这是我尝试画线的课程
package gps;
import java.awt.*;
import java.awt.geom.Line2D;
import java.util.*;
import javax.swing.*;
public class RoadMap extends JPanel {
public void paintComponent(Graphics2D g)
{
super.paintComponent(g);
g.setColor(Color.blue);
for(int i = 0; i < Graph.getEdges().length; i++)
{
Shape s = new Line2D.Double(Graph.vMap.get(Graph.getEdges()[i].i1).x,
Graph.vMap.get(Graph.getEdges()[i].i1).y,
Graph.vMap.get(Graph.getEdges()[i].i2).x,
Graph.vMap.get(Graph.getEdges()[i].i2).y);
g.draw(s);
}
}
}
Graph.vMap.get(Graph.getEdges()[i].i2).x
和Graph.vMap.get(Graph.getEdges()[i].i2).y
访问线端点的x
和y
值,我已经对其进行了测试,并返回了正确的值。但是,与此无关,在我的JFrame中什么也没有显示。尝试用for循环之外的设置值绘制其他行实际上是可行的。 最佳答案
x1 = 43.12929,x2 = 43.12976,y1 = -77.626956,y2 = -77.62679
这些y
值在面板之外。 AWT / Swing组件的可见坐标空间从(0, 0)
到(width-1, height-1)
。
检查您在哪里计算值。如果您希望(0, 0)
成为中心,则需要通过例如Graphics2D#translate(int, int)
。
此外:
public void paintComponent(Graphics2D g)
如果尝试覆盖
paintComponent
,则尚未这样做。 paintComponent
使用Graphics
,而不是Graphics2D
:@Override
protected void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
尝试覆盖时,请始终使用
@Override
批注,因为它会导致错误并告诉您是否不是覆盖。请参见https://docs.oracle.com/javase/tutorial/java/IandI/override.html。可能是您打算使用以下方式:
public class RoadMap extends JPanel {
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.translate(getWidth() / 2, getHeight() / 2);
g2.setColor(Color.blue);
for(int i = 0; i < Graph.getEdges().length; i++) {
Shape s = new Line2D.Double(
Graph.vMap.get(Graph.getEdges()[i].i1).x,
Graph.vMap.get(Graph.getEdges()[i].i1).y,
Graph.vMap.get(Graph.getEdges()[i].i2).x,
Graph.vMap.get(Graph.getEdges()[i].i2).y);
g2.draw(s);
}
g2.dispose();
}
}