如何在java中删除绘制的线？
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How to delete Drawn Line in java?
提问by Jeyjey
The problem is how can I delete the old lines? I mean, make only the current x and y lines appear on the screen, make the intersection between both lines "follow" the mouse pointer.
问题是如何删除旧行？我的意思是，只让当前的 x 和 y 线出现在屏幕上，让两条线之间的交点“跟随”鼠标指针。
This is the updated code:
这是更新后的代码：
import javax.swing.*;
import javax.*;
import java.awt.*;
import java.awt.Color;
import java.awt.Graphics.*;
import java.awt.event.*;
import javax.swing.UIManager;
public class SimpleGUI extends JFrame {
public SimpleGUI() {
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ;
}
public void go() {
Drawpanel = new Mypanel();
JFrame frame = new JFrame("Chasing Line");
JButton mybutton1 = new JButton("Please");
JButton mybutton2 = new JButton("Help");
JButton mybutton3 = new JButton("Me!!");
Drawpanel.add(mybutton1);
Drawpanel.add(mybutton2);
Drawpanel.add(mybutton3);
frame.getContentPane().add(BorderLayout.CENTER, Drawpanel);
frame.setSize(300,300);
frame.setVisible(true);
Drawpanel.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() {
public void mouseMoved(java.awt.event.MouseEvent evt) {
DrawpanelMouseMoved(evt);
}
});
}
public void DrawpanelMouseMoved(java.awt.event.MouseEvent evt) {
xpos=evt.getX();
ypos=evt.getY();
System.out.println("Coordinates : X :"+ xpos+"Y: "+ypos);
Drawpanel.paintImage(xpos,ypos);
}
class Mypanel extends JPanel {
public void paintImage(int xpost,int ypost){
Graphics d = getGraphics();
d.clearRect(0,0, this.getWidth(), this.getHeight());
d.setColor(Color.black);
d.drawLine(xpost, 0, xpost, this.getHeight());
d.setColor(Color.red);
d.drawLine(0, ypost, this.getWidth(),ypost);
this.validate();
}
} // end the inner class
public static void main(String[] args){
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
} catch(Exception e) {
System.err.println("Look and feel not set");
}
SimpleGUI win = new SimpleGUI();
win.go();
}
Mypanel Drawpanel;
private int xpos=0;
private int ypos=0;
} // close SimpleGUI class
The question is how can I keep those 3 buttons with out altering their state?
问题是我怎样才能保留这 3 个按钮而不改变它们的状态？
回答by Jonas
The problem is how can i delete the old lines?, i mea,make only the current x and y lines appear on the screen, make the intersection between both lines "follow" the mouse pointer.
问题是如何删除旧行？，我的意思是，让屏幕上只显示当前的 x 和 y 线，使两条线之间的交点“跟随”鼠标指针。
- Save all your lines that you want to keep in a LinkedList or similar.
- Start painting with drawing the background again, this will clear your old lines.
- Paint all your lines in your LinkedList.
- 将所有要保留的行保存在 LinkedList 或类似内容中。
- 再次绘制背景开始绘画，这将清除您的旧线条。
- 在 LinkedList 中绘制所有线条。
Or if you don't want to save any lines:
或者，如果您不想保存任何行：
- Draw the background again, this removes the old lines.
- Draw your lines.
- 再次绘制背景，这将删除旧线条。
- 画出你的线条。
You can draw the background again with:
您可以再次绘制背景：
clearRect(int x, int y, int width, int height)
回答by chris
you'll need to do d.clear();just after the Graphics d = getGraphics();line, this will clear the existing graphics and what you draw on it after that will be all that's shown.
您需要d.clear();在该Graphics d = getGraphics();行之后执行此操作，这将清除现有图形，之后您在其上绘制的内容将显示所有内容。
回答by camickr
You should never use code that invokes getGraphics(). Custom painting is done by overriding the paintComponent() method.
永远不要使用调用 getGraphics() 的代码。自定义绘画是通过覆盖paintComponent() 方法完成的。
Custom Painting Approachesshows 2 different approaches for doing some basic painting.
自定义绘画方法展示了两种不同的基本绘画方法。
I'm not sure I understand your question about the "widgets", but the examples have buttons that are not affected by the painting.
我不确定我是否理解您关于“小部件”的问题，但示例中的按钮不受绘画影响。
