使用2个JPanel时Swing Java重新绘制不起作用

正如您从代码中看到的，我希望在DrawingPanel上看到一个矩形，但我不确定为什么repaint（）方法不起作用。任何帮助都将不胜感激。我还尝试了重新验证方法，但也不起作用

以下是我的课程：

import javax.swing.*;
import java.awt.*;

public class Designer extends JFrame {

static JFrame f = new Designer();

JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT);
DrawingPanel drawingPanel = new DrawingPanel();
PropertyPanel propertyPanel = new PropertyPanel();

 public Designer(){

    Rectangle bounds = GraphicsEnvironment
            .getLocalGraphicsEnvironment()
            .getMaximumWindowBounds();

    splitPane.setTopComponent(propertyPanel);
    splitPane.setBottomComponent(drawingPanel);

    add(splitPane, BorderLayout.CENTER);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(bounds);
    setVisible(true);

 }

 public static void main(String[] args) {
    System.out.println("App started...");
 }
}

第一个Jpanel的类：PropertyPanel.Java

import javax.swing.*;
import java.awt.event.*;

public class PropertyPanel extends JPanel {

  private DrawingPanel drawingPanel = new DrawingPanel();

  public PropertyPanel(){

    JButton addShapesBtn = new JButton("Add");

    addShapesBtn.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            drawingPanel.addRectangle();
        }
    });
    add(addShapesBtn);
  }

}

import javax.swing.*;
import java.awt.*;
import java.util.ArrayList;
import java.util.List;

public class DrawingPanel extends JPanel{

  private List<Rectangle> squares = new ArrayList<Rectangle>();


 @Override
 protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    Graphics2D g2 = (Graphics2D) g;

    System.out.println("painting");

    for (Rectangle rect : squares) {
        g2.draw(rect);
    }

}


  public void addRectangle() {

    Rectangle rectx = new Rectangle(10, 10, 100, 100);
    squares.add(rectx);
    repaint(); <-- this is not working
  }
}

第二个Jpanel的类：DrawingPanel.Java

import javax.swing.*;
import java.awt.event.*;

public class PropertyPanel extends JPanel {

  private DrawingPanel drawingPanel = new DrawingPanel();

  public PropertyPanel(){

    JButton addShapesBtn = new JButton("Add");

    addShapesBtn.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            drawingPanel.addRectangle();
        }
    });
    add(addShapesBtn);
  }

}

import javax.swing.*;
import java.awt.*;
import java.util.ArrayList;
import java.util.List;

public class DrawingPanel extends JPanel{

  private List<Rectangle> squares = new ArrayList<Rectangle>();


 @Override
 protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    Graphics2D g2 = (Graphics2D) g;

    System.out.println("painting");

    for (Rectangle rect : squares) {
        g2.draw(rect);
    }

}


  public void addRectangle() {

    Rectangle rectx = new Rectangle(10, 10, 100, 100);
    squares.add(rectx);
    repaint(); <-- this is not working
  }
}

import javax.swing.*；
导入java.awt.*；
导入java.util.ArrayList；
导入java.util.List；
公共类DrawingPanel扩展了JPanel{
私有列表方块=新的ArrayList（）；
@凌驾
受保护组件（图形g）{
超级组件（g）；
图形2d g2=（图形2d）g；
系统输出打印（“绘制”）；
用于（矩形矩形：正方形）{
g2.绘制（rect）；
}
}
公共void addRectangle（）{
矩形rectx=新矩形（10,10,100,100）；
正方形。添加（rectx）；
重新绘制（）；您的重新绘制工作正常。您的问题是，您正在调用
addRectangle（）
到错误的DrawingPanel实例，而不是当前显示在GUI中的实例。要解决此问题，请将显示实例的引用传递到需要调用该方法的代码

要查看这一点是否正确，只需在此页面中搜索
new DrawingPanel（）
。您应该在自己的代码（以及发布的代码）中只看到一次。您看到它两次，这意味着您已经创建了两个实例

e、 例如，改变这一点：

public class PropertyPanel extends JPanel {   
    private DrawingPanel drawingPanel = new DrawingPanel();

    public PropertyPanel(){

为此：

public class PropertyPanel extends JPanel {    
    private DrawingPanel drawingPanel;  // don't create new

    public PropertyPanel(DrawingPanel drawingPanel){
        this.drawingPanel = drawingPanel;

然后在创建时将true DrawingPanel传入此对象：

DrawingPanel drawingPanel = new DrawingPanel();
PropertyPanel propertyPanel = new PropertyPanel(drawingPanel);


更好的方法是：以M-V-C的方式构造代码，并使用依赖项注入来建立连接——但这对于您的简单GUI来说可能有些过分。
非常感谢。这确实很有帮助。@VK321：不客气，但它有意义吗？另外，请参阅编辑以回答问题。