Java 每个循环中的数组错误
我正在为一个带有swing UI的基本刽子手游戏编写代码。我使用for循环启动字母的所有按钮。然而,我在第39行得到一个空指针异常。我已经看过了,不知道为什么它不能正常工作。下面10行左右的代码是引发问题的代码Java 每个循环中的数组错误,java,arrays,swing,jbutton,Java,Arrays,Swing,Jbutton,我正在为一个带有swing UI的基本刽子手游戏编写代码。我使用for循环启动字母的所有按钮。然而,我在第39行得到一个空指针异常。我已经看过了,不知道为什么它不能正常工作。下面10行左右的代码是引发问题的代码 import java.awt.Color; import javax.swing.*; public class GameUI { public static void main(String[] args){ GameUI ui =
import java.awt.Color;
import javax.swing.*;
public class GameUI {
public static void main(String[] args){
GameUI ui = new GameUI();
ui.initializeUI();
}
public void initializeUI(){
//initialize the window
JFrame window = new JFrame();
window.setSize(500,500);
window.setResizable(false);
window.setVisible(true);
//initialize main panel
JPanel wrapper = new JPanel();
wrapper.setLayout(null);
Color BGColor = new Color(240,230,140);
wrapper.setBackground(BGColor);
window.getContentPane().add(wrapper);
//Creates JLAbel title, this is used for the title of the game
JLabel title = new JLabel("Hangman v0.1");
title.setBounds(10, 5, 200, 50);
wrapper.add(title);
//=================================================================
//Creates JButtons for each letter (ERROR OCCURS BELLOW ON FIRST LINE AFTER LOOP BEIGNS)
//=================================================================
char[] alphabet = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
JButton[] letterButtons = new JButton[26];
int counter = 0;
for (char letter:alphabet){
letterButtons[counter].setText("" + letter);
//sets positions for each button
int posY = 50;
int posX = counter*5 + 10;
letterButtons[counter].setBounds(posX, posY, 10, 10);
wrapper.add(letterButtons[counter]);
counter++;
}
}
}
Java中的对象默认为空。对象数组中的对象也不例外。您需要先初始化JButton数组letterbutton,然后再尝试对其调用任何操作
for (int i=0; i < letterButtons.length; i++) {
letterButtons[i] = new JButton();
}
JButton[]letterbutton=新JButton[26];将每个数组元素初始化为null。您必须在数组中循环,并为每个位置分配一个新的JButton谢谢您的帮助!我很感激!