Java 马克赢了'；不变_Java_Swing_Applet_Geometry_Japplet

Java 马克赢了'；不变

java swing geometry

Java 马克赢了'；不变,java,swing,applet,geometry,japplet,Java,Swing,Applet,Geometry,Japplet,这是创建此的源代码：这里的问题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。请告诉我要做哪些更改以及原因这里有几个问题第一个原因因为您的程序无法运行，原因如下：将对象（a或b或ctrl）的副本指定给selectedPointa。当您在mouseDragged中修改它时，实际上是在修改其中一个对象（selectedPoint）的副本，而不是原始对象。因此，重建曲线时： package CreatingWindows; import javax.swing.*; impo

这是创建此的源代码：

这里的问题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。请告诉我要做哪些更改以及原因

这里有几个问题

第一个原因因为您的程序无法运行，原因如下：

将对象（a或b或ctrl）的副本指定给

selectedPoint

a。当您在
mouseDragged
中修改它时，实际上是在修改其中一个对象（selectedPoint）的副本，而不是原始对象。因此，重建曲线时：

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(); }
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（selectedPoint）的副本
要解决此问题，您需要直接修改所需的对象。在您的例子中，我会在标记中添加一个字段（es.string名称），然后保存标记而不是点。比如：

quadCurve = new QuadCurve2D.Double(a.x, a.y, ctrl.x, ctrl.y, b.x, b.y);
然后，拖动鼠标时，检查哪个标记处于活动状态，并直接更改位置：

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; } }
第二个原因是
mouseListener
和
mouseMotionListener
使用了两个不同的MouseHandler实例。因此，您有两个selectedPoint（或更好的selectedMarker）副本，一个用于
MouseDragged
（mouseMotionListener），另一个用于
MouseClicked
（MouseListener）
您可以将selectedMarker声明为静态以解决此问题

您的程序中还有其他错误。特别是：

直接覆盖绘制是错误的。替代
paintComponent
并调用基本方法：
public void paintComponent（Graphics g）{super.paintComponent（g）；

在帧时创建对象无效：您正在paintComponent方法中实例化新对象。这可能会带来很大的开销。请将它们实例化一次，并在实际修改对象坐标时修改所需的对象

名称约定：类使用大写字母

下面是一个有一些修复的工作片段：

public void mouseDragged(MouseEvent e){ if(selectedMarker !=null){ if (0 == selectedMarker.getName().compareTo("ctrlMark")) ctrl.x = e.getX(); ctrl.y = e.getY(); } }

最初，要创建曲线，您必须单击applet三次，然后单击applet->restart请学习java命名约定并坚持使用Kleopatra是正确的。+1无论如何，对于发布了SSCE的用户。请告诉我哪里没有遵循约定：）包和顶级类名：-）好的，我将引用分配到
selectedPoint
这样就不会有问题了，对吗？所做的任何更改都将直接应用于对象？是的。您可以直接修改MouseDrag内的坐标（这更好，因为您可以避免在每一帧处出现新曲线）。我保留您的结构只是为了显示错误。
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(); }