我似乎不能使用两个继承为我的java，扩展一个类在另一个类 [英] I can't seem to use two inheritance for my java, extending a class in another class

问题描述

 包图; 
 
 import java.awt.Graphics; 
 import java.awt.Polygon; 
 import javax.swing.JFrame; 
 import javax.swing.JPanel; 
 

下面是我的类，覆盖所有其他类，并扩展JFrame， Netbeans中的new> Java Frame选项在一个名为Graph的包中创建，这个文件名是GraphFrame.Java。

  public class GraphFrame extends javax.swing.JFrame {
 
 
 public GraphFrame（）{
 
} 
  pre> 
 
 
以下行来自我的JFrame自动创建代码。
  / ** 
 *此方法从构造函数中调用以初始化窗体。 
 *警告：请勿修改此代码。此方法的内容总是
 *由表单编辑器重新生成。 
 * / 
 @SuppressWarnings（unchecked）
 //< editor-fold defaultstate =collapseddesc =Generated Code> 
  
以下这些行是我的主要方法
  public static void main（String args []）{
 
 
 / *创建并显示表单* / 
 // java .awt.EventQueue.invokeLater（new Runnable（）{
 // public void run（）{
 GraphFrame Frame = new GraphFrame（）; 
 Frame.setVisible（true）; 
 Frame.setTitle（Functional Dependency）; 
 Frame.setSize（500，500）; 
 
 //} 
 //}）; 
} 
  
 
 
这些行是我的DrawGraph类，我在GraphFrame类中创建了INSIDE。除此之外，它扩展了我的JPanel，我通过拖动从摇摆容器的JPanel图标（对不起，如果这是错误的方式添加JPanel）
  class DrawGraph extends JPanel {
 @Override 
 protected void paintComponent（Graphics g）{
 super.paintComponent（g）; 
 
 g.drawLine（10，100，380，100）; 
 g.drawLine（200，30，200，190）; 
 
 g.drawLine（380，100，370，90）; 
 g.drawLine（380，100，370，110）; 
 g.drawLine（200，30，190，40）; 
 g.drawLine（200，30，210，40）; 
 
 g.drawString（X，360，80）; 
 g.drawString（Y，220，40）; 
 
 
 
 
} 
 
} 
 //变量声明 - 不要修改
 private javax.swing .Button jButton1; 
 private javax.swing.JButton jButton2; 
 private javax.swing.JButton jButton3; 
 private javax.swing.JPanel jPanel1; 
 //变量声明结束
} 
  
我的问题是，的图我已经编码，没有出现。我有谷歌，StackOverflowed，浏览我的实验室练习，我似乎找不到这个解决方案。是的，这可能需要更多的阅读，但老实说，我不太明白是什么问题。
解决方案
问题是你永远不会将你的JPanel添加到你创建的框架。
 
 
 
这应该做你想做的。 
  public class GraphFrame extends JFrame {
 
 private DrawGraph graph; 
 
 public GraphFrame（）{
 super（）; 
 graph = new DrawGraph（）; 
 this.add（graph）; 
} 
 class DrawGraph extends JPanel {
 @Override 
 protected void paintComponent（Graphics g）{
 super.paintComponent（g）; 
 g.drawLine（10，100，380，100）; 
 g.drawLine（200，30，200，190）; 
 
 g.drawLine（380，100，370，90）; 
 g.drawLine（380，100，370，110）; 
 g.drawLine（200，30，190，40）; 
 g.drawLine（200，30，210，40）; 
 
 g.drawString（X，360，80）; 
 g.drawString（Y，220，40）; 
} 
} 
} 
  
注意this.add graph）可以被调用，因为 GraphFrame 扩展JFrame。  .add（）方法是JFrame类的一部分，因此可以从 GraphFrame  
 
 
 
您还应该考虑为DrawGraph类创建一个新文件，因为如果您想向 GraphFrame或DrawGraph 。
 
package Graph;

import java.awt.Graphics;
import java.awt.Polygon;
import javax.swing.JFrame;
import javax.swing.JPanel;
Below here is my class which covers all other classes, and extends JFrame, which I have created by selecting "new > Java Frame" options in Netbeans.I created this in a package called Graph, and this filename is GraphFrame.Java.
public class GraphFrame extends javax.swing.JFrame {


public GraphFrame() {

}
The lines below is from my JFrame auto creating codes.
/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
These lines below here is my main method
public static void main(String args[]) {


    /* Create and display the form */
    //java.awt.EventQueue.invokeLater(new Runnable() {
        //public void run() {
            GraphFrame Frame=new GraphFrame();
            Frame.setVisible(true);
            Frame.setTitle("Functional Dependency");
            Frame.setSize(500, 500);

        //}
   // });
}
These lines is my DrawGraph class, which I created INSIDE the GraphFrame class. Besides that, it extends my JPanel which I made by dragging the JPanel icon from the Swing Containers (Sorry if that is the wrong way to add JPanel)
class DrawGraph extends JPanel{
@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    g.drawLine(10, 100, 380, 100);
    g.drawLine(200, 30, 200, 190);

    g.drawLine(380, 100, 370, 90);
    g.drawLine(380, 100, 370, 110);
    g.drawLine(200, 30, 190, 40);
    g.drawLine(200, 30, 210, 40);

    g.drawString("X", 360, 80);
    g.drawString("Y", 220, 40);




    }

}
// Variables declaration - do not modify                     
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JButton jButton3;
private javax.swing.JPanel jPanel1;
// End of variables declaration                   
}
My problem is, the lines of graph which I have coded, did not appear.I have googled, StackOverflowed, browsed through my lab exercises, and I can't seem to find the solution to this. Yes, this may need more reading, but to be honest, I couldn't quite understand what's wrong.
解决方案
The problem is that you never add your JPanel to the frame you created.

This should do what you want. 
public class GraphFrame extends JFrame {

private DrawGraph graph;

public GraphFrame(){
    super();
    graph = new DrawGraph();
    this.add(graph);
}
class DrawGraph extends JPanel{
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawLine(10, 100, 380, 100);
        g.drawLine(200, 30, 200, 190);

        g.drawLine(380, 100, 370, 90);
        g.drawLine(380, 100, 370, 110);
        g.drawLine(200, 30, 190, 40);
        g.drawLine(200, 30, 210, 40);

        g.drawString("X", 360, 80);
        g.drawString("Y", 220, 40);
        }
    }
}
Note that this.add(graph) can be called because GraphFrame extends JFrame. The .add() method is a part of the JFrame class and can thus be called from GraphFrame

You should also consider creating a new file for the DrawGraph class as it can get messy if you want to add more functionality to either GraphFrame or DrawGraph.

                        
这篇关于我似乎不能使用两个继承为我的java，扩展一个类在另一个类的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！