[Android] 透過Volley發送HTTP Request(使用政府公開資料-臺北捷運資訊)

目前各縣市政府都有提供許多各式各樣的公開資料，那要如何在App上，得到這些資料呢? 

原理與網頁相似，發送Request並接收Response，Android提供了許多方法，像是HttpURLConnection、Volley等，這邊我使用Volley，可以省去一些繁瑣的撰寫，公開資料我使用了臺北市政府資料開放平台-台北捷運列車到站站名，可以得知目前列車進站的站名、該列車終點站更新時間等資訊。

完成圖↓

一樣拿之前專案來繼續實作，要使用Volley我們需要在build.gradle中增加

dependencies {
    ...
    compile 'com.android.volley:volley:1.0.0'
}

修改我們之前RecyclerView放資料的容器「recycler_textview.xml」，改為「recycler_metroinfo.xml」，並新增多個TextView，用來顯示資訊。

recycler_metroinfo.xml

	<?xml version="1.0" encoding="utf-8"?>
	<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:card_view="http://schemas.android.com/apk/res-auto"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_gravity="center"
	android:layout_margin="8dp"
	card_view:cardBackgroundColor="@color/colorAccent"
	card_view:cardCornerRadius="4dp">
	<LinearLayout
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:orientation="vertical"
	android:layout_marginTop="5dp"
	android:layout_marginBottom="5dp"
	android:layout_marginLeft="5dp">
	<LinearLayout
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:orientation="horizontal">
	<TextView
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:text="@string/station"
	android:textColor="@color/white"/>
	<TextView xmlns:android="http://schemas.android.com/apk/res/android"
	android:id="@+id/tvStation"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:layout_gravity="left"
	android:textColor="@color/white" />
	</LinearLayout>
	<LinearLayout
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:orientation="horizontal">
	<TextView
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:text="@string/destination"
	android:textColor="@color/white"/>
	<TextView xmlns:android="http://schemas.android.com/apk/res/android"
	android:id="@+id/tvDestination"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:layout_gravity="left"
	android:textColor="@color/white" />
	</LinearLayout>
	<LinearLayout
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:orientation="horizontal">
	<TextView
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:text="@string/update_time"
	android:textColor="@color/white"/>
	<TextView xmlns:android="http://schemas.android.com/apk/res/android"
	android:id="@+id/tvTime"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:layout_gravity="left"
	android:textColor="@color/white" />
	</LinearLayout>
	</LinearLayout>
	</android.support.v7.widget.CardView>

view raw recycler_metroinfo.xml hosted with ❤ by GitHub

修改「fragmentlist_one.xml」，新增一個ProgressBar，當在請求資料時，有一個loaing圖示，當資料處理完畢，再將資料RecyclerView顯現出來。

fragmentlist_one.xml

	<?xml version="1.0" encoding="utf-8"?>
	<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="horizontal" android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:background="@color/white"
	android:gravity="center">
	<ProgressBar
	style="?android:attr/progressBarStyle"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:id="@+id/progressBar"
	android:layout_gravity="center_vertical" />
	<android.support.v7.widget.RecyclerView
	android:id="@+id/recyclerView"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:clipToPadding="false"
	android:visibility="gone"/>
	</LinearLayout>

view raw fragmentlist_one.xml hosted with ❤ by GitHub

再來修改FragmentList_One.java，使用Volley來獲取臺北捷運列車到站資訊。

FragmentList_One.java

	package com.example.solinari.GetTaipeiMetroInfo;
	import android.os.Bundle;
	import android.support.v4.app.Fragment;
	import android.support.v7.widget.LinearLayoutManager;
	import android.support.v7.widget.RecyclerView;
	import android.util.Log;
	import android.view.LayoutInflater;
	import android.view.View;
	import android.view.ViewGroup;
	import android.widget.ProgressBar;
	import android.widget.Toast;
	import com.android.volley.Request;
	import com.android.volley.RequestQueue;
	import com.android.volley.Response;
	import com.android.volley.VolleyError;
	import com.android.volley.toolbox.JsonObjectRequest;
	import com.android.volley.toolbox.Volley;
	import org.json.JSONArray;
	import org.json.JSONException;
	import org.json.JSONObject;
	/**
	* Created by Solinari on 2016/12/31.
	*/
	public class FragmentList_One extends Fragment{
	private RecyclerView recyclerView;
	private ProgressBar progressBar;
	private RecyclerView.Adapter recyclerAdapter;
	private String[] MetroInfo;
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
	Bundle savedInstanceState) {
	View view = inflater.inflate(R.layout.fragmentlist_one, container, false);
	recyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
	progressBar = (ProgressBar) view.findViewById(R.id.progressBar);
	getMetroInfo();//取得台北捷運列車到站資訊
	return view;
	}
	public void setRecyclerView(){
	recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
	recyclerAdapter = new RecyclerViewAdapter(MetroInfo);//設置RecyclerView.Adapter
	recyclerView.setAdapter(recyclerAdapter);
	progressBar.setVisibility(View.GONE);//Loading圖隱藏
	recyclerView.setVisibility(View.VISIBLE);//資料呈現
	}
	public void getMetroInfo(){
	RequestQueue queue = Volley.newRequestQueue(getActivity());//創建一個RequestQueue
	//台北捷運到站資料網址，按終點站排序
	String url = "http://data.taipei/opendata/datalist/apiAccess?scope=resourceAquire&rid=55ec6d6e-dc5c-4268-a725-d04cc262172b&sort=Destination";
	//對URL發出Request取得JsonObject的Response
	JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, url, null,
	new Response.Listener<JSONObject>() {
	@Override
	public void onResponse(JSONObject response) {
	try {
	//Response的JSONObject中，我們要的資訊是results(JSONArray)
	//{"result":{"offset":0,"limit":10000,"count":25,"sort":"Destination","results":[{"_id":"1","Station":"士林站","Destination":"大安站","UpdateTime":"2017-04-10T20:59:27.577"},...}]}}
	JSONArray info = response.getJSONObject("result").getJSONArray("results");
	MetroInfo = new String[info.length()];
	for(int i = 0; i < info.length();i++){
	JSONObject jsonObject = info.getJSONObject(i);
	//{"_id":"1","Station":"士林站","Destination":"大安站","UpdateTime":"2017-04-10T20:59:27.577"}
	String time = jsonObject.getString("UpdateTime").substring(11,19);
	MetroInfo[i] = jsonObject.getString("Station") + "_" + jsonObject.getString("Destination") + "_" + time;
	}
	setRecyclerView();//設置RecyclerView
	} catch (JSONException e) {
	e.printStackTrace();
	}
	}
	}, new Response.ErrorListener() {
	@Override
	public void onErrorResponse(VolleyError error) {
	//當發生錯誤時，提示使用者發生錯誤
	MetroInfo = new String[1];
	MetroInfo[0] = "Error_Error_Error";
	setRecyclerView();
	Toast.makeText(getActivity(),"Get data error !",Toast.LENGTH_LONG).show();
	}
	}
	);
	//將Request加入RequestQueue
	queue.add(jsonObjectRequest);
	}
	}

view raw FragmentList_One.java hosted with ❤ by GitHub

最後，修改Adapter「RecyclerViewAdapter.java」。

RecyclerViewAdapter.java

	package com.example.solinari.GetTaipeiMetroInfo;
	import android.support.v7.widget.RecyclerView;
	import android.view.LayoutInflater;
	import android.view.View;
	import android.view.ViewGroup;
	import android.widget.TextView;
	/**
	* Created by Solinari on 2017/1/21.
	*/
	public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
	private String[] MetroInfo;
	public static class ViewHolder extends RecyclerView.ViewHolder {
	public TextView tvStation;
	public TextView tvDestination;
	public TextView tvTime;
	public ViewHolder(View v) {
	super(v);
	tvStation =(TextView) v.findViewById(R.id.tvStation);
	tvDestination =(TextView) v.findViewById(R.id.tvDestination);
	tvTime =(TextView) v.findViewById(R.id.tvTime);
	}
	}
	public RecyclerViewAdapter(String[] info) {
	MetroInfo = info;
	}
	@Override
	public RecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
	int viewType) {
	View v = LayoutInflater.from(parent.getContext())
	.inflate(R.layout.recycler_metroinfo, parent, false);
	ViewHolder vh = new ViewHolder(v);
	return vh;
	}
	@Override
	public void onBindViewHolder(ViewHolder holder, int position) {
	//MetroInfo[position] 士林站_大安站_20:59:27 ，用"_"來區分各個欄位
	String[] tmp = MetroInfo[position].split("_");
	holder.tvStation.setText(tmp[0]);
	holder.tvDestination.setText(tmp[1]);
	holder.tvTime.setText(tmp[2]);
	}
	@Override
	public int getItemCount() {
	return MetroInfo.length;
	}
	}

view raw RecyclerViewAdapter.java hosted with ❤ by GitHub

資料來源：Sending a Simple Request
                    Making a Standard Request
完整專案：Solinari GitHub