如何从 HTTP 获取字符串并使用它来构建 JSON 对象？

Question

我尝试从 HTTP 服务器获取字符串（实际上是 JSON 文件）来存储有关 Twitch 流的数据。

连接得到的字符串：api.twitch.tv/kraken/streams/lainkk

我想在 String 变量中获取这个 String 并从这个 String 构建一个 JSON 对象。

我写了一些方法，但在调用这些方法时总是在日志中出现 SystemErr：

这是我自己的 Twitch API class :

package com.linkpulsion.bibix;

import android.util.Log;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;

public class Twitch {
    private String channel;
    public final static String TWITCH_API_SERVER = "https://api.twitch.tv/kraken/";

/**
 * Constructor of Java Twitch API Json Generator
 * @param channel The cannel name to get the infos
 */
public Twitch(String channel){
    if(channel != null){
        this.channel = channel;
    }
}

/**
 * Getter for channel name
 * @return String the channel name
 */
public String getChannel(){
    return this.channel;
}

protected String getJson(String mode){
    String apiUri = TWITCH_API_SERVER + mode + "/" + this.channel;
    try{
        URL website = new URL(apiUri);
        URLConnection connection = website.openConnection();
        BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        StringBuilder response = new StringBuilder();
        String inputLine;
        while ((inputLine = in.readLine()) != null)
            response.append(inputLine);
        in.close();
        return response.toString();
    }catch (Exception e){
        e.printStackTrace();
        return null;
    }
}

protected JSONObject buildJSON(String jsonRaw){
    JSONObject json = null;
    try{
        json = new JSONObject(jsonRaw);
    }catch (Exception e){
        e.printStackTrace();
    }
    return json;
}

public void isSreaming(){
    String jsonRaw = getJson("streams");
    Log.d(null,"RETOUR " + jsonRaw);
}
}

谢谢！

Answer 1

我运行你的原始代码并得到一个 NetworkOnMainThreadException。

我制作了一个简单的 AsyncTask，它成功了：

private class TwitchAsync extends AsyncTask<Void, Void, String> {
    @Override
    protected String doInBackground(Void... params) {
        String str = twitch.getJson("streams");
        return str;
    }

    @Override
    protected void onPostExecute(String result){
        Toast.makeText(MainActivity.this, "result: " + result, Toast.LENGTH_LONG).show();

        //testing buildJSON:
        JSONObject obj = twitch.buildJSON(result);

        Log.d("JSON Result: ",  obj.toString());
    }
}

这是完整的 class 我用来测试的：

public class MainActivity extends AppCompatActivity {

    Twitch twitch;
    JSONObject jsonObj;  //instance variable which can be accessed anywhere in the class code

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        twitch = new Twitch("aksynial");
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        int id = item.getItemId();

        if (id == R.id.action_settings) {

            System.out.println("REFRESHING");
            new TwitchAsync().execute();

            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private class TwitchAsync extends AsyncTask<Void, Void, String> {
        @Override
        protected String doInBackground(Void... params) {
            String str = twitch.getJson("streams");
            return str;
        }

        @Override
        protected void onPostExecute(String result){
            Toast.makeText(MainActivity.this, "result: " + result, Toast.LENGTH_LONG).show();

            //testing buildJSON:
            //assign to the instance variable jsonObj
            jsonObj = twitch.buildJSON(result);

            Log.d("JSON Result: ",  jsonObj.toString());
        }
    }
}

在 onPostExecute() 中记录结果：

 D/JSON Result:﹕ {"_links":{"channel":"https:\/\/api.twitch.tv\/kraken\/channels\/aksynial","self":"https:\/\/api.twitch.tv\/kraken\/streams\/aksynial"},"stream":null}

如何从 HTTP 获取字符串并使用它来构建 JSON 对象？

How to get a String from HTTP and use it to build a JSON Object?

java

android

json

network-programming