1page.title=Spinners 2page.tags="adapterview","spinneradapter" 3@jd:body 4 5<div id="qv-wrapper"> 6<div id="qv"> 7 8<h2>In this document</h2> 9<ol> 10 <li><a href="#Populate">Populate the Spinner with User Choices</a></li> 11 <li><a href="#SelectListener">Responding to User Selections</a></li> 12</ol> 13<h2>Key classes</h2> 14<ol> 15 <li>{@link android.widget.Spinner}</li> 16 <li>{@link android.widget.SpinnerAdapter}</li> 17 <li>{@link android.widget.AdapterView.OnItemSelectedListener}</li> 18</ol> 19 20</div> 21</div> 22 23<p>Spinners provide a quick way to select one value from a set. In the default state, a spinner 24shows its currently selected value. Touching the spinner displays a dropdown menu with all other 25available values, from which the user can select a new one.</p> 26 27<img src="{@docRoot}images/ui/spinner.png" alt="" /> 28 29<p>You can add a spinner to your layout with the {@link android.widget.Spinner} object. You 30should usually do so in your XML layout with a {@code <Spinner>} element. For example:</p> 31 32<pre> 33<Spinner 34 android:id="@+id/planets_spinner" 35 android:layout_width="fill_parent" 36 android:layout_height="wrap_content" /> 37</pre> 38 39<p>To populate the spinner with a list of choices, you then need to specify a {@link 40android.widget.SpinnerAdapter} in your {@link android.app.Activity} or {@link android.app.Fragment} 41source code.</p> 42 43<h2 id="Populate">Populate the Spinner with User Choices</h2> 44 45<p>The choices you provide for the spinner can come from any source, but must be provided through 46an {@link android.widget.SpinnerAdapter}, such as an {@link android.widget.ArrayAdapter} if the 47choices are available in an array or a {@link android.widget.CursorAdapter} if the choices are 48available from a database query.</p> 49 50<p>For instance, if the available choices for your spinner are pre-determined, you can provide 51them with a string array defined in a <a 52href="{@docRoot}guide/topics/resources/string-resource.html">string 53resource file</a>:</p> 54 55<pre> 56<?xml version="1.0" encoding="utf-8"?> 57<resources> 58 <string-array name="planets_array"> 59 <item>Mercury</item> 60 <item>Venus</item> 61 <item>Earth</item> 62 <item>Mars</item> 63 <item>Jupiter</item> 64 <item>Saturn</item> 65 <item>Uranus</item> 66 <item>Neptune</item> 67 </string-array> 68</resources> 69</pre> 70 71 <p>With an array such as this one, you can use the following code in your {@link 72android.app.Activity} or {@link android.app.Fragment} to supply the spinner with the array using 73an instance of {@link android.widget.ArrayAdapter}: 74 75<pre> 76Spinner spinner = (Spinner) findViewById(R.id.spinner); 77// Create an ArrayAdapter using the string array and a default spinner layout 78ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, 79 R.array.planets_array, android.R.layout.simple_spinner_item); 80// Specify the layout to use when the list of choices appears 81adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 82// Apply the adapter to the spinner 83spinner.setAdapter(adapter); 84</pre> 85 86<p>The {@link 87android.widget.ArrayAdapter#createFromResource(Context,int,int) createFromResource()} method allows 88you to create an {@link android.widget.ArrayAdapter} from the string array. The third argument for 89this method is a layout resource that defines how the selected choice appears in the 90spinner control. The {@link android.R.layout#simple_spinner_item} layout is provided by the 91platform and is the default layout you should use unless you'd like to define your own layout 92for the spinner's appearance.</p> 93 94<p>You should then call {@link android.widget.ArrayAdapter#setDropDownViewResource(int)} to specify 95the layout the adapter should use to display the list of spinner choices ({@link 96android.R.layout#simple_spinner_dropdown_item} is another standard layout defined by the 97platform).</p> 98 99<p>Call {@link android.widget.AdapterView#setAdapter setAdapter()} to apply the adapter to your 100{@link android.widget.Spinner}.</p> 101 102 103<h2 id="SelectListener">Responding to User Selections</h2> 104 105<p>When the user selects an item from the drop-down, the {@link android.widget.Spinner} object 106receives an on-item-selected event.</p> 107 108<p>To define the selection event handler for a spinner, implement the {@link 109android.widget.AdapterView.OnItemSelectedListener} interface and the corresponding {@link 110android.widget.AdapterView.OnItemSelectedListener#onItemSelected onItemSelected()} callback method. 111For example, here's an implementation of the interface in an {@link android.app.Activity}:</p> 112 113<pre> 114public class SpinnerActivity extends Activity implements OnItemSelectedListener { 115 ... 116 117 public void onItemSelected(AdapterView<?> parent, View view, 118 int pos, long id) { 119 // An item was selected. You can retrieve the selected item using 120 // parent.getItemAtPosition(pos) 121 } 122 123 public void onNothingSelected(AdapterView<?> parent) { 124 // Another interface callback 125 } 126} 127</pre> 128 129<p>The {@link android.widget.AdapterView.OnItemSelectedListener} requires the {@link 130android.widget.AdapterView.OnItemSelectedListener#onItemSelected(AdapterView,View,int,long) 131onItemSelected()} and {@link 132android.widget.AdapterView.OnItemSelectedListener#onNothingSelected(AdapterView) 133onNothingSelected()} callback methods.</p> 134 135<p>Then you need to specify the interface implementation by calling {@link 136android.widget.AdapterView#setOnItemSelectedListener setOnItemSelectedListener()}:</p> 137 138<pre> 139Spinner spinner = (Spinner) findViewById(R.id.spinner); 140spinner.setOnItemSelectedListener(this); 141</pre> 142 143<p>If you implement the {@link 144android.widget.AdapterView.OnItemSelectedListener} interface with your {@link 145android.app.Activity} or {@link android.app.Fragment} (such as in the example above), you can pass 146<code>this</code> as the interface instance.</p>
