I create a class extends DialogFragment class, my code is as below, my problem is the dialog hides under status bar(in the system) and the toolbar(in the activity), I refer the question here  DialogFragment not floating, acts embeded or as another fragment add  the onCreate function and set the style, but the dialog still only hides under toolbar, not as the tutorial said it will float on the activity window.
public class PasswordDialog extends DialogFragment {
......
public static PasswordDialog newInstance(PdfFragment pdfFragment) {
    Log.i(sClassTag,"newInstance in PdfFragmentPasswordDialog");
    PdfFragmentPasswordDialog passwordDialog = new PdfFragmentPasswordDialog();
    passwordDialog.mPdfFragment = pdfFragment;
    setInteractionListener(pdfFragment);
    return passwordDialog;
}
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Pick a style based on the num.
    int style = DialogFragment.STYLE_NORMAL, theme = 0;
    setStyle(style, theme);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    Log.i(sClassTag,"onCreateView in PdfFragmentPasswordDialog");
    // Inflate the layout to use as dialog or embedded fragment
    mView = inflater.inflate(R.layout.layout_password, container, false);
    addButtonListener();
    addEdittextListener();
    return mView;
}
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    Log.i(sClassTag,"onCreateView in onCreateDialog");
    Dialog dialog = super.onCreateDialog(savedInstanceState);
    dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
    return dialog;
}
void showPasswordDialog(boolean isFirstTime) {
....
 FragmentManager fragmentManager = getActivity().getFragmentManager();
 show(fragmentManager, "dialog");
 ...
}
The layout file is
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ImageView
    android:layout_width="48dp"
    android:layout_height="48dp"
    android:src="@drawable/ic_img_passwordkey_48"
    android:id="@+id/key_icon"
    android:layout_gravity="center_horizontal"
    android:layout_marginTop="20dp"
    android:contentDescription="@string/password_input_hint_message"/>
<Space
    android:layout_width="match_parent"
    android:layout_height="16dp" />
<EditText
    android:imeOptions="flagNoExtractUi"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="textPassword"
    android:textColorHint="@color/password_dialogUI_hint_text_color"
    android:textColor="@color/password_dialogUI_text_color"
    android:textSize="12sp"
    android:hint="@string/password_input_hint_message"
    android:ems="10"
    android:id="@+id/dialogUI_edit_text"
    android:textCursorDrawable="@null"
    android:fontFamily="sans-serif"
    android:layout_marginStart="8dp"
    android:layout_marginEnd="8dp"
    android:textDirection="locale"/>
<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="@string/password_error_warning_message"
    android:textColor="@color/password_dialogUI_warning_color"
    android:id="@+id/dialogUI_warning_text"
    android:textSize="12sp"
    android:visibility="invisible"
    android:fontFamily="sans-serif"
    android:paddingStart="4dp"
    android:paddingEnd="4dp"
    android:layout_marginStart="8dp"/>
<Space
    android:layout_width="match_parent"
    android:layout_height="8dp" />
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="8dp">
<Button
    android:text="@string/password_ok_button"
    android:textColor="@drawable/layout_disable_text_color"
    android:minWidth="64dp"
    android:layout_width="wrap_content"
    android:layout_height="36dp"
    android:id="@+id/password_dialogUI_ok_button"
    android:layout_alignParentEnd="true"
    style="?android:attr/borderlessButtonStyle"
    android:background="@drawable/layout_password_button_background"
    android:layout_marginEnd="8dp"/>
<Button
    android:text="@string/password_cancel_button"
    android:textColor="@drawable/layout_disable_text_color"
    android:minWidth="64dp"
    android:layout_width="wrap_content"
    android:layout_height="36dp"
    android:id="@+id/password_dialogUI_cancel_button"
    style="?android:attr/borderlessButtonStyle"
    android:layout_toStartOf="@+id/password_dialogUI_ok_button"
    android:background="@drawable/layout_password_button_background"
    android:layout_marginEnd="8dp"/>
 
     
     
    