下拉列表视图不在Android工作室中显示，但显示下拉图标

Question

我正在尝试开发listview下拉列表，但是，当我运行应用程序时，我只能看到工具栏，然后带有箭头的listview，但是它不显示或不显示listview选项。请帮忙。

Second.Java 公共类PlaceActivity扩展了AppCompatActivity实现         OnItemClickListener {

public ArrayList<GetterSetter> myArrayList;
private Toolbar toolbar;
private Spinner spinner;
ListView myList;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_place);

    myList = (ListView) findViewById(R.id.myList);
    toolbar = (Toolbar) findViewById(R.id.tool_bar);


    setSupportActionBar(toolbar);

    spinner= (Spinner) findViewById(R.id.action_bar_spinner);

    ArrayAdapter<CharSequence> list = ArrayAdapter.createFromResource(PlaceActivity.this, R.array.places, android.R.layout.simple_spinner_item);
    list.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

}



@Override public void onItemSelected(AdapterView<?> parent, View view,int itemPosition, long itemId) {
    dialog = ProgressDialog.show(this, "", "Please wait", true);

    new readFromGooglePlaceAPI()
            .execute("https://maps.googleapis.com/maps/api/place/nearbysearch/json?"
                    + "location=53.795984,-1.759398&radius=100000&sensor=true&"
                    + "key=APIKey0&types="
                    + places[itemPosition]);

    myList.setOnItemClickListener(this);
    return true;


}

Second.XML

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".SecondActivity" >


    <include
        layout="@layout/tool_bar"
        android:id="@+id/tool_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Spinner
        android:id="@+id/spinner_toolbar"
        android:layout_width="wrap_content"
        android:layout_height="41dp" />

    <TextView
        android:id="@+id/nodata"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="No data"
        android:textColor="#ff3b5998"
        android:textSize="18sp"
        android:layout_gravity="center"/>

    <ListView
        android:id="@+id/myList"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:dividerHeight="5dp">
    </ListView>

</LinearLayout>