Android程式:下拉菜單的實作（Spinner和OnItemSelectedListener）

實作的效果：

MainActivity：

public class MainActivity extends Activity implements OnItemSelectedListener {

    private TextView textView;
    private Spinner spinner;
    private List<String>list;
    private ArrayAdapter<String>adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        textView = (TextView) findViewById(R.id.textView);
        spinner=(Spinner) findViewById(R.id.spinner);

        //1.設定資料源(使用List)
        list=new ArrayList<String>();
        list.add("北京");
        list.add("上海");
        list.add("廣州");
        list.add("深圳");

        //2.建立數組擴充卡（ArrayAdatper），simple_spinner_item這個是未下拉的樣式
        adapter=new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, list);

        //3.adapter設定一個下拉清單（菜單）樣式
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        //4.spinner加載擴充卡
        spinner.setAdapter(adapter);

        //5.設定點選事件
        spinner.setOnItemSelectedListener(this);


    }
    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position,
            long id) {
        //将選擇的城市顯示在textview中
        textView.setText("你選擇了："+list.get(position));
        //也可以用adapter.getItem(position),效果是一樣的
    }
    @Override
    public void onNothingSelected(AdapterView<?> parent) {

    }

}
           

main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textColor="#ff0000"
        android:textSize="20sp" />

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>