当我在JScrollPane中滚动水平和垂直滚动条时未调用paintComponent

问题描述

我在使用Swing和JScrollPane时遇到麻烦.我的行为很奇怪.

I am having trouble with Swing and the JScrollPane.I am having a strange behaviour.

我扩展了 JScrollPane .我在其中显示图像，并在其上绘制矩形以定义区域.对于大图像，我有一个水平和垂直滚动条.

I extended JScrollPane. I display an image in it and draw rectangles over it to define areas.With a big image, I have an Horizontal and a Vertical scrollbars.

我-好的-当我移动一个滚动条或另一个滚动条时，我也看到图像也应移动.II-不正常-当我移动一个滚动条并使其停留在最大和最小位置之间时，那么当我移动第二个滚动条时，我的图像就会消失.

I - ok - When I move one scrollbar or the other I see my image move too as it should.II - not ok - When I move one scrollbar an leave it in between max and min position, then when I move my second scrollbar my image disappears.

通过一些调试打印，我发现在情况II中没有调用 paintComponent .

With some debug prints, I found out that paintComponent, is not called when in case II.

我想知道为什么它不调用 paintComponent 以及如何解决它.

I would like to know why it is not calling paintComponent and how I can fix it.

以下是我的课程:

package GUI;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Point;
import javax.swing.JScrollPane;

public class DrawingPanel extends JScrollPane {

    private static final long serialVersionUID = 1L;
    private static final Color DRAWING_COLOR = new Color(255, 100, 200);
    private static final Color FINAL_DRAWING_COLOR = Color.red;
    private static final double ZOOMING_STEP = 1.1;

    private Image sImg;
    private Point startPt;
    private Point endPt;
    private Point currentPt;

    private int prefW;
    private int prefH;
    private double zoomFactor = 1;
    private boolean zoomer    = false;
    private boolean loaded    = false;

    public DrawingPanel() {
        setFocusable(true);
        setFocusTraversalKeysEnabled(false);
    }

    public void loadImage(Image img) {
        sImg       = img;
        prefW      = sImg.getWidth(null);
        prefH      = sImg.getHeight(null);
        zoomFactor = getSize().getWidth() / prefW;
        zoomer     = true;
        loaded     = true;

        repaint();
        revalidate();
    }

    int countPaint = 0;

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        System.out.println("paintComponent " + countPaint);

        if (loaded) {
            int zoomWidth  = (int) (prefW * zoomFactor);
            int zoomHeight = (int) (prefH * zoomFactor);

            if (zoomer) {
                ((Graphics2D) g).scale(zoomFactor, zoomFactor);
                setSize(zoomWidth, zoomHeight);
                zoomer = false;
            }

            g.drawImage(sImg, 0, 0, zoomWidth, zoomHeight, null);
            drawRectangle(g);
        }

        g.dispose();
        countPaint++;
    }

    @Override
    public Dimension getPreferredSize() {
        return loaded ?
            this.getSize() :
            new Dimension((int) (prefW*zoomFactor), (int) (prefH*zoomFactor));
    }

    private void drawRectangle(Graphics g) {
        Point secondPoint = (currentPt != null) ? currentPt : endPt;
        Color color       = (currentPt != null) ? DRAWING_COLOR : FINAL_DRAWING_COLOR;

        if (startPt!=null && secondPoint!=null) {
            int x = Math.min(startPt.x, secondPoint.x);
            int y = Math.min(startPt.y, secondPoint.y);
            int rectangleWidth = Math.abs(startPt.x - secondPoint.x);
            int rectangleHeight = Math.abs(startPt.y - secondPoint.y);

            g.setColor(color);
            g.drawRect(x, y, rectangleWidth, rectangleHeight);
        }
    }

    public void deleteRectangle(){
        startPt = null;
        endPt   = null;
    }

    public void increaseZoom(Point p) {
        double oldZoom = zoomFactor;
        zoomFactor    *= ZOOMING_STEP;

        repositonPointAfterZoom(oldZoom, zoomFactor);
    }

    public void decreaseZoom(Point p) {
        double oldZoom = zoomFactor;
        zoomFactor    /= ZOOMING_STEP;

        repositonPointAfterZoom(oldZoom, zoomFactor);
    }

    public void repositonPointAfterZoom(double oldZoom, double newZoom) {
        double evolution = newZoom/oldZoom;

        if (startPt!=null) {
            startPt.setLocation(startPt.x * evolution, startPt.y * evolution);
        }

        if (endPt!=null) {
            endPt.setLocation(endPt.x * evolution, endPt.y * evolution);
        }

        repaint();
    }

    // Getter et setter

    public void setStartPt(Point startPt) {
        this.startPt = startPt;
    }

    public void setEndPt(Point endPt) {
        this.endPt = endPt;
    }

    public void setCurrentPt(Point currentPt) {
        this.currentPt = currentPt;
    }

    public int getZoomCalculateX(int value){
        return (int) (value / zoomFactor);
    }

    public int getZoomCalculateY(int value){
        return (int) (value / zoomFactor);
    }

    public void setZoomer(boolean zoomer) {
        this.zoomer = zoomer;
    }
}

波纹管是使用DrawingPanel的类(简化)，因此您可以得到可复制的示例.

EDIT : Bellow is the class (simplified) that uses DrawingPanel so you can have a reproducible exemple.

package GUI;

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;
import org.apache.commons.io.FilenameUtils;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
import fileHandler.*;

public class GUI {

    private JFrame frame;
    private MenuBar menubar;
    private DrawingPanel panelImage;
    private JScrollPane scroll;
    private GroundTruth openFile;
    private int[] panelImageDown = new int[2];
    private int[] panelImageUp   = new int[2];
    private Menu CoordinateMenu1 = new Menu();
    private Menu CoordinateMenu2 = new Menu();
    private int actualPagePdf;
    private PDFRenderer renderer;

    public static void main(String[] args) throws IOException {
        new GUI();
    }

    public GUI() throws IOException {
        JFrame frame = CreateFrame();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private JFrame CreateFrame() throws IOException {
        frame = new JFrame();

        frame.setMenuBar(CreateMenuBar());
        frame.setContentPane(SplitScreen());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setTitle("GTA - Ground Truth Annotator");
        frame.setExtendedState(frame.getExtendedState() | JFrame.MAXIMIZED_BOTH);

        return frame;
    }

    private MenuBar CreateMenuBar() {
        menubar = new MenuBar();

        menubar.add(CreateFileMenu());
        menubar.add(new Menu("Selection coordinates:"));
        menubar.add(CoordinateMenu1);
        menubar.add(new Menu("Width/Height:"));
        menubar.add(CoordinateMenu2);

        return menubar;
    }

    private Menu CreateFileMenu() {
        Menu mFile = new Menu("File");
        MenuItem miOpenImage = new MenuItem("Open Image/PDF File");
        mFile.add(miOpenImage);
        miOpenImage.addActionListener(OpenFileActionListener);
        mFile.addSeparator();
        MenuItem miExit = new MenuItem("Exit Program");
        mFile.add(miExit);
        miExit.addActionListener(ExitActionListener);

        return mFile;
    }

    private JPanel SplitScreen() throws IOException {
        JPanel splittedScreen = new JPanel(new GridLayout(1, 2));

        splittedScreen.add(CreateLeftPanel());
        splittedScreen.add(CreateRightPanel());

        return splittedScreen;
    }

    private JLayeredPane CreateLeftPanel() throws IOException {
        JLayeredPane panel = new JLayeredPane();

        panel.setLayout(new BorderLayout());
        panel.setBorder(BorderFactory.createLineBorder(Color.gray));
        panel.add(CreateImageScrollPane());

        return panel;
    }

    private JScrollPane CreateImageScrollPane() throws IOException {
        scroll  = new JScrollPane(CreateImagePanel((String) null));

        scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
        scroll.getViewport().setScrollMode(JViewport.BLIT_SCROLL_MODE);

        return scroll;
    }

    private DrawingPanel CreateImagePanel(String path) throws IOException {
        if (panelImage == null) {
            panelImage = new DrawingPanel();
        }

        if (path != null) {
            panelImage.loadImage(ImageIO.read(new File(path)));
        }

        panelImage.addMouseListener(PanelImageMouseListener);
        panelImage.addMouseWheelListener(PanelImageMouseWheelListener);
        panelImage.addMouseMotionListener(PanelImageMouseMotionAdapter);
        panelImage.setOpaque(false);
        panelImage.revalidate();
        panelImage.repaint();
        panelImage.requestFocus();

        return panelImage;
    }

    private DrawingPanel CreateImagePanel(Image image) throws IOException {
        if (panelImage == null) {
            panelImage = new DrawingPanel();
        }

        panelImage.loadImage(image);
        panelImage.addMouseListener(PanelImageMouseListener);
        panelImage.addMouseWheelListener(PanelImageMouseWheelListener);
        panelImage.addMouseMotionListener(PanelImageMouseMotionAdapter);
        panelImage.setOpaque(false);
        panelImage.revalidate();
        panelImage.repaint();

        return panelImage;
    }

    private JPanel CreateRightPanel() {
        JPanel panel = new JPanel(new GridLayout(0, 1));

        //...

        return panel;
    }

    ActionListener OpenFileActionListener = new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
           OpenFile();
        }
    };

    ActionListener ExitActionListener = new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            Object[] options = {"Yes, quit now", "No, go back"};
            int n = JOptionPane.showOptionDialog(
                    frame, "ATTENTION: closing without saving will cause any unsaved files to be lost. Do you want to proceed?",
                    "Warning", JOptionPane.YES_NO_OPTION, JOptionPane.WARNING_MESSAGE, null, options, options[0]
            );

            switch (n) {
                case JOptionPane.YES_OPTION:
                    System.exit(0);
                case JOptionPane.NO_OPTION:

                case JOptionPane.CANCEL_OPTION:
            }
        }

    };

    MouseListener PanelImageMouseListener = new MouseListener() {
        public void mousePressed(MouseEvent me) {
            panelImageDown = new int[]{
                    panelImage.getZoomCalculateX(me.getX()), panelImage.getZoomCalculateY(me.getY())
            };
            panelImageUp = null;

            CoordinateMenu1.setLabel(String.format("%s:%s", panelImageDown[0],  panelImageDown[1]));
            CoordinateMenu2.setLabel("");
            panelImage.setStartPt(me.getPoint());
            panelImage.repaint();
        }

        public void mouseReleased(MouseEvent me) {
            panelImageUp = new int[]{
                    Math.abs(panelImage.getZoomCalculateX(me.getX()) - panelImageDown[0]),
                    Math.abs(panelImageDown[1] - panelImage.getZoomCalculateY(me.getY()))
            };

            CoordinateMenu2.setLabel(String.format("%s:%s", panelImageUp[0], panelImageUp[1]));
            panelImage.setEndPt(me.getPoint());
            panelImage.setCurrentPt(null);
            panelImage.repaint();
        }

        public void mouseClicked(MouseEvent arg0) {
        }

        public void mouseEntered(MouseEvent arg0) {
        }

        public void mouseExited(MouseEvent arg0) {
        }
    };


    MouseMotionAdapter PanelImageMouseMotionAdapter = new MouseMotionAdapter() {
        @Override
        public void mouseDragged(MouseEvent me) {
            panelImageUp = new int[]{
                    Math.abs(panelImage.getZoomCalculateX(me.getX()) - panelImageDown[0]),
                    Math.abs(panelImageDown[1] - panelImage.getZoomCalculateY(me.getY()))
            };

            CoordinateMenu2.setLabel(String.format("%s:%s", panelImageUp[0], panelImageUp[1]));
            panelImage.setCurrentPt(me.getPoint());
            panelImage.repaint();
        }
    };

    MouseWheelListener PanelImageMouseWheelListener = new MouseWheelListener() {
        public void mouseWheelMoved(MouseWheelEvent me) {
            if (me.isAltDown()) {
                if (me.getWheelRotation() < 0) {
                    panelImage.setZoomer(true);
                    panelImage.increaseZoom();
                    panelImage.repaint();
                    panelImage.requestFocus();
                    //scroll.repaint();
                //Zoom out
                } else if(me.getWheelRotation() > 0) {
                    panelImage.setZoomer(true);
                    panelImage.decreaseZoom();
                    panelImage.repaint();
                    panelImage.requestFocus();
                    //scroll.repaint();
                }
            }
        }
    };

    private void OpenFile() {
        openFile                 = new GroundTruth();
        JFileChooser fileChooser = new JFileChooser();

        fileChooser.setCurrentDirectory(new File(System.getProperty("user.home")));
        fileChooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
        fileChooser.setAcceptAllFileFilterUsed(false);
        fileChooser.addChoosableFileFilter(new FileNameExtensionFilter(
                "Images / PDF Scan",
                "bmp", "jpeg", "jpg", "png", "tif", "tiff", "pdf"
        ));

        if (fileChooser.showOpenDialog(frame) != 0) {
            return;
        }

        openFile.setFilename(fileChooser.getSelectedFile().getAbsolutePath());

        if (getExtension(fileChooser.getSelectedFile().getName()).equals("pdf")) {
            try {
                PDDocument doc = PDDocument.load(fileChooser.getSelectedFile());
                numberPagePdf  = doc.getNumberOfPages();
                actualPagePdf  = 0;
                renderer       = new PDFRenderer(doc);

                setPdfPage(actualPagePdf);
            } catch (IOException e) {
                e.printStackTrace();
            }
        } else {
            try {
                CreateImagePanel(fileChooser.getSelectedFile().getAbsolutePath());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void setPdfPage(int pageNumber){
        try {
            BufferedImage bim = renderer.renderImageWithDPI(pageNumber, 300);

            refreshInfoPageSection();
            CreateImagePanel(bim);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // refresh the label who indicate the page display and set visible or inivisble the previous and next button
    private void refreshInfoPageSection(){
        panelImage.deleteRectangle();
    }

    public String getExtension(String filename) {
        return FilenameUtils.getExtension(filename);
    }
}

推荐答案

这是图纸 JPanel 的简化示例，它比滚动的 JPanel 大.

Here's a simplified example of a drawing JPanel that's larger than the scrolling JPanel.

您可以在图像中看到，图形 JPanel 在水平和垂直方向上都比滚动的 JPanel 大.

You can see in the image that the drawing JPanel is larger both horizontally and vertically than the scrolling JPanel.

在此代码中，我根本没有调用 paintComponent 方法.因为我正确设置了GUI，所以在移动滚动条时，Swing本身会调用 repaint 方法.

I don't call the paintComponent method at all in this code. Because I set up the GUI properly, Swing itself calls the repaint method when you move the scroll bars.

这是我所做的重要事情.

Here are the important things I did.

1. 我通过调用 SwingUtilities invokeLater 方法启动了Swing GUI.此方法确保在事件调度上创建并执行Swing组件.线程.

1. I started the Swing GUI with a call to the SwingUtilities invokeLater method. This method makes sure that the Swing components are created and executed on the Event Dispatch Thread.

我使用了 JFrame ，两个 JPanels 和一个 JScrollPane .我扩展了 JPanel 以创建绘图面板.我使用了 JScrollPane ， JPanel 和 JFrame .仅有当您想覆盖一个或多个类方法时，才扩展Swing组件或任何Java类.

I used a JFrame, two JPanels, and a JScrollPane. I extended JPanel to create the drawing panel. I used a JScrollPane, JPanel, and JFrame. The only time you extend a Swing component, or any Java class, is when you want to override one or more class methods.

我使用了 Swing布局管理器.我为 JFrame 使用了 BorderLayout ，并滚动了 JPanel .

I used Swing layout managers. I used a BorderLayout for the JFrame and scrolling JPanel.

这是完整的可运行代码.为什么，您甚至可以称其为最小的可复制示例！

Here's the complete runnable code. Why, you can even call it a minimal reproducible example!

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;

public class LargeDrawingPanel implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new LargeDrawingPanel());
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("Large Drawing Panel");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(createMainPanel(), BorderLayout.CENTER);

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel createMainPanel() {
        JPanel panel = new JPanel(new BorderLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        panel.setPreferredSize(new Dimension(400, 400));

        JScrollPane scrollPane = new JScrollPane(new DrawingPanel());
        panel.add(scrollPane, BorderLayout.CENTER);

        return panel;
    }

    public class DrawingPanel extends JPanel {

        private static final long serialVersionUID = 1L;

        public DrawingPanel() {
            this.setBackground(Color.WHITE);
            this.setPreferredSize(new Dimension(2000, 2000));
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

            g.setColor(Color.BLUE);
            int x = 100;
            int y = 100;
            for (int i = 0; i < 10; i++) {
                for (int j = 0; j < 10; j++) {
                    g.fillRect(x, y, 100, 100);
                    x += 200;
                }
                y += 200;
                x = 100;
            }
        }

    }

}

编辑后添加:OP在评论中发布了其他问题.

Edited to add: The OP posted additional questions in a comment.

非常简单.使用 ImageIO 类读取图像，将图像保存在一个或多个普通Java getter/setter类组成的应用程序模型中，并使用 Graphics drawImage 绘制图像的方法.

Pretty simple. Read an image using the ImageIO class, save the image in an application model consisting of one or more plain Java getter / setter classes and use the Graphics drawImage method to draw the image.

您实际上运行了我提供的代码吗?我一次只能移动一个滚动条.绘图 JPanel 沿水平和垂直方向延伸.

Did you actually run the code I provided? I can only move one scrollbar at a time. The drawing JPanel extends both horizontally and vertically.

您的示例充满了错误.重新开始，使用合理的原理一次构建一个Swing应用程序一个Swing组件.Oracle教程使用JFC/Swing创建GUI 将显示您是创建Swing应用程序的正确方法.您可以跳过"Netbeans"部分.

Your example is riddled with errors. Start over, building a Swing application one Swing component at a time using sound principles. The Oracle tutorial, Creating a GUI With JFC/Swing, will show you the correct way to create a Swing application. You can skip the Netbeans section.

这篇关于当我在JScrollPane中滚动水平和垂直滚动条时未调用paintComponent的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！