【发布时间】：2018-10-26 18:37:33
【问题描述】：
我正在尝试制作一个JFrame 程序，该程序将 binary-decimal-hexadecimal 转换器与按钮接口。其中的一部分，我想画圆圈来代表一排圆圈中的二进制数，实心圆圈代表一，空心圆圈代表零。但是，当我尝试调用 repaint 来绘制任何东西时，它不会执行 paintComponent() 方法，我知道这是因为它不执行其中的 print 语句。完整代码如下：
package e2;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.FlowLayout;
public class DecBin extends JPanel {
String theText = "IT WORKS";
int style = Font.BOLD; // bold only
Font font = new Font("Arial", style, 40);
DecBin() {
JFrame f = new JFrame("Decimal to binary and binary to decimal converter");
f.setSize(1000, 1000);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setLayout(new FlowLayout());
Font font = new Font("Arial", style, 40);
JLabel textLabel = new JLabel(theText);
textLabel.setFont(font);
JButton b = new JButton("DectoBin");
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String msg = JOptionPane.showInputDialog("input a decimal number");
int num = Integer.parseInt(msg);
theText = num + " is " + decToBin(num) + " in binary";
textLabel.setText(theText);
}
});
f.add(b);
JButton d = new JButton("BintoDec");
d.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String msg = JOptionPane.showInputDialog("input a binary number");
System.out.print("The decimal form of " + msg + " is " + binToDec(msg));
theText = msg + " is " + binToDec(msg) + " in decimal";
textLabel.setText(theText);
}
});
f.add(d);
JButton hd = new JButton("hexToDec");
hd.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String msg = JOptionPane.showInputDialog("input a hexadecimal number");
theText = msg + " is " + hexToDec(msg) + " in decimal";
textLabel.setText(theText);
}
});
f.add(hd);
JButton dh = new JButton("DectoHex");
dh.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String msg = JOptionPane.showInputDialog("input a decimal number");
int num = Integer.parseInt(msg);
theText = num + " is " + decToHex(num) + " in hexadecimal";
textLabel.setText(theText);
}
});
f.add(dh);
JButton bh = new JButton("BinToHex");
bh.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String msg = JOptionPane.showInputDialog("input a binary number");
theText = msg + " is " + decToHex(binToDec(msg)) + " in hexadecimal";
textLabel.setText(theText);
}
});
f.add(bh);
JButton hb = new JButton("HexToBin");
hb.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String msg = JOptionPane.showInputDialog("input a Hexadecimal number");
theText = msg + " is " + decToBin(hexToDec(msg)) + " in hexadecimal";
textLabel.setText(theText);
}
});
f.add(hb);
JButton c = new JButton("Draw");
c.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
System.out.print("test1");
validate();
repaint();
}
});
f.add(c);
f.add(textLabel, BorderLayout.SOUTH);
f.setVisible(true);
}
public static void main(String[] args) {
new DecBin();
}
static String decToBin(int d) {
StringBuilder binary = new StringBuilder("");
while (d != 0) {
binary.insert(0, d % 2);
d = d / 2;
}
return binary.toString();
}
static int binToDec(String b) {
int total = 0;
int x;
for (int i = b.length(); i > 0; i--) {
x = Integer.parseInt(Character.toString(b.charAt(i - 1)));
if (x == 1) {
total += Math.pow(2, b.length() - i);
}
}
return total;
}
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.red);
g2.fillOval(100, 100, 20, 20);
System.out.print("painted components");
}
static String decToHex(int d) {
StringBuilder Hex = new StringBuilder("");
while (d != 0) {
int remainder = d % 16;
if (remainder < 10) {
Hex.insert(0, d % 16);
} else if (remainder == 10) {
Hex.insert(0, 'A');
} else if (remainder == 11) {
Hex.insert(0, 'B');
} else if (remainder == 12) {
Hex.insert(0, 'C');
} else if (remainder == 13) {
Hex.insert(0, 'D');
} else if (remainder == 14) {
Hex.insert(0, 'E');
} else if (remainder == 15) {
Hex.insert(0, 'F');
}
d = d / 16;
}
return Hex.toString();
}
static int hexToDec(String b) {
int total = 0;
int len = b.length();
for (int i = len - 1; i >= 0; i--) {
if (b.charAt(i) == 'A') {
total += 10 * Math.pow(16, len - i - 1);
} else if (b.charAt(i) == 'B') {
total += 11 * Math.pow(16, len - i - 1);
} else if (b.charAt(i) == 'C') {
total += 12 * Math.pow(16, len - i - 1);
} else if (b.charAt(i) == 'D') {
total += 13 * Math.pow(16, len - i - 1);
} else if (b.charAt(i) == 'E') {
total += 14 * Math.pow(16, len - i - 1);
} else if (b.charAt(i) == 'F') {
total += 15 * Math.pow(16, len - i - 1);
} else {
total += Character.getNumericValue(b.charAt(i)) * Math.pow(16, len - i - 1);
}
}
return total;
}
}
我认为相关的代码是：
DecBin() {
JFrame f=new JFrame("Decimal to binary and binary to decimal converter");
f.setSize(1000,1000);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setLayout(new FlowLayout());
JButton c =new JButton("Draw");
c.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
System.out.print("test1");
validate();
repaint();
}
});
f.add(c);
f.setVisible(true);
}
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.red);
g2.fillOval(100, 100, 20, 20);
System.out.print("painted components");
}
public static void main(String[] args) {
new DecBin();
}
我已经花了几个小时研究这个问题，但还没有找到一个可以打印“绘制组件”的解决方案。
【问题讨论】：
-
在
JPanel子类构造函数中初始化JFrame是一种非常不标准的做事方式，并且可能是导致您的问题的一个因素。您应该在 main 方法中初始化JFrame，然后在其中添加您的DecBin。
标签： java swing jframe paintcomponent repaint