使用 okHttp 的 GET 方式讀取 JSON 資料

如下圖所示，本範例使用 OKHttp 來讀取 JSON 多筆資料，並由 GSON(GSON是Google 開發用來解析JSON 格式資料的 Library) 來解析 JSON 格式資料，並由App顯示出相關訊息。

1.找到對應的module ，依照步驟下載 GSON 和 OKHttp 的 Library。

2.OKHttp官網裡有提供GET的範例，可直接套用。

3.lauout.xml。

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="gae.melvin.com.app_welcomeview.WelcomeActivity">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/imageView"
        android:src="@drawable/diary"
        android:layout_gravity="center_vertical"
        android:scaleType="fitCenter" />

</LinearLayout>

4.Book.java。

package gae.melvin.com.app_okhttp_gson;

public class Book {
    private long key;
    private String title;
    private String author;
    private String price;
    private long time;

    public long getKey() {
        return key;
    }

    public void setKey(long key) {
        this.key = key;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getPrice() {
        return price;
    }

    public void setPrice(String price) {
        this.price = price;
    }

    public long getTime() {
        return time;
    }

    public void setTime(long time) {
        this.time = time;
    }
}

5.MainActivity.java。

package gae.melvin.com.app_okhttp_gson;


import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;
import com.google.gson.Gson;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import java.io.IOException;



public class MainActivity extends AppCompatActivity {

    private TextView textView;

    @Override

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

        textView = (TextView)findViewById(R.id.textView);
        new RunWrok().start();

    }


    /*上網抓資料，需要另外開執行緒做處理(Android機制)*/
    class RunWrok extends Thread
    {
        String path_json ="http://android0620-1348.appspot.com/query";
        String result_json = null;

        /* This program downloads a URL and print its contents as a string.*/
        OkHttpClient client = new OkHttpClient();
        String run(String url) throws IOException {
            Request request = new Request.Builder()
                    .url(url)
                    .build();

            Response response = client.newCall(request).execute();
            return response.body().string();
        }

        Runnable task = new Runnable()
        {
            @Override
            public void run() {
                //使用 gson 解析 json 資料
                Gson gson = new Gson();
                Book[] books = gson.fromJson(result_json,Book[].class);

                StringBuilder sb = new StringBuilder();
                for(Book book :books){
                    sb.append("書名:").append(book.getTitle()).append(" ")
                            .append("作者:").append(book.getAuthor()).append(" ")
                            .append("價錢:").append(book.getPrice()).append("\n\n");
                }
                textView.setText(sb);

            }
        };

        @Override
        public void run()
        {
            try {
                //1.抓資料
                result_json = run(path_json);
                //2.改變畫面內容只能用主執行緒(Android機制)
                runOnUiThread(task);
            } catch (IOException e) {
                e.printStackTrace();
            }

        }

    }


}

6.AndroidManifest.xml，上網權限要開。