这个东东大家在开发中可能不太能用到，所以总是容易被忽略，由于工作原因，我最近琢磨了一下onNothingSelected方法的调用时机问题，其实很简单，只要我们稍微看一下源码就明白了：

        /**

         * Callback method to be invoked when the selection disappears from this

         * view. The selection can disappear for instance when touch is activated

         * or when the adapter becomes empty.

         *

         * @param parent The AdapterView that now contains no selected item.

         */

        void onNothingSelected(AdapterView<?> parent);

源码里边说的很明白了，当我们的adapter为空的时候就会调用到这个方法，那么我做了一个小Demo，来测试一下这个效果，核心代码如下：

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.activity_main);

		initData();

		provinces = (Spinner) this.findViewById(R.id.provinces);

		adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item,

				data);

		provinces.setAdapter(adapter);

		provinces.setOnItemSelectedListener(new OnItemSelectedListener() {

			@Override

			public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

				Log.d("qianfeng", "您选择了" + data.get(position));

			}

			@Override

			public void onNothingSelected(AdapterView<?> parent) {

				Log.d("qianfeng", "NothingSelected");

			}

		});

	}

	/**

	 * 点击button时，将集合中的数据全部移除，同时调用adapter的notifyDataSetChanged方法

	 * @param view

	 */

	public void btnClick(View view){

		data.removeAll(data);

		adapter.notifyDataSetChanged();

	}

	private void initData() {

		data = new ArrayList<String>();

		data.add("山东");

		data.add("广西");

		data.add("陕西");

		data.add("广东");

	}

我们来看一下运行效果：