java 在 JPanel 上绘制矩形
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Drawing rectangles on a JPanel
提问by infoSyStem
I have a JScrollPane and on top of it I have a JPanel named 'panel1'. I want some rectangles to be drawn on this JPanel.
我有一个 JScrollPane，最重要的是我有一个名为“panel1”的 JPanel。我想在这个 JPanel 上绘制一些矩形。
I have a class named DrawRectPanel which extends JPanel and does all the drawing stuff. The problem is that, I tried to draw the rectangles on panel1 by writing the following code :
我有一个名为 DrawRectPanel 的类，它扩展了 JPanel 并完成了所有绘图工作。问题是，我尝试通过编写以下代码在 panel1 上绘制矩形：
panel1.add(new DrawRectPanel());
but nothing appeared on panel1 then I tried, just as a test to the class DrawRectPanel :
但是没有出现在 panel1 上然后我尝试了，就像对 DrawRectPanel 类的测试一样：
JFrame frame = new JFrame();
frame.setSize(1000, 500);
Container contentPane = frame.getContentPane();
contentPane.add(new DrawRectPanel());
frame.show();
This worked, and produced the drawings but on a separate JFrame How can I draw the rectangles on panel1 ? Thanks in advance.
这有效，并在单独的 JFrame 上生成了图纸如何在 panel1 上绘制矩形？提前致谢。
EDIT : code for DrawRectPanel
编辑：DrawRectPanel 的代码
public class DrawRectPanel extends JPanel {
DrawRectPanel() {
Dimension g = new Dimension(400,400);
this.setPreferredSize(g);
System.out.println("label 1");
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println("label 2");
g.setColor(Color.red);
g.fillRect(20, 10, 80, 30);
}
}
only label 1 is printed on the screen
屏幕上仅打印标签 1
采纳答案by mKorbel
still no idea,
还是不知道
for example
例如
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JComponent;
import javax.swing.JFrame;
public class CustomComponent extends JFrame {
private static final long serialVersionUID = 1L;
public CustomComponent() {
setTitle("Custom Component Graphics2D");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void display() {
add(new CustomComponents());
pack();
// enforces the minimum size of both frame and component
setMinimumSize(getSize());
setVisible(true);
}
public static void main(String[] args) {
CustomComponent main = new CustomComponent();
main.display();
}
}
class CustomComponents extends JComponent {
private static final long serialVersionUID = 1L;
@Override
public Dimension getMinimumSize() {
return new Dimension(100, 100);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(400, 300);
}
@Override
public void paintComponent(Graphics g) {
int margin = 10;
Dimension dim = getSize();
super.paintComponent(g);
g.setColor(Color.red);
g.fillRect(margin, margin, dim.width - margin * 2, dim.height - margin * 2);
}
}
回答by gtiwari333
instead of adding
而不是添加
contentPane.add(new DrawRectPanel());
you should do
你应该做
contentPane.add(panel1);
Because you already have new DrawRectPanelin panel1. But in your code you are adding another instance of DrawRectPanelin contentPane. And never added panel1in none of your container.
因为您DrawRectPanel在 panel1 中已经有了 new 。但是在您的代码中，您正在添加DrawRectPanelin 的另一个实例contentPane。并且从未添加panel1过您的container.
回答by Funny Geeks
to fix your problem, change "paintComponent" to "paint" when the window repaints automatically, it should work.
要解决您的问题，请在窗口自动重新绘制时将“paintComponent”更改为“paint”，它应该可以工作。
