Hello, Spinner

A Spinner is a widget that allows the user to select an item from a group. It is similar to a dropdown list and will allow scrolling when the list exceeds the available vertical space on the screen.

1. Start a new project/Activity called HelloSpinner.
2. Open the layout file. Make it like so:

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
       android:orientation="vertical"
       android:padding="10dip"
       android:layout_width="fill_parent"
       android:layout_height="wrap_content">
   
       <TextView
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:layout_marginTop="10dip"
           android:text="Please select a planet:"
       />
   
       <Spinner 
           android:id="@+id/spinner"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           android:drawSelectorOnTop="true"
           android:prompt="@string/planet_prompt"
       />
   
   </LinearLayout>
   

   Notice that the Spinner's android:prompt is a string resource. In this case, Android does not allow it to be a string, it must be a reference to a resource. So...

3. Open the strings.xml file in res/values/ and add the following <string> element inside the <resources> element:

   <string name="planet_prompt">Choose a planet</string>
   

4. Create a new XML file in res/values/ called arrays.xml. Insert the following:

   <resources>
   
       <string-array name="planets">
           <item>Mercury</item>
           <item>Venus</item>
           <item>Earth</item>
           <item>Mars</item>
           <item>Jupiter</item>
           <item>Saturn</item>
           <item>Uranus</item>
           <item>Neptune</item>
       </string-array>
       
   </resources>
   

   This is the list of items (planets) that the user can select from in the Spinner widget.

5. Now open the HelloSpinner.java file. Insert the following code into the HelloSpinner class:

   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
   
       Spinner s = (Spinner) findViewById(R.id.spinner);
       ArrayAdapter adapter = ArrayAdapter.createFromResource(
               this, R.array.planets, android.R.layout.simple_spinner_item);
       adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
       s.setAdapter(adapter);
   }
   

   That's it. We start by creating a Spinner from our layout. We then create an ArrayAdapter that binds each element of our string array to a layout view—we pass createFromResource our Context, the array of selectable items and the type of layout we'd like each one bound to. We then call setDropDownViewResource() to define the type of layout in which to present the entire collection. Finally, we set this Adapter to associate with our Spinner, so the string items have a place to go.

6. Now run it.

It should look like this:

Resources

• R.layout
• ArrayAdapter
• Spinner