Android Volleyの導入


## はじめに
　AndroidStdudioへのVolleyの導入とVolleyを用いて、JSONパラメータ付きのリクエストを発行し、受け取ったJSONをパースすることについて説明する。

## Android Volleyの導入
[Androidプロジェクトを新規作成してVolleyが使えるようになるまで](http://kwmt27.net/index.php/2014/07/10/how-to-use-volley-library/)を参考にした。


## JSONパラメーターを付加する
まずは送信パラメータを作る。



```TopActivity.java
package me.strobo.volleytest;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;

import android.util.Log;
import java.util.Map;
import java.util.HashMap;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;


public class TopActivity extends Activity {
    public static final String LOG_TAG = "volley_test";
    private RequestQueue mQueue;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_top);
        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    .commit();
        }

        mQueue = Volley.newRequestQueue(this);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.top, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_top, container, false);
            return rootView;
        }
    }

    public void connectBtn_onClick(View view) {
        //String url = "http://weather.livedoor.com/forecast/webservice/json/v1?city=130010";
        String url = "https://strobospoon-staging.herokuapp.com/api/v0/user";

        HashMap<String, String> params = new HashMap<String, String>();
        params.put("sex", "1");
        params.put("height", "199");
        params.put("weight", "60");
        params.put("birthyear", "1919");
        params.put("activelevel", "1.5");
        JSONObject jsonParams = new JSONObject(params);

        final ProgressDialog progressDialog = new ProgressDialog(this);
        progressDialog.setMessage("Loading");
        progressDialog.show();

        JsonObjectRequest jsonObjectReq = new JsonObjectRequest(
                Request.Method.POST, url, jsonParams,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {
                        Log.d(LOG_TAG, response.toString());
                        try {
                            Log.d(LOG_TAG, "Value: " + response.getString("value"));
                            Log.d(LOG_TAG, "Status: " + response.getString("status"));
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                        progressDialog.hide();
                    }
                },

                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.d(LOG_TAG, error.toString());
                        progressDialog.hide();
                    }
                }
        );

        mQueue.add(jsonObjectReq);
    }
}
```

## その他の参考文献
- [ネットワーク通信用ライブラリVolleyを使いこなす](http://techbooster.org/android/hacks/16474/)