我的目标是创建一个包含矩形的类,然后使用它并在其他类中更改它。我试着写这段代码并创建一个Rect rect = new Rect();
对象,但是当我启动程序时,矩形并没有显示出来。我也试着用window.add(rect);
添加它,但遇到了同样的问题,我确定我做错了什么,但我真的不知道是什么。
我尝试的另一件事是从其他类Rect.drawRect(g);
调用方法,但它要求“参数”,如果我像在方法drawRect中那样添加参数g,它会显示"g无法解析为变量“。
我希望有人能解释并告诉我我做错了什么,如果知道如何制作矩形或圆形,然后在其他类中使用它,可能还会改变它的颜色和大小,那就太好了,我只在一个类中发现了如何做。
import javax.swing.JFrame;
public class Main extends Rect{
public static void main(String[] args ) {
JFrame window = new JFrame("test");
window.setSize(1000, 800);
window.setVisible(true);
window.setResizable(false);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Rect rect = new Rect();
}
}
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
public class Rect extends JPanel{
public void drawRect(Graphics g){
g.setColor(Color.RED);
g.fillRect(100, 100, 200, 200);
}
}
发布于 2018-07-26 07:19:16
最重要的是,您需要编写一些代码来完成绘制。这是通过在你的Rect类中重写paintComponent
方法来完成的,有点像这样:
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.RED);
g.fillRect(100, 100, 200, 200);
}
您的第二个问题是,您希望能够从其他类中更改矩形的颜色和大小。举个简单的例子,这可以通过在Rect
类中添加一些静态值来轻松实现:
public static Color myColor = Color.RED;
public static int myX = 100;
public static int myY = 100;
public static int myWidth = 200;
public static int myHeight = 200;
现在更新您的paint方法以使用静态值:
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(myColor);
g.fillRect(myX, myY, myWidth, myHeight);
}
现在,无论何时何地使用Rect
面板,它都会根据静态值显示矩形。
例如,下面是一个简单的工作程序,请注意它是如何使用以下内容的:
//create Rect
Rect rect = new Rect();
//set the size of the new panel
rect.setPreferredSize(new Dimension(800, 600));
//add the rect to your JFrame
window.add(rect);
//now you can change the color for all Rect instances
//Note how I use Rect instead of rect, however, both will work.
Rect.myColor = Color.BLUE;
//And dont forget to repaint it if you want to see the changes immediatly
rect.repaint();
完整示例,main类:
import javax.swing.JFrame;
import java.awt.Color;
public class Main{
//Note how we don't need to extend the Rect class (It just adds confusion)
public static void main(String[] args ) {
JFrame window = new JFrame("test");
window.setSize(1000, 800);
window.setVisible(true);
window.setResizable(false);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//create Rect
Rect rect = new Rect();
//set the size of the new panel
rect.setPreferredSize(new Dimension(800, 600));
//add the rect to your JFrame
window.add(rect);
//now you can change the color for all Rect instances
//Note how I use Rect instead of rect, however both will work.
Rect.myColor = Color.BLUE;
//And dont forget to update it
rect.repaint();
}
}
和Rect类:
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
public class Rect extends JPanel{
public static Color myColor = Color.RED;
public static int myX = 10;
public static int myY = 10;
public static int myWidth = 200;
public static int myHeight = 200;
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(myColor);
g.fillRect(myX, myY, myWidth, myHeight);
}
}
注意,如果您不想每次更改颜色/大小时都调用Rect.repaint()
,那么只需创建一个更改每个值并包含repaint()
的新方法,例如:
public void changeWidth(int width){
myWidth = width;
repaint();
}
发布于 2018-07-26 05:48:20
UDP:您需要重写void paintComponent(Graphics g)
而不是void drawRect(Graphics g)
,并在方法内部调用super.paintComponent(g)
。然后你就可以使用window.add(rect);
了。感谢@FredK更正
https://stackoverflow.com/questions/51527748
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