如何在具有动态下拉菜单的 Android 中制作表格

Question

I am very new to android and I am making a form in android. I want this form to have 2 drop down list. In first drop down user has to select the state and the second drop down should show cities of that state only from which user can select any city/district.

Answer 1

What you are mentioning dropdown here in android we called it spinner.There is default spinner in android and also you have the option to customize your spinner Here is the official documentation by google how you can use it

https://developer.android.com/guide/topics/ui/controls/spinner

Answer 2

[1]. After selecting item of your country dropdown like

spinner_country.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                if(i>0)
                {
                   //Load your spinner of state and call your data regarding country
                }
            }

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

            }
        });

Answer 3

First you need to create 2 different model like below:

Create City and State data model like below:

public class State{
    private int id;
    private String name;

    public State(int id, String name){
       this.id=id;
       this.name=name;
    }

    public int getId(){
       return id;
    }

    public void setId(int id){
       this.id= id;
    }
    public String getName(){
       return name;
    }

    public void setName(String name){
       this.name=name;
    }

}


public class City{
    private int id;
    private String name;
    private int stateId;

    public State(int id, String name, int stateId){
       this.id=id;
       this.name=name;
       this.stateId=stateId;
    }

    public int getId(){
       return id;
    }

    public void setId(int id){
       this.id= id;
    }
    public String getName(){
       return name;
    }

    public void setName(String name){
       this.name=name;
    }

    public int getStateId(){
       return stateId;
    }

    public void setStateId(int id){
       this.stateId= id;
    }

}

Now you need to create Custom Spinner adapter for State:

public class StateSpinnerAdapter extends ArrayAdapter<State> {

    public StateSpinnerAdapter (Context context, ArrayList<State> dataList) {
        super(context, 0, dataList);
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        return initView(position, convertView, parent);
    }

    @Override
    public View getDropDownView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        return initView(position, convertView, parent);
    }

    private View initView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(getContext()).inflate(
                    R.layout.spinner_row, parent, false
            );
        }
        TextView textViewName = convertView.findViewById(R.id.tv_name);
        District currentItem = getItem(position);
        if (currentItem != null) {
            textViewName.setText(currentItem.getName());
        }
        return convertView;
    }
}

Now you need to make CitySpinnerAdapter like below:

public class CitySpinnerAdapter extends ArrayAdapter<City> {

    public CitySpinnerAdapter (Context context, ArrayList<City> dataList) {
        super(context, 0, dataList);
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        return initView(position, convertView, parent);
    }

    @Override
    public View getDropDownView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        return initView(position, convertView, parent);
    }

    private View initView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(getContext()).inflate(
                    R.layout.spinner_row, parent, false
            );
        }
        TextView textViewName = convertView.findViewById(R.id.tv_name);
        Upazila currentItem = getItem(position);
        if (currentItem != null) {
            textViewName.setText(currentItem.getName());
        }
        return convertView;
    }
}

Now MainActivity should be like this:

public class MainActivity extends AppCompatActivity{

    private Context mContext;
    private Activity mActivity;
    private ArrayList<State> states;
    private ArrayList<City> cities;

    private StateSpinnerAdapter stateAdapter;
    private CitySpinnerAdapter cityAdapter;

   private Spinner spState, spCity;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initVariable();
        initView();
        initListener();
    }

    private void initVariable() {
        mContext = getApplicationContext();
        mActivity = MainActivity.this;


        states = new ArrayList<>();
        cities = new ArrayList<>();
    }
    private void initView() {
        setContentView(R.layout.activity_main);
        spState = findViewById(R.id.spState);
        spCity = findViewById(R.id.cityState);

        stateAdapter = new StateSpinnerAdapter(mContext,states);
        spState.setAdapter(stateAdapter);

        cityAdapter = new CitySpinnerAdapter(mContext,cities);
        spCity.setAdapter(cityAdapter);

        loadStateData();

    }

    private void initListener(){
        spState.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                loadCityData(states.get(i).getId());
            }

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

            }
        });


    }

    private void loadStateData(){
       states.add(new State(1,"state 1"));
       states.add(new State(2,"state 1"));
       states.add(new State(3,"state 1"));
       states.add(new State(4,"state 1"));
       stateAdapter.notifyDataSetChanged();

    }

    private loadCityData(int stateId){
       ArrayList<City> cityList= new ArrayList<>();
       cityList.add(new City(1,"City 1", 1));
       cityList.add(new City(2,"City 2", 1));
       cityList.add(new City(3,"City 3", 2));
       cityList.add(new City(4,"City 4", 2));
       cityList.add(new City(5,"City 5", 3));
       cityList.add(new City(6,"City 6", 3));
       cityList.add(new City(7,"City 7", 4));
       cityList.add(new City(8,"City 8", 4));

       cities.addAll(cityList.stream().filter(city -> city.getStateId == stateId).collect(Collectors.toList()));
       cityAdapter.notifyDataSetChanged();

    }

}