लेआउट एक्सएमएल में कस्टम दृश्य के साथ नल पॉइंटर एक्सेप्शन

Question

यहाँ कस्टम दृश्य कोड जो मुझे इस दृश्य का उपयोग करता है जो एक्सएमएल के लेआउट टैब में एक नल पॉइंटर एक्सेप्शन देता है:

public class BoardView extends View { 

    // Drawables for the board boxes, the playable zone 
    public Drawable[][] block = new Drawable[20][10]; 
    // Drawables for the wall (yes, it's done with tiles) 
    public Drawable[] wall = new Drawable[102]; 
    // Drawable for the background, and boolean for drawing it or not 
    Drawable mbg; 
    boolean bg = false; 
    // Context and canvas to be used along the class 
    Context context; 
    Canvas c; 

    /*************************************************/ 
    /* Class constructor **************************** */ 
    /*************************************************/ 
    /* Defines the context and the canvas *********** */ 
    /*************************************************/ 
    public BoardView(Context cont, AttributeSet attrs) { 
     super(cont, attrs); 
     context = cont; 
    } 

    /*************************************************/ 
    /* Initializes drawables for playable boxes ***** */ 
    /*************************************************/ 
    /* Must be initialized one by one from the Game * */ 
    /* activity, passing all the parameters ********* */ 
    /*************************************************/ 
    public void initialize(int i, int j, int left, int top, int side) { 
     block[i][j] = context.getResources().getDrawable(R.drawable.alpha); 
     block[i][j].setBounds(left, top, left + side, top + side); 
    } 

    /*************************************************/ 
    /* Draws the board wall ************************* */ 
    /*************************************************/ 
    /* Needs the top-left point of the board frame ** */ 
    /* and the width of the wall ******************** */ 
    /*************************************************/ 
    public void createWall(int left, int top, int side) { 
     int i = 0, x, y; 
     x = left - side/2; 
     y = top; 
     // The left wall 
     while (i < 40) { 
      wall[i] = context.getResources().getDrawable(R.drawable.brick); 
      wall[i].setBounds(x, y, x + side/2, y + side/2); 
      y = y + side/2; 
      i = i + 1; 
     } 
     x = left + side * 10; 
     y = top; 
     // The right wall 
     while (i < 80) { 
      wall[i] = context.getResources().getDrawable(R.drawable.brick); 
      wall[i].setBounds(x, y, x + side/2, y + side/2); 
      y = y + side/2; 
      i = i + 1; 
     } 
     x = left - side/2; 
     // The floor 
     while (i < 102) { 
      wall[i] = context.getResources().getDrawable(R.drawable.brick); 
      wall[i].setBounds(x, y, x + side/2, y + side/2); 
      x = x + side/2; 
      i = i + 1; 
     } 
    } 

    /*************************************************/ 
    /* Draws the board background ******************* */ 
    /*************************************************/ 
    /* Needs the top-left point of the board frame ** */ 
    /* and the width of the wall ******************** */ 
    /*************************************************/ 
    public void createBg(int left, int top, int side) { 
     // Set board background (if any) 
     bg = false; 
     int bgn = 1 + (int) (Math.random() * 19); 
     switch (bgn) { 
     case 1: 
      mbg = getResources().getDrawable(R.drawable.bg1); 
      break; 
     case 2: 
      mbg = getResources().getDrawable(R.drawable.bg2); 
      break; 
     case 3: 
      mbg = getResources().getDrawable(R.drawable.bg3); 
      break; 
     case 4: 
      mbg = getResources().getDrawable(R.drawable.bg4); 
      break; 
     case 5: 
      mbg = getResources().getDrawable(R.drawable.bg5); 
      break; 
     case 6: 
      mbg = getResources().getDrawable(R.drawable.bg6); 
      break; 
     case 7: 
      mbg = getResources().getDrawable(R.drawable.bg7); 
      break; 
     case 8: 
      mbg = getResources().getDrawable(R.drawable.bg8); 
      break; 
     case 9: 
      mbg = getResources().getDrawable(R.drawable.bg9); 
      break; 
     case 10: 
      mbg = getResources().getDrawable(R.drawable.bg11); 
      break; 
     case 11: 
      mbg = getResources().getDrawable(R.drawable.bg11); 
      break; 
     case 12: 
      mbg = getResources().getDrawable(R.drawable.bg12); 
      break; 
     case 13: 
      mbg = getResources().getDrawable(R.drawable.bg13); 
      break; 
     case 14: 
      mbg = getResources().getDrawable(R.drawable.bg14); 
      break; 
     case 15: 
      mbg = getResources().getDrawable(R.drawable.bg15); 
      break; 
     case 16: 
      mbg = getResources().getDrawable(R.drawable.bg16); 
      break; 
     case 17: 
      mbg = getResources().getDrawable(R.drawable.bg17); 
      break; 
     case 18: 
      mbg = getResources().getDrawable(R.drawable.bg18); 
      break; 
     case 19: 
      mbg = getResources().getDrawable(R.drawable.bg19); 
      break; 
     } 
     mbg.setBounds((int) (left), (int) (top), (int) (left + side * 10), 
       (int) (top + 20 * side)); 
    } 

    /*************************************************/ 
    /* Draws the board ****************************** */ 
    /*************************************************/ 
    /* Draws the walls, the bg and all the boxes **** */ 
    /*************************************************/ 
    @Override 
    protected void onDraw(Canvas canvas) { 
     c = canvas; 
     super.onDraw(canvas); 
     if (bg) 
      mbg.draw(canvas); 
     for (int i = 0; i < 102; i++) 
      wall[i].draw(c); 
     for (int i = 0; i < 20; i++) 
      for (int j = 0; j < 10; j++) { 
       block[i][j].draw(canvas); 
      } 
     // Actually draw 
     invalidate(); 
    } 

    /*************************************************/ 
    /* Canvas getter ******************************** */ 
    /*************************************************/ 
    public Canvas getCanvas() { 
     return c; 
    } 

    /*************************************************/ 
    /* Colors a box ********************************* */ 
    /*************************************************/ 
    /* Changes the drawable for the indicated box to */ 
    /* to 'c'. Can also be COLOR_NONE to undraw ***** */ 
    /*************************************************/ 
    public void setColor(int i, int j, byte c) { 
     Rect rect; 
     rect = block[i][j].getBounds(); 
     switch (c) { 
     case Values.COLOR_NONE: 
      block[i][j] = context.getResources().getDrawable(R.drawable.alpha); 
      ; 
      break; 
     case Values.COLOR_RED: 
      block[i][j] = context.getResources().getDrawable(
        R.drawable.block_red); 
      break; 
     case Values.COLOR_GREEN: 
      block[i][j] = context.getResources().getDrawable(
        R.drawable.block_green); 
      break; 
     case Values.COLOR_BLUE: 
      block[i][j] = context.getResources().getDrawable(
        R.drawable.block_blue); 
      break; 
     case Values.COLOR_YELLOW: 
      block[i][j] = context.getResources().getDrawable(
        R.drawable.block_yellow); 
      break; 
     case Values.COLOR_PINK: 
      block[i][j] = context.getResources().getDrawable(
        R.drawable.block_pink); 
      break; 
     case Values.COLOR_PURPLE: 
      block[i][j] = context.getResources().getDrawable(
        R.drawable.block_purple); 
      break; 
     case Values.COLOR_WHITE: 
      block[i][j] = context.getResources().getDrawable(
        R.drawable.block_white); 
      break; 
     } 
     block[i][j].setBounds(rect); 
    } 
} 

और यहाँ त्रुटि लॉग है:

wall[i].draw(c); 

मैं इसे कैसे ठीक कर सकते हैं:

java.lang.NullPointerException 
    at com.seavenois.tetris.BoardView.onDraw(BoardView.java:166) 
    at android.view.View.draw(View.java:6880) 
    at android.view.ViewGroup.drawChild(ViewGroup.java:1646) 
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373) 
    at android.view.ViewGroup.drawChild(ViewGroup.java:1644) 
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373) 
    at android.view.ViewGroup.drawChild(ViewGroup.java:1644) 
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373) 
    at android.view.ViewGroup.drawChild(ViewGroup.java:1644) 
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373) 
    at android.view.ViewGroup.drawChild(ViewGroup.java:1644) 
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373) 
    at android.view.View.draw(View.java:6883) 
    at android.view.ViewGroup.drawChild(ViewGroup.java:1646) 
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373) 
    at android.view.View.draw(View.java:6883) 
    at com.android.layoutlib.bridge.impl.RenderSessionImpl.render(RenderSessionImpl.java:466) 
    at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:320) 
    at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:325) 
    at com.android.ide.eclipse.adt.internal.editors.layout.gle2.RenderService.createRenderSession(RenderService.java:372) 
    at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.renderWithBridge(GraphicalEditorPart.java:1640) 
    at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.recomputeLayout(GraphicalEditorPart.java:1391) 
    at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.activated(GraphicalEditorPart.java:1165) 
    at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditorDelegate.partActivated(LayoutEditorDelegate.java:734) 
    at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditorDelegate.partBroughtToTop(LayoutEditorDelegate.java:744) 
    at org.eclipse.ui.internal.PartListenerList$2.run(PartListenerList.java:87) 
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42) 
    at org.eclipse.core.runtime.Platform.run(Platform.java:888) 
    at org.eclipse.ui.internal.PartListenerList.fireEvent(PartListenerList.java:57) 
    at org.eclipse.ui.internal.PartListenerList.firePartBroughtToTop(PartListenerList.java:85) 
    at org.eclipse.ui.internal.PartService.firePartBroughtToTop(PartService.java:208) 
    at org.eclipse.ui.internal.WorkbenchPagePartList.firePartBroughtToTop(WorkbenchPagePartList.java:76) 
    at org.eclipse.ui.internal.WorkbenchPagePartList.fireActiveEditorChanged(WorkbenchPagePartList.java:52) 
    at org.eclipse.ui.internal.PartList.setActiveEditor(PartList.java:162) 
    at org.eclipse.ui.internal.WorkbenchPage.makeActiveEditor(WorkbenchPage.java:1355) 
    at org.eclipse.ui.internal.WorkbenchPage.setActivePart(WorkbenchPage.java:3629) 
    at org.eclipse.ui.internal.WorkbenchPage.requestActivation(WorkbenchPage.java:3159) 
    at org.eclipse.ui.internal.PartPane.requestActivation(PartPane.java:279) 
    at org.eclipse.ui.internal.EditorPane.requestActivation(EditorPane.java:98) 
    at org.eclipse.ui.internal.PartPane.setFocus(PartPane.java:325) 
    at org.eclipse.ui.internal.EditorPane.setFocus(EditorPane.java:127) 
    at org.eclipse.ui.internal.PartStack.presentationSelectionChanged(PartStack.java:837) 
    at org.eclipse.ui.internal.PartStack.access$1(PartStack.java:823) 
    at org.eclipse.ui.internal.PartStack$1.selectPart(PartStack.java:137) 
    at org.eclipse.ui.internal.presentations.util.TabbedStackPresentation$1.handleEvent(TabbedStackPresentation.java:133) 
    at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.fireEvent(AbstractTabFolder.java:269) 
    at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.fireEvent(AbstractTabFolder.java:278) 
    at org.eclipse.ui.internal.presentations.defaultpresentation.DefaultTabFolder.access$1(DefaultTabFolder.java:1) 
    at org.eclipse.ui.internal.presentations.defaultpresentation.DefaultTabFolder$2.handleEvent(DefaultTabFolder.java:88) 
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84) 
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053) 
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1077) 
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1062) 
    at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:774) 
    at org.eclipse.swt.custom.CTabFolder.setSelection(CTabFolder.java:2746) 
    at org.eclipse.swt.custom.CTabFolder.onMouse(CTabFolder.java:1433) 
    at org.eclipse.swt.custom.CTabFolder$1.handleEvent(CTabFolder.java:257) 
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84) 
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053) 
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4165) 
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3754) 
    at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2701) 
    at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2665) 
    at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2499) 
    at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:679) 
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) 
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:668) 
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149) 
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:123) 
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196) 
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110) 
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79) 
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:344) 
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
    at java.lang.reflect.Method.invoke(Unknown Source) 
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:622) 
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577) 
    at org.eclipse.equinox.launcher.Main.run(Main.java:1410) 
    at org.eclipse.equinox.launcher.Main.main(Main.java:1386) 

यहाँ लाइन BoardView.java की 166 है? मुझे यह कोड टेट्रिस स्रोत कोड से मिला है और मैं भविष्य के संदर्भ के लिए इसका अध्ययन करना चाहता हूं लेकिन मैं खेल

Answer 1

आप वर्तमान में अपने onDraw() में जाँच किसी भी NULL नहीं कर रहे हैं।

NULL चेक होने से आपको अधिक स्थिर कोड बनाने में मदद मिलेगी और आपकी समस्या को तेज़ी से ढूंढने में आपकी सहायता मिलेगी।

मैं नीचे की तरह कुछ NULL की जाँच में जोड़ना होगा:

protected void onDraw(Canvas canvas) { 
    if (canvas != null) { 
     c = canvas; 
     super.onDraw(canvas); 
     if (bg) { 
      if (mbg != null) { 
       mbg.draw(canvas); 
      } else { 
       /* 
       * Handle null value 
       * print to logcat this was null 
       */ 
      } 
     } 
     for (int i = 0; i < 102; i++) { 
      if (wall[i] != null) { 
       wall[i].draw(c); 
      } else { 
       /* 
       * Handle null value 
       * print to logcat this was null 
       */ 
      } 
     } 
     for (int i = 0; i < 20; i++) { 
      for (int j = 0; j < 10; j++) { 
       if (block[i][j] != null) { 
        block[i][j].draw(canvas); 
       } else { 
        /* 
        * Handle null value 
        * print to logcat this was null 
        */ 
       } 
      } 
     } 
     //Actually draw 
     invalidate(); 
    } else { 
     /* 
     * Handle null value 
     * print to logcat this was null 
     */ 
    } 

} 

Answer 2

के लेआउट को नहीं देख सकता हूं, मुझे प्रारंभिकरण विधियों की वास्तविक कॉल नहीं दिखाई दे रही है।

जैसे:

initialize(i, j, left, top, side); 

तो मैं लगता है कि आप कि बाहर से और कुछ पर बाहर याद आती तो है कि या तो एक दीवार, ब्लॉक या MBG अभी भी अशक्त रहे हैं।

शायद यह संकेत कि आप कितना उपयोग करते हैं और अपना दृश्य प्रारंभ करते हैं, तो यह संकेत पर्याप्त नहीं है।

(या, लेकिन thats उम्मीद है कि नहीं मामला है, मैं गलत हूँ!)