[英]Add new data to Graphics2D panel in a Java Swing application
我正在編寫一個用於數據處理的 Java Swing 應用程序。 我需要添加的功能之一是以圖形方式可視化數據。 為此,我想使用 Graphics2D class。
我創建了一個 GUI,集成了我的程序以及一個使用 Graphics2D class 繪制圖形的面板。
但我的問題是,在從 GUI 選擇和加載文件后,我無法弄清楚如何調用 drawLine 方法
下面是簡短的代碼示例,顯示了我的問題。 它只包含一個帶有 2 個面板的基本 GUI 和一個帶有加載選項的菜單來解釋我的問題:
在 de MyFrame.java 文件中,我在第 87 行添加了注釋,以准確顯示我卡在哪里。
該應用程序基於 3 個文件: main:在這里它創建 GUI 的 MyFrame 實例 MyFrame:創建 GUI 和數據的進一步處理 MyPanel:使用基本藍色矩形框作為開始視圖制作 Graphics2D 的 Jpanel。
如果有人能給我一個關於如何從 MyFrame() 構造函數外部調用這個 drawLine 方法的提示......
我仍然不完全理解如何在類之間進行交互的全部要點......
這是 GUI 外觀的圖片:在此處輸入圖像描述
謝謝你在這方面幫助我
public class main {
public static void main(String[] args) {
// TODO Auto-generated method stub
new MyFrame();
}
}
public class MyFrame extends JFrame {
JTextComponent tc;
String fileName;
MyFrame() {
this.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
this.setLayout(null);
this.setBounds(0,0,464,312);
tc = new JTextPane();
tc.setBounds(0,520,450,50);
tc.setPreferredSize(new Dimension(450,50));
JScrollPane sp = new JScrollPane(tc);
JMenuBar mb = new JMenuBar();
JMenu fm = new JMenu("File");
JMenuItem loadItem = new JMenuItem("Load file");
loadItem.addActionListener(e -> {tc.setText("loading"+"\n");
SDprocess();});
fm.add(loadItem);
mb.add(fm);
MyPanel p1 = new MyPanel();
p1.setBounds(0,0,450,200);
p1.setPreferredSize(new Dimension(450,200));
JPanel p2 = new JPanel();
p2.setBounds(0,200,450,50);
p2.setPreferredSize(new Dimension(450,50));
p2.add(sp);
this.setJMenuBar(mb);
this.add(p1);
this.add(p2);
this.setResizable(false);
this.setVisible(true);
}
public void SDprocess() {
File fr = null;
JFileChooser fc = new JFileChooser();
int result = fc.showOpenDialog(this);
if (result == JFileChooser.APPROVE_OPTION) {
fr = fc.getSelectedFile();
fileName=fr.getName();
System.out.println(fileName);
}
try {
Scanner sc = new Scanner(fr);
tc.setText(fileName +" loading\n");
while (sc.hasNextLine()) {
String line = sc.nextLine();
// ...
// rest of code to get the x and y data for drawing
// lines using drawLine(x1,y1,x2,y2) method.
//
// at this point I need to call this drawLine method but how ???
// i just don't know how to call this method from this point and how to
// and update the graphics panel p1 after adding the data....
}
sc.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class MyPanel extends JPanel {
Graphics2D g2D;
MyPanel() {
this.setPreferredSize(new Dimension (450,200));
}
public void paint (Graphics g) {
g2D = (Graphics2D) g;
g2D.setStroke(new BasicStroke(1));
g2D.setPaint(Color.blue);
g2D.drawLine(5, 5, 445,5);
g2D.drawLine(445, 5, 445,195);
g2D.drawLine(445, 195, 5,195);
g2D.drawLine(5, 195, 5,5);
}
}
這是“讀取文件”之前修改后的 GUI。
這是“讀取文件”后修改后的 GUI。
我創建了一個應用程序 model 來保存線段。 將此 model 傳遞給繪圖JPanel
以便可以在繪圖JPanel
的paintComponent
方法中繪制線段。
我清理了你的 GUI。 我使用Swing 布局管理器來創建 GUI。 我將JPanels
的創建與JFrame
的創建分開,這樣代碼更易於人們閱讀和理解。
這是完整的可運行代碼。 我制作了附加類內部類,因此我可以將此代碼作為一個塊發布。
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.util.ArrayList;
import java.util.List;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.SwingUtilities;
import javax.swing.text.JTextComponent;
public class ExampleDrawingGUI {
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new ExampleDrawingGUI().new MyFrame());
}
public class MyFrame extends JFrame {
private static final long serialVersionUID = 1L;
private ExampleDrawingModel model;
JTextComponent tc;
MyPanel p1;
public MyFrame() {
super("My Frame");
this.model = new ExampleDrawingModel();
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setJMenuBar(createMenuBar());
p1 = new MyPanel(model);
this.add(p1, BorderLayout.CENTER);
this.add(createTextPanel(), BorderLayout.SOUTH);
this.pack();
this.setLocationByPlatform(true);
// this.setResizable(false);
this.setVisible(true);
}
private JMenuBar createMenuBar() {
JMenuBar mb = new JMenuBar();
JMenu fm = new JMenu("File");
JMenuItem loadItem = new JMenuItem("Load file");
loadItem.addActionListener(e -> {
tc.setText("loading" + "\n");
model.readFile();
p1.repaint();
});
fm.add(loadItem);
mb.add(fm);
return mb;
}
private JPanel createTextPanel() {
JPanel panel = new JPanel(new BorderLayout());
panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
tc = new JTextPane();
tc.setPreferredSize(new Dimension(450, 50));
JScrollPane sp = new JScrollPane(tc);
panel.add(sp, BorderLayout.CENTER);
return panel;
}
public void repaint() {
p1.repaint();
}
}
public class MyPanel extends JPanel {
private static final long serialVersionUID = 1L;
private ExampleDrawingModel model;
public MyPanel(ExampleDrawingModel model) {
this.model = model;
this.setPreferredSize(new Dimension(450, 200));
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2D = (Graphics2D) g;
paintBorder(g2D);
for (LineSegment line : model.getLines()) {
Point startPoint = line.getStartPoint();
Point endPoint = line.getEndPoint();
g2D.drawLine(startPoint.x, startPoint.y, endPoint.x, endPoint.y);
}
}
private void paintBorder(Graphics2D g2D) {
int margin = 5;
int x1 = margin;
int x2 = getWidth() - margin;
int y1 = margin;
int y2 = getHeight() - margin;
g2D.setStroke(new BasicStroke(3f));
g2D.setPaint(Color.blue);
g2D.drawLine(x1, y1, x1, y2);
g2D.drawLine(x1, y1, x2, y1);
g2D.drawLine(x2, y1, x2, y2);
g2D.drawLine(x1, y2, x2, y2);
}
}
public class ExampleDrawingModel {
private List<LineSegment> lines;
public ExampleDrawingModel() {
this.lines = new ArrayList<>();;
}
public void readFile() {
this.lines.clear();
// Here's where you'd read a file and create a list of lines.
lines.add(new LineSegment(new Point(100, 100), new Point(100, 150)));
}
public List<LineSegment> getLines() {
return lines;
}
}
public class LineSegment {
private final Point startPoint, endPoint;
public LineSegment(Point startPoint, Point endPoint) {
this.startPoint = startPoint;
this.endPoint = endPoint;
}
public Point getStartPoint() {
return startPoint;
}
public Point getEndPoint() {
return endPoint;
}
}
}
首先,您的代碼存在一些問題:
class MyFrame extends JFrame {
//....
MyFrame() {
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(null); // !! Good God, no don't do this!
this.setBounds(0, 0, 464, 312); // and don't do this
避免像瘟疫一樣的 null 布局和 setBounds,因為這會導致非常不靈活的 GUI,雖然它們在一個平台上看起來不錯,但在大多數其他平台或屏幕分辨率上看起來很糟糕,並且很難更新和維護。 相反,您需要學習和學習布局管理器,然后嵌套 JPanel,每個 JPanel 都使用自己的布局管理器來創建在所有操作系統上看起來都不錯的令人愉悅且復雜的 GUI。
另外,不要忘記在添加組件之后和設置可見之前調用 JFrame 上的pack()
,以便布局管理器執行他們的操作。
接着:
class MyPanel extends JPanel {
// ...
Graphics2D g2D; //!! -- no, don't do this
如果您創建一個 Graphics 或 Graphics2D 字段,您很想在繪制方法之外使用它,這是一個災難的秘訣,因為從組件中獲得的任何 Graphics 都是短暫的,這樣做有創建易碎圖形或拋出 NullPointerException 的風險
public void paint (Graphics g) {
g2D = (Graphics2D) g;
g2D.setStroke(new BasicStroke(1));
g2D.setPaint(Color.blue);
g2D.drawLine(5, 5, 445,5);
g2D.drawLine(445, 5, 445,195);
g2D.drawLine(445, 195, 5,195);
g2D.drawLine(5, 195, 5,5);
}
不要覆蓋paint,而是要覆蓋paintComponent,因為它的風險較小(paint 有更大的責任,你不想搞砸)並且如果需要的話,動畫更平滑,因為paintComponent 默認使用雙緩沖。
此外,您幾乎總是應該在自己的覆蓋中調用 super 的繪畫方法,因此改為:
@Override
protected void paintComponent(Graphics g) {
// first call the super's method:
super.paintComponent(g);
Graphics2D g2D = (Graphics2D) g.create();
現在對於您的實際問題,在渲染 GUI 之后創建圖像和繪圖,可能最簡單的方法是創建一個 BufferedImage 並在您的 GUI 中使用它進行繪制。 您可以通過調用 Graphics 方法drawImage(...)
輕松做到這一點。 您可以隨時將 BufferedImage 傳遞到繪圖 JPanel 中。 例如,您的代碼可能看起來像...
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class Foo {
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
JFrame frame = new JFrame("GUI");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
MainPanel mainPanel = new MainPanel();
MyMenu myMenu = new MyMenu();
myMenu.setMyPanel(mainPanel.getMyPanel());
myMenu.setMainPanel(mainPanel);
frame.add(mainPanel);
frame.setJMenuBar(myMenu);
frame.pack();
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
});
}
}
class MainPanel extends JPanel {
private static final int GAP = 5;
private JTextArea textArea = new JTextArea(4, 40);
private MyPanel myPanel = new MyPanel();
public MainPanel() {
textArea.setFocusable(false);
JScrollPane scrollPane = new JScrollPane(textArea);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
setLayout(new BorderLayout(GAP, GAP));
add(myPanel);
add(scrollPane, BorderLayout.PAGE_END);
}
public MyPanel getMyPanel() {
return myPanel;
}
public void appendTextAreaText(String text) {
textArea.append(text);
}
public void setBuffImg(BufferedImage bImage) {
myPanel.setBuffImg(bImage);
}
}
class MyMenu extends JMenuBar {
private MainPanel mainPanel;
private MyPanel myPanel;
public MyMenu() {
JMenu fm = new JMenu("File");
JMenuItem loadItem = new JMenuItem("Load file");
loadItem.addActionListener(e -> {
// Emulate reading file here in a background thread
if (myPanel != null) {
int width = MyPanel.MY_WIDTH;
int height = MyPanel.MY_HEIGHT;
BufferedImage bImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = bImg.createGraphics();
// draw with g2 here using data from file
// emulating this:
g2.setColor(Color.RED);
float strokeWidth = (float) (2 + 6 * Math.random());
g2.setStroke(new BasicStroke(strokeWidth));
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
int x2 = (int) (MyPanel.MY_WIDTH * (1 + Math.random()) / 2);
int y2 = (int) (MyPanel.MY_HEIGHT * (1 + Math.random()) / 2);
g2.drawLine(5, 5, x2, y2);
g2.dispose();
myPanel.setBuffImg(bImg);
if (mainPanel != null) {
mainPanel.appendTextAreaText("adding image \n");
}
}
});
fm.add(loadItem);
add(fm);
}
public void setMyPanel(MyPanel myPanel) {
this.myPanel = myPanel;
}
public void setMainPanel(MainPanel mainPanel) {
this.mainPanel = mainPanel;
}
}
class MyPanel extends JPanel {
private static final int GAP = 5;
public static final int MY_WIDTH = 450;
public static final int MY_HEIGHT = 200;
private BufferedImage bImg = null;
// Graphics2D g2D; //!! -- no, never do this!!
MyPanel() {
// this.setPreferredSize(new Dimension(450, 200));
setBackground(Color.WHITE);
}
// better to override getPreferredSize
@Override
public Dimension getPreferredSize() {
return new Dimension(MY_WIDTH + 2 * GAP, MY_HEIGHT + 2 * GAP);
}
public void setBuffImg(BufferedImage bImg) {
this.bImg = bImg;
repaint();
}
@Override
protected void paintComponent(Graphics g) {
// first call the super's method:
super.paintComponent(g);
if (bImg != null) {
g.drawImage(bImg, GAP, GAP, null);
}
Graphics2D g2D = (Graphics2D) g.create();
g2D.setStroke(new BasicStroke(1));
g2D.setPaint(Color.blue);
Rectangle rect = new Rectangle(GAP, GAP, getWidth() - 2 * GAP, getHeight() - 2 * GAP);
g2D.draw(rect);
}
// Don't override paint but rather paintComponent
// public void paint (Graphics g) {
}
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