A custom DialogFragment that can be positioned and set size. Make sure to use 9patch background. Ref: http://stackoverflow.com/questions/9698410/position-of-dialogfragment-in-android

fragment_user_panel.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:gravity="center_horizontal"
    android:background="@drawable/bg_user_panel">

    <!-- dummy to set width -->
    <View
        android:layout_width="100dp"
        android:layout_height="0dp" />

    <TextView
        android:id="@+id/register"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="4dp"
        android:paddingBottom="4dp"
        android:layout_marginTop="4dp"
        android:text="@string/register"
        style="@style/TextLarge"
        android:background="@drawable/bg_btn_feedback"/>

    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:layout_margin="4dp"
        android:background="@color/darkGray" />

    <TextView
        android:id="@+id/login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="4dp"
        android:paddingBottom="4dp"
        android:text="@string/login"
        style="@style/TextLarge"
        android:background="@drawable/bg_btn_feedback"/>

    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:layout_margin="4dp"
        android:background="@color/darkGray" />

    <TextView
        android:id="@+id/feedback"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="4dp"
        android:paddingBottom="4dp"
        android:layout_marginBottom="4dp"
        android:text="@string/feedback"
        style="@style/TextLarge"
        android:background="@drawable/bg_btn_feedback"/>

</LinearLayout>

UserPanelDialogFragment.java

public class UserPanelDialogFragment extends DialogFragment implements View.OnClickListener {
    private boolean isLogin = false;

    private TextView mRegister;
    private TextView mLogin;
    private TextView mFeedback;

    private TextView mUserId;
    private TextView mLogout;

    public static UserPanelDialogFragment newInstance(boolean isLogin) {
        UserPanelDialogFragment fragment =  new UserPanelDialogFragment();
        fragment.isLogin = isLogin;
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setStyle(STYLE_NO_FRAME, android.R.style.Theme_Dialog);
    }

    @Override
    public void onStart() {
        super.onStart();
        Window window = getDialog().getWindow();
        WindowManager.LayoutParams params = window.getAttributes();
        params.dimAmount = 0.6f;
        window.setAttributes(params);
        window.setBackgroundDrawableResource(android.R.color.transparent);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = null;
        if (isLogin) {
            view = inflater.inflate(R.layout.user_panel_logedin, container, false);
            mUserId = (TextView) view.findViewById(R.id.user_id);
            mLogout = (TextView) view.findViewById(R.id.logout);
            mFeedback = (TextView) view.findViewById(R.id.feedback);

            mUserId.setOnClickListener(this);
            mLogout.setOnClickListener(this);
            mFeedback.setOnClickListener(this);
        } else {
            view = inflater.inflate(R.layout.user_panel, container, false);
            mRegister = (TextView) view.findViewById(R.id.register);
            mLogin = (TextView) view.findViewById(R.id.login);
            mFeedback = (TextView) view.findViewById(R.id.feedback);

            mRegister.setOnClickListener(this);
            mLogin.setOnClickListener(this);
            mFeedback.setOnClickListener(this);
        }

        setDialogPosition();
        return view;
    }

    @Override
    public void onClick(View v) {
        int id = v.getId();
        if (id == R.id.register) {
            // todo: add response
        } else if (id == R.id.login) {

        } else if (id == R.id.user_id) {

        } else if (id == R.id.logout) {

        } else if (id == R.id.feedback) {

        }
    }

    private void setDialogPosition() {
        Window window = getDialog().getWindow();
        window.setGravity(Gravity.BOTTOM | Gravity.LEFT);

        WindowManager.LayoutParams params = window.getAttributes();
        params.y = dpToPx(60);
        window.setAttributes(params);
    }

    private int dpToPx(int dp) {
        DisplayMetrics metrics = getActivity().getResources().getDisplayMetrics();
        return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, metrics);
    }
}

You are getting null pointer exception because you are not checking if the dialog is available or not. you can do something like:
private void setDialogPosition() { if(getDialog() != null){ Window window = getDialog().getWindow(); window.setGravity(Gravity.BOTTOM | Gravity.LEFT); WindowManager.LayoutParams params = window.getAttributes(); params.y = dpToPx(60); window.setAttributes(params); } }