使用mouseDrag滚动时临时禁用或阻止重新绘制JViewPort [英] Temporarily disable or prevent repainting JViewPort on scrolling with a mouseDrag

问题描述

我编写了如下定义的MouseListener，以便可以移动JButton来重新排序JPanel中的组件. JPanel在JScrollPane之内，因此添加多个组件时可以滚动它们.

I have written a MouseListener as defined below so that I can move a JButton around to reorder the components that are within the JPanel. The JPanel is within a JScrollPane so that when multiple components are added they can be scrolled.

我遇到的问题是，当拖动组件并且鼠标移出滚动窗格/视口时，组件将重新回到其在JPanel中的位置，然后将其绘制在正确的位置.我认为此行为是由于视口在调用scrollRectToVisible()

The problem I have is that when dragging the component and the mouse goes out of the scrollpane/viewport then the component will snap back to its position within the JPanel then will be drawn in the correct location. I assume that this behavior is due to the Viewport calling a repaint of its children when I call scrollRectToVisible()

有办法防止这种情况发生吗?

Is there a way that I can prevent this from happening?

请注意，我仅限于Java 5

Please note that I am limited to Java 5

监听器

import java.awt.Component;
import java.awt.Container;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import javax.swing.JViewport;
import javax.swing.SwingUtilities;
import javax.swing.event.MouseInputAdapter;

public class DragListener extends MouseInputAdapter
{
    private Point location;
    private MouseEvent pressed;
    private MouseEvent dragged;
    private MouseEvent dropped;

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

    @Override
    public void mouseDragged(MouseEvent me)
    {
        dragged = me;
        Component component = dragged.getComponent();
        Container parent = component.getParent();
        Container superParent = parent.getParent();

        if(superParent instanceof JViewport)
        {
            JViewport vp = (JViewport)superParent;
            Rectangle vpb = vp.getBounds();
            Point pt = MouseInfo.getPointerInfo().getLocation();
            SwingUtilities.convertPointFromScreen(pt, vp);

            if(!vpb.contains(pt))
            {
                int yDiff = (pt.y < vpb.y ) ? pt.y : pt.y - vpb.height;
                vpb.translate(0, yDiff);
                vp.scrollRectToVisible(vpb);
            }
        }

        location = component.getLocation(location);
        int x = location.x - pressed.getX() + me.getX();
        int y = location.y - pressed.getY() + me.getY();
        component.setLocation(x, y);
    }

    // Mouse release omitted
}

Gui (在NetBeans中创建)

Gui (Created in NetBeans)

import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.MouseMotionListener;
import javax.swing.JButton;
import javax.swing.JPanel;

public class DragginTest extends javax.swing.JFrame
{
    public DragginTest()
    {
        initComponents();
        addListeners(jButton1, jButton2, jButton3, jButton4, jButton5, jButton6, jButton7, jButton8, jButton9);
    }

    private void addListeners(JButton... buttons)
    {
        DragListener drag = new DragListener();
        for(JButton b : buttons)
        {
            b.addMouseListener(drag);
            b.addMouseMotionListener(drag); 
        }   
    }

    @SuppressWarnings("unchecked")

    private void initComponents()
    {
        jLayeredPane1 = new javax.swing.JLayeredPane();
        jScrollPane1 = new javax.swing.JScrollPane();
        mainPanel = new javax.swing.JPanel();
        jButton1 = new javax.swing.JButton();
        jButton2 = new javax.swing.JButton();
        jButton3 = new javax.swing.JButton();
        jButton4 = new javax.swing.JButton();
        jButton5 = new javax.swing.JButton();
        jButton6 = new javax.swing.JButton();
        jButton7 = new javax.swing.JButton();
        jButton8 = new javax.swing.JButton();
        jButton9 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setPreferredSize(new java.awt.Dimension(450, 450));

        mainPanel.setLayout(new java.awt.GridLayout(5, 2, 2, 2));

        // Below Repeated for buttons 1-9 (left out for conciseness)
        jButton1.setFont(new java.awt.Font("Tahoma", 1, 48)); // NOI18N
        jButton1.setForeground(new java.awt.Color(255, 0, 0));
        jButton1.setText("1");
        mainPanel.add(jButton1);
        // End Repeat

        jScrollPane1.setViewportView(mainPanel);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addGap(40, 40, 40)
            .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 205, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(38, 38, 38))
        );
        layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(40, 40, 40)
            .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 226, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(53, Short.MAX_VALUE))
        );

        pack();
    }

    public static void main(String args[])
    {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                new DragginTest().setVisible(true);
            }
        });
    }

    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JButton jButton4;
    private javax.swing.JButton jButton5;
    private javax.swing.JButton jButton6;
    private javax.swing.JButton jButton7;
    private javax.swing.JButton jButton8;
    private javax.swing.JButton jButton9;
    private javax.swing.JLayeredPane jLayeredPane1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JPanel mainPanel;
}

推荐答案

我在您的DragListener代码中添加了一个hack.基本上，它会在您拖动时删除布局管理器，因此重新验证无效，并且在释放鼠标时会恢复布局管理器:

I added a hack to your DragListener code. Basically it removes the layout manager while you are dragging so the revalidates do nothing and it restores the layout manager when the mouse is released:

import java.awt.*;
import java.awt.Container;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import javax.swing.JViewport;
import javax.swing.SwingUtilities;
import javax.swing.event.MouseInputAdapter;

public class DragListener extends MouseInputAdapter
{
    private Point location;
    private MouseEvent pressed;
    private MouseEvent dragged;
    private MouseEvent dropped;
    private LayoutManager layout;

    @Override
    public void mousePressed(MouseEvent me)
    {
        pressed = me;
        Component component = me.getComponent();
        Container parent = component.getParent();
        parent.setPreferredSize(parent.getPreferredSize());
        layout = parent.getLayout();
        parent.setLayout(null);
    }

    @Override
    public void mouseDragged(MouseEvent me)
    {
        dragged = me;
        Component component = dragged.getComponent();
        Container parent = component.getParent();
        Container superParent = parent.getParent();

        if(superParent instanceof JViewport)
        {
            JViewport vp = (JViewport)superParent;
            Rectangle vpb = vp.getBounds();
            Point pt = MouseInfo.getPointerInfo().getLocation();
            SwingUtilities.convertPointFromScreen(pt, vp);

            if(!vpb.contains(pt))
            {
                int yDiff = (pt.y < vpb.y ) ? pt.y : pt.y - vpb.height;
                vpb.translate(0, yDiff);
                vp.scrollRectToVisible(vpb);
            }
        }

        location = component.getLocation(location);
        int x = location.x - pressed.getX() + me.getX();
        int y = location.y - pressed.getY() + me.getY();
        component.setLocation(x, y);
    }

    // Mouse release omitted
    @Override
    public void mouseReleased(MouseEvent me)
    {
        Component component = me.getComponent();
        Container parent = component.getParent();
        parent.setPreferredSize( null );
        parent.setLayout(layout);
        parent.validate();
        parent.repaint();
    }
}

当然，我假设您真正的mouseReleased代码将具有将按钮插入Container中适当位置的逻辑，以便其实际位置可以由GridLayout维护，否则组件将回到其原始位置.

Of course I assume your real mouseReleased code will have logic to insert the button into the appropriate place in the Container so its real location can be maintained by the GridLayout, otherwise the component will just go back to its original location.

这是释放鼠标按钮时将按钮移到新位置的版本.有点复杂，因为您需要担心ZOrder.那就是将组件向下拖动是可以的.但是，如果您尝试将一个组件向上拖动，则该组件将被绘制在其他按钮下方.临时重置ZOrder可以解决此问题.

Here is a version that moves the button to its new location when the mouse button is released. A little complicated because you need to worry about ZOrder. That is dragging a component down is ok. But if you try to drag a component up, then it gets painted below the other buttons. Temporarily resetting the ZOrder solves this problem.

男孩，代码开始成为一个大问题:)临时的null布局和临时的ZOrder.

Boy the code is beginning to be a big hack:) Temporary null layout and temporary ZOrder.

反正这里是代码:

import java.awt.*;
import java.awt.Container;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import javax.swing.*;
import javax.swing.SwingUtilities;
import javax.swing.event.MouseInputAdapter;

public class DragListener extends MouseInputAdapter
{
    private Point location;
    private MouseEvent pressed;
    private MouseEvent dragged;
    private MouseEvent dropped;
    private LayoutManager layout;
    private Rectangle originalBounds;
    private int originalZOrder;

    @Override
    public void mousePressed(MouseEvent me)
    {
        pressed = me;
        Component component = me.getComponent();
        Container parent = component.getParent();
        originalBounds = component.getBounds();
        originalZOrder = parent.getComponentZOrder(component);
        parent.setPreferredSize(parent.getPreferredSize());
        layout = parent.getLayout();
        parent.setLayout(null);
        parent.setComponentZOrder(component, 0);
    }

    @Override
    public void mouseDragged(MouseEvent me)
    {
        JComponent source = (JComponent) me.getComponent();
        JComponent parent = (JComponent) source.getParent();

        Point p = me.getPoint();
        p = SwingUtilities.convertPoint(source, p, parent);

        Rectangle bounds = source.getBounds();
        bounds.setLocation(p);

        bounds.x -= pressed.getX();
        bounds.y -= pressed.getY();
        source.setLocation(0, bounds.y);
        parent.scrollRectToVisible(bounds);
    }

    @Override
    public void mouseReleased(MouseEvent me)
    {
        boolean moved = false;
        Component component = me.getComponent();
        Container parent = component.getParent();
        Point location = component.getLocation();

        if (location.y < 0)
        {
            parent.add(component, 0);
            moved = true;
        }
        else
        {
            for (int i = 0; i < parent.getComponentCount(); i++)
            {
                Component c = parent.getComponent(i);
                Rectangle bounds = c.getBounds();

                if (c == component)
                    bounds = originalBounds;

                //  Component is released in the space originally occupied
                //  by the component or over an existing component

                if (bounds.contains(0, location.y))
                {
                    if (c == component)
                    {
                        parent.setComponentZOrder(component, originalZOrder);
                    }
                    else
                    {
                        parent.add(component, i);
                    }

                    moved = true;
                    break;
                }
            }
        }

        //  Component is positioned below all components in the container

        if (!moved)
        {
            parent.add(component, parent.getComponentCount() - 1);
        }

        //  Restore layout manager

        parent.setPreferredSize( null );
        parent.setLayout(layout);
        parent.validate();
        parent.repaint();
        component.requestFocusInWindow();
    }

    private static void createAndShowGUI()
    {
        JPanel panel = new JPanel( new GridLayout(0, 1) );
        DragListener drag = new DragListener();

        for (int i = 0; i <10; i++)
        {
            JButton button = new JButton("" + i);
            button.setFont(new java.awt.Font("Tahoma", 1, 48));
            button.setForeground(new java.awt.Color(255, 0, 0));
            button.addMouseListener(drag);
            button.addMouseMotionListener(drag);
            panel.add( button );
        }

        JFrame frame = new JFrame("SSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( new JScrollPane(panel) );
        frame.setLocationByPlatform( true );
        frame.setSize(200, 400);
        frame.setVisible( true );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowGUI();
            }
        });
    }
}

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