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：
