Java 尝试用 JPanel 画线
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/16206417/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Trying to draw lines with JPanel
提问by Blank1268
I am trying to draw lines using JPaneland I have hit somewhat of a wall. I can get two sides down but once it comes to subtracting from the x cord it all goes wrong.
我正在尝试绘制线条JPanel，但我撞到了一面墙。我可以让两侧向下，但是一旦要从 x 线中减去，一切都会出错。
package GUIstuff;
import java.awt.Graphics;
import javax.swing.JPanel;
public class DrawPanel extends JPanel{
public void paintComponent (Graphics g){
super.paintComponent(g);
int width = getWidth();
int height = getHeight();
int drawCounter = 0; // counters for all the while statements
int drawCounter2 = 0;
int drawCounter3 = 0;
int drawCounter4 = 0;
int x1 = 0; // cords change with the while statemetns
int x2 = 0;
int y1 = 0;
int y2 = 0;
while (drawCounter <= 15){ // counter
y2 = 250;
g.drawLine(x1, y1, x2, y2);
x2 = x2 + 15;
y1 = y1 + 15;
drawCounter++; }
int u1 = 0;
int u2 = 0;
int v1 = 0;
int v2 = 0;
while (drawCounter2 <= 15){
u2 = 250;
g.drawLine(u1, v1, u2, v2);
u1 = u1 + 15;
v2 = v2 + 15;
drawCounter2++;
}
int a1 = 0;
int a2 = 0;
int b1 = 0;
int b2 = 0;
while (drawCounter3 <= 15){
a2 = 250;
g.drawLine(a1, b1, a2, b2);
b1 = b1 + 15;
a2 = a2 - 15;
drawCounter3++;
}
}
}
Here is my runner class
这是我的跑步课程
package GUIstuff;
import javax.swing.JFrame;
public class DrawPanelTest {
public static void main (String args[]){
DrawPanel panel = new DrawPanel();
JFrame application = new JFrame();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
application.add(panel);
application.setSize (250, 250);
application.setVisible(true);
}
}
I have a the lines in the bottom left and the upper right but when I try to subtract from x I just get lines going a crossed the whole box.
我在左下角和右上角有一条线，但是当我尝试从 x 中减去时，我只会让线穿过整个框。
采纳答案by camickr
When doing custom painting you should override the getPreferredSize()method so the panel can be displayed at its preferred size.
在进行自定义绘画时，您应该覆盖该getPreferredSize()方法，以便面板可以以其首选大小显示。
When you draw the lines two variable are the same and two variables differ. Use the width/height variable when appropriate instead of hardcoding a number. In the example below I did the left and bottom sides. The bottom side shows how to subtract. I'll let you figure out the pattern for the other two side.
绘制线条时，两个变量相同，两个变量不同。适当时使用宽度/高度变量，而不是对数字进行硬编码。在下面的示例中，我做了左侧和底部。底部显示如何减去。我会让你弄清楚另外两个方面的模式。
Also, I made the panel a little more dynamic so it will be easy to configure the number of lines you want painted and the gap between the lines.
此外，我使面板更具动态性，因此可以轻松配置要绘制的线条数和线条之间的间隙。
import java.awt.*;
import javax.swing.*;
public class DrawSSCCE extends JPanel
{
private int lines;
private int lineGap;
public DrawSSCCE(int lines, int lineGap)
{
this.lines = lines;
this.lineGap = lineGap;
}
@Override
public Dimension getPreferredSize()
{
int size = lines * lineGap;
return new Dimension(size, size);
}
@Override
public void paintComponent(Graphics g)
{
int width = getWidth();
int height = getHeight();
// Draw lines starting from left to bottom
int x = lineGap;
int y = 0;
for (int i = 0; i < lines; i++)
{
g.drawLine(0, y, x, height);
x += lineGap;
y += lineGap;
}
// Draw lines starting from bottom to right
x = 0;
y = height - lineGap;
for (int i = 0; i < lines; i++)
{
g.drawLine(x, height, width, y);
x += lineGap;
y -= lineGap;
}
// Draw lines starting from right to top
// Draw lines starting from top to left
}
private static void createAndShowUI()
{
JFrame frame = new JFrame("DrawSSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add( new DrawSSCCE(15, 15) );
frame.pack();
frame.setLocationByPlatform( true );
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}
