android-片段中开放数据库上的NullPointerException

我有一个关于我的活动的幻灯片，它有4个片段。每个片段都包含一个listView，我用baseAdapter填充这个listView

我已经发布了我的应用程序，我经常遇到这样的错误：

STACK_TRACE = java.lang.NullPointerException
at android.content.ComponentName.<init>(ComponentName.java:75)
at android.content.Intent.<init>(Intent.java:3970)
at ir.radaar.goblin.Fragment_E$ListAdapter.<init>(Fragment_E.java:396)
at ir.radaar.goblin.Fragment_E$GetContacts.onPostExecute(Fragment_E.java:359)
at ir.radaar.goblin.Fragment_E$GetContacts.onPostExecute(Fragment_E.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:176)
at android.app.ActivityThread.main(ActivityThread.java:5317)
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:1102)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
at dalvik.system.NativeStart.main(Native Method)

你能帮我吗。为什么会出现这个错误

---

谢谢

您是否检查了getActivity（）是否在这一行返回null：db_e=new DatabaseHandler（getActivity（））@xploader，我自己没有收到这个错误，但是在日志中我有太多的人有这个问题。getActivity（）是否可能为null？假设您正确初始化ListAdapter，我不这么认为。无论如何，如果从未使用过数据库，为什么要在适配器内打开它？另外，此处的FistActivity.class而不是FistActivity.classreplace getActivity（）为activity，看起来像是一个错误。

public class ListAdapter extends BaseAdapter {
    Activity activity;
    public ArrayList<HashMap<String, String>> list;
    DatabaseHandler db_e;

    public ListAdapter(Activity activity, ArrayList<HashMap<String, String>> list) {
        super();
        this.activity = (Activity) activity;
        this.list = list;
        try {
                db_e = new DatabaseHandler(getActivity());
                if (!db_e.isOpen())
                    db_e.open();

        } catch (Exception e) {
            startActivity(new Intent (getActivity(), FistActiivty.class));
        }
        ostan = getResources().getStringArray(R.array.ostan);
    }

    public int getCount() {
        return list.size();

    }

    public Object getItem(int position) {
        return list.get(position);
    }

    public HashMap<String, String> geting(int position) {
        return list.get(position);
    }

    public long getItemId(int arg0) {
        return 0;
    }

    private class ViewHolder {
        ImageView img;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        LayoutInflater inflater = activity.getLayoutInflater();
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.ads_ekhtesasi, null);
            holder = new ViewHolder();
            holder.img = (ImageView) convertView.findViewById(R.id.img);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }


        return convertView;
    }

    public void clear() {
        if (this.list.size() > 0)
            this.list.clear();
    }
}

public DatabaseHandler open() {
    helper = new OpenHelper(context);
    myDB = helper.getWritableDatabase();
    return this;
}