        DragListener drag = new DragListener();

        DragLayout dl = new DragLayout();
        dl.setUsePreferredSize(false);

        JPanel panel = new JPanel( dl );
        panel.setBorder( new MatteBorder(10, 10, 10, 10, Color.YELLOW) );

        createLabel(drag, panel, "North", 150, 0);
        createLabel(drag, panel, "West", 0, 100);
        createLabel(drag, panel, "East", 300, 100);
        createLabel(drag, panel, "South", 150, 200);
        createLabel(drag, panel, "Center", 150, 100);

        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new JFrame( "Drag Layout" );
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( new JScrollPane(panel) );
        frame.pack();
        frame.setLocationRelativeTo( null );
        frame.setVisible( true );
    }

    public static void createLabel(MouseInputAdapter drag, JPanel panel, String text, int x, int y)
    {
        JLabel label = new JLabel( text );
        label.setOpaque(true);
        label.setBackground( Color.ORANGE );
        label.setLocation(x, y);
        panel.add( label );
        label.addMouseListener( drag );
        label.addMouseMotionListener( drag );
    }

    static class DragListener extends MouseInputAdapter
    {
        Point location;
        MouseEvent pressed;

        public void mousePressed(MouseEvent me)
        {
            pressed = me;
        }

        public void mouseDragged(MouseEvent me)
        {
            Component component = me.getComponent();
            location = component.getLocation(location);
            int x = location.x - pressed.getX() + me.getX();
            int y = location.y - pressed.getY() + me.getY();
            component.setLocation(x, y);
            ((JComonent)component.getParent()).revalidate();
         }
    }
}

---

.Layout manager通过使用组件的

首选/最小/最大

属性来决定如何以最佳方式布局组件，因为您没有覆盖这些方法中的任何一种，所以在大多数情况下，布局管理器会假定组件的最佳大小为

0x0

（除非布局管理器完全忽略这些属性）感谢您的回复。因此，我只需要覆盖首选/最小/最大值，而不需要调用setBounds（）？我将尝试一下。我将尝试DragLayout，而不是我自己的布局管理器。谢谢。

gatesPanel.add(new GateAND());

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;

public class DragLayoutTest
{
    public static void main( String[] args )
    {
        DragListener drag = new DragListener();

        DragLayout dl = new DragLayout();
        dl.setUsePreferredSize(false);

        JPanel panel = new JPanel( dl );
        panel.setBorder( new MatteBorder(10, 10, 10, 10, Color.YELLOW) );

        createLabel(drag, panel, "North", 150, 0);
        createLabel(drag, panel, "West", 0, 100);
        createLabel(drag, panel, "East", 300, 100);
        createLabel(drag, panel, "South", 150, 200);
        createLabel(drag, panel, "Center", 150, 100);

        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new JFrame( "Drag Layout" );
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( new JScrollPane(panel) );
        frame.pack();
        frame.setLocationRelativeTo( null );
        frame.setVisible( true );
    }

    public static void createLabel(MouseInputAdapter drag, JPanel panel, String text, int x, int y)
    {
        JLabel label = new JLabel( text );
        label.setOpaque(true);
        label.setBackground( Color.ORANGE );
        label.setLocation(x, y);
        panel.add( label );
        label.addMouseListener( drag );
        label.addMouseMotionListener( drag );
    }

    static class DragListener extends MouseInputAdapter
    {
        Point location;
        MouseEvent pressed;

        public void mousePressed(MouseEvent me)
        {
            pressed = me;
        }

        public void mouseDragged(MouseEvent me)
        {
            Component component = me.getComponent();
            location = component.getLocation(location);
            int x = location.x - pressed.getX() + me.getX();
            int y = location.y - pressed.getY() + me.getY();
            component.setLocation(x, y);
            ((JComonent)component.getParent()).revalidate();
         }
    }
}