如何填充行与行之间的空格？

Question

我正在尝试制作一个简单的绘画程序。我正在尝试制作一种像铅笔这样可以自由绘图的工具。到目前为止我的代码是：

NPaintMain

public class NPaintMain {
    public static void main(String[] args) {
        new NPaintWindow();
    }
}

NPaintWindow

public class NPaintWindow {
    private JFrame windowFrame;
    private String windowTitle;
    private NPaintCanvas canvas;
    private Container easel;    
    public NPaintWindow() {
        windowTitle = "NPaint - a simple paint program.";
        windowFrame = new JFrame(windowTitle);
        windowFrame.setDefaultCloseOperation(windowFrame.EXIT_ON_CLOSE);
        windowFrame.setSize(500, 500);
        windowFrame.setLocationRelativeTo(null);
        canvas = new NPaintCanvas();
        easel = windowFrame.getContentPane();
        easel.add(canvas);   
        windowFrame.setVisible(true);
    }
}

NPaintCanvas

public class NPaintCanvas extends JPanel {
    double x, y, px, py;
    ArrayList<Line2D> l;
    public NPaintCanvas() {
        new NPaintMouseEvents(this);
        x = y = px = py = 0;
        l = new ArrayList<>();
    }
    @Override
    public void paintComponent(Graphics g){
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g;
            for(Line2D ll: l){
                g2d.draw(ll);
            }
            l.add(new Line2D.Double(px, py, x, y));
            g.dispose();
            repaint();
    }
}

NPaintMouseEvents

public class NPaintMouseEvents implements MouseListener,MouseMotionListener {

    NPaintCanvas canvas;

    public NPaintMouseEvents(NPaintCanvas canvas) {
        this.canvas = canvas;
        this.canvas.addMouseMotionListener(this);
        this.canvas.addMouseListener(this);
    }

    @Override
    public void mouseDragged(MouseEvent e) {
        if(canvas.px == 0 && canvas.py == 0){
           canvas.px = e.getX();
            canvas.py = e.getY();
        }
        canvas.x = e.getPoint().x;
        canvas.y = e.getPoint().y;
        canvas.px = canvas.x;
        canvas.py = canvas.y;
    }
}

我这里的主要问题是，在拖动点时绘制了点，但它们之间有 space like this。我想加入连续行。任何有关进一步提示的帮助将不胜感激。

Answer 1

您正在修改 paintXXX 中的对象状态 - 这是错误的。 paint 方法仅用于绘制当前状态。

您应该在 MouseListener 中将鼠标点添加到列表中并调用 rapaint 以标记您的 canvas class 将在 EDT 中重新绘制。

并且paintComponent应该总是只绘制当前列表。

所以你应该这样做:

public class NPaintCanvas extends JPanel {
    ArrayList<Line2D> l;
    public NPaintCanvas() {
        new NPaintMouseEvents(this);
        l = new ArrayList<>();
    }
    @Override
    public void paintComponent(Graphics g){
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g;
            for(Line2D ll: l){
                g2d.draw(ll);
            }
    }
}


public class NPaintMouseEvents implements MouseListener,MouseMotionListener {

    NPaintCanvas canvas;
    Point2D prev;
    public NPaintMouseEvents(NPaintCanvas canvas) {
        this.canvas = canvas;
        this.canvas.addMouseMotionListener(this);
        this.canvas.addMouseListener(this);
    }

    @Override
    public void mouseDragged(MouseEvent e) {
        if (prev==null) {
            prev=e.getPoint();
            return;
        }
        Point2D p = new Line2D.Double(e.getPoint().x,e.getPoint().y);
        if (p.equals(prev)) return ; //not really moved
        canvas.l.add(prev, p);
        p=prev;
        canvas.repaint();
    }
}

注意：为了获得最佳解决方案，您应该保留积分并使用 GeneralPath。

Answer 2

您的问题是您为每次鼠标拖动移动绘制了一个点。

对于每条绘制的线：x1 和 x2 相同，y1 和 y2 相同。
你应该在两个不同的点之间画一条线。我已经更新了您的代码以通过引入两个不同的点来处理该问题：prev 点和实际点。
简单的说，只有前一个点和实际的点有值，才会画一条线。
并且当绘制一条线时，最后一个实际绘制的点成为下一条绘制线的前一个点。这样，你的行与行之间就没有空洞了。

在canvas Class :

if (previousPoint != null && actualPoint != null) {
     l.add(new Line2D.Double(previousPoint.x, previousPoint.y, actualPoint.x, actualPoint.y));
     previousPoint = new Point(actualPoint.x, actualPoint.y);
}

如果您松开鼠标按钮，前一个点和实际点将设置为空。

事件中 class :

 @Override
    public void mouseReleased(MouseEvent e) {
      canvas.mouseReleased();
    }

在canvas Class :

  public void mouseReleased() {
    previousPoint = null;
    actualPoint = null;
  }

这样你就可以根据需要独立绘制多条线了。

此外，我通过使用 Point 实例（而不是双精度）简化了代码，它使用整数作为坐标，但您可以使用多个双精度字段，这在实践中并没有改变很多东西。

package paint;

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.geom.Line2D;

import java.util.ArrayList;

import javax.swing.JPanel;

public class NPaintCanvas extends JPanel {
    ArrayList<Line2D> l;
    Point actualPoint;
    Point previousPoint;

    public NPaintCanvas() {
    new NPaintMouseEvents(this);
      l = new ArrayList<>();
    }



  @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        for (Line2D ll : l) {
            g2d.draw(ll);
        }
        if (previousPoint != null && actualPoint != null) {
            l.add(new Line2D.Double(previousPoint.x, previousPoint.y, actualPoint.x, actualPoint.y));
            previousPoint = new Point(actualPoint.x, actualPoint.y);
        }
        g.dispose();
        repaint();
    }

    public void mouseReleased() {
        previousPoint = null;
        actualPoint = null;
    }

    public void mousePressed(int x, int y) {
        previousPoint = new Point(x, y);
    }
}

NPaintMouseEvent

package paint;

import java.awt.Point;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

public class NPaintMouseEvents implements MouseListener, MouseMotionListener {

    NPaintCanvas canvas;

    public NPaintMouseEvents(NPaintCanvas canvas) {
      this.canvas = canvas;
      this.canvas.addMouseMotionListener(this);
      this.canvas.addMouseListener(this);
    }

    @Override
    public void mouseDragged(MouseEvent e) {
      if (canvas.actualPoint == null) {
         canvas.actualPoint = new Point();
      }
      canvas.actualPoint.x = e.getPoint().x;
      canvas.actualPoint.y = e.getPoint().y;
    }

    @Override
    public void mouseMoved(MouseEvent e) {
    }

    @Override
    public void mouseClicked(MouseEvent e) {
    }

    @Override
    public void mousePressed(MouseEvent e) {
      canvas.mousePressed((int) e.getX(), (int) e.getY());
    }

    @Override
    public void mouseReleased(MouseEvent e) {
      canvas.mouseReleased();
    }

    @Override
    public void mouseEntered(MouseEvent e) {
    }

    @Override
    public void mouseExited(MouseEvent e) {
    }
}

如何填充行与行之间的空格？

how to fill spaces between lines?

java

swing

line

paintcomponent