Expandablelist comes hidden initially

Question

Every time I start Activity with Expandablelist comes hidden, then I have to press the off button and turn it on so it shows.

How do I fix it?

my Expandablelist

<ExpandableListView
        android:id="@+id/lvExp"
        android:layout_width="match_parent"
        android:layout_height="450dp"
        android:layout_weight="1"/>

EDITION

All of my Layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorCorpo"
    android:orientation="vertical"
    tools:context="ham.org.br.nutricao.activity.CardapioActivity">

    <include
        android:id="@+id/toolbarCardapio"
        layout="@layout/toolbar" />
    <ExpandableListView
        android:id="@+id/lvExp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        />

    <Button
        android:id="@+id/btn_acao"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Button" />


</LinearLayout>

Activity

protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.cardapio_activity);
     expListView = ( ExpandableListView ) findViewById( R.id.lvExp );
     toolbar = (Toolbar) findViewById( R.id.toolbarCardapio );
     toolbar.setTitle( "Cardápio" );
     setSupportActionBar( toolbar );

     listAdapter = new ExpandableListAdapter( this, listGrupo, listaItem );
     //setando list adapter
     expListView.setAdapter( listAdapter );
     int idTipoRef = bundle.getInt( "tipo" );
     String data   = bundle.getString( "data" );
     chamarTipoPratos( service, idTipoRef, data );

}

private void chamarTipoPratos( Service service, int idTipoRef, String data ){
        listGrupo = new ArrayList<String>();
        listaItem = new HashMap<String, List<String>>();
        listIngredientes = new HashMap<String, String>();
        listIngrediente = new ArrayList<String>();
        final Call<List<TipoPrato>> listTipoPratos = service.getlistTipoPratos("R", idTipoRef, data);
        listTipoPratos.enqueue( new Callback<List<TipoPrato>>() {
            @Override
            public void onResponse(Call<List<TipoPrato>> call, Response<List<TipoPrato>> response) {
           //     Log.i("onResponse TipoPratos",response.toString());

                if( response.isSuccessful() ){
                    List<TipoPrato> tipoPratos = response.body();
                    int i = 0;
                    for( TipoPrato tipoPrato : tipoPratos ){

                        //Log.i("Tipo", tipoPrato.getTipoprato());
                        ArrayList<Prato> listaPratos = tipoPrato.getPratoList();

                        listGrupo.add(tipoPrato.getTipoprato());
                        ArrayList<String> pratos = new ArrayList<String>();
                        ArrayList<String> ingredientes = new ArrayList<String>();

                        for ( Prato prato : listaPratos ){
                       //     Log.i("Pratos", prato.getPrato());
                            pratos.add( prato.getPrato() );
                            ingredientes.add( prato.getIngrediente() );
                            listIngredientes.put( prato.getPrato(), prato.getIngrediente() );
                        }

                        listaItem.put( listGrupo.get( i ), pratos );

                        i++;

                }

            }
            }

            @Override
            public void onFailure(Call<List<TipoPrato>> call, Throwable t) {
                Log.i("onFailure TipoPrato", t.getMessage());
            }
        });
    }

Answer 1

I saw three options that might be making this happen, probably the visibility of the parent layout is like Gone or Invisible, may have some layout over the View,or the initialization of Expandablelistview or the parent layout within Activity or Fragment, is being Gone or Invisible.