我刚开始使用java中的Graphics,我已经卡住了。我试图将JPanel的颜色设置为红色,但似乎没有任何效果!任何帮助都非常感谢。
JFrame类:
import javax.swing.JPanel;
import javax.swing.JFrame;
import java.awt.Color;
public class redBoxFrame{
public static void main(String[]args){
JFrame f = new JFrame();
f.setSize(400, 200);
f.setTitle("A red box");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel p = new redBoxPanel();
p.setBackground(Color.RED);
f.add(p);
f.setVisible(true);
}
}
JPanel类:
import java.awt.Graphics;
import javax.swing.JPanel;
import java.awt.Color;
public class redBoxPanel extends JPanel {
public void paintComponent(Graphics g){
g.fillRect(0, 0, 100, 100);
g.setColor(Color.RED);
}
}
正如您所看到的,我已经尝试在JFrame类和JPanel类中声明颜色,但它们似乎都不起作用。谢谢!
这里的每个人似乎都错过了在绘图之前应该设置颜色的事实。
为了演示目的,我将主背景设置为BLUE。
public static void main(String[] args) {
//...
JPanel p = new redBoxPanel();
// BLUE bg. This covers the whole panel.
p.setBackground(Color.BLUE);
//...
}
而现在红色的盒子!
public static class redBoxPanel extends JPanel {
@Override public void paintComponent(Graphics g) {
// You need to call the superclass' paintComponent() so that the
// setBackground() you called in main() is painted.
super.paintComponent(g);
// You need to set the colour BEFORE drawing your rect
g.setColor(Color.RED);
// Now that we have a colour, perform the drawing
g.fillRect(0, 0, 100, 100);
// More, for fun
g.setColor(Color.GREEN);
g.drawLine(0, 0, 100, 100);
}
}
我认为你在paintComponent方法中缺少qazxsw poi。
我相信解决方案正在运行,但就像您在问题中所说的那样,在JFrame类和JPanel类中设置背景。如果从JFrame类中删除setBackground,则应该只看到要绘制的矩形。请尝试以下解决方案,并告知我们是否有效。
JFrame类:
super.paintComponent(g);
JPanel类:
import javax.swing.JPanel;
import javax.swing.JFrame;
import java.awt.Color;
public class redBoxFrame{
public static void main(String[]args){
JFrame f = new JFrame();
f.setSize(400, 200);
f.setTitle("A red box");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel p = new redBoxPanel();
f.add(p);
f.setVisible(true);
}
}