android asynctask-android-AsyncTask更新列表

android-AsyncTask更新列表

求助——
在AsyncTask中調用MainActivity，更新了adapter，但是LogCat給出了onPostExecture的NullPointerException，我檢查了列表，裡面有值，不是空的啊。

AsyncTask.java

protected void onPostExecute(List<MoviesCategory> result){
    super.onPostExecute(result);
    //Here i have Error, i cheked result it's not null.
    //On AsyncTask i have Constructor when i get Activity.
    activity.mMoviesAdapter.addCategory(result);
}

Adapter.java

List<MoviesCategory> mListMovies;

public void addCategory(List<MoviesCategory> list){
    mListMovies.addAll(list);
    notifyDataSetChanged();
}

我做的更新：

更新

FATAL EXCEPTION: main
java.lang.NullPointerException
    at uz.afishamedia.Adapter.MoviesAdapter.addCategory(MoviesAdapter.java:49)
    at uz.afishamedia.Utils.LoadMovies.onPostExecute(LoadMovies.java:74)
    at uz.afishamedia.Utils.LoadMovies.onPostExecute(LoadMovies.java:1)
    at android.os.AsyncTask.finish(AsyncTask.java:631)
    at android.os.AsyncTask.access$600(AsyncTask.java:177)
    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:5191)
    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:795)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
    at dalvik.system.NativeStart.main(Native Method)

最佳回答：

問題出在mListMovies本來就是空的，需要對它先初始化

Adapter.java:

List<MoviesCategory> mListMovies = new ArrayList<MoviesCategory>();