Question

从代码中我可以看到我希望在DrawingPanel上看到一个矩形，但我不确定为什么repaint（）方法不起作用。任何帮助都感激不尽。我也尝试过revalidate方法，但这也不起作用。

以下是我的课程：

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);
  }

}

第一个Jpanel的类： PropertyPanel.Java

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

  <PropertyGroup>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
    <ProjectGuid>{B64EE74D-F171-4438-8E7A-ACAE7B40C6C8}</ProjectGuid>
    <OutputType>Exe</OutputType>
    <RootNamespace>Olbert.CommunityScanner</RootNamespace>
    <AssemblyName>CommunityScannerTopShelf</AssemblyName>
    <TargetFrameworkVersion>v4.6.2</TargetFrameworkVersion>
    <FileAlignment>512</FileAlignment>
    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
    <NuGetPackageImportStamp>
    </NuGetPackageImportStamp>
  </PropertyGroup>

Answer 1

你的重画工作正常。您的问题是，您正在向{strong>错误的 DrawingPanel实例调用addRectangle()，而不是当前在GUI中显示的实例。要解决此问题，请将显示的引用传递给需要调用方法的代码。

要查看这是正确的，只需在此页面中搜索new DrawingPanel()即可。您应该在自己的代码中看到一次（并且您的代码已发布）。你看到它两次意味着你已经创建了两个这样的实例。

例如，改变这个：

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

    public PropertyPanel(){

到此：

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

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

然后在创建时将真实的DrawingPanel传递给此对象：

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

更好的是：以M-V-C方式构建代码，并使用依赖注入来建立连接 - 但这对于简单的GUI来说可能是过度的。

Swing Java重绘不使用2个jpanels

1 个答案: