Java 如何在Android中创建一个具有动态下拉列表的表单
我对android非常陌生,我正在用android制作一个表单。我希望此表单有2个下拉列表。在第一个下拉列表中,用户必须选择州,第二个下拉列表应显示该州的城市,用户只能从中选择任何城市/地区。您在android中提到的下拉列表我们称之为微调器。android中有默认微调器,您也可以选择自定义微调器 这是谷歌的官方文档,你可以如何使用它Java 如何在Android中创建一个具有动态下拉列表的表单,java,android,ajax,database,forms,Java,Android,Ajax,Database,Forms,我对android非常陌生,我正在用android制作一个表单。我希望此表单有2个下拉列表。在第一个下拉列表中,用户必须选择州,第二个下拉列表应显示该州的城市,用户只能从中选择任何城市/地区。您在android中提到的下拉列表我们称之为微调器。android中有默认微调器,您也可以选择自定义微调器 这是谷歌的官方文档,你可以如何使用它 [1]。选择您所在国家/地区的项目后,如 spinner_country.setOnItemSelectedListener(new AdapterView.On
[1]。选择您所在国家/地区的项目后,如
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) {
}
});
spinner\u country.setOnItemSelectedListener(新的AdapterView.OnItemSelectedListener(){
@凌驾
已选择公共视图(AdapterView AdapterView、View视图、int i、long l){
如果(i>0)
{
//加载州微调器并调用有关国家/地区的数据
}
}
@凌驾
未选择公共无效(AdapterView AdapterView){
}
});
首先,您需要创建两个不同的模型,如下所示:
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;
}
}
创建城市和州数据模型,如下所示:
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;
}
}
现在需要为状态创建自定义微调器适配器:
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;
}
}
公共类StateSpinnerAdapter扩展了ArrayAdapter{
public StateSpinnerAdapter(上下文上下文,ArrayList数据列表){
super(上下文,0,数据列表);
}
@非空
@凌驾
公共视图getView(int位置,@Nullable视图convertView,@NonNull视图组父级){
返回初始视图(位置、转换视图、父级);
}
@凌驾
公共视图getDropDownView(int位置,@Nullable视图convertView,@NonNull视图组父级){
返回初始视图(位置、转换视图、父级);
}
私有视图initView(int位置、视图转换视图、视图组父视图){
if(convertView==null){
convertView=LayoutFlater.from(getContext())。充气(
R.layout.spinner\u行,父级,false
);
}
TextView textViewName=convertView.findViewById(R.id.tv\u名称);
地区currentItem=getItem(位置);
如果(currentItem!=null){
textViewName.setText(currentItem.getName());
}
返回视图;
}
}
现在,您需要制作CitySpinnerAdapter,如下所示:
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;
}
}
公共类CitySpinnerAdapter扩展了ArrayAdapter{
公共城市PinnerAdapter(上下文上下文,ArrayList数据列表){
super(上下文,0,数据列表);
}
@非空
@凌驾
公共视图getView(int位置,@Nullable视图convertView,@NonNull视图组父级){
返回初始视图(位置、转换视图、父级);
}
@凌驾
公共视图getDropDownView(int位置,@Nullable视图convertView,@NonNull视图组父级){
返回初始视图(位置、转换视图、父级);
}
私有视图initView(int位置、视图转换视图、视图组父视图){
if(convertView==null){
convertView=LayoutFlater.from(getContext())。充气(
R.layout.spinner\u行,父级,false
);
}
TextView textViewName=convertView.findViewById(R.id.tv\u名称);
Upazila currentItem=getItem(位置);
如果(currentItem!=null){
textViewName.setText(currentItem.getName());
}
返回视图;
}
}
现在主要活动应该是这样的:
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();
}
}
public类MainActivity扩展了AppCompatActivity{
私有上下文;
私人活动能力;
私营ArrayList州;
私人集市;
私有状态适配器stateAdapter;
私人城市公寓;城市公寓;
spState私人纺纱厂,spCity;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
initVariable();
initView();
initListener();
}
私有void initVariable(){
mContext=getApplicationContext();
mActivity=MainActivity.this;
states=新的ArrayList();
城市=新阵列列表();
}
私有void initView(){
setContentView(R.layout.activity_main);
spState=findviewbyd(R.id.spState);
spCity=findviewbyd(R.id.cityState);
stateAdapter=新的StateSpinnerAdapter(mContext,states);
setAdapter(stateAdapter);
cityAdapter=新的CitySpinnerAdapter(mContext,城市);
setAdapter(cityAdapter);
loadStateData();
}
私有void initListener(){
spState.setOnItemSelectedListener(新的AdapterView.OnItemSelectedListener(){
@凌驾
已选择公共视图(AdapterView AdapterView、View视图、int i、long l){
loadCityData(states.get(i.getId());
}
@凌驾
未选择公共无效(AdapterView AdapterView){
}
});
}
私有void loadStateData(){
添加(新的州(1,“州1”);
添加(新的州(2,“州1”);
添加(新的州(3,“州1”);
添加(新的州(4,“州1”);
stateAdapter.notifyDataSetChanged();
}
专用loadCityData(int stateId){
ArrayList cityList=新的ArrayList();
添加(新城市(1,“城市1”,1));
城市列表。添加(新城市(2,“城市2”,1));
城市列表。添加(新城市(3,“城市3”,2));
城市列表。添加(新城市(4,“城市4”,2));
城市列表。添加(新城市(5,“城市5”,3));
城市列表。添加(新城市(6,“城市6”,3));
城市列表。添加(新城市(7,“城市7”,4));
城市列表。添加(新城市(8,“城市8”,4));
cities.addAll(cityList.stream().filter(city->city.getStateId==stateId).collect(Collectors.toList());
cityAdapter.notifyDataSetChanged();
}
}
您如何识别它是动态的还是非动态的?我的意思是您可以使用任何da