这是自定义视图代码，它在使用此视图的 XML 的布局选项卡中给了我一个空指针异常：
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);
}
}
这是错误日志：
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)
这是第 166 行BoardView.java：
wall[i].draw(c);
我怎样才能解决这个问题？我从俄罗斯方块源代码中得到了这段代码，我想研究它以供将来参考，但我无法查看游戏的布局