Android Dependent Two-Way Data Binding

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <data>
        <variable name="property" type="net.petrabarus.testandroid.dynamicdatabinding.PropertyViewModel"/>
    </data>
    <RelativeLayout
        android:id="@+id/activity_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingBottom="@dimen/activity_vertical_margin"
        android:paddingLeft="@dimen/activity_horizontal_margin"
        android:paddingRight="@dimen/activity_horizontal_margin"
        android:paddingTop="@dimen/activity_vertical_margin"
        tools:context="net.petrabarus.testandroid.dynamicdatabinding.MainActivity">

        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="17dp"
            android:id="@+id/test_layout">

            <EditText
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:inputType="textPersonName"
                android:text="@={property.title}"
                android:ems="10"
                android:id="@+id/editText"
                />

            <LinearLayout
                android:orientation="vertical"
                android:layout_width="match_parent"
                android:layout_height="377dp"
                android:id="@+id/dynamic_layout">

                <net.petrabarus.testandroid.dynamicdatabinding.ProvinceSpinner
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    app:province="@={property.province}"
                    >

                </net.petrabarus.testandroid.dynamicdatabinding.ProvinceSpinner>

                <net.petrabarus.testandroid.dynamicdatabinding.CitySpinner
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    app:province="@{property.province}"
                    app:city="@={property.city}">
                </net.petrabarus.testandroid.dynamicdatabinding.CitySpinner>
            </LinearLayout>
        </LinearLayout>

        <Button
            android:text="Button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_alignParentRight="true"
            android:layout_alignParentEnd="true"
            android:id="@+id/button"
            android:onClick="handleOnClick"
            />

    </RelativeLayout>

</layout>

CitySpinner.java

package net.petrabarus.testandroid.dynamicdatabinding;

import android.content.Context;
import android.databinding.BindingAdapter;
import android.databinding.InverseBindingAdapter;
import android.databinding.InverseBindingListener;
import android.databinding.InverseBindingMethod;
import android.databinding.InverseBindingMethods;
import android.databinding.Observable;
import android.util.AttributeSet;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

import java.util.ArrayList;
import java.util.Arrays;

@InverseBindingMethods({
        @InverseBindingMethod(type = String.class, attribute = "city"),
})
public class CitySpinner extends Spinner {

    private String province;

    private String city; //support data binding

    private ArrayList<String> entries = new ArrayList<String>();

    public CitySpinner(Context context) {
        super(context);
        init();
    }

    public CitySpinner(Context context, int mode) {
        super(context, mode);
        init();
    }

    public CitySpinner(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        loadEntries();
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
        loadEntries();
    }

    @InverseBindingAdapter(attribute = "city")
    public static String getCity(CitySpinner view) {
        view.province = view.getSelectedItem().toString();
        return view.province;
    }

    @BindingAdapter("city")
    public static void setCity(CitySpinner view, String city) {
        view.city = city;
        if (view.entries != null) {
            int selectedPosition = view.entries.indexOf(city);
            view.setSelection(selectedPosition);
        }
    }

    @BindingAdapter("cityAttrChanged")
    public static void setProvinceListener(CitySpinner view, final InverseBindingListener cityChange) {
        if (cityChange == null) {
            view.setOnItemSelectedListener(null);
        } else {
            OnItemSelectedListener listener = new OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                    cityChange.onChange();
                }

                @Override
                public void onNothingSelected(AdapterView<?> parent) {
                    cityChange.onChange();
                }
            };
            view.setOnItemSelectedListener(listener);
        }
    }

    private void loadEntries() {
        if (province == null) {
            return;
        }
        String[] entries;
        switch (province) {
            case "Jawa Barat":
                entries = new String[] {
                        "Bandung",
                        "Bogor",
                        "Bekasi"
                };
                break;
            case "DKI Jakarta":
                entries = new String[] {
                        "Jakarta Timur",
                        "Jakarta Barat",
                };
                break;
            case "Jawa Timur":
                entries = new String[] {
                        "Malang",
                        "Surabaya",
                };
                break;
            default:
                return;
        }
        this.entries = new ArrayList<String>(Arrays.asList(entries));
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                getContext(),
                android.R.layout.simple_list_item_1,
                entries
        );
        setAdapter(adapter);
    }
}

MainActivity.java

package net.petrabarus.testandroid.dynamicdatabinding;

import android.databinding.DataBindingUtil;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

import net.petrabarus.testandroid.dynamicdatabinding.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {

    private PropertyViewModel propertyViewModel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        propertyViewModel = new PropertyViewModel();
        binding.setProperty(propertyViewModel);
    }

    public void handleOnClick(View view) {
        propertyViewModel.province.set("DKI Jakarta");
        propertyViewModel.city.set("Jakarta Barat");
    }
}

PropertyViewModel.java

package net.petrabarus.testandroid.dynamicdatabinding;

import android.databinding.ObservableField;

public class PropertyViewModel {

    public ObservableField<String> title = new ObservableField<>();

    public ObservableField<String> province = new ObservableField<>();

    public ObservableField<String> city = new ObservableField<>();
}

ProvinceSpinner.java

package net.petrabarus.testandroid.dynamicdatabinding;

import android.content.Context;
import android.databinding.BindingAdapter;
import android.databinding.InverseBindingAdapter;
import android.databinding.InverseBindingListener;
import android.databinding.InverseBindingMethod;
import android.databinding.InverseBindingMethods;
import android.support.v7.widget.AppCompatSpinner;
import android.util.AttributeSet;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

import java.util.ArrayList;
import java.util.Arrays;

@InverseBindingMethods({
    @InverseBindingMethod(type = String.class, attribute = "province"),
})
public class ProvinceSpinner extends Spinner {

    private String province;

    private ArrayList<String> entries;

    public ProvinceSpinner(Context context) {
        super(context);
        init();
    }

    public ProvinceSpinner(Context context, int mode) {
        super(context, mode);
        init();
    }

    public ProvinceSpinner(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        loadEntries();
    }

    @InverseBindingAdapter(attribute = "province")
    public static String getProvince(ProvinceSpinner view) {
        view.province = view.getSelectedItem().toString();
        return view.province;
    }

    @BindingAdapter("province")
    public static void setProvince(ProvinceSpinner view, String province) {
        view.province = province;
        int selectedPosition = view.entries.indexOf(province);
        view.setSelection(selectedPosition);
    }

    @BindingAdapter("provinceAttrChanged")
    public static void setProvinceListener(ProvinceSpinner view, final InverseBindingListener provinceChange) {
        if (provinceChange == null) {
            view.setOnItemSelectedListener(null);
        } else {
            OnItemSelectedListener listener = new OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                    provinceChange.onChange();
                }

                @Override
                public void onNothingSelected(AdapterView<?> parent) {
                    provinceChange.onChange();
                }
            };
            view.setOnItemSelectedListener(listener);
        }
    }

    private void loadEntries() {
        String[] entries = new String[] {
                "Jawa Barat",
                "DKI Jakarta",
                "Jawa Timur"
        };
        this.entries = new ArrayList<String>(Arrays.asList(entries));
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                getContext(),
                android.R.layout.simple_list_item_1,
                entries
        );
        setAdapter(adapter);
    }

}