spinner中的onNothingSelected方法到底什么时候调用?

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:

spinner中的onNothingSelected方法到底什么时候调用?

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