我的 JTextArea 不显示，也没有显示任何错误或问题。它是一个 Java GUI 计算器。
主类代码:
import javax.swing.JFrame;
public class calulator_main{
public static void main(String[] args) {
// TODO Auto-generated method stub
calulator_ui frame = new calulator_ui();
frame.frame.setVisible(true);
}
}
计算器代码:
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class calulator_ui extends calulator_main {
JFrame frame = new JFrame("cal");
JPanel panel = new JPanel(new FlowLayout());
JPanel screen = new JPanel(new BorderLayout());
JTextArea text = new JTextArea(1,20);
JButton button1 = new JButton("1");
JButton button2 = new JButton("2");
JButton button3 = new JButton("3");
JButton button4 = new JButton("4");
JButton button5 = new JButton("5");
JButton button6 = new JButton("6");
JButton button7 = new JButton("7");
JButton button8 = new JButton("8");
JButton button9 = new JButton("9");
JButton button0 = new JButton("0");
JButton add = new JButton("+");
JButton subtract = new JButton("-");
JButton mutliple = new JButton("*");
JButton divide = new JButton("/");
JButton equals = new JButton("=");
JButton clear = new JButton("C");
JLabel label = new JLabel();
double numberone,numbertwo,result;
int addc=0, subc=0,mutlic=0,divc=0;
public calulator_ui() {
ui();
placeComponets();
createListeners();
}
public void placeComponets(){
screen.add(text, BorderLayout.NORTH);
panel.add(button0);
panel.add(button1);
panel.add(button2);
panel.add(button3);
panel.add(button4);
panel.add(button5);
panel.add(button6);
panel.add(button7);
panel.add(button8);
panel.add(button9);
panel.add(add);
panel.add(mutliple);
panel.add(subtract);
panel.add(divide);
panel.add(clear);
panel.add(equals);
panel.add(label);
}
public void ui(){
frame.setVisible(true);
frame.setSize(250,200);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(panel);
}
public void createListeners(){
this.button0.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button1.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button2.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button3.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button4.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button5.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button6.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button7.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button8.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.button9.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.add.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.subtract.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.mutliple.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.divide.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
this.equals.addActionListener(
new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
onCutClicked(ae);
}
});
}
void onCutClicked(ActionEvent ae){
Object source = ae.getSource();
if(source==button0)
{
text.append("0");
}
if(source==button1)
{
text.append("1");
}
if(source==button2)
{
text.append("2");
}
if(source==button3)
{
text.append("3");
}
if(source==button4)
{
text.append("4");
}
if(source==button5)
{
text.append("5");
}
if(source==button6)
{
text.append("6");
}
if(source==button7)
{
text.append("7");
}
if(source==button8)
{
text.append("8");
}
if(source==button9)
{
text.append("9");
}
if (source==add)
{
numberone=number_reader();
text.setText("");
addc=1;
subc=0;
mutlic=0;
divc=0;
}
if (source==subtract)
{
numberone=number_reader();
text.setText("");
addc=0;
subc=1;
mutlic=0;
divc=0;
}
if (source==mutliple)
{
numberone=number_reader();
text.setText("");
addc=0;
subc=0;
mutlic=1;
divc=0;
}
if (source==divide)
{
numberone=number_reader();
text.setText("");
addc=0;
subc=0;
mutlic=0;
divc=1;
}
if (source==equals)
{
numbertwo=number_reader();
if (addc>0)
{
result=numberone+numbertwo;
text.setText(Double.toString(result));
}
if (subc>0)
{
result=numberone-numbertwo;
text.setText(Double.toString(result));
}
if (divc>0)
{
result=numberone/numbertwo;
text.setText(Double.toString(result));
}
if (mutlic>0)
{
result=numberone*numbertwo;
text.setText(Double.toString(result));
}
}
}
public double number_reader()
{
double returnnumber;
String numberstring;
numberstring=text.getText();
returnnumber=Double.valueOf(numberstring);
return returnnumber;
}
}
对代码的改进有什么建议吗？
最佳答案
您正在将 JTextArea、文本添加到屏幕 JPanel，
screen.add(text, BorderLayout.NORTH);
但是您没有添加屏幕，因此 JTextArea 不会显示是完全有道理的。您应该将 JTextArea 添加到容器中，该容器以某种方式直接或间接添加到 JFrame 中，否则它不会显示。这里没有魔法——GUI 只会显示您添加到其中的内容。
请注意，既然您的 JTextArea 被写入单行，为什么不直接使用 JTextField 呢？但无论如何，该组件的容器层次结构必须到达顶层窗口。
顺便说一句，阅读并了解数组和 ArrayList，因为您可以使用它和 for 循环来大大缩短您的程序，使其更易于阅读、理解和调试。
请查看this example中的代码看看我的意思。它将产生这个 GUI:
关于Java 图形用户界面计算器，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28972519/