我制作了这个程序，在JFrame中绘制一个多边形然后填充它。我最近更改了它，以便我有控制多边形移动的按钮。除了一个问题之外，该运动也起作用：当我按下按钮以移动方向时，在新的点中创建一个新的多边形，但原始的仍保持可见。
我需要的是在调用repaint（）之前清除JFrame，因为调用repaint（）本身并没有清除JFrame（即使我认为应该这样）。
我已经尝试了以下内容：
removeAll();
revalidate();
repaint();
但我没有运气。
编辑：这是我的班级
public class Assign3 extends javax.swing.JPanel
{
/**
* Creates new form Assign3
*/
public Assign3()
{
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jButton3 = new javax.swing.JButton();
jButton4 = new javax.swing.JButton();
jButton5 = new javax.swing.JButton();
jButton6 = new javax.swing.JButton();
jButton7 = new javax.swing.JButton();
jButton8 = new javax.swing.JButton();
jButton3.setText("Up");
jButton3.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton3ActionPerformed(evt);
}
});
jButton4.setText("Down");
jButton4.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton4ActionPerformed(evt);
}
});
jButton5.setText("Left");
jButton5.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton5ActionPerformed(evt);
}
});
jButton6.setText("Right");
jButton6.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton6ActionPerformed(evt);
}
});
jButton7.setText("Zoom (+)");
jButton7.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton7ActionPerformed(evt);
}
});
jButton8.setText("Zoom (-)");
jButton8.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton8ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
this.setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(272, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jButton3, javax.swing.GroupLayout.PREFERRED_SIZE, 110, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton4, javax.swing.GroupLayout.PREFERRED_SIZE, 110, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton5, javax.swing.GroupLayout.PREFERRED_SIZE, 110, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton6, javax.swing.GroupLayout.PREFERRED_SIZE, 110, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton7, javax.swing.GroupLayout.PREFERRED_SIZE, 110, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton8, javax.swing.GroupLayout.PREFERRED_SIZE, 110, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(18, 18, 18))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addGap(30, 30, 30)
.addComponent(jButton3)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jButton4)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jButton5)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jButton6)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jButton7)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jButton8)
.addContainerGap(102, Short.MAX_VALUE))
);
}// </editor-fold>
//UP PRESSED
private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
//1) get the current y coordinates
//2) move the y coordinates up
upPressed();
}
//DOWN BUTTON
private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
//1) get the current y coordinates
//2) move the y coordinates down
downPressed();
}
//LEFT BUTTON
private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
//1) get the current x coordinates
//2) move the x coordinates to the left
leftPressed();
}
//RIGHT BUTTON
private void jButton6ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
//1) get the current x coordinates
//2) move the x coordinates to the right
rightPressed();
}
//ZOOM IN BUTTON
private void jButton7ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
//translate center to origin
//caculate scaling
//tanslate back
zoomInPressed();
}
//ZOOM OUT BUTTON
private void jButton8ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
zoomOutPressed();
}
//UP BUTTON
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
//1) get the current y coordinates
//2) move the y coordinates up
upPressed();
}
int left_most_edge, right_most_edge, scan = 0;
int wxl = 50, wxh = 362, wyl = 246, wyh = 62;
double[] xcoord;
double[][] table = new double[4][200]; //2d array containing:
//[0][-] -> ymax, [1][-] -> ymin, [2][-] -> dx, [3][-] -> x
double[] px = {100, 150, 250, 300, 250, 150, 100}; //contains all x coord.
double[] py = {125, 100, 200, 150, 100, 200, 200}; //contains all y coord.
int outnum;
double[] lastl = new double[2];
double[] lastr = new double[2];
double[] lastt = new double[2];
double[] lastb = new double[2];
public void initializeTable()
{
int i, j;
for (i = 0; i < 4; i++)
{
for (j = 0; j < 200; j++)
{
table[i][j] = 0;
}//end for
}//end for
}//end initializeTable
public void upPressed()
{
for (int i = 0; i < py.length; i++)
{
py[i] -= 5;
}//end for
repaint();
}//end upPressed
public void downPressed()
{
for (int i = 0; i < py.length; i++)
{
py[i] += 5;
}//end for
repaint();
}//end upPressed
public void leftPressed()
{
for (int i = 0; i < px.length; i++)
{
px[i] -= 5;
}//end for
repaint();
}//end upPressed
public void rightPressed()
{
for (int i = 0; i < px.length; i++)
{
px[i] += 5;
}//end for
repaint();
}//end upPressed
public void zoomInPressed()
{
}//end zoomInPressed
public void zoomOutPressed()
{
}//end zoomOutPressed
public void clipPolygon(Graphics g, int number_entered_edges)
{
lastl[0] = px[number_entered_edges - 1];
lastl[1] = py[number_entered_edges - 1];
lastr[0] = wxl;
lastb[0] = wxl;
lastt[0] = wxl;
lastr[1] = wyl;
lastb[1] = wyl;
lastt[1] = wyl;
outnum = 0;
for (int i = 0; i < number_entered_edges - 1; i++)
{
clipL(px[i], py[i]);
}//end for
outnum = 0;
for (int i = 0; i < number_entered_edges - 1; i++)
{
clipL(px[i], py[i]);
}//end for
}//end clipPolygon
public void clipL(double x, double y)
{
if ((lastl[0] < wxl && wxl <= x) || (x <= wxl && wxl < lastl[0]))
clipR(wxl, (((y - lastl[1]) * (wxl - x)) / x - lastl[0]) + y);
lastl[0] = x;
lastl[1] = y;
if (wxl < x)
clipR(x, y);
}//end clipL
public void clipR(double x, double y)
{
if ((x <= wxh && wxh < lastr[0]) || (lastr[0] < wxh && wxh <= x))
clipB(wxh, (((y - lastr[1]) * (wxh - x)) / x - lastr[0]) + y);
lastr[0] = x;
lastr[1] = y;
if (x < wxh)
clipB(x, y);
}//end clipR
public void clipB(double x, double y)
{
if ((lastb[1] < wyl && wyl <= y) || y <= wyl && wyl < lastb[1])
clipT((((x - lastb[0]) * (wyl - y)) / y - lastb[1]) + x, wyl);
lastb[0] = x;
lastb[1] = y;
if (wyl < y)
clipT(x, y);
}//end clipB
public void clipT(double x, double y)
{
if ((lastt[1] > wyh && wyh >= y) || y >= wyh && wyh > lastt[1])
store((((x - lastt[0]) * (wyh - y)) / y - lastt[1]) + x, wyh);
lastt[0] = x;
lastt[1] = y;
if (wyh > y)
store(x, y);
}//end clipT
public void store(double x, double y)
{
outnum++;
px[outnum] = x;
py[outnum] = y;
}//end store
public double max(double x, double y)
{ //determines the greater of two values
double max;
if (x > y)
max = x;
else
max = y;
return max;
}//end max
public void edgeInsert(double xStart, double yStart, double xEnd, double yEnd, int number_entered_edges)
{ //inserting edges into the edge table
int j = number_entered_edges; //removing the - 1 removes line on left side
double x;
if (yStart > yEnd)
{
table[0][j] = yStart;
table[1][j] = yEnd;
}//end if
else
{
table[0][j] = yEnd;
table[1][j] = yStart;
}//end else
if (table[1][j] == xStart)
x = xStart;
else
x = xEnd;
if (table[0][j] == yStart)
table[2][j] = -(-(xEnd - xStart) / (yEnd - yStart));
else
table[2][j] = -(xEnd - xStart) / (yEnd - yStart);
table[3][j] = x + table[2][j] / 2;
help(j);
}//end edgeInsert
public void loadTable(int number_vertices, int number_entered_edges,
double[] px, double[] py)
{ //take the x and y coordinates and build an edge table based off of them
int k;
double xStart, yStart, xEnd, yEnd;
xStart = px[number_vertices - 1];
yStart = trunc(py[number_vertices - 1]) + 0.5;
//start off with no edges in edge table
number_entered_edges = 0;
for (k = 0; k < number_vertices; k++)
{
xEnd = px[k];
yEnd = trunc(py[k]) + 0.5;
if (yStart == yEnd)
{
xStart = xEnd;
}//end if
else
{
//add edge to edge table
number_entered_edges++;
edgeInsert(xStart, yStart, xEnd, yEnd, number_entered_edges);
yStart = yEnd;
xStart = xEnd;
}//end else
}//end for
scan = (int) trunc(table[1][0]); //start at the top of the polygon
}//end loadTable
public void include(int number_entered_edges)
{ //pushing the right most edge
while ((right_most_edge + 1 < number_entered_edges) && (table[1][right_most_edge + 1] < scan))
{
right_most_edge++;
}//end while
}//end include
public void exclude()
{ //excluding edges that we no longer care about
for (int i = left_most_edge; i <= right_most_edge; i++)
{
if (table[0][i] < scan)
{
left_most_edge++;
for (int j = i; j >= left_most_edge; j--)
{
table[0][j] = table[0][j - 1];
table[2][j] = table[2][j - 1];
table[3][j] = table[3][j - 1];
}//end for
}//end if
}//end for
}//end exclude
public void help(int i)
{
double helpX, helpDX, helpYMax, helpYMin;
for (int j = i - 1; j >= 0; j--)
{
if ((table[1][j] == table[1][j + 1] && table[3][j] > table[3][j + 1]) || table[1][j] > table[1][j + 1])
{
helpYMax = table[0][j];
table[0][j] = table[0][j + 1];
table[0][j + 1] = helpYMax;
helpYMin = table[1][j];
table[1][j] = table[1][j + 1];
table[1][j + 1] = helpYMin;
helpDX = table[2][j];
table[2][j] = table[2][j + 1];
table[2][j + 1] = helpDX;
helpX = table[3][j];
table[3][j] = table[3][j + 1];
table[3][j + 1] = helpX;
}//end if
}//end for
}//end help
public void updateX()
{ //increment x based on dx
for (int i = left_most_edge; i <= right_most_edge; i++)
{
table[3][i] += table[2][i];
}//end for
}//end updateX
public void sortOnX()
{ //sorting x values from least to greatest in edge table
int l = 0;
double t;
xcoord = new double[right_most_edge - left_most_edge + 1];
for (int i = left_most_edge; i <= right_most_edge; i++)
{
xcoord[l] = table[3][i];
for (int j = l - 1; j >= 0; j--)
{
if (xcoord[j] > xcoord[j + 1])
{
t = xcoord[j];
xcoord[j] = xcoord[j + 1];
xcoord[j + 1] = t;
}//end if
}//end for
l++;
}//end for
}//end sortOnX
public void fillScan(Graphics g)
{ //determines the line to be drawn for filling
for (int i = 0; i < xcoord.length; i += 2)
{
drawMyHorizontalLine(g, (int) Math.round(xcoord[i]), scan, (int) Math.round(xcoord[i + 1]));
}//end for
}//end fillScan
public double trunc(double num)
{ //trucates the number passed in to remove any decimal
double rem;
if ((num % 2) == 0)
return num;
else
{
rem = num % 2;
return num - rem;
}//end else
}//end trunc
public void drawMyPolygon(Graphics g)
{ //draws the polygon
g.setColor(Color.RED);
g.drawLine((int) px[0], (int) py[0], (int) px[1], (int) py[1]);
g.drawLine((int) px[1], (int) py[1], (int) px[2], (int) py[2]);
g.drawLine((int) px[2], (int) py[2], (int) px[3], (int) py[3]);
g.drawLine((int) px[3], (int) py[3], (int) px[4], (int) py[4]);
g.drawLine((int) px[4], (int) py[4], (int) px[5], (int) py[5]);
g.drawLine((int) px[5], (int) py[5], (int) px[6], (int) py[6]);
g.drawLine((int) px[6], (int) py[6], (int) px[0], (int) py[0]);
}//end drawMyPolygon
public void drawMyHorizontalLine(Graphics g, int x1, int y, int x2)
{ //draws the line for filling
g.setColor(Color.GREEN);
g.drawLine(x1, y, x2, y);
}//end drawMyHorizontalLine
public void fillMyPolygon(Graphics g, int number_vertices, int number_entered_edges)
{ //calls methods to deal with edge table and fill the polygon
if (number_entered_edges < 3 || number_entered_edges > 200)
{
System.out.println("Polygon size error");
}//end if
else
{
loadTable(number_vertices, number_entered_edges, px, py);
while (left_most_edge < number_entered_edges) {
scan++; //move down the screen
exclude();
updateX();
include(number_entered_edges);
sortOnX();
fillScan(g);
}//end while
}//end else
}//end fillMyPolygon
public void drawWindow(Graphics g)
{
g.setColor(Color.BLACK);
g.drawLine(50, 62, 50, 246);
g.drawLine(50, 62, 362, 62);
g.drawLine(50, 246, 362, 246);
g.drawLine(362, 62, 362, 246);
}//end drawWindow
public void buttons()
{
jButton1.setVisible(true);
jButton2.setVisible(true);
jButton3.setVisible(true);
jButton4.setVisible(true);
jButton5.setVisible(true);
jButton6.setVisible(true);
}//end buttons
@Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
//initialize the edge table to all zeroes
initializeTable();
clipPolygon(g, 7);
//begin filling the polygon
fillMyPolygon(g, 7, 7);
//draw polygon with red outline
drawMyPolygon(g);
//draw viewing window
drawWindow(g);
//set buttons to visible
buttons();
}//end paintComponent
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JButton jButton3;
private javax.swing.JButton jButton4;
private javax.swing.JButton jButton5;
private javax.swing.JButton jButton6;
private javax.swing.JButton jButton7;
private javax.swing.JButton jButton8;
// End of variables declaration
}
答案 0 :(得分：1)
绘制到JFrame是否不赞成......这无关紧要，因为这只是为了学习经验而且我知道我应该绘制到JPanel。我只是通过添加super.paint（g）修复了我的问题。在我对paint（）方法的调用中调用。
答案 1 :(得分：0)
JFrame是一个没有实际显示的对象。它只是一个容纳其他GUI对象的容器，例如JPanel，后者又支持JButtons等。
话虽这么说，你所有的实际绘画都应该在Panel中进行，而不是Frame。此外，您是否拥有用于绘制和绘制多边形的其余代码？那里也可能发生一些事情。
答案 2 :(得分：0)
很难说根据您提供的最新信息可能出现什么问题，所以我能做的就是提供一般性建议：
paintComponent(...)方法内部绘制。