我正在使用JME3和Nifty GUI开发游戏。我有一个具有Nifty成员变量的外部类。无论访问修饰符如何，内部类都应该能够访问该变量。在构造函数中，我为它分配了一个新的Nifty对象。但是，当我在内部类中访问该变量时，我遇到了问题。我做了一些调试，发现它是因为内部类认为Nifty成员变量为空，我无法弄清楚原因。它在外层不是空的。由于这是一个JME3游戏，我试图让内部类实现AppState接口，但它仍然将Nifty成员变量显示为null。这是代码：
public class MenuScreen extends SimpleApplication {
/** Used to configure Nifty GUI. */
private Nifty mNifty;
private NiftyJmeDisplay mNiftyDisplay;
private Element popup;
//*******************
// Overridden medhods
//*******************
/** This method is used to initialize everything needed to display the game screen. */
@Override
public void simpleInitApp() {
guiNode.detachAllChildren();
initNifty();
flyCam.setDragToRotate(true);
}
/**
* The game's main update loop.
*
* @param tpf Time Per Fram, the time it takes each loop to run.
*/
@Override
public void simpleUpdate(float tpf) {
// not used
}
@Override
public void simpleRender(RenderManager rm) {
// not used
}
public static void main(String[] args) {
MenuScreen app = new MenuScreen();
app.start();
}
/**
* Helper method to initialize and configure Nifty GUI.
*/
private void initNifty() {
mNiftyDisplay = new NiftyJmeDisplay(assetManager, inputManager, audioRenderer, guiViewPort);
mNifty = mNiftyDisplay.getNifty();
guiViewPort.addProcessor(mNiftyDisplay);
// If this is being run on a desktop then load the desktop main menu.
if (Strings.OS_NAME.contains("windows") || Strings.OS_NAME.contains("mac") || Strings.OS_NAME.contains("linux")) {
mNifty.fromXml("Interface/XML/DesktopMenuScreenGui.xml", "start", new MenuScreen().new MenuScreenGui());
}
// If its an Android device load the mobile main menu.
else if (Strings.OS_NAME.contains("android")) {
mNifty.fromXml("Interface/XML/MobileMenuScreenGui.xml", "mobile", new MenuScreen().new MenuScreenGui());
}
}
//**************
// Inner Classes
//**************
/**
* © Jason Crosby 2012 <p>
*
* This class handles all the GUI interactions like button clicks.
*
* @author Jason Crosby
*/
public class MenuScreenGui implements ScreenController, EventTopicSubscriber<MenuItemActivatedEvent>,
AppState {
@Override
public void initialize(AppStateManager stateManager, Application app) {
}
@Override
public void cleanup() {
}
@Override
public boolean isEnabled() {
return false;
}
@Override
public boolean isInitialized() {
return false;
}
@Override
public void postRender() {
}
@Override
public void setEnabled(boolean active) {
}
@Override
public void stateAttached(AppStateManager stateManager) {
}
@Override
public void stateDetached(AppStateManager stateManager) {
}
@Override
public void render(RenderManager rm) {
}
@Override
public void update(float tpf) {
}
@Override
public void bind(Nifty nifty, Screen screen) {
// not used
}
@Override
public void onEndScreen() {
// not used
}
@Override
public void onStartScreen() {
// not used
}
@Override
public void onEvent(String string, MenuItemActivatedEvent t) {
}
//**************
// Class methods
//**************
/**
* Called when the play button is clicked.
*/
public void playButton() {
}
/**
* Called when the high scores button is clicked.
*/
public void highScoresButton() {
}
/**
* Called when the settings button is clicked.
*/
public void settingsButton() {
}
public void quitButton() {
showDialog();
}
/**
* Called when the rate button is clicked. Only Available on mobile.
*/
public void rateButton() {
}
/**
* Called when the feedback button is clicked. Only on mobile devices.
*/
public void feedbackButton() {
}
/**
* Called when the help button is clicked.
*/
public void helpButton() {
}
/**
* Called when the dialog needs to be shown.
*/
public void showDialog() {
System.out.println("WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW");
popup = new Nifty().createPopup("popup");
System.out.println("ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ");
//Menu myMenu = popup.findNiftyControl("#menu", Menu.class);
//myMenu.setWidth(new SizeValue("100px")); // must be set
//myMenu.addMenuItem("Click me!", new menuItem("menuItemid", "blah blah")); // menuItem is a custom class
//mNifty.subscribe(mNifty.getCurrentScreen(), myMenu.getId(), MenuItemActivatedEvent.class, this);
mNifty.showPopup(mNifty.getCurrentScreen(), popup.getId(), null);
}
public void clsoseDialog() {
}
/**
* Used to return a String to the Nifty xml file.
*
* @param name The name key associated with the String.
* @return The String associated with the key.
*/
public String getString(String name) {
if (name.equals("play")) {
return Strings.PLAY_BUTTON;
}
else if (name.equals("high_score")) {
return Strings.HIGH_SCORES_BUTTON;
}
else if (name.equals("settings")) {
return Strings.SETTINGS_BUTTON;
}
else if (name.equals("quit")) {
return Strings.QUIT_BUTTON;
}
else if (name.equals("rate")) {
return Strings.RATE_BUTTON;
}
else if (name.equals("feedback")) {
return Strings.FEEDBACK_BUTTON;
}
else if (name.equals("rules")) {
return Strings.RULES_BUTTON;
}
return null;
}
}
}
我点击退出调用quitButton()方法的按钮会发生什么。这很好。这反过来调用问题所在的showDialog()。在showDialog()方法中，这一行是popup = new Nifty().createPopup("popup");，它位于该行mNifty为空时不应该为空。任何帮助表示赞赏。
答案 0 :(得分：1)
该行
popup = new Nifty().createPopup("popup");
不使用mNifty。它会创建Nifty的新实例，然后在此新实例上调用creatPopup()。从早些时候开始，通过调用看起来像工厂方法
mNifty
mNifty = mNiftyDisplay.getNifty();
很有可能通过Nifty获取new并不会返回完全初始化的实例。由于您尚未发布Nifty的代码，因此尚不清楚发生了什么。
我会仔细检查以确保通过Nifty创建new将返回一个完全初始化的实例，并且您确实需要一个新实例。