我正在做一个项目，我正在尝试制作一个绘画程序。到目前为止，我已经使用Netbeans创建了一个GUI并设置了该程序。
到目前为止，我可以调用所有必要的协调来绘制内部，但我对如何在其中进行实际绘制非常困惑。
在我的代码结束时，我尝试在面板内绘图失败。
谁能解释/展示如何在这样的例子中使用图形？
我找到的所有示例都创建了一个类并使用JPanel扩展它，但我不知道是否可以执行此操作，因为它是在netbeans中生成的。
我需要在我的JPanel里面画一个JFrame。我不知道在哪里放图形类。
package javapaint;
import java.awt.*;
import javax.swing.*;
public class JavaPaintUI extends javax.swing.JFrame {
public JavaPaintUI() {
initComponents();
}
private void initComponents() {
jPanel2 = new javax.swing.JPanel();
jPanel2.setBackground(new java.awt.Color(255, 255, 255));
jPanel2.setBorder(javax.swing.BorderFactory.createBevelBorder(javax.swing.border.BevelBorder.RAISED));
jPanel2.addMouseListener(new java.awt.event.MouseAdapter() {
public void mousePressed(java.awt.event.MouseEvent evt) {
jPanel2MousePressed(evt);
}
public void mouseReleased(java.awt.event.MouseEvent evt) {
jPanel2MouseReleased(evt);
}
});
jPanel2.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() {
public void mouseDragged(java.awt.event.MouseEvent evt) {
jPanel2MouseDragged(evt);
}
});
pack();
}// </editor-fold>
int currentX, currentY, oldX, oldY;
private void jPanel2MouseDragged(java.awt.event.MouseEvent evt) {
if (tool == 1) {
currentX = evt.getX();
currentY = evt.getY();
oldX = currentX;
oldY = currentY;
System.out.println(currentX + " " + currentY);
System.out.println("PEN!!!!");
}
}
private void jPanel2MousePressed(java.awt.event.MouseEvent evt) {
oldX = evt.getX();
oldY = evt.getY();
System.out.println(oldX + " " + oldY);
}
//mouse released//
private void jPanel2MouseReleased(java.awt.event.MouseEvent evt) {
if (tool == 2) {
currentX = evt.getX();
currentY = evt.getY();
System.out.println("line!!!! from" + oldX + "to" + currentX);
}
}
//set ui visible//
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new JavaPaintUI().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JPanel jPanel2;
// End of variables declaration
class jPanel2 extends JPanel {
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString("BLAH", 20, 20);
g.drawRect(200, 200, 200, 200);
}
}
}
整个事情是JFrame，中间的白色部分是jPanel2，这是我想要绘制的。
请注意额外的评论。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
class JavaPaintUI extends JFrame {
private int tool = 1;
int currentX, currentY, oldX, oldY;
public JavaPaintUI() {
initComponents();
}
private void initComponents() {
// we want a custom Panel2, not a generic JPanel!
jPanel2 = new Panel2();
jPanel2.setBackground(new java.awt.Color(255, 255, 255));
jPanel2.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
jPanel2.addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent evt) {
jPanel2MousePressed(evt);
}
public void mouseReleased(MouseEvent evt) {
jPanel2MouseReleased(evt);
}
});
jPanel2.addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent evt) {
jPanel2MouseDragged(evt);
}
});
// add the component to the frame to see it!
this.setContentPane(jPanel2);
// be nice to testers..
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
}// </editor-fold>
private void jPanel2MouseDragged(MouseEvent evt) {
if (tool == 1) {
currentX = evt.getX();
currentY = evt.getY();
oldX = currentX;
oldY = currentY;
System.out.println(currentX + " " + currentY);
System.out.println("PEN!!!!");
}
}
private void jPanel2MousePressed(MouseEvent evt) {
oldX = evt.getX();
oldY = evt.getY();
System.out.println(oldX + " " + oldY);
}
//mouse released//
private void jPanel2MouseReleased(MouseEvent evt) {
if (tool == 2) {
currentX = evt.getX();
currentY = evt.getY();
System.out.println("line!!!! from" + oldX + "to" + currentX);
}
}
//set ui visible//
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
public void run() {
new JavaPaintUI().setVisible(true);
}
});
}
// Variables declaration - do not modify
private JPanel jPanel2;
// End of variables declaration
// This class name is very confusing, since it is also used as the
// name of an attribute!
//class jPanel2 extends JPanel {
class Panel2 extends JPanel {
Panel2() {
// set a preferred size for the custom panel.
setPreferredSize(new Dimension(420,420));
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString("BLAH", 20, 20);
g.drawRect(200, 200, 200, 200);
}
}
}
HFOE作为该线程的第一条评论提供了一个很好的链接。 Camickr还描述了在BufferedImage文章中主动绘画与绘画到Custom Painting Approaches。
另见使用painting in a BufferedImage的这种方法。
使用图形用户界面时，您需要记住窗格上的绘图是在Java AWT/Swing event queue中完成的。你不能只使用Graphics / paint() / etc之外的paintComponent()对象。方法。
但是，您可以使用一种名为“Frame buffering”的技术。基本上，你需要有一个BufferedImage并直接在它上面绘制（参见它的createGraphics()方法;你可以在同一个BufferedImage实例上保留和重用多个操作的图形上下文，不需要一直重新创建它，只有在创建一个新的时候实例）。然后，在你的JPanel的paintComponent()中，你只需要将BufferedImage实例绘制到JPanel。使用此技术，您可以通过affine transformations轻松执行缩放，平移和旋转操作。
这是一个简单的例子。我想这很容易理解：
import java.awt.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Graph extends JFrame {
JFrame f = new JFrame();
JPanel jp;
public Graph() {
f.setTitle("Simple Drawing");
f.setSize(300, 300);
f.setDefaultCloseOperation(EXIT_ON_CLOSE);
jp = new GPanel();
f.add(jp);
f.setVisible(true);
}
public static void main(String[] args) {
Graph g1 = new Graph();
g1.setVisible(true);
}
class GPanel extends JPanel {
public GPanel() {
f.setPreferredSize(new Dimension(300, 300));
}
@Override
public void paintComponent(Graphics g) {
//rectangle originates at 10,10 and ends at 240,240
g.drawRect(10, 10, 240, 240);
//filled Rectangle with rounded corners.
g.fillRoundRect(50, 50, 100, 100, 80, 80);
}
}
}
输出看起来像这样：
Java 8接受的Bijaya Bidari代码的变化，没有关于构造函数中的可覆盖方法调用的警告：
public class Graph extends JFrame {
JPanel jp;
public Graph() {
super("Simple Drawing");
super.setSize(300, 300);
super.setDefaultCloseOperation(EXIT_ON_CLOSE);
jp = new GPanel();
super.add(jp);
}
public static void main(String[] args) {
Graph g1 = new Graph();
g1.setVisible(true);
}
class GPanel extends JPanel {
public GPanel() {
super.setPreferredSize(new Dimension(300, 300));
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
//rectangle originated at 10,10 and end at 240,240
g.drawRect(10, 10, 240, 240);
//filled Rectangle with rounded corners.
g.fillRoundRect(50, 50, 100, 100, 80, 80);
}
}
}