使用事件更改绘图程序中线条的颜色

Question

我正在尝试创建一个使用点绘制线的程序。我做了这一点。然后，当程序最小化并再次最大化时，该行需要重绘。这是我第一个问题发生的地方。假设我绘制了2条线，第一条线的最后一点和第二条线的第一个点在最大化时连接在一起。

然而，这不是我的主要问题。我想实现一个键处理程序，这样，当按下1-9键时，每个键代表该行的不同颜色变化。我已经尝试过实现一个密钥处理程序，但显然出现了问题，因为我无法完成它。任何帮助，将不胜感激。我的代码如下所示。

package part2;

import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import java.awt.Point;
import java.awt.Color;

public class ScribbleComponentRepaint extends JComponent implements Scribbler {
    int w = 640;
    int h = 360;
    Point c;
    ArrayList<Point> line;
    ArrayList<ArrayList<Point>> lines;

    public static void main(String[] args) {
        ScribbleComponentRepaint sc = new ScribbleComponentRepaint();
        new JEasyFrame(sc, "Scribble");
        sc.addMouseListener(new Clicker(sc));
        sc.addMouseMotionListener(new Mover(sc));
        sc.addKeyListener(new Keys(sc));
    }

    public ScribbleComponentRepaint() {
        line = new ArrayList<Point>();
        lines = new ArrayList<ArrayList<Point>>();
    }

    public void handleKey(int e) {

        switch (e) {
            case KeyEvent.VK_1:

                break;
            default: {
                System.out.println("Default");
            }
        }
    }


    public void paintComponent(Graphics g) {
        for (ArrayList<Point> line : lines) {
            int n = 0;
            int limit = 1;
            if (line.size() > 0) {
                for (Point p : line) {
                    Point c = line.get(Math.max(n - limit, 0));
                    n++;
                    g.setColor(Color.RED);
                    g.drawLine(c.x, c.y, p.x, p.y);
                }
            }
        }
    }

    public void penDown(Point p) {
        c = p;

    }

    public void penUp(Point p) {
        drawTo(p);
        c = null;

    }

    public void drawTo(Point p) {
        if (c != null) {
            Graphics g = getGraphics();
            g.setColor(Color.BLUE);
            g.drawLine(c.x, c.y, p.x, p.y);
            c = p;
        }
        line.add(c);
        lines.add(line);

    }

    public void drag(Point p) {
        //should not be null
        drawTo(p);
    }


    public Dimension getPreferredSize() {
        return new Dimension(w, h);
    }

}

package part2; import javax.swing.*; import java.awt.*; import java.awt.event.KeyEvent; import java.util.ArrayList; import java.awt.Point; import java.awt.Color; public class ScribbleComponentRepaint extends JComponent implements Scribbler { int w = 640; int h = 360; Point c; ArrayList<Point> line; ArrayList<ArrayList<Point>> lines; public static void main(String[] args) { ScribbleComponentRepaint sc = new ScribbleComponentRepaint(); new JEasyFrame(sc, "Scribble"); sc.addMouseListener(new Clicker(sc)); sc.addMouseMotionListener(new Mover(sc)); sc.addKeyListener(new Keys(sc)); } public ScribbleComponentRepaint() { line = new ArrayList<Point>(); lines = new ArrayList<ArrayList<Point>>(); } public void handleKey(int e) { switch (e) { case KeyEvent.VK_1: break; default: { System.out.println("Default"); } } } public void paintComponent(Graphics g) { for (ArrayList<Point> line : lines) { int n = 0; int limit = 1; if (line.size() > 0) { for (Point p : line) { Point c = line.get(Math.max(n - limit, 0)); n++; g.setColor(Color.RED); g.drawLine(c.x, c.y, p.x, p.y); } } } } public void penDown(Point p) { c = p; } public void penUp(Point p) { drawTo(p); c = null; } public void drawTo(Point p) { if (c != null) { Graphics g = getGraphics(); g.setColor(Color.BLUE); g.drawLine(c.x, c.y, p.x, p.y); c = p; } line.add(c); lines.add(line); } public void drag(Point p) { //should not be null drawTo(p); } public Dimension getPreferredSize() { return new Dimension(w, h); } }

package part2;

import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

public class Keys extends KeyAdapter {

    Scribbler sc;

    public Keys(Scribbler sc){
        this.sc = sc;
    }

    public void keyPressed(KeyEvent e) {
        //System.out.println(k);
        sc.handleKey(e.getKeyCode());
    }
}

package part2; import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; public class Keys extends KeyAdapter { Scribbler sc; public Keys(Scribbler sc){ this.sc = sc; } public void keyPressed(KeyEvent e) { //System.out.println(k); sc.handleKey(e.getKeyCode()); } }

Answer 1

在主要结束时：

    sc.setFocusable(true);
    sc.requestFocusInWindow();

顺便说一句

• GUI应该在EDT上构建。
• 考虑使用键绑定而不是KeyListener
• 设计精美的代码（定义接口和编码的代码），但为了更好地提供帮助，请发布SSCCE。我必须对代码进行一些更改才能测试我的理论，即检测键的问题是“焦点”。

Answer 2

嗯，你只需要定义一个颜色变量。此变量将在您的处理键方法中设置，并在您的paint方法中使用。此外，您需要在按下一个键后刷新屏幕。

 public class ScribbleComponentRepaint extends JComponent implements Scribbler {
   Color color = Color.BLUE; // var definition
 ...
    public void handleKey(int e) {

    switch (e) {
        case KeyEvent.VK_1:
            color = Color.RED; // setting the new color
            break;
        default: {
            System.out.println("Default");
        }
    }
    repaint(); // updates the screen
}
...
public void paintComponent(Graphics g) {
    for (ArrayList<Point> line : lines) {
        int n = 0;
        int limit = 1;
        if (line.size() > 0) {
            for (Point p : line) {
                Point c = line.get(Math.max(n - limit, 0));
                n++;
                g.setColor(color); // uses the color var
                g.drawLine(c.x, c.y, p.x, p.y);
            }
        }
    }
}
...