如何根据用户输入在 paint 方法中绘制墙

Question

我对编程还很陌生，所以我决定介绍一下 java class。我有一个任务，我必须使用 for 循环创建一堵墙，该循环根据用户输入改变墙的高度。我想我的大部分代码都是正确的，但我似乎无法将用户输入与 for 循环连接起来。任何帮助将不胜感激。

//Package List
import java.awt.*;
import java.applet.*;
import javax.swing.*;
import java.util.*;
import java.awt.event.*;

public class Wall extends JApplet implements ActionListener{

//Component declaration
JLabel directions;
JTextField input = new JTextField( 10 );
private JButton go;
//Variable declaration
int userinput;


//Method declaration
public void init() 
{
    getContentPane().setBackground(new Color (128, 128, 128));//Changes backround of JApplet to black
    //Set JButton and JLabel
    setLayout (new FlowLayout( ));
    directions = new JLabel("Enter in any number between 1 and 20 and then press Enter on your keyboard.");
    go = new JButton( "Go!" );
    go.setBackground( Color.GREEN );
    go.setFocusPainted( false );
    go.addActionListener( this );
    add (directions );
    add (input); 
    add( go );
}

 public void actionPerformed( ActionEvent ae )
{
    String text = input.getText();
    userinput = Integer.parseInt( text );
    repaint();
}

//Method declaration 
public void paint(Graphics g) 
{
    super.paint(g);
    int startX = 50;
    int startY = 650;
    int width = 50;
    int height = 20;
    int spacing = 2;
    int xOffset = 0;
    for (int row = 0; row < userinput; row++) {
        int y = startY + (row * ( height + spacing));
        if ( row % 2 == 0) {
            xOffset = width / 2;
        } else {
            xOffset = 0;
        }
        for (int col = 0; col < 8; col++) {
            int x = xOffset + (startX + (col * (width + spacing)));
            System.out.println(x + "x" + y);
            g.setColor( Color.RED );
            g.fillRect( x, y, width, height);
        }
}
}
}

Answer 1

基本上，您的代码可以工作，但是您的 starty 太大了，似乎在屏幕上作画。

通常，您应该避免覆盖 paint 顶级容器，例如 JApplet（为什么要使用小程序？！），而是使用 JPanel 等组件。

这有几个原因，但你会运行的一个原因是 paint 可以在子组件上绘制，但是，由于绘制的工作方式，那些子组件，当已更新，可以在您已绘制的内容上绘制...总的来说，这对用户来说很奇怪。

相反，将您的代码分成逻辑单元，每个单元应该负责一个（逻辑）单元工作

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Wall extends JApplet implements ActionListener {

//Component declaration
    JLabel directions;
    JTextField input = new JTextField(10);
    private JButton go;

    private WallPanel wallPanel;

//Method declaration
    public void init() {
        getContentPane().setBackground(new Color(128, 128, 128));//Changes backround of JApplet to black
        //Set JButton and JLabel
        setLayout(new BorderLayout());

        JPanel controls = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        directions = new JLabel("Enter in any number between 1 and 20 and then press Enter on your keyboard.");
        go = new JButton("Go!");
        go.setBackground(Color.GREEN);
        go.setFocusPainted(false);
        go.addActionListener(this);
        controls.add(directions, gbc);
        controls.add(input, gbc);
        controls.add(go, gbc);

        wallPanel = new WallPanel();

        add(controls, BorderLayout.NORTH);
        add(wallPanel);
    }

    public void actionPerformed(ActionEvent ae) {
        String text = input.getText();
        wallPanel.setRowCount(Integer.parseInt(text));
        repaint();
    }

    public class WallPanel extends JPanel {

        private int rowCount;

        public void setRowCount(int rowCount) {
            this.rowCount = rowCount;
            repaint();
        }

        public int getRowCount() {
            return rowCount;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g); 
            int startX = 50;
            int startY = 0;
            int width = 50;
            int height = 20;
            int spacing = 2;
            int xOffset = 0;
            for (int row = 0; row < getRowCount(); row++) {
                int y = startY + (row * (height + spacing));
                if (row % 2 == 0) {
                    xOffset = width / 2;
                } else {
                    xOffset = 0;
                }
                for (int col = 0; col < 8; col++) {
                    int x = xOffset + (startX + (col * (width + spacing)));
                    g.setColor(Color.RED);
                    g.fillRect(x, y, width, height);
                }
            }
        }

    }
}

所以，基本上，我在这里所做的就是将 "wall painting" 移动到它自己的 component/class 并提供一个简单的 setter（和 getter）用于更改行数

如何根据用户输入在 paint 方法中绘制墙

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