如何在 JPanel 中绘图?(摆动/图形Java) [英] How to draw in JPanel? (Swing/graphics Java)
问题描述
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 并设置了程序.
I'm working on a project in which I am trying to make a paint program. So far I've used Netbeans to create a GUI and set up the program.
截至目前，我能够调用在其中绘制所需的所有协调功能，但我对如何在其中实际绘制感到非常困惑.
As of right now I am able to call all the coordinated necessary to draw inside it but I am very confused with how to actually paint inside it.
在我的代码即将结束时，我尝试在面板内绘图失败.
Towards the end of my code I have a failed attempt at drawing inside the panel.
谁能解释/展示如何在这样的例子中使用图形?
Can anyone explain/show how to use graphics in a example like this?
我发现的所有示例都创建了一个类并使用 JPanel 对其进行扩展，但我不知道是否可以这样做，因为它是在 netbeans 中生成的.
All examples I have found make a class and extend it with JPanel but I don't know if I can do this since it was generated in netbeans.
我需要在 JPanel 内绘制，在我的 JFrame 内.我不知道把图形类放在哪里.
I need to draw inside a JPanel, inside my JFrame. I don't know where to put the graphics class.
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);
}
}
}
屏幕截图
整个东西是一个JFrame，中间的白色部分是jPanel2，这是我想要绘制的.
Screen shot
The whole thing is a JFrame and the white section in the center is jPanel2 which is what I want to draw on.
推荐答案
注意额外的注释.
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);
}
}
}
屏幕截图
HFOE 将一个很好的链接作为该线程的第一个评论.Camickr 还在 自定义绘画方法 文章.
HFOE put a good link as the first comment on this thread. Camickr also has a description of active painting vs. drawing to a BufferedImage in the Custom Painting Approaches article.
另请参阅使用 在 BufferedImage 中绘制的这种方法.
See also this approach using painting in a BufferedImage.
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