我正在尝试编写一个程序，允许用户通过单击窗口中的JButton创建正方形或圆形，然后单击窗口中的某个位置（而不是按钮）。
我目前正在为不同的按钮使用两个actionListener，这些按钮将Square或Circle添加到Shape类型的arrayList（方形和圆形实现的接口）。我有一个名为frameListener的类，它实现MouseListener和MouseMotionListener，它在鼠标移动时更新方形或圆的位置，如果鼠标离开窗口则删除方形或圆形，或者在单击鼠标时停止更新它（制作永久）。
我还有一个名为MyPanel的类，它扩展了JPanel，并使用paintComponent（Graphics g）方法在背景上绘制正方形和圆形。
package smys01;
import java.util.ArrayList;
import java.text.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class SMYS01 extends JFrame {
private Color c = new Color(0, 0, 0);
private static ArrayList<Shape> shapes = new ArrayList();
private static ArrayList<Shape> deleted = new ArrayList();
private Point a;
private boolean makeSquare = false, makeCircle = false, makeSquiggle = false;
public static void main(String[] args) {
SMYS01 window = new SMYS01();
}
//good main
//0 is empty for making things, 1 is having a square selected to change, 2 is background;
private JButton makeSquareB = new JButton("New Square" /*, add icon later*/);
private JButton makeCircleB = new JButton("New Circle");
private Color background = new Color(0, 150, 0);
public SMYS01() {
makeSquareB.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("making square");
if(!makeCircle&&!makeSquare){
makeSquare = true;
shapes.ensureCapacity(shapes.size());
shapes.add(new Square((int) a.getX(), (int) a.getY(), c));
}else if(makeSquare){
}else if(makeCircle){
makeCircle=false;
makeSquare=true;
shapes.remove(shapes.size()-1);
shapes.ensureCapacity(shapes.size());
shapes.add(new Square((int) a.getX(), (int) a.getY(), c));
}
}
});
makeCircleB.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("making circle");
if(!makeCircle&&!makeSquare){
makeCircle = true;
shapes.ensureCapacity(shapes.size());
shapes.add(new Circle((int) a.getX(), (int) a.getY(), c));
}else if(makeCircle){
}else if(makeSquare){
makeSquare=false;
shapes.remove(shapes.size()-1);
shapes.ensureCapacity(shapes.size());
shapes.add(new Circle((int) a.getX(), (int) a.getY(), c));
}
}
});
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane();
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
MyPanel thing = new MyPanel();
frame.addMouseListener(new FrameListener());
frame.setContentPane(thing);
frame.setSize(thing.getPreferredSize());
frame.setTitle("Art!");
frame.addMouseMotionListener(new FrameListener());
}
private class MyPanel extends JPanel {
public MyPanel() {
GroupLayout layout = new GroupLayout(this);
layout.setHorizontalGroup(
layout.createSequentialGroup()
.addComponent(makeCircleB)
.addComponent(makeSquareB)
);
layout.setVerticalGroup(
layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(makeCircleB)
.addComponent(makeSquareB)
)
);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(500, 500);
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(background);
g.drawRect((int)g.getClipBounds().getX(),(int)g.getClipBounds().getY(),(int)g.getClipBounds().getWidth(),(int)g.getClipBounds().getHeight());
g.fillRect((int)g.getClipBounds().getX(),(int)g.getClipBounds().getY(),(int)g.getClipBounds().getWidth(),(int)g.getClipBounds().getHeight());
System.out.println(shapes.size());
for (Shape i : shapes) {
int[] a = i.getDim();
g.setColor(new Color(a[4], a[5], a[6], a[7]));
if(i instanceof Square){
g.drawRect(a[0], a[1], a[2], a[3]);
g.fillRect(a[0], a[1], a[2], a[3]);
}else if(i instanceof Circle){
g.drawOval(a[0], a[1], a[2], a[3]);
g.fillOval(a[0], a[1], a[2], a[3]);
}
}
}
}
class FrameListener implements MouseListener, MouseMotionListener {
public void mousePressed(MouseEvent e) {
System.out.println("pressed");
a = new Point(e.getPoint());
if (makeSquare) {
makeSquare = false;
System.out.println("square made!");
}
if (makeCircle) {
makeCircle = false;
System.out.println("cirlce made!");
}
//use this for sliders, nothing else.
}
public void mouseReleased(MouseEvent e) {
System.out.println("released");
a = new Point(e.getPoint());
//use for sliders, nothing else.
}
public void mouseClicked(MouseEvent e) {
System.out.println("clicked");
a = new Point(e.getPoint());
//don't need this
//makeSquare = false;
//makeCircle = false;
//makeSquiggle too.
}
public void mouseMoved(MouseEvent e) {
//showing up as false atm
a = new Point(e.getPoint());
System.out.println(a);
if (makeSquare||makeCircle) {
Shape b = shapes.get(shapes.size()-1);
b.updateLocation((int) a.getX(), (int) a.getY());
}
}
public void mouseDragged(MouseEvent e) {
//only check if over a JSlider
}
//complete methods:
public void mouseEntered(MouseEvent e) {
System.out.println("entered");
//nothing, Mouse re-entering doesn't effect the program.
}
public void mouseExited(MouseEvent e) {
System.out.println("exited");
makeSquare = false;
makeCircle = false;
makeSquiggle = false;
//if mouse leaves the window while trying to make one of these, stop it.
}
}
}
Shape接口的代码：
package smys01;
public interface Shape {
public void updateLocation(int newXPos, int newYPos);
public void updateDimensions(int newXDim, int newYDim);
public void delete();
public void purge();
public void restore();
public int[] getDim();
}
广场代码： 注意！这段代码写了一些，并且有一些部分根本不相关甚至完整（但完全未使用）。这适用于构造函数，updateDimensions（）方法和updateLocation（）方法
package smys01;
import java.awt.Color;
public class Square implements Shape{
//tbr=to be returned.
boolean deleted=false;
boolean purged=false;
private int xPos, yPos, xDim, yDim;
private int saveXPos, saveYPos, saveXDim, saveYDim, saveR, saveG, saveB, saveA;
private Color fill;
public Square(int initX, int initY, Color a){
xPos=initX;
yPos=initY;
xDim=50;
yDim=50;
fill=a;
}
public void updateDimensions(int newXDim, int newYDim){
if(purged||deleted)
return;
if(newXDim<=2){
xDim=2;
}else{
xDim=newXDim;
}
if(newYDim<=2){
yDim=2;
}else{
yDim=newYDim;
}
}
public void updateLocation(int newXPos, int newYPos){
if(purged){
return;
}
if(newXPos<=5){
xPos=5;
}else{
xPos=newXPos;
}
if(newYPos<=25){
yPos=25;
}else{
yPos=newYPos;
}
}
public void delete(){
if(!deleted){
saveXPos=xPos;
saveYPos=yPos;
saveXDim=xDim;
saveYDim=yDim;
saveR=fill.getRed();
saveB=fill.getBlue();
saveG=fill.getGreen();
saveA=fill.getAlpha();
deleted=true;
xPos=-5;
yPos=-5;
xDim=1;
yDim=1;
}
}
public void purge(){
saveXPos=-10;
saveYPos=-10;
saveXDim=3;
saveYDim=3;
//use in an if statement, and if true (will be, set the square value to null, so this reference will go away, preventing data overflow
}
public void restore(){
xPos=saveXPos;
yPos=saveYPos;
xDim=saveXDim;
yDim=saveYDim;
deleted=false;
}
public int[] getDim(){
int[] tbr={xPos,yPos, xDim, yDim,fill.getRed(), fill.getBlue(), fill.getGreen(), fill.getAlpha()};
return tbr;
}
public String toString(){
String tbr="Square: ("+xPos+", "+yPos+"); ("+xDim+", "+yDim+"); ("+fill.toString();
return tbr;
}
}
Circle类的代码完全相同，但对象类型允许paintComponent方法区分它们。
我试图在调用mouseMoved时调用paintComponent，但是我似乎无法做到这一点。我尝试过使用repaint（），我已经找了几个小时试图解决这个问题。
到目前为止，我已经看到，基本上，Swing会在需要时调用paintComponent（当窗口大小改变时，或者窗口被最小化并重新打开）。
但是，我不确定如何在按下按钮或移动鼠标时调用它，并且repaint（）将无法正常工作。
我道歉，如果有些代码很草率，我已经重写了几次，有些部分是不必要的，但仍然存在。
有没有办法从匿名操作类或FrameListener类中主动调用paintComponent方法？
答案 0 :(得分：1)
经过@MadProgrammer的一些输入后，我发现了什么不起作用。 mouseListener附加到JFrame而不是JPanel，因此事件被触发，但paintComponent（通过repaint（））不是。我将它添加到面板并将repaint（）添加到mouseMoved（）方法的末尾，它运行正常。