public class MainActivity extends AppCompatActivity         implements AdapterView.OnItemSelectedListener { private TextView textview;     private Spinner spinner;     private List
    
      list;     private ArrayAdapter adapter;     @Override     protected void onCreate(Bundle savedInstanceState)  {
           super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         textview=(TextView) findViewById(R.id.textView);         spinner=(Spinner)findViewById(R.id.sPinner);         list=new ArrayList
     
      ();   //1.数据源         list.add("北京");         list.add("上海");         list.add("广州");         list.add("美国");  //2.适配器         adapter=new ArrayAdapter(this,android.R.layout.simple_spinner_item,list); //3.adapter设置一个下拉列表样式         adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); //4.装载适配器         spinner.setAdapter(adapter); //5.设置监听器         spinner.setOnItemSelectedListener(this);     }     @Override//监听事件     public void onItemSelected(AdapterView
       adapterView, View view, int i, long l) {
           //String name=(String) adapter.getItem(i);         String name=(String)list.get(i);        textview.setText("你选择的城市是"+name);     }     @Override     public void onNothingSelected(AdapterView
       adapterView) {
       } }