遇到个空指针错误，没有指出错误在哪，求指教。用jxl.jar生成一个GraphicalView，addView()到一个LinearLayout里产生的
java.lang.NullPointerException
at android.graphics.Canvas.throwIfRecycled(Canvas.java:954)
at android.graphics.Canvas.drawBitmap(Canvas.java:980)
at org.achartengine.GraphicalView.onDraw(GraphicalView.java:174)
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.View.draw(View.java:6883)
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.View.draw(View.java:6883)
at android.widget.FrameLayout.draw(FrameLayout.java:357)
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.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 android.view.ViewGroup.drawChild(ViewGroup.java:1646)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
at android.view.View.draw(View.java:6883)
at android.widget.FrameLayout.draw(FrameLayout.java:357)
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 android.widget.FrameLayout.draw(FrameLayout.java:357)
at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1862)
at android.view.ViewRoot.draw(ViewRoot.java:1522)
at android.view.ViewRoot.performTraversals(ViewRoot.java:1258)
at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
[解决办法]
这不就是出错位置吗？第174行
at org.achartengine.GraphicalView.onDraw(GraphicalView.java:174)
[解决办法]
你通过LinearLayout chartView; 只定义了chartView这个对象类型，但是未看到有实始对像的代码，也就是说chartView是null，你要在onCreate里面再增加一个代码：
chartView = new LinearLayout(getApplicationContext());
