检索JSON对象的Andr​​oid [英] Retrieve JSON Object Android

问题描述

我试图从URL获得一个JSON字符串，但我不断收到一个NetworkOnMainThreadException。我以为我把我的网络code到另一个线程，但显然不是。

I'm trying to get a JSON String from a URL but I keep getting a "NetworkOnMainThreadException". I thought I moved my network code to another thread but obviously not.

下面是错误：

Here is the error:

JSONParser

JSONParser

package com.example.jsonparsing;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.BasicHttpParams;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    public String getJSONFromUrl(String url) {

        DefaultHttpClient   httpclient = new DefaultHttpClient(new BasicHttpParams());
        HttpPost httppost = new HttpPost("http://api.androidhive.info/contacts/");
        // Depends on your web service
        httppost.setHeader("Content-type", "application/json");

        InputStream inputStream = null;
        String result = null;
        HttpResponse response = null;
        try {
            response = httpclient.execute(httppost);
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }           
        HttpEntity entity = response.getEntity();

        try {
            inputStream = entity.getContent();
        } catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        // json is UTF-8 by default i beleive
        BufferedReader reader = null;
        try {
            reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        StringBuilder sb = new StringBuilder();

        String line = null;
        try {
            while ((line = reader.readLine()) != null)
            {
                sb.append(line + "\n");
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return result = sb.toString();
    }
}

主要活动

package com.example.jsonparsing;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

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

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;

public class MainActivity extends Activity{

    // url to make request
    private static String url = "http://api.androidhive.info/contacts/";

    // contacts JSONArray
    JSONArray contacts = null;

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

        // Hashmap for ListView
        ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();

        RetrieveJSONString retrieveJSON = new RetrieveJSONString();
        retrieveJSON.run();
        String whatever = retrieveJSON.getJSONString();
    }
}

class RetrieveJSONString implements Runnable{

    JSONParser jParser;
    String jsonString;

    public void run() {
         // Creating JSON Parser instance
        JSONParser jParser = new JSONParser();

        // getting JSON string from URL
        String jsonString = jParser.getJSONFromUrl("http://api.androidhive.info/contacts/");

    }

    public String getJSONString(){

        return jsonString;
    }

}

清单

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.jsonparsing"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="16"
        android:targetSdkVersion="15" />
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

如果任何人都可以阐明这个问题一些轻我会AP preciate呢！

If anybody can shed some light on the problem I would appreciate it!

推荐答案

您获得的是错误，因为你正在尝试做的UI线程上的HTTP调用，你永远不应该这样做:)使用一个替代的AsyncTask。下面是一个简单的例子：

You are getting that error because you are trying to do HTTP calls on the UI-thread, and you should never do that :) Use an AsyncTask instead. Here is a simple example:

GetJsonAsync getJson = new GetJsonAsync();
getJson.execute();

private class GetJsonAsync extends AsyncTask <String, Void, String> {

        @Override
        protected void onPreExecute() {
            // Do stuff before the operation
        }

        @Override
        protected String doInBackground(String... params){
            getJSONFromUrl();
            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            // Do stuff after the operation
        }
    }

这篇关于检索JSON对象的Andr​​oid的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！