Question

我正在处理我的代码以绘制用户输入的多条线，并且第一个端点以y坐标为中心，而第二个端点以高度/（线数）彼此分开用户输入）。我验证了我的代码，一切似乎工作得很好，除了JPanel没有按照它应该缩放的事实，对应于主框架的大小。有人可以给我一个建议吗？

import java.awt.Graphics; 
import javax.swing.JPanel; 
import java.util.Scanner; 

public class DrawPanel extends JPanel
{
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        int width = getWidth(); 
        int height = getHeight(); 

        Scanner input = new Scanner(System.in); //create object input from Scanner class
        System.out.println("Enter number of lines + 1 to draw: "); //ask for user input
        int stepSize = input.nextInt(); //initialize stepSize to take user input
        int endX = width; //starting position of second pt for x
        int endY = height; //starting position of second pt for y

        for(int i = 0; i < stepSize + 1; i++)
        {
            int verticalStep = height / stepSize; //separate y-coordinate second endpts apart
            int midPoint = height / 2; 
            g.drawLine(0, midPoint, endX, endY); 
            endY = endY - verticalStep; 
        }   
    }
}

import javax.swing.JFrame; 

public class DrawPanelTest 
{

    public static void main(String[] args) 
    {
        DrawPanel panel = new DrawPanel(); 
        JFrame window = new JFrame(); 

        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        window.add(panel); 
        window.setSize(500, 500); //set size of the application
        window.setVisible(true); //display the application
    }
}

Answer 1

JPanel的默认布局为FlowLayout，它使用所包含组件的首选大小。相反，请使用GridLayout。随着框架调整大小，它会增长和缩小。不是setSize()，而是为您的小组提供preferred size的初始here。

Answer 2

感谢您的反馈。我已经弄清楚如何做到这一点，因为我不应该使用Scanner类来询问用户输入。以下是我为此作业编辑的代码：

 public class DrawPanel extends JPanel
{
   private int userChoice; 
   public DrawPanel(int choice)
   {
      userChoice = choice; 
   }

   public void paintComponent(Graphics g)
   {
      super.paintComponent(g);//call paintComponent to ensure the window displays correctly
      int width = getWidth(); //total width
      int height = getHeight();//total height

      int endX = width; //starting position of second pt for x
      int endY = height; //starting position of second pt for y

      //increment from 0 to the user inputted stepSize to draw lines    
      for(int i = 1; i <= userChoice + 1; i++)
      {
         int verticalStep = height / userChoice; //separate y-coordinate second endpts apart
         int midPoint = height / 2; //center the starting position in the y-axis of first endpoint
         g.drawLine(0, midPoint, endX, endY); //draw lines
         endY = endY - verticalStep; //move the second endpoints either up or down
      } 
   }
}


public class DrawPanelTest 
{
   public static void main(String[] args) 
   {
      int choice = Integer.parseInt(args [0]); 
      DrawPanel panel = new DrawPanel(choice);//create a panel that contains the lines 
      JFrame window = new JFrame(); //create a frame to hold the panel

      window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //set frame to exit when closed
      window.add(panel); //add panel to the frame
      window.setSize(500, 500);//set size for the frame
      window.setVisible(true); //display the frame
   }

调整主框架大小时，JPanel窗口不缩放

2 个答案: