自定義GUI將不會在第一次啓動應用程序時顯示

Question

我正在嘗試用android遊戲杆（d-pad）構建GUI。我大部分都在工作。有一個大問題：第一次在任何Android設備上打開它時，GUI不會加載。我已經查明瞭這個問題，但是我不清楚是什麼導致了這個問題。

在JoystickGui類中，我在構造器中創建了一個joystick對象。稍後drawJoystickGUI()由擴展Activity的類調用，它將在畫布上繪製位圖。每次我第一次啓動應用程序（或手動清空RAM）時，我都設法發現對遊戲杆對象的引用是空的，即使它是在構造函數中創建的。

在該方法中drawJoystickGUI()我使用了一個System.Out.println看有無joystick對象實際上exitst並返回空。我不得不使用try和catch來防止應用在啓動時崩潰。

我真的很希望有人能向我解釋是什麼導致了這個問題。

這裏是我的代碼：

public class JoystickGUI implements OnTouchListener { 

// Screen size for positioning purposes 
private float screenWidth, screenHeight; 

// Used to determine if the Joystick Graphical User Interface is actually 
public static boolean use; 

private boolean useButtons = true; 

// Will hold all non-Joystick objects 
private ArrayList<Button> buttons = new ArrayList<Button>(); 

// Joystick object 
private Joystick joystick; 

Display display; 

// Touch input identification 
private int jsPointerID; 
final private int INVALID_POINTER_ID = -1; 

@SuppressWarnings("deprecation") 
public JoystickGUI() { 
    if(use){ 

     display = ((WindowManager) GameEngine.getAppContext().getSystemService(
      Context.WINDOW_SERVICE)).getDefaultDisplay(); 

     screenWidth = display.getWidth(); 
     screenHeight = display.getHeight(); 

     System.out.println("ScreenWidth: " + screenWidth + ". ScreenHeight: " 
       + screenHeight + "."); 

     joystick = new Joystick(100, screenHeight - 100); 

     if (useButtons) { 

      Sprite buttonA = new Sprite("buttonajoystickgui"); 
      buttons.add(new RoundButton(buttonA, screenWidth - 125, 
        screenHeight - 75)); 
      Sprite buttonB = new Sprite("buttonbjoystickgui"); 
      buttons.add(new RoundButton(buttonB, screenWidth - 75, 
        screenHeight - 125)); 

     } 

     setTransparency(150); 

     Log.d("JoystickGUI", "Initialized"); 
    } 

} 

/** 
* The following methods are used for handling the touch input 
*/ 

public boolean onTouch(View v, MotionEvent event) { 

     switch (event.getAction() & MotionEvent.ACTION_MASK) { 
     case MotionEvent.ACTION_DOWN: 
      buttonPressed(event); 
      break; 
     case MotionEvent.ACTION_POINTER_DOWN: 
      buttonPressed(event); 
      break; 
     case MotionEvent.ACTION_MOVE: 
      buttonMoved(event); 
      break; 
     case MotionEvent.ACTION_UP: 
      buttonReleased(event, 0); 
      break; 
     case MotionEvent.ACTION_POINTER_UP: 
      buttonReleased(event, event.getActionIndex()); 
      break; 
     default: 
      break; 

    } 
    return true; 
} 

public void buttonPressed(MotionEvent e) { 

    for (int p = 0; p < e.getPointerCount(); p++) { 
     if (joystick.isWithinJoystick(e, p) && !Joystick.isActive) { 
      Joystick.isActive = true; 
      jsPointerID = e.getActionIndex(); 
     } 
     for (int i = 0; i < buttons.size(); i++) { 
      if (buttons.get(i).isPressed(e, p) && !buttons.get(i).isActive) { 
       buttons.get(i).setActive(true); 
       buttons.get(i).setPointerID(e.getActionIndex()); 
       Log.d("JoystickGUI", "Button #" + i + " pressed."); 
      } 
     } 
    } 

} 

public void buttonMoved(MotionEvent e) { 

    for (int p = 0; p < e.getPointerCount(); p++) { 
     if (Joystick.isActive && e.getPointerId(p) == jsPointerID) { 
      joystick.updateButtonPos(e, p); 
     } 

    } 

} 

public void buttonReleased(MotionEvent e, int pointerIndex) { 
    if (Joystick.isActive && e.getPointerId(pointerIndex) == jsPointerID) { 
     Joystick.isActive = false; 
     joystick.resetJoystick(); 
     jsPointerID = INVALID_POINTER_ID; 

    } 

    for (int i = 0; i < buttons.size(); i++) { 
     if (buttons.get(i).isActive 
       && e.getPointerId(pointerIndex) == buttons.get(i) 
         .getPointerID()) { 
      buttons.get(i).setActive(false); 
      buttons.get(i).resetPointerID(); 
     } 
    } 

} 

/** 
* The following methods are used for drawing all button-objects to the 
* canvas. 
* 
* @param canvas 
*/ 

public void drawJoystickGUI(Canvas canvas) { 
    if(use){ 

     try { 
      joystick.drawJoystick(canvas); 
     } catch (Exception e) { 
      System.out.println(joystick); 
      Log.d("JoystickGUI", "Drawing joystick failed!"); 
     } 

     for (int i = 0; i < buttons.size(); i++) { 
      try { 
       buttons.get(i).drawButton(canvas); 
      } catch (Exception e) { 
       Log.d("JoystickGUI", "Drawing Button " + i + " failed"); 
       System.out.println(buttons.get(i)); 
      } 
     } 
    } 

} 

private void setTransparency(int alpha) { 

    joystick.setAlpha(alpha); 
    for (int i = 0; i < buttons.size(); i++) { 
     buttons.get(i).setAlpha(alpha); 
    } 

} 

/** 
* The following (static) methods are used to get input. 
* 
* @return 
*/ 

public static boolean isJoystickActive() { 
    return Joystick.isActive; 
} 

public static double getJoystickAngle() { 
    return Joystick.getAngle(); 
} 

public static float getPower() { 
    return Joystick.getPower(); 
} 
} 

是應該正常運行遊戲引擎，我帶人非必要的東西了。 InitializeTouch在GameLoop中被調用。

public abstract class GameEngine extends Activity { 

/** 
* Gameloop is a gameThread that handles the timing of the game 
*/ 
private GameLoop gameloop; 
/** 
* View deals with the proper rendering of the game 
*/ 
private static GameView view; 
/** 
* The width and height of the device 
*/ 
private static int screenWidth, screenHeight; 
/** 
* JoystickGUI handles input by touch via the joystick interface 
*/ 
public JoystickGUI joystickGUI; 

/** 
* A vectorlist that holds all the active GameObjects. Can be used if you 
* mannualy want to delete/change GameObjects. For instance, you could loop 
* through this list and remove health of every GameObject. 
*/ 
public static Vector<GameObject> items; 
/** 
* A vectorlist that holds all the newly created GameObjects during this 
* cycle of the game loop. At the end of the cycle, all items in this list 
* will be moved to the items-list and the object become active 
*/ 
public static Vector<GameObject> newItems; 
/** 
* A vectorlist that holds all the active alarms. Can be used if you 
* manually want to delete/change alarms. 
*/ 
public static Vector<Alarm> gameAlarms; 


/** 
* Holds context of the application 
*/ 
private static Context appContext; 
/** 
* The main thread of the gameloop 
*/ 
private Thread gameThread; 




@Override 
protected final void onCreate(Bundle savedInstanceState) { 

    requestWindowFeature(Window.FEATURE_NO_TITLE); 
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, 
      WindowManager.LayoutParams.FLAG_FULLSCREEN); 
    getWindow().setFlags(
      WindowManager.LayoutParams.SOFT_INPUT_ADJUST_UNSPECIFIED, 
      WindowManager.LayoutParams.SOFT_INPUT_ADJUST_UNSPECIFIED); 

    vibrator = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE); 
    appContext = getApplicationContext(); 

    joystickGUI = new JoystickGUI(); // Added 

    screenWidth = getWindow().getWindowManager().getDefaultDisplay() 
      .getWidth(); 
    screenHeight = getWindow().getWindowManager().getDefaultDisplay() 
      .getHeight(); 

    gameloop = new GameLoop(this); 
    gameThread = new Thread(gameloop); 
    gameThread.setPriority(7); 

    view = new GameView(this, gameThread); 
    gameloop.setView(view); 

    setContentView(view); 
    view.setKeepScreenOn(true); 

    super.onCreate(savedInstanceState); 

} 


/** 
* Initialize the Listener for the screen (general touch OR screenButtons) 
*/ 
protected void initializeTouch() { 

    if (JoystickGUI.use) { // added 
     Log.d("JoystickEnabled", "USING JOYSTICK"); 
      view.setOnTouchListener(joystickGUI); 
     } 
} 

public final void drawInterface(Canvas canvas) { 
    if(JoystickGUI.use){ 
     joystickGUI.drawJoystickGUI(canvas); 
    } 
} 

編輯：

我已經初始化「操縱桿」和「按鈕」繪製函數中的對象，有一個簡單的布爾以防止不必要的CPU使用率解決了這個問題。但我只是開始尋求真正的解決方案而不是解決方案。

Answer 1

我不確定你的代碼有什麼問題。

你試過AndEngine？它是免費且開源的。您可以從Google Play下載examples應用程序。

它的joystick example是模擬的。這不像你的遊戲杆代碼例子那麼簡單，但是如果你可以調整你的遊戲來接收模擬輸入，那麼它就是一個很好的開箱即用的例子。