所以我的问题是当我创建的状态被调用时，我得到NullPointerException。
事情是，它不是nul l，至少我是这么认为的。有人能告诉我NPE的来源吗？
PS：这是草率的代码，因为我没有清理它。
粗体线出现错误。
public class NewPlayerState extends BasicGameState {
private int stateID;
private boolean mouseDown;
private int mouseX;
private int mouseY;
private Random rand;
private String allTheStats;
private Image classPreview;
private Image genderSelector;
private Player player;
private Write write;
private String className = "paladin";
private String name = "JamacanGuy";
private int hitPoints = 0;
private int str = 0;
private int dex = 0;
private int sta = 0;
private int intel = 0;
private int cha = 0;
private boolean male = true;
private int hpMod = 0;
private int strMod = 0;
private int dexMod = 0;
private int staMod = 0;
private int intelMod = 0;
private int chaMod = 0;
private Input input;
public NewPlayerState(int stateID) {
this.stateID = stateID;
}
/*
*
* Initiation method, brings up relevant variables and get this Initializes them!
*
*/
@Override
public void init(GameContainer gc, StateBasedGame sbg)
throws SlickException {
// Ready the PARSER!!!!
rand = new Random();
write = new Write();
// init classPreview as paladin
classPreview = new Image("gfx/player/previews/paladin_male.png");
// init gender icons
genderSelector = new Image("gfx/extra/new_player/gender_selector.png");
allTheStats = "Hitpoints: " + hitPoints + " + HP Modifier: " + hpMod + " = " + (hitPoints + hpMod) + "\n" +
"Strength: " + str + " + STR Modifier: " + strMod + " = " + (str + strMod) + "\n" +
"Dexterity: " + dex + " + DEX Modifier: " + dexMod + " = " + (dex + dexMod) + "\n" +
"Stamina: " + sta + " + STA Modifier: " + staMod + " = " + (sta + staMod) + "\n" +
"Inteligence: " + intel + " + INT Modifier: " + intelMod + " = " + (intel + intelMod) + "\n" +
"Charisma: " + cha + " + CHA Modifier: " + chaMod + " = " + (cha + chaMod) + "\n"
;
}
@Override
public void render(GameContainer gc, StateBasedGame sbg, Graphics g)
throws SlickException {
renderAll(g, sbg);
}
@Override
public void update(GameContainer gc, StateBasedGame sbg, int delta)
throws SlickException {
input = gc.getInput();
mouseDown = input.isMouseButtonDown(0);
mouseX = input.getMouseX();
mouseY = input.getMouseY();
checkGender();
updatePreview();
updateStatModifier();
updateStatDisplay();
}
private void renderAll(Graphics g , StateBasedGame sbg) throws SlickException {
// draw background
g.setColor(Color.white);
g.fillRect(875, 455, 305, 405);
// draw background
// draw class preview
**classPreview.draw(880, 460, 300, 400);** // Error is here
// draw class preview
// Select your class
// Paladin
if (mouseOver(875, 410, 80, 40)) {
g.setColor(Color.darkGray);
if (mouseDown) {
className = "paladin";
}
} else {
g.setColor(Color.blue);
}
g.fillRoundRect(875, 410, 80, 40, 5);
g.setColor(Color.white);
g.drawString("Paladin", 885, 420);
// Paladin
// Select your class
// Select Gender
genderSelector.draw(875, 300, 220, 100);
// Select Gender
// Roll for your stats
// Roll button
if(!mouseOver(100, 200, 100, 50)){
g.setColor(Color.white);
}else if(mouseOver(100, 200, 100, 50)){
g.setColor(Color.darkGray);
if(mouseDown){
rollForStats();
}
}
g.fillRoundRect(100, 200, 100, 50, 10);
g.setColor(Color.black);
g.drawString("Roll", 130, 215);
// Roll button
// Display stats
//Ugghhghghghghhghghghghgh!!!!!!
g.setColor(Color.white);
g.drawString(allTheStats, 80, 26);
// Display stats
// Roll for your stats
// exit and write to file, then open new level
if(!mouseOver(100, 600, 100, 50)){
g.setColor(Color.white);
}else if(mouseOver(100, 600, 100, 50)){
g.setColor(Color.darkGray);
if(mouseDown){
closeUp(sbg);
}
}
g.fillRoundRect(100, 600, 100, 50, 10);
g.setColor(Color.black);
g.drawString("Play!", 130, 615);
// exit and write to file, then open new level
}
private void closeUp(StateBasedGame sbg) throws SlickException {
//set all that data
player = new Player();
player.setClassName(className);
player.setName(name);
player.setHealth(hitPoints);
player.setStr(str);
player.setDex(dex);
player.setSta(sta);
player.setCha(cha);
player.setIntel(intel);
player.setStaMod(staMod);
player.setChaMod(chaMod);
player.setDexMod(dexMod);
player.setStrMod(strMod);
player.setIntelMod(intelMod);
player.setGender(male);
//save to xml
XStream xstream = new XStream(new StaxDriver());
String xml = xstream.toXML(player);
write.writeToFile(xml, "save");
// begin game
//Main.ps.setFirstLoad(true);
sbg.enterState(Main.PLAYSTATE, new FadeOutTransition(), new FadeInTransition());
// prevent multiple clicks
mouseDown = false;
}
private void rollForStats(){
hitPoints = rand.nextInt(20) + 1;
str = rand.nextInt(20) + 1;
dex = rand.nextInt(20) + 1;
sta = rand.nextInt(20) + 1;
intel = rand.nextInt(20) + 1;
cha = rand.nextInt(20) + 1;
}
private boolean mouseOver(int x, int y, int width, int height) {
if (mouseX > x && mouseX < x + width && mouseY > y
&& mouseY < y + height) {
return true;
} else {
return false;
}
}
private void updateStatDisplay() {
allTheStats = "Hitpoints: " + hitPoints + " + HP Modifier: " + hpMod + " = " + (hitPoints + hpMod) + "\n" +
"Strength: " + str + " + STR Modifier: " + strMod + " = " + (str + strMod) + "\n" +
"Dexterity: " + dex + " + DEX Modifier: " + dexMod + " = " + (dex + dexMod) + "\n" +
"Stamina: " + sta + " + STA Modifier: " + staMod + " = " + (sta + staMod) + "\n" +
"Inteligence: " + intel + " + INT Modifier: " + intelMod + " = " + (intel + intelMod) + "\n" +
"Charisma: " + cha + " + CHA Modifier: " + chaMod + " = " + (cha + chaMod) + "\n"
;
}
private void updatePreview() throws SlickException {
switch(className){
case "paladin":
if(male){
classPreview = new Image("gfx/player/previews/paladin_male.png");
}else {
classPreview = new Image("gfx/player/previews/paladin_female.png");
}
break;
default:
classPreview = new Image("gfx/player/previews/paladin_male.png");
break;
}
}
private void checkGender() throws SlickException {
if (!mouseOver(875, 300, 220, 100)) {
genderSelector = new Image(
"gfx/extra/new_player/gender_selector.png");
} else if (mouseOver(875, 300, 220, 100)) {
if (mouseX > 985) {
genderSelector = new Image(
"gfx/extra/new_player/male_selected.png");
if (mouseDown) {
male = true;
}
} else {
genderSelector = new Image(
"gfx/extra/new_player/female_selected.png");
if (mouseDown) {
male = false;
}
}
}
}
public void updateStatModifier() {
switch (className) {
case "paladin":
if(male){
hpMod = 6;
strMod = 6;
dexMod = 2;
staMod = 4;
intelMod = 5;
chaMod = 3;
}else{
hpMod = 6;
strMod = 3;
dexMod = 2;
staMod = 4;
intelMod = 5;
chaMod = 5;
}
break;
}
}
@Override
public int getID() {
return stateID;
}
}
答案 0 :(得分：0)
而不是这个
classPreview.draw(880, 460, 300, 400);
你可以尝试
g.drawImage(classPreview, 800, ...
在这里查看slick2d Graphics类的不同drawImage（）方法： http://slick.cokeandcode.com/javadoc/org/newdawn/slick/Graphics.html