Question

给定一个JFrame，我通过处理MouseListener来绘制线条。现在我添加了一个按钮，从Color chooser中选择一种颜色。我希望在选择颜色后，我绘制的所有线条都会选择颜色。

以下是我尝试向ButtonListener添加代码的代码，但无法取得任何成功。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class myJPanelstd extends JPanel implements MouseMotionListener
{
JButton bmessage;
JPanel p1;
JButton changeColor;
public myJPanelstd(){
setBackground(Color.pink);
setLayout(new BorderLayout());
p1 = new JPanel();
p1.setLayout(new GridLayout(3,3));
bmessage = new JButton();
    changeColor= new JButton("CHANGE COLOR");
p1.add(bmessage);
    p1.add(changeColor);
add(p1,"South");
    changeColor.addActionListener(new ButtonListener());
    addMouseMotionListener(this);
}
public void mouseMoved(MouseEvent evt)
{
    Point pt = evt.getPoint();
    String sx = "x = " + pt.getX();
    String sy = "y = " + pt.getY();
    bmessage.setText("you are doing fine");
}
private class ButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
  //Color c = JColorChooser.showDialog(null, "Choose a Color", sampleText.getForeground());
  //if (c != null)
    //sampleText.setForeground(c);
}
}
public void mouseDragged(MouseEvent evt)
{
    bmessage.setText("Nice Drawing!");
    Point pt = evt.getPoint();
    Graphics gg = getGraphics();
    gg.setColor(Color.RED);         
    gg.fillRect(pt.x,pt.y,5,5);        
    getGraphics().setColor(Color.RED);         
    getGraphics().fillRect(pt.x,pt.y,5,5);
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.blue); 
Image myImage = Toolkit.getDefaultToolkit().getImage("images/fred.jpg");
g.drawImage(myImage, 0, 0, this);
g.setColor(Color.yellow);
g.drawString("Draw on Me", 250,150); 
}
}

Answer 1

您需要存储所有绘制的元素并在paintComponent()中重新绘制它们，否则当您最小化/调整大小/覆盖窗口并发现/等时它们将消失。

例如，您创建的每一行都存储在ArrayList中并在paintComponent()开头的循环中重新绘制它们，然后当您更改颜色时，所有线条都将以新颜色绘制。

不要忘记在换色后重绘（）

简单的伪代码 - 只是为了看到这个想法 - 它不会编译

class A extends JPanel
{
  ArrayList<Shape> shapes;

  public A()
  {
      shapes = new ArrayList<Shape>();
  }

  public void afterMouseRelease();
  {
     //paint the shape 
     shapes.add(yourNewShape);  // store it for later
  }

  public void paintComponen(Graphics g)
  {
     super.paintComponent();
     setColor()
     for(Shape s : shapes)
     {
         // paint it again
     }

     // rest of painting
  }
}

前一段时间我在我的应用程序中使用了java.awt.Shape的Shape类和Graphics2D。

Answer 2

使用JColorChooser.showDailog(-,-);在动作监听器下选择颜色

使用Java swing

引用样本颜色选择器

// ColorPicker.java
// A quick test of the JColorChooser dialog.
//
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ColorPicker extends JFrame {

  public ColorPicker() {
    super("JColorChooser Test Frame");
    setSize(200, 100);
    final Container contentPane = getContentPane();
    final JButton go = new JButton("Show JColorChooser");
    go.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        Color c;
        c = JColorChooser.showDialog(
                  ((Component)e.getSource()).getParent(),
                  "Demo", Color.blue);
        contentPane.setBackground(c); 
      }
    });
    contentPane.add(go, BorderLayout.SOUTH);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
  }

  public static void main(String args[]) {
    ColorPicker cp = new ColorPicker();
    cp.setVisible(true);
  }
}

选择颜色以绘制线条

2 个答案: