编辑：好的，这是我的完整代码，因为你们要求它：
import javax.swing.*;
import java.awt.*;
public class Panel extends JPanel {
private JTextField username_field;
private JTextField skype_field;
private JTextField raidcall_field;
private JTextField teamspeak_field;
private JComboBox server_combobox;
private JComboBox levels_combobox;
private JComboBox mytier_combobox;
private JComboBox mydiv_combobox;
private JComboBox partner_tier_combobox;
private JComboBox partner_div_combobox;
private JComboBox myrole_combobox;
private JComboBox partner_role_combobox;
private JRadioButton normal,ranked;
private String region;
private String tier;
private String division;
private String skype;
private String raidcall;
private String teamspeak;
private String partner_role;
private int mode;
public Panel(AppUI.Panels panel){
String star = "<span style='color:#ff0000;'>*</span>";
switch (panel) {
case NORTHPANEL :
setBackground(Color.getHSBColor(20,20,20));
JLabel title = new JLabel();
title.setText("<html>fields marked with " + star + " are required to be filled.</html>");
title.setFont(new Font("Tahoma", Font.BOLD, 10));
add(title);
break;
case CENTERPANEL :
setLayout(new GridBagLayout());
setBackground(Color.LIGHT_GRAY);
username_field = new JTextField(10);
username_field.setToolTipText("Enter your Summoner name here");
String[] servers = { "NA", "EUW", "EUNE", "TR", "BR", "LAN", "LAS", "RU", "OCE" };
server_combobox = new JComboBox<String>(servers);
server_combobox.setToolTipText("Select the region your account is in");
String[] levels = {"1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16"
,"17","18","19","20","21","22","23","24","25","26","27","28","29","30"};
levels_combobox = new JComboBox<String>(levels);
levels_combobox.setToolTipText("Select the level your summoner is");
addItem(this, new JLabel("<html>Summoner name :" + star + "</html>") , 0, 0, 1, 1);
addItem(this, username_field ,1,0,1,1);
addItem(this, new JLabel("<html>Summoner level :" + star + "</html>"), 0,1,1,1);
addItem(this, levels_combobox, 1,1,1,1);
addItem(this, new JLabel("<html>Server :" + star + " </html>"), 0,2,1,1);
addItem(this, server_combobox, 1, 2, 1, 1);
break;
case SOUTHPANEL :
JLabel require = new JLabel();
JLabel require1 = new JLabel();
JLabel require2 = new JLabel();
setLayout(new GridBagLayout());
setBackground(Color.getHSBColor(20,20,20));
ButtonGroup bg = new ButtonGroup();
normal = new JRadioButton("Normal game");
ranked = new JRadioButton("Solo/Duo Ranked game");
bg.add(normal);
bg.add(ranked);
Box queue = Box.createHorizontalBox();
queue.add(new JLabel("<html>I want to play a :" + star + "</html>"));
queue.add(Box.createHorizontalStrut(5));
queue.add(normal);
queue.add(ranked);
String[] tiers = {"Bronze", "Silver" , "Gold", "Platinum", "Diamond"};
String[] divs = {"I", "II", "III", "IV", "V"};
mytier_combobox = new JComboBox<>(tiers);
mydiv_combobox = new JComboBox<>(divs);
Box myRank = Box.createHorizontalBox();
myRank.add(new JLabel("<html>My Solo Queue rank is : "));
myRank.add(require);
myRank.add(Box.createHorizontalStrut(15));
myRank.add(mytier_combobox);
myRank.add(Box.createHorizontalStrut(15));
myRank.add(mydiv_combobox);
String[] myroles = {"Jungler", "Top laner", "Mid laner", "ADC", "Support"};
String[] partner_roles = {"Jungler", "Top laner", "Mid laner", "ADC", "Support"};
myrole_combobox = new JComboBox<>(myroles);
partner_role_combobox = new JComboBox<>(partner_roles);
Box roles = Box.createHorizontalBox();
roles.add(new JLabel("I am a "));
roles.add(Box.createHorizontalStrut(5));
roles.add(myrole_combobox);
roles.add(Box.createHorizontalStrut(5));
roles.add(new JLabel("<html>" + star + " Looking for a </html>"));
roles.add(Box.createHorizontalStrut(5));
roles.add(partner_role_combobox);
roles.add(require1);
partner_tier_combobox = new JComboBox<>(tiers);
partner_div_combobox = new JComboBox<>(divs);
Box partner_min_rank = Box.createHorizontalBox();
partner_min_rank.add(new JLabel("Looking for a partner with a minimum rank of "));
partner_min_rank.add(require2);
partner_min_rank.add(Box.createHorizontalStrut(5));
partner_min_rank.add(partner_tier_combobox);
partner_min_rank.add(Box.createHorizontalStrut(5));
partner_min_rank.add(partner_div_combobox);
JButton button = new JButton("Results");
button.addActionListener(e -> {
System.out.println("[TEST] Your summoner level is : " + getLevel());
});
addItem(this, queue, 0, 0, 1, 1);
addItem(this, myRank , 0, 1, 1, 1);
addItem(this, roles, 0, 2, 1, 1);
addItem(this, partner_min_rank, 0, 3, 1, 1);
addItem(this, button, 0, 4, 1,1);
ranked.addActionListener(e -> {
if (ranked.isSelected()){
require.setText("<html>"+ star + "</html>");
require1.setText("<html>" + star + "</html>");
require2.setText("<html>"+ star + "</html>");
}
});
normal.addActionListener(e -> {
if (normal.isSelected()){
require.setText("");
require1.setText("");
require2.setText("");
}
});
break;
case EASTPANEL :
setLayout(new GridBagLayout());
skype_field = new JTextField(5);
raidcall_field = new JTextField(5);
teamspeak_field = new JTextField(5);
Box skype= Box.createHorizontalBox();
skype.add(new JLabel(" Username :"));
skype.add(Box.createHorizontalStrut(5));
skype.add(skype_field);
skype.setBorder(BorderFactory.createTitledBorder("Skype"));
Box raidcall = Box.createHorizontalBox();
raidcall.add(new JLabel("Username :"));
raidcall.add(Box.createHorizontalStrut(5));
raidcall.add(raidcall_field);
raidcall.setBorder(BorderFactory.createTitledBorder("Raidcall"));
Box teamspeak = Box.createHorizontalBox();
teamspeak.add(new JLabel("Username :"));
teamspeak.add(Box.createHorizontalStrut(5));
teamspeak.add(teamspeak_field);
teamspeak.setBorder(BorderFactory.createTitledBorder("Teamspeak"));
addItem(this, skype, 0, 0, 1, 1);
addItem(this, raidcall, 0, 1, 1, 1);
addItem(this, teamspeak, 0, 2, 1, 1);
break;
default :
System.out.println("Panel not found!");
}
}
public String getSummonerName(){
return username_field.getText();
}
public int getLevel(){
return this.levels_combobox.getSelectedIndex() + 1;
}
public String getTier() {
switch (mytier_combobox.getSelectedIndex()) {
case 0 :
tier = "Bronze";
break;
case 1 :
tier = "Silver";
break;
case 2 :
tier = "Gold";
break;
case 3 :
tier = "Platinum";
break;
case 4 :
tier = "Diamond";
break;
default :
System.out.println("Tier not found!");
}
return tier;
}
public String getDivision(){
switch (mydiv_combobox.getSelectedIndex()){
case 0 :
division = "I";
break;
case 1 :
division = "II";
break;
case 2 :
division = "III";
break;
case 3 :
division = "IV";
break;
case 4 :
division = "V";
break;
default :
System.out.println("Division not found!");
}
return division;
}
public String getRegion(){
switch (server_combobox.getSelectedIndex()) {
case 0 :
region = "North America";
break;
case 1 :
region = "Europe West";
break;
case 2 :
region = "Europe Nordic & East";
break;
case 3 :
region = "Turkey";
break;
case 4 :
region = "Brazil";
break;
case 5 :
region = "Latin America North";
break;
case 6 :
region = "Latin America South";
break;
case 7 :
region = "Russia";
break;
case 8 :
region = "Oceania";
break;
default :
System.out.println("Region not found!");
}
return region;
}
public int getGameMode(){
if (normal.isSelected()){
mode = 0;
} else {
mode = 1;
}
return mode;
}
public String getSkype() {
if (skype_field.getText().isEmpty())
skype = "Not specified";
else
skype = skype_field.getText();
return skype;
}
public String getRaidcall(){
if (raidcall_field.getText().isEmpty())
raidcall = "Not specified";
else
raidcall = raidcall_field.getText();
return raidcall;
}
public String getTeamspeak(){
if (teamspeak_field.getText().isEmpty())
teamspeak = "Not specified";
else
teamspeak = teamspeak_field.getText();
return teamspeak;
}
public String getMyRole(){
String myrole = "";
switch (myrole_combobox.getSelectedIndex()){
case 0 :
myrole = "Jungler";
break;
case 1 :
myrole = "Top laner";
break;
case 2 :
myrole = "Mid laner";
break;
case 3 :
myrole = "ADC";
break;
case 4 :
myrole = "Support";
break;
default :
System.out.println("Role not found!");
}
return myrole;
}
public String getPartnerRole(){
switch (partner_role_combobox.getSelectedIndex()){
case 0 :
partner_role = "Jungler";
break;
case 1 :
partner_role = "Top laner";
break;
case 2 :
partner_role = "Mid laner";
break;
case 3 :
partner_role = "ADC";
break;
case 4 :
partner_role = "Support";
break;
default :
System.out.println("Role not found!");
}
return partner_role;
}
public String getPartnerMinTier(){
String tier = "";
switch(partner_tier_combobox.getSelectedIndex()){
case 0 :
tier = "Bronze";
break;
case 1 :
tier = "Silver";
break;
case 2 :
tier = "Gold";
break;
case 3 :
tier = "Platinum";
break;
case 4 :
tier = "Diamond";
break;
default :
System.out.println("Tier not found!");
}
return tier;
}
public String getPartnerMinDiv(){
String div = "";
switch (partner_div_combobox.getSelectedIndex()){
case 0 :
div = "I";
break;
case 1 :
div = "II";
break;
case 2 :
div = "III";
break;
case 3 :
div = "IV";
break;
case 4 :
div = "V";
break;
default :
System.out.println("Division not found!");
}
return div;
}
public void addItem(JPanel p, JComponent c, int x, int y, int width, int height){
GridBagConstraints gc = new GridBagConstraints();
gc.gridx = x;
gc.gridy = y;
gc.gridwidth = width;
gc.gridheight = height;
gc.insets = new Insets(5,5,5,5);
gc.fill = GridBagConstraints.NONE;
p.add(c, gc);
}
}
嗯，我有这个吸气剂：
public int getLevel(){
return levels_combobox.getSelectedIndex() + 1;
}
这是我的变量levels_combobox：
private JComboBox levels_combobox;
是的，它在方法中实例化：
String[] levels = {"1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16"
,"17","18","19","20","21","22","23","24","25","26","27","28","29","30"};
levels_combobox = new JComboBox<String>(levels);
当我尝试用这个测试输出时，为什么会出现NullPointerException：
System.out.println("[TEST] Your summoner level is : " + getLevel());
答案 0 :(得分：2)
你正在switch语句的case块中初始化JComboBox，不能保证在调用有问题的方法之前调用它。
解决方案：您的代码设计很糟糕，因此您必须修复它。初始化构造函数中的所有关键组件，而不依赖于switch / case块。
我不确定你为什么在构造函数中有这样的switch语句，因为它看起来很奇怪和危险，我建议你考虑重新设计你的构造函数，这样就不需要了。也许你真的想要创建某种工厂。
修改
您的Panel代码试图做太多而且不遵守Single responsibility principle，
每个班级都应该承担一项责任，并且该责任应该由班级完全封装。它的所有服务都应该与这一责任保持一致。
顺便说一句，我会重新命名Panel类，以便该名称不会与同名的核心Java类java.awt.Panel类冲突。如果你解决这个问题，将不再需要你的switch / case语句，你的错误可能会消失。
作为第二个，我敢打赌你正在使用看起来像这样的枚举：
class AppUI {
enum Panels {
NORTHPANEL, CENTERPANEL, SOUTHPANEL, EASTPANEL
}
}
答案 1 :(得分：0)
除非您通过了CENTERPANEL，否则您不会指定levels_combobox。你应该在构造函数的开头给它一些默认值。