我正在开发一个项目，其中解析程序从输入文件中读取数据，对其进行标记，然后从中构建GUI。在这种情况下，它是一个计算器GUI。我正在尝试编写计算器操作的代码，而我在将ActionListeners添加到计算器的按钮时遇到了麻烦。它们存储在ArrayList中，当我尝试使用addActionListener（）函数时，我收到以下错误：
以下是构建器文件的代码：
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class GUIBuilder implements ActionListener {
//Declare variables
boolean[] function = new boolean[4];
double[] temp = {0, 0};
static JFrame outputFrame; //Declare GUI window frame
static JPanel panel1, panel2, panel3, panel4; //Declare GUI panel variables
static Container container; //Declare GUI container variable
static JTextField textField; //Declare GUI text field variable
static ArrayList<JButton> button;
static ArrayList<JLabel> label;
static ArrayList<JRadioButton> radio;
static GUIParser guiParser; //Create instance of GUIParser
public static void main(String[] args) throws Exception {
//Instantiates a GUIParser object
guiParser = new GUIParser();
//Instantiates ArrayList objects
button = new ArrayList<>();
label = new ArrayList<>();
radio = new ArrayList<>();
//Instantiates a GUIBuilder object that invokes frameConstructor() method
GUIBuilder guiBuilder = new GUIBuilder();
guiBuilder.frameConstructor();
}
public void frameConstructor() {
//Instantiates a JFrame object
outputFrame = new JFrame();
//Sets window size
outputFrame.setSize(this.guiParser.getWindowWidth(),this.guiParser.getWindowHeight()); //Sets size of outputFrame to the return value of getWindowWidth method
//Sets window name
outputFrame.setTitle(this.guiParser.getWindowName()); //Sets title of window to return value of getWindowName method
outputFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Sets the default close operation to exit
container = outputFrame.getContentPane();
if (this.guiParser.getWindowLayout() == 0) { //If return value of getWindowLayout is 0, use flow layout
container.setLayout(new FlowLayout());
} else { //If return value is other than 0, use grid layout
if (this.guiParser.getHorizontalSpace() != 0 && this.guiParser.getVerticalSpace() != 0) { //If return values of getHorizontalSpace and getVerticalSpace are zero, create Grid layout with these dimensions
container.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns(),
this.guiParser.getHorizontalSpace(),this.guiParser.getVerticalSpace()));
} else { //Otherwise create a Grid layout with these dimensions
container.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns()));
}
}
//Instantiates new JPanel objects
panel1 = new JPanel();
panel2 = new JPanel();
panel3 = new JPanel();
panel4 = new JPanel();
if (this.guiParser.getPanelLayout() == 0) { //If return value of getPanelLayout is zero, use flow layout
panel1.setLayout(new FlowLayout());
panel2.setLayout(new FlowLayout());
panel3.setLayout(new FlowLayout());
} else { //Otherwise use grid layout, set dimensions according to input values
if (this.guiParser.getHorizontalSpace() != 0 && this.guiParser.getVerticalSpace() != 0) {
panel1.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns(),
this.guiParser.getHorizontalSpace(),this.guiParser.getVerticalSpace()));
panel2.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns(),
this.guiParser.getHorizontalSpace(),this.guiParser.getVerticalSpace()));
panel3.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns(),
this.guiParser.getHorizontalSpace(),this.guiParser.getVerticalSpace()));
panel4.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns(),
this.guiParser.getHorizontalSpace(),this.guiParser.getVerticalSpace()));
} else {
panel1.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns()));
panel2.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns()));
panel3.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns()));
panel4.setLayout(new GridLayout
(this.guiParser.getNumRows(),this.guiParser.getNumColumns()));
}
}
//Instantiates a JTextField object and sets text field width with the return value of getTextWidth()
textField = new JTextField("", this.guiParser.getTextWidth());
container.add(textField); //Add the text field to the Jframe container
panel1.add(textField); //Add the text field to panel 1
//Walk through the buttonList array and add buttons to the container and panel 2
int i = 0;
Iterator<String> iterator = this.guiParser.getButtonList().iterator();
while (iterator.hasNext()) {
button.add(new JButton(iterator.next()));
container.add(button.get(i));
panel2.add(button.get(i));
button.addActionListener(this);
i++;
}
//Walk through the radioList array and add radio buttons to the container and panel 3
i = 0;
iterator = this.guiParser.getRadioList().iterator();
while (iterator.hasNext()) {
radio.add(new JRadioButton(iterator.next()));
container.add(radio.get(i));
panel3.add(radio.get(i));
i++;
}
//Walk through the labelList array and add labels to the container and panel 4
i = 0;
iterator = this.guiParser.getLabelList().iterator();
while (iterator.hasNext()) {
label.add(new JLabel(iterator.next()));
container.add(label.get(i));
panel4.add(label.get(i));
i++;
}
//Add each panel to the output frame and set its visibility
outputFrame.add(panel1);
outputFrame.add(panel2);
outputFrame.add(panel3);
outputFrame.setVisible(true);
for(i = 0; i < 16; i++){
}
}
public void clear(){
try{
textField.setText("");
for(int i = 0; i < 4; i++){
function[i] = false;
}
for(int i = 0; i < 2; i++){
temp[i] = 0;
}
} catch(NullPointerException e){
}
}
public void calcResult(){
double result = 0;
temp[1] = Double.parseDouble(textField.getText());
String temp0 = Double.toString(temp[0]);
String temp1 = Double.toString(temp[1]);
try{
if(temp0.contains("-")){
String[] temp00 = temp0.split("-", 2);
temp[0] = (Double.parseDouble(temp00[1]) * -1);
}
if(temp1.contains("-")){
String[] temp11 = temp1.split("-", 2);
temp[1] = (Double.parseDouble(temp11[1]) * -1);
}
} catch(ArrayIndexOutOfBoundsException e){
}
try{
if(function[2] == true){
result = temp[0] * temp[1];
} else if(function[3] == true){
result = temp[0] / temp[1];
} else if(function[0] == true){
result = temp[0] + temp[1];
} else if(function[1] == true){
result = temp[0] - temp[1];
}
textField.setText(Double.toString(result));
for(int i = 0; i < 4; i++){
function[i] = false;
}
} catch(NumberFormatException e){
}
}
@Override
public void actionPerformed( ActionEvent ae) {
if(ae.getSource() == button.get(0)){
textField.setText("1");
}
if(ae.getSource() == button.get(1)){
textField.setText(textField.getText().concat("2"));
}
if(ae.getSource() == button.get(2)){
textField.setText(textField.getText().concat("3"));
}
if(ae.getSource() == button.get(3)){
textField.setText(textField.getText().concat("4"));
}
if(ae.getSource() == button.get(4)){
textField.setText(textField.getText().concat(""));
}
if(ae.getSource() == button.get(5)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(6)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(7)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(8)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(9)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(10)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(11)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(12)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(13)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(14)){
textField.setText(textField.getText().concat("1"));
}
if(ae.getSource() == button.get(15)){
textField.setText(textField.getText().concat("1"));
}
}
}
答案 0 :(得分：4)
您的button.addActionListener(this);应为button.get(i).addActionListener(this);。
话虽这么说，你应该保留对每次迭代中创建的按钮的引用，而不是每次随后在该循环中修改它时从ArrayList中检索它：
while (iterator.hasNext()) {
JButton newButton = new JButton(iterator.next());
button.add(newButton);
container.add(newButton);
panel2.add(newButton);
newButton.addActionListener(this);
}
答案 1 :(得分：3)
你的按钮变量是一个ArrayList，所以这个：
button.addActionListener(this);
毫无意义，因为将ActionListener添加到ArrayList没有意义。您希望将ActionListener添加到由
button.get(i).addActionListener(this);
其他问题：
catch(NullPointerException e){。如果您的代码抛出了NPE，那么它的代码就会被破坏，需要修复。