Android实现城市选择三级联动

Android实现城市选择三级联动攻略

在Android开发中，有时会需要实现城市选择功能，而且还需要支持三级联动，即选择省份后展示该省份下的市区列表，选择城市后展示该城市下的县区列表。这里提供一份Android实现城市选择三级联动的攻略。

一、搭建数据源

实现城市选择三级联动首先需要有一个完整的城市数据源，可以采用第三方库提供的数据，也可以自己搭建。以下是自己搭建数据源的示例代码：

// Province.java省份实体类
public class Province {
    public String name; // 省名称
    public List<City> cities; // 省下的城市列表

    public Province(String name, List<City> cities) {
        this.name = name;
        this.cities = cities;
    }
}

// City.java城市实体类
public class City {
    public String name; // 城市名称
    public List<County> counties; // 城市下的县区列表

    public City(String name, List<County> counties) {
        this.name = name;
        this.counties = counties;
    }
}

// County.java县区实体类
public class County {
    public String name; // 县区名称

    public County(String name) {
        this.name = name;
    }
}

// 初始化数据源
List<Province> provinceList = new ArrayList<>();
List<City> cities1 = new ArrayList<>();
cities1.add(new City("杭州", Arrays.asList(new County("滨江"), new County("拱墅"))));
cities1.add(new City("宁波", Arrays.asList(new County("海曙"), new County("江北"))));
provinceList.add(new Province("浙江", cities1));

List<City> cities2 = new ArrayList<>();
cities2.add(new City("北京", Arrays.asList(new County("东城"), new County("西城"), new County("朝阳"))));
cities2.add(new City("天津", Arrays.asList(new County("和平"), new County("河北"))));
provinceList.add(new Province("北京", cities2));

二、实现三级联动选择功能

第二步需要实现以下功能：

1. 展示省份列表

2. 选择省份后展示该省份下的城市列表

3. 选择城市后展示该城市下的县区列表

以下是示例代码：

// CityPickerActivity.java城市选择界面
public class CityPickerActivity extends AppCompatActivity {
    private List<Province> provinceList; // 省份数据源
    private String[] pArray, cArray, coArray; // 省、市、县区列表
    private int pIndex, cIndex, coIndex; // 省、市、县区选中索引

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_city_picker);
        // 初始化数据源
        provinceList = initData();
        initViews();
    }

    // 初始化数据源
    private List<Province> initData() {
        // 省、市、县区数据源初始化代码（同上述代码）
    }

    // 初始化视图
    private void initViews() {
        // 省份选择器
        final NumberPicker provincePicker = findViewById(R.id.province_picker);
        pArray = new String[provinceList.size()];
        for (int i = 0; i < provinceList.size(); i++) {
            pArray[i] = provinceList.get(i).name;
        }
        provincePicker.setMinValue(0);
        provincePicker.setMaxValue(pArray.length - 1);
        provincePicker.setDisplayedValues(pArray);
        provincePicker.setWrapSelectorWheel(false);
        provincePicker.setOnValueChangedListener((picker, oldVal, newVal) -> {
            pIndex = newVal;
            // 切换省份后更新市的数据源和界面
            cIndex = 0;
            coIndex = 0;
            CityPickerAdapter adapter = (CityPickerAdapter) cityPicker.getAdapter();
            adapter.update(provinceList.get(pIndex).cities);
            countyPicker.setAdapter(new CountyPickerAdapter(provinceList.get(pIndex).cities.get(0).counties));
        });

        // 城市选择器
        final NumberPicker cityPicker = findViewById(R.id.city_picker);
        String[] cArray = new String[provinceList.get(0).cities.size()];
        for (int i = 0; i < provinceList.get(0).cities.size(); i++) {
            cArray[i] = provinceList.get(0).cities.get(i).name;
        }
        cityPicker.setMinValue(0);
        cityPicker.setMaxValue(cArray.length - 1);
        cityPicker.setDisplayedValues(cArray);
        cityPicker.setWrapSelectorWheel(false);
        cityPicker.setOnValueChangedListener((picker, oldVal, newVal) -> {
            cIndex = newVal;
            // 切换城市后更新县区的数据源和界面
            coIndex = 0;
            CountyPickerAdapter adapter = (CountyPickerAdapter) countyPicker.getAdapter();
            adapter.update(provinceList.get(pIndex).cities.get(cIndex).counties);
        });

        // 县区选择器
        final NumberPicker countyPicker = findViewById(R.id.county_picker);
        String[] coArray = new String[provinceList.get(0).cities.get(0).counties.size()];
        for (int i = 0; i < provinceList.get(0).cities.get(0).counties.size(); i++) {
            coArray[i] = provinceList.get(0).cities.get(0).counties.get(i).name;
        }
        countyPicker.setMinValue(0);
        countyPicker.setMaxValue(coArray.length - 1);
        countyPicker.setDisplayedValues(coArray);
        countyPicker.setWrapSelectorWheel(false);
        countyPicker.setOnValueChangedListener((picker, oldVal, newVal) -> {
            coIndex = newVal;
        });
}

以上代码是以NumberPicker为例，其他控件选择方式类似。

三、获取选择结果

最后一步需要获取选择的结果，可能需要使用SharedPreferences、回调函数等方法返回结果，这里只提供SharedPreferences存储选择结果的示例代码：

// 选择结果存储方法
private void storeResult() {
    SharedPreferences sp = getSharedPreferences("city", MODE_PRIVATE);
    SharedPreferences.Editor editor = sp.edit();
    editor.putString("province", pArray[pIndex]);
    editor.putString("city", cArray[cIndex]);
    editor.putString("county", coArray[coIndex]);
    editor.apply();
}

// 获取选择结果方法
private String getResult() {
    SharedPreferences sp = getSharedPreferences("city", MODE_PRIVATE);
    String province = sp.getString("province", "");
    String city = sp.getString("city", "");
    String county = sp.getString("county", "");
    return province + " - " + city + " - " + county;
}

以上就是Android实现城市选择三级联动的攻略，通过自己搭建数据源并使用NumberPicker作为选择控件，最后可以通过SharedPreferences存储选择结果。