当我在布局中使用自定义小部件类型时，出现空指针异常。我的 src 文件中也有该小部件，但找不到此异常出现的原因。
它在com.siliconithub.android.zoom.ImageZoomView的编译时间上给出以下错误：
java.lang.NullPointerException
异常详细信息记录在窗口 > 显示视图 > 错误日志中
这是我的 item_image_detail.xml 文件。
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="320dp"
android:layout_height="fill_parent"
android:background="#FFF"
android:minWidth="320dp"
android:orientation="vertical" >
<LinearLayout
android:id="@+id/frameImage"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:background="#000"
android:gravity="center_horizontal" >
<com.siliconithub.android.zoom.ImageZoomView
android:id="@+id/imgWithZoom"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
</LinearLayout>
<TableRow
android:id="@+id/rowOptionsImage"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:background="@drawable/bg_bottom"
android:gravity="center" >
<TextView
android:id="@+id/totalLikes"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingRight="10dp"
android:textColor="#FFF" />
<ImageButton
android:id="@+id/btnLike"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@android:color/transparent"
android:contentDescription="@string/description_btnlike"
android:src="@drawable/btn_like" />
<TextView
android:id="@+id/totalComments"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawableLeft="@drawable/ic_comment"
android:gravity="center_vertical"
android:paddingLeft="50dp"
android:textColor="#FFF" />
</TableRow>
可能是什么原因？
编辑 ：
这是它的日志：
java.lang.NullPointerException
at com.siliconithub.android.zoom.ImageZoomView.onLayout(ImageZoomView.java:166)
at android.view.View.layout(View.java:11278)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1617)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1401)
at android.view.View.layout(View.java:11278)
at android.view.ViewGroup.layout(ViewGroup.java:4224)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:925)
at android.view.View.layout(View.java:11278)
at android.view.ViewGroup.layout(ViewGroup.java:4224)
at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
at android.view.View.layout(View.java:11278)
at android.view.ViewGroup.layout(ViewGroup.java:4224)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
at android.view.View.layout(View.java:11278)
at android.view.ViewGroup.layout(ViewGroup.java:4224)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
at android.view.View.layout(View.java:11278)
at android.view.ViewGroup.layout(ViewGroup.java:4224)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.render(RenderSessionImpl.java:449)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:326)
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:1638)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.recomputeLayout(GraphicalEditorPart.java:1389)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.activated(GraphicalEditorPart.java:1163)
at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditorDelegate.delegatePageChange(LayoutEditorDelegate.java:674)
at com.android.ide.eclipse.adt.internal.editors.common.CommonXmlEditor.pageChange(CommonXmlEditor.java:360)
at org.eclipse.ui.part.MultiPageEditorPart$2.widgetSelected(MultiPageEditorPart.java:290)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:240)
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)
ImageZoomView 代码：
public class ImageZoomView extends View implements Observer {
/** Paint object used when drawing bitmap. */
private final Paint mPaint = new Paint(Paint.FILTER_BITMAP_FLAG);
/** Rectangle used (and re-used) for cropping source image. */
private final Rect mRectSrc = new Rect();
/** Rectangle used (and re-used) for specifying drawing area on canvas. */
private final Rect mRectDst = new Rect();
/** Object holding aspect quotient */
private final AspectQuotient mAspectQuotient = new AspectQuotient();
/** The bitmap that we're zooming in, and drawing on the screen. */
private Bitmap mBitmap;
/** State of the zoom. */
private ZoomState mState;
// Public methods
/**
* Constructor
*/
public ImageZoomView(Context context, AttributeSet attrs) {
super(context, attrs);
}
/**
* Set image bitmap
*
* @param bitmap The bitmap to view and zoom into
*/
public void setImage(Bitmap bitmap) {
mBitmap = bitmap;
mAspectQuotient.updateAspectQuotient(getWidth(), getHeight(), mBitmap.getWidth(), mBitmap
.getHeight());
mAspectQuotient.notifyObservers();
invalidate();
}
/**
* Set object holding the zoom state that should be used
*
* @param state The zoom state
*/
public void setZoomState(ZoomState state) {
if (mState != null) {
mState.deleteObserver(this);
}
mState = state;
mState.addObserver(this);
invalidate();
}
/**
* Gets reference to object holding aspect quotient
*
* @return Object holding aspect quotient
*/
public AspectQuotient getAspectQuotient() {
return mAspectQuotient;
}
// Superclass overrides
@Override
protected void onDraw(Canvas canvas) {
if (mBitmap != null && mState != null) {
final float aspectQuotient = mAspectQuotient.get();
final int viewWidth = getWidth();
final int viewHeight = getHeight();
final int bitmapWidth = mBitmap.getWidth();
final int bitmapHeight = mBitmap.getHeight();
final float panX = mState.getPanX();
final float panY = mState.getPanY();
final float zoomX = mState.getZoomX(aspectQuotient) * viewWidth / bitmapWidth;
final float zoomY = mState.getZoomY(aspectQuotient) * viewHeight / bitmapHeight;
// Setup source and destination rectangles
mRectSrc.left = (int)(panX * bitmapWidth - viewWidth / (zoomX * 2));
mRectSrc.top = (int)(panY * bitmapHeight - viewHeight / (zoomY * 2));
mRectSrc.right = (int)(mRectSrc.left + viewWidth / zoomX);
mRectSrc.bottom = (int)(mRectSrc.top + viewHeight / zoomY);
mRectDst.left = getLeft();
mRectDst.top = getTop();
mRectDst.right = getRight();
mRectDst.bottom = getBottom();
// Adjust source rectangle so that it fits within the source image.
if (mRectSrc.left < 0) {
mRectDst.left += -mRectSrc.left * zoomX;
mRectSrc.left = 0;
}
if (mRectSrc.right > bitmapWidth) {
mRectDst.right -= (mRectSrc.right - bitmapWidth) * zoomX;
mRectSrc.right = bitmapWidth;
}
if (mRectSrc.top < 0) {
mRectDst.top += -mRectSrc.top * zoomY;
mRectSrc.top = 0;
}
if (mRectSrc.bottom > bitmapHeight) {
mRectDst.bottom -= (mRectSrc.bottom - bitmapHeight) * zoomY;
mRectSrc.bottom = bitmapHeight;
}
canvas.drawBitmap(mBitmap, mRectSrc, mRectDst, mPaint);
}
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
mAspectQuotient.updateAspectQuotient(right - left, bottom - top, mBitmap.getWidth(),
mBitmap.getHeight());
mAspectQuotient.notifyObservers();
}
// implements Observer
public void update(Observable observable, Object data) {
invalidate();
}
}