标记不会改变
package CreatingWindows;
import javax.swing.*;
import java.awt.geom.*;
import java.awt.*;
import javax.swing.event.MouseInputAdapter;
import java.awt.event.MouseEvent;
public class myCurveApplet extends JApplet{
@Override
public void init(){
this.add(pane);
pane.addMouseListener(new MouseHandler());
pane.addMouseMotionListener(new MouseHandler());
}
private class CurvePane extends JComponent{
@Override
public void paint(Graphics g){
Graphics2D g2D = (Graphics2D)g;
if(a!=null&&b!=null&&ctrl!=null){
System.out.println("Repainted!");
String text;
aMark = new Marker(a);
bMark = new Marker(b);
ctrlMark = new Marker(ctrl);
quadCurve = new QuadCurve2D.Double(a.x, a.y, ctrl.x, ctrl.y, b.x, b.y);
aMark.draw(g);
g2D.setPaint(Color.BLACK);
text = "A"+"\n"+"("+a.x+","+a.y+")";
g2D.drawString(text,(int)a.x,(int)a.y+30);
bMark.draw(g);
g2D.setPaint(Color.BLACK);
text = "B"+"\n"+"("+b.x+","+b.y+")";
g2D.drawString(text,(int)b.x,(int)b.y+30);
ctrlMark.draw(g);
g2D.setPaint(Color.BLACK);
text = "Control"+"\n"+"("+ctrl.x+","+ctrl.y+")";
g2D.drawString(text,(int)ctrl.x,(int)ctrl.y+30);
g2D.setPaint(Color.BLACK);
g2D.draw(quadCurve);
}
}
}
private class MouseHandler extends java.awt.event.MouseAdapter{
@Override
public void mouseClicked(MouseEvent e){
if(a==null||b==null||ctrl==null){
if(a==null){
a = new Point2D.Double(e.getX(), e.getY());
}else if(b==null){
b = new Point2D.Double(e.getX(), e.getY());
}else{
ctrl = new Point2D.Double(e.getX(), e.getY());
}
}else if(aMark!=null&&bMark!=null&&ctrlMark!=null){
if(aMark.contains(e.getX(),e.getY())){
selectedPoint = a;
}else if(bMark.contains(e.getX(),e.getY())){
selectedPoint = b;
}else if(ctrlMark.contains(e.getX(),e.getY())){
selectedPoint = ctrl;
}
}
}
@Override
public void mouseDragged(MouseEvent e){
if(selectedPoint!=null){
selectedPoint.x = e.getX();
selectedPoint.y = e.getY();
}
}
@Override
public void mouseReleased(MouseEvent e){
selectedPoint = null;
pane.repaint();
}
private Point2D.Double selectedPoint;
}
private class Marker{
public Marker(Point2D.Double center){
this.center.setLocation(center);
circle = new Ellipse2D.Double(center.x,center.y,r,r);
}
public void draw(Graphics g){
Graphics2D g2D = (Graphics2D)g;
if(circle!=null){
g2D.setPaint(selectedColor);
g2D.draw(circle);
}
}
public boolean contains(int x,int y){
return circle.contains(x, y);
}
public void setLocation(int x,int y){
center.x = x;
center.y = y;
circle = new Ellipse2D.Double(center.x,center.y,r,r);
}
public Point2D.Double center = new Point2D.Double();
private Ellipse2D.Double circle;
private static final double r = 6;
}
private Point2D.Double a;
private Point2D.Double b;
private Point2D.Double ctrl;
private QuadCurve2D.Double quadCurve;
Marker aMark;
Marker bMark;
Marker ctrlMark;
private Color selectedColor = Color.orange;
private CurvePane pane = new CurvePane();
}
这是创建此内容的源代码：
这里的事情是允许用户通过在屏幕上拖动点来改变曲线，但不知何故我无法做到。请告诉我要做出哪些改变以及为什么！
1 个答案:
答案 0 :(得分：6)
那里有几个问题。
第一个原因，因为您的程序不能正常运行，如下所示：
您为selectedPoint分配了一个对象（a或b或ctrl）的副本。
在mouseDragged内修改它时，实际上是在修改其中一个对象（selectedPoint）的副本，而不是原始对象的副本。所以当你重建曲线时：
quadCurve = new QuadCurve2D.Double(a.x, a.y, ctrl.x, ctrl.y, b.x, b.y);
a b和ctrl始终具有相同的初始值，因为您只修改了其中一个的副本（selectedPoint）。
要解决此问题，您需要直接修改所需的对象。在你的情况下，我会在你的Marker中添加一个字段（例如字符串名称），然后我会保存标记而不是点。 类似的东西：
if(aMark!=null&&bMark!=null&&ctrlMark!=null){
if(aMark.contains(e.getX(),e.getY())){
selectedMarker = aMark;
}else if(bMark.contains(e.getX(),e.getY())){
selectedMarker = bMark;
}else if(ctrlMark.contains(e.getX(),e.getY())){
selectedMarker = ctrlMark;
}
}
然后当您拖动鼠标时检查哪个标记处于活动状态并直接更改位置：
public void mouseDragged(MouseEvent e){
if(selectedMarker !=null){
if (0 == selectedMarker.getName().compareTo("ctrlMark"))
ctrl.x = e.getX();
ctrl.y = e.getY();
}
}
第二个原因是mouseListener和mouseMotionListener使用2个不同的MouseHandler实例。
因此，您有2个selectedPoint（或更好的selectedMarker）副本，一个由MouseDragged（mouseMotionListener）使用，另一个由MouseClicked使用（MouseListener）。
您可以将selectedMarker声明为静态以解决此问题。
你的程序中还有其他错误。 特别：
- 直接覆盖绘图是错误的。改为覆盖
paintComponent并调用基本方法：public void paintComponent(Graphics g){super.paintComponent(g); - 在帧时间无用的对象创建：您正在paintComponent方法中实例化新对象。这可能是一个很大的开销。实例化它们一次，只需在实际修改对象坐标时修改所需的坐标
- 名称约定：对类使用大写字母。
这是一个包含很少修复的工作代码段：
import javax.swing.*;
import java.awt.geom.*;
import java.awt.*;
import javax.swing.event.MouseInputAdapter;
import java.awt.event.MouseEvent;
public class MyCurveApplet extends JApplet{
private static Marker selectedMarker;
@Override
public void init(){
this.add(pane);
pane.addMouseListener(new MouseHandler());
pane.addMouseMotionListener(new MouseHandler());
}
private class CurvePane extends JComponent{
@Override
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2D = (Graphics2D)g;
if(a!=null&&b!=null&&ctrl!=null){
System.out.println("Repainted!");
String text;
aMark = new Marker(a,"a");
bMark = new Marker(b,"b");
ctrlMark = new Marker(ctrl,"ctrl");
quadCurve = new QuadCurve2D.Double(a.x, a.y, ctrl.x, ctrl.y, b.x, b.y);
aMark.draw(g);
g2D.setPaint(Color.BLACK);
text = "A"+"\n"+"("+a.x+","+a.y+")";
g2D.drawString(text,(int)a.x,(int)a.y+30);
bMark.draw(g);
g2D.setPaint(Color.BLACK);
text = "B"+"\n"+"("+b.x+","+b.y+")";
g2D.drawString(text,(int)b.x,(int)b.y+30);
ctrlMark.draw(g);
g2D.setPaint(Color.BLACK);
text = "Control"+"\n"+"("+ctrl.x+","+ctrl.y+")";
g2D.drawString(text,(int)ctrl.x,(int)ctrl.y+30);
g2D.setPaint(Color.BLACK);
g2D.draw(quadCurve);
}
}
}
private class MouseHandler extends java.awt.event.MouseAdapter{
@Override
public void mousePressed(MouseEvent e){
if(a==null||b==null||ctrl==null){
System.out.println("FOO");
if(a==null){
a = new Point2D.Double(e.getX(), e.getY());
}else if(b==null){
b = new Point2D.Double(e.getX(), e.getY());
}else{
ctrl = new Point2D.Double(e.getX(), e.getY());
}
}else if(aMark!=null&&bMark!=null&&ctrlMark!=null){
if(aMark.contains(e.getX(),e.getY())){
System.out.println("SelecteMarker A");
selectedMarker = aMark;
}else if(bMark.contains(e.getX(),e.getY())){
System.out.println("SelecteMarker B");
selectedMarker = bMark;
}else if(ctrlMark.contains(e.getX(),e.getY())){
System.out.println("SelecteMarker CTRL");
selectedMarker = ctrlMark;
}
}
}
@Override
public void mouseDragged(MouseEvent e){
if(selectedMarker!=null){
if (0 == selectedMarker.name.compareTo("a")){
a.x = e.getX();
a.y = e.getY();
}else if (0 == selectedMarker.name.compareTo("b")){
b.x = e.getX();
b.y = e.getY();
}else if (0 == selectedMarker.name.compareTo("ctrl")){
ctrl.x = e.getX();
ctrl.y = e.getY();
}
pane.repaint();
}
}
@Override
public void mouseReleased(MouseEvent e){
System.out.println("SelectedMark NULL");
selectedMarker = null;
pane.repaint();
}
}
private class Marker{
public String name;
public Marker(Point2D.Double center, String name){
this.name = name;
this.center.setLocation(center);
circle = new Ellipse2D.Double(center.x,center.y,r,r);
}
public void draw(Graphics g){
Graphics2D g2D = (Graphics2D)g;
if(circle!=null){
g2D.setPaint(selectedColor);
g2D.draw(circle);
}
}
public boolean contains(int x,int y){
return circle.contains(x, y);
}
public void setLocation(int x,int y){
center.x = x;
center.y = y;
circle = new Ellipse2D.Double(center.x,center.y,r,r);
}
public Point2D.Double center = new Point2D.Double();
private Ellipse2D.Double circle;
private static final double r = 6;
}
private Point2D.Double a;
private Point2D.Double b;
private Point2D.Double ctrl;
private QuadCurve2D.Double quadCurve;
Marker aMark;
Marker bMark;
Marker ctrlMark;
private Color selectedColor = Color.orange;
private CurvePane pane = new CurvePane();
}
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