1.導入Gson與okhttp

dependencies {
    implementation "com.squareup.okhttp3:okhttp:4.3.1"
    implementation "com.google.code.gson:gson:2.8.6"
}

2.程式碼

public class MainActivity extends AppCompatActivity {

private List<String> cities;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    AutoCompleteTextView textView = findViewById(R.id.multiAutoCompleteTextView);
    cities = new ArrayList<>();
    ArrayAdapter<String> arrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_activated_1, cities);
    textView.setAdapter(arrayAdapter);

    Request request = new Request.Builder()
            .url("https://api.myjson.com/bins/130mpi")
            .build();

    new OkHttpClient().newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(@NotNull Call call, @NotNull IOException e) {

        }

        @Override
        public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {
            String json = response.body().string();
            Gson gson = new Gson();
            List<CityModel> cityModel = gson.fromJson(json, new TypeToken<List<CityModel>>(){}.getType());

            for (CityModel model : cityModel) {
                //取得縣市
                String cityName = model.getCityName();
                for (AreaModel areaModel : model.getAreaList()) {
                    //取得區域
                    String areaName = areaModel.getAreaName();
                    //合成縣市與區域
                    String cityData = cityName + areaName;
                    cities.add(cityData);
                }
            }
        }
    });
}
}