Here's the custom view code that gives me a null pointer exception on the XML layout tab that uses this view:
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 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); } }
and here is the error log:
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)
Here is line 166 of BoardView.java :
wall[i].draw(c);
How can i fix this? I got this code from the Tetris source code and I want to learn this for a future reference, but I can’t view the game’s layout