On Android, how do I populating spinner value depending on the value of edit text

Question

I have a page that has layout like the following:

<EditText android:id="@+id/code"
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:layout_below="@id/manualTitle"
          android:inputType="number|phone"
          android:maxLength="20"
          android:singleLine="true"/>

<Spinner android:id="@+id/companySpinner"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:layout_below="@id/code"
         android:visibility="gone"/>

<Button
    android:id="@+id/returnButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/code"
    android:layout_alignParentRight="true"
    android:layout_marginTop="5sp"
    android:layout_marginLeft="8sp"
    android:text="@string/button_goback"/>


<Button
    android:id="@+id/saveButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_toLeftOf="@id/returnButton"
    android:layout_alignBaseline="@id/returnButton"
    android:text="@string/button_save"/>

Initially the spinner's visibility is gone. First I want to make it visible if users input numbers(0 - 9) to the EditText. Secondly I would like to populate the spinner with values depending on the length of value that users typed into the EditText.

How should I do that? I tried setting an onKey listener for the EditText, but did not achieve the result I want. Am I doing that right? Or should I try listeners other than that?

Any hint or clue or direction is appreciated. Thanks in advance.