刚刚在调试自己的APP项目的时候报错java.lang.IllegalArgumentException: The observer is null.,而之前是可以运行通过,所以百思不得其解,后来在网上查找相关资料,终于弄明白是咋回事,现在记录如下,一来算是积累调错方面的知识,二来或许可以帮到出现同样错误的人。
出错的主要原因是在ViewPager中使用到了GridView这样的控件,当销毁包含该ViewPager控件的Activity时,如切换Fragment或Activity或退出应用,则会报java.lang.IllegalArgumentException: The observer is null.的错误,主要原因是GridView使用的是适配器模式来显示视图,采用观察者模式来更新视图,在移除View时会调用BaseAdapter.unregisterDataSetObserver方法,所以如果GridView在移除View时如果对同一个View移除多次,则会报java.lang.IllegalArgumentException: The observer is null.错误。解决方案很简单,只需在GridView的适配器类中重写unregisterDataSetObserver方法,在其中加一个判空语句即可,注意该错误同样适用于ListView,因为ListView同样使用的是适配器模式。
错误代码如下:
java.lang.IllegalArgumentException: The observer is null. at android.database.Observable.unregisterObserver(Observable.java:64) at android.widget.BaseAdapter.unregisterDataSetObserver(BaseAdapter.java:42) at android.widget.AbsListView.onDetachedFromWindow(AbsListView.java:2872) at android.view.View.dispatchDetachedFromWindow(View.java:11908) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2647) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2645) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2645) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2645) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2645) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2645) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2645) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2645) at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2645) at android.view.ViewRootImpl.dispatchDetachedFromWindow(ViewRootImpl.java:2685) at android.view.ViewRootImpl.doDie(ViewRootImpl.java:4044) at android.view.ViewRootImpl.die(ViewRootImpl.java:4027) at android.view.WindowManagerImpl.removeViewImmediate(WindowManagerImpl.java:375) at android.view.WindowManagerImpl$CompatModeWrapper.removeViewImmediate(WindowManagerImpl.java:170) at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3352) at android.app.ActivityThread.access$1200(ActivityThread.java:140) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1266) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4914) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:808) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:575) at dalvik.system.NativeStart.main(Native Method)
解决代码如下:
public class GridViewAdapter extends SimpleAdapter { public GridViewAdapter(Context context, List<? extends Map<String, ?>> data, int resource, String[] from, int[] to) { super(context, data, resource, from, to); // TODO Auto-generated constructor stub } @Override public void unregisterDataSetObserver(DataSetObserver observer) { if (observer != null) { super.unregisterDataSetObserver(observer); } } }即在自己适配器类中重写unregisterDataSetObserver方法,在其中加一个判空语句,如果observer不为空,才调用super.unregisterDataSetObserver(observer);语句。