当 select 其他父微调器时微调器项目未设置为默认值

Question

I'm a newbie to android programming. It might be a silly question. I've made 2 spinner items. When selecting first spinner, the second spinner item view not get refreshed at the first time. But the content of second spinner shows correctly!

public class SpinnerActivity extends AppCompatActivity {
    Spinner spinner,spinner1;
    TextView textView;
    String jsonString=null;
    JSONObject jsonObject;
    ArrayList<String> countries;
    ArrayList<String> cities;
    ArrayAdapter arrayAdapter;
    ArrayAdapter arrayAdapter1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_spinner);

        textView=findViewById(R.id.textView5);
        spinner=findViewById(R.id.spinner);
        spinner1=findViewById(R.id.spinner1);

        countries=new ArrayList<>();
        cities=new ArrayList<>();

        jsonString=getStringFromJsonFile();

        arrayAdapter=getCountryFromJson();
        spinner.setAdapter(arrayAdapter);
        spinner.setPrompt("Select Country");

        arrayAdapter1=getCityFromCountry("Afghanistan");
        spinner1.setAdapter(arrayAdapter1);
        spinner1.setPrompt("Select City");

        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                arrayAdapter1=getCityFromCountry(countries.get(position));
                textView.setText(cities.get(0));
                arrayAdapter.notifyDataSetChanged();
                arrayAdapter1.notifyDataSetChanged();
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {
            }
        });

        spinner1.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                textView.setText(cities.get(position));
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });
    }

    public ArrayAdapter getCityFromCountry(String s) {

        try {
            cities.clear();
            JSONArray cityJR=jsonObject.getJSONArray(s);
            for(int i=0;i<cityJR.length();i++)
            {
                cities.add(cityJR.get(i).toString());
            }
            Collections.sort(cities);
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item, cities);
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();
        overridePendingTransition(R.anim.slide_from_left,R.anim.slide_to_right);
    }

    public String getStringFromJsonFile(){

        try {
            InputStream jsonIpStream=getApplicationContext().getAssets().open("countries.txt");
            byte[] bytes = new byte[1000];
            StringBuilder x = new StringBuilder();
            int numRead = 0;
            while ((numRead = jsonIpStream.read(bytes)) >= 0) {
                x.append(new String(bytes, 0, numRead));
            }
            return x.toString();

        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }

    public ArrayAdapter getCountryFromJson(){

        try {
            countries.clear();
            jsonObject=new JSONObject(jsonString);
            JSONArray countryJR=jsonObject.names();
            for(int i = 0; i<countryJR.length(); i++)
            {
                countries.add(countryJR.get(i).toString());
            }
            Collections.sort(countries);
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item, countries);
    }
}

Answer 1

In the below code:

spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            arrayAdapter1=getCityFromCountry(countries.get(position));
            textView.setText(cities.get(0));
            arrayAdapter.notifyDataSetChanged();
            arrayAdapter1.notifyDataSetChanged();
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {
        }
});

Replace this line

arrayAdapter1.notifyDataSetChanged();

with

spinner1.setAdapter(arrayAdapter1);