Error while creating custom dialog

Question

I am trying to create a custom dialog box with two spinners ( spinner_month and spinner_year ).

For guidance, I took the sample provided in Google dev guide.

MainActivity code:

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setView(R.layout.calender_view);
AlertDialog alertDialog = builder.create();
Spinner spinner = (Spinner) alertDialog.findViewById(R.id.spinner_month);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,R.array.months_array,     android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);

My calender_view.xml is as follows

<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:id="@+id/layout_category"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_weight="1"
          android:orientation="horizontal"
          android:padding="5dp">

    <Spinner
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/spinner_year"
        android:layout_weight="1"/>

    <Spinner
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/spinner_month"
        android:layout_weight="1"
        android:spinnerMode="dialog"/>
</LinearLayout>

When I run it I get the following error:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method void android.widget.Spinner.setAdapter(android.widget.SpinnerAdapter) on a null object reference

This is because the 'spinner' object is null , but I'm not sure why. Is there something I am missing?

Answer 1

Try this one

    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    LayoutInflater li = LayoutInflater.from(this);
    View view = li.inflate(R.layout.calender_view, null, false);
    builder.setView(view);
    AlertDialog alertDialog = builder.create();

    Spinner spinner = (Spinner) view.findViewById(R.id.spinner_month);
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,R.array.months_array,     android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);