如何将同一类中的 2D 图形和图像分别绘制到同一个 JPanel

Question

我有一个方法(drawImages(，它将缓冲图像的数组列表绘制到扩展的JPanel。但是，只有在调用另一个方法(drawPerfectRect(时，才会在paintComponent方法中调用它。

此方法(drawPerfectRect(负责使用传递给它的坐标，使用用户单击的点绘制矩形。

从本质上讲，我遇到的两个问题是：

1. 它不会绘制缓冲图像的数组列表，直到用户单击并拖动以创建一个矩形(希望在单击选择目录 (JButton( 后绘制图像(。
2. 它还为绘制的每个后续矩形再次绘制缓冲图像。

似乎只有在绘制矩形时才绘制缓冲图像。

import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.border.Border;
import java.awt.*;
import java.awt.event.*;
import com.sun.tools.internal.ws.wsdl.document.Import;
import net.coobird.thumbnailator.*;
import com.mortennobel.imagescaling.*;
import java.awt.Graphics2D;
import java.awt.Graphics;
import java.awt.geom.RoundRectangle2D;
import java.io.IOException;
import java.awt.image.BufferedImage;
import java.io.File;
import java.nio.Buffer;
import java.util.ArrayList;
import java.util.Timer;
public class ImportWorkspace extends JPanel{
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
int x, y, x2, y2;
ArrayList<BufferedImage> thumbnailList = new ArrayList<BufferedImage>();
int ContentPanelWidth;
private boolean addThumbnails = false;
public ImportWorkspace(){
x = y = x2 = y2 = 0;
setLayout(null);
setBackground(Color.decode("#2a2e37"));
setBounds(85, 0, screenSize.width-85, screenSize.height);
//System.out.println("W: " + super.getWidth() + ", H: " + super.getHeight());
ContentPanelWidth = getWidth();
System.out.println(ContentPanelWidth);
JLabel dataIcon =  new JLabel(new ImageIcon(new ImageIcon ("folder.png").getImage().getScaledInstance(256,256, Image.SCALE_DEFAULT)));
dataIcon.setBounds((getWidth()/2)-128, (getHeight()/2)-200, 256, 256);
add(dataIcon);
JLabel askImport = new JLabel("No Data Files have been selected: To begin importing data please select a directory.");
askImport.setFont(new Font("Helvetica", Font.PLAIN, 20));
askImport.setForeground(Color.white);
askImport.setBounds((getWidth()/2)-375, (getHeight()/2)+50, 750, 100);
add(askImport);
JButton selectDirectory = new JButton("Select Directory");
selectDirectory.setBounds((getWidth()/2)-75, (getHeight()/2)+150, 150, 50); //+half of width or height
add(selectDirectory);
selectDirectory.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
removeAll();
revalidate();
repaint();
setLayout(new FlowLayout(FlowLayout.LEFT));
ImportingImages getImages = new ImportingImages();
getImages.importFiles();
File curDir = new File("");
File[] files = curDir.listFiles();
long noFiles = curDir.length();
for (File f : files) {
String fileName = f.getName();
String hiddenFile = ".DS_Store";
if (fileName.equals(hiddenFile)){
//System.out.println("Do nothing");
} else {
String thumbnailPath = curDir + "/" + f.getName();
try {
BufferedImage thumbnailIcon = ImageIO.read(new File(thumbnailPath));
thumbnailList.add(thumbnailIcon);
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
MyMouseListener listener = new MyMouseListener();
addMouseListener(listener);
addMouseMotionListener(listener);
//DisplayImages(thumbnailList, ContentPanelWidth);
}
});
}
public void setStartPoint(int x, int y) {
this.x = x;
this.y = y;
}
public void setEndPoint(int x, int y) {
x2 = (x);
y2 = (y);
}

public void drawPerfectRect(Graphics g, int x, int y, int x2, int y2) {
int px = Math.min(x,x2);
int py = Math.min(y,y2);
int pw = Math.abs(x-x2);
int ph = Math.abs(y-y2);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
int alpha = 100; // 127 50% transparent
Color cyanTransparent = new Color(0,206,209, alpha);
g2.setColor(cyanTransparent);
g2.fillRoundRect(px, py, pw, ph, 5, 5);
g2.setColor(Color.cyan);
g2.setStroke(new BasicStroke(1));
g2.drawRoundRect(px, py, pw, ph, 5, 5);
}
public void drawImages(Graphics g){
int xSpacing = 10;
int ySpacing = 20;
int noImages = 0;
for (BufferedImage thumbnail : thumbnailList){
g.drawImage(thumbnail, xSpacing, ySpacing,null );
if ((xSpacing+100) > (ContentPanelWidth-100)){
ySpacing = ySpacing + 77;
xSpacing = 10;
} else{
xSpacing = xSpacing + 110;
}
noImages = noImages + 1;
//System.out.println(noImages);
}
}
class MyMouseListener extends MouseAdapter {
public void mousePressed(MouseEvent e) {
setStartPoint(e.getX(), e.getY());
}
public void mouseDragged(MouseEvent e) {
setEndPoint(e.getX(), e.getY());
revalidate();
repaint();
}
public void mouseReleased(MouseEvent e) {
setEndPoint(e.getX(), e.getY());
revalidate();
repaint();
}
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
System.out.println(addThumbnails);
drawImages(g2);
drawPerfectRect(g2, x, y, x2, y2);  
}
}

Answer 1

改进添加到selectDirectory按钮的操作侦听器，如下所示：

1. 删除操作侦听器中的repaint()调用(稍后会修复它(。
2. 每次按下按钮时清除缩略图列表。也就是说，thumbnailList.clear()在操作侦听器内部。这样，每个目录选择只会显示最后导入的图像。
3. 在for循环之后，在按钮的操作侦听器中调用repaint()，该循环在列表中添加缩略图。这样，在图像实际加载到列表中后，面板将被重新绘制(使用新图像(。

因此，ImportWorkspace构造函数可以编写如下：

public ImportWorkspace(){
x = y = x2 = y2 = 0;
setLayout(null);
setBackground(Color.decode("#2a2e37"));
setBounds(85, 0, screenSize.width-85, screenSize.height);
//System.out.println("W: " + super.getWidth() + ", H: " + super.getHeight());
ContentPanelWidth = getWidth();
System.out.println(ContentPanelWidth);
JLabel dataIcon =  new JLabel(new ImageIcon(new ImageIcon ("folder.png").getImage().getScaledInstance(256,256, Image.SCALE_DEFAULT)));
dataIcon.setBounds((getWidth()/2)-128, (getHeight()/2)-200, 256, 256);
add(dataIcon);
JLabel askImport = new JLabel("No Data Files have been selected: To begin importing data please select a directory.");
askImport.setFont(new Font("Helvetica", Font.PLAIN, 20));
askImport.setForeground(Color.white);
askImport.setBounds((getWidth()/2)-375, (getHeight()/2)+50, 750, 100);
add(askImport);
JButton selectDirectory = new JButton("Select Directory");
selectDirectory.setBounds((getWidth()/2)-75, (getHeight()/2)+150, 150, 50); //+half of width or height
add(selectDirectory);
selectDirectory.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
removeAll();
revalidate();
//repaint();           //Removed this line. It is not necessary in this place. Will be re-added AFTER the `for` loop below...
thumbnailList.clear(); //Added this line.
setLayout(new FlowLayout(FlowLayout.LEFT));
ImportingImages getImages = new ImportingImages();
getImages.importFiles();
File curDir = new File("");
File[] files = curDir.listFiles();
long noFiles = curDir.length();
for (File f : files) {
String fileName = f.getName();
String hiddenFile = ".DS_Store";
if (fileName.equals(hiddenFile)){
//System.out.println("Do nothing");
} else {
String thumbnailPath = curDir + "/" + f.getName();
try {
BufferedImage thumbnailIcon = ImageIO.read(new File(thumbnailPath));
thumbnailList.add(thumbnailIcon);
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
repaint(); //Added this line! Now the newly loaded images shall be painted.
MyMouseListener listener = new MyMouseListener();
addMouseListener(listener);
addMouseMotionListener(listener);
//DisplayImages(thumbnailList, ContentPanelWidth);
}
});
}