相关疑难解决方法(0)

以英语为母语的人,所以我要对你们的英语技能不好抱歉.

我从5周前开始学习Android.我试图实现一个微调器,我的导师问为什么需要onNothingSelected方法.我无话可说.

那么,为什么我需要那种方法？你能回复吗？

以下代码是我的微调器.它正确地做了我想要的.

public class SpinnerViewPractice extends Activity {
private Spinner spinner;
private String spinner_value = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.spinnerviewpractice);

    spinner = (Spinner)findViewById(R.id.spinner1);

    String[] str = {"","good", "dislike", "like", "hate", "moderate"};
    spinner.setPrompt("Set Text");
    ArrayAdapter<String> list = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, str); 
    spinner.setAdapter(list);
    spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

        @Override
        public void onItemSelected(AdapterView<?> arg0, View arg1,
                int arg2, long arg3) {
            TextView tv = (TextView)arg1;
            spinner_value = tv.getText().toString();
            if(spinner_value.length() == 0)
            {
                spinner_value = "Nothing";                  
            }
            Toast.makeText(SpinnerViewPractice.this, spinner_value, …