Question

我正在学习JSON Parser。我按照androidhive教程并复制其代码，但遗憾的是，我不能。它不显示任何内容并且有这些类型的错误：

 11-22 17:27:12.132: E/AndroidRuntime(1938): Caused by: android.os.NetworkOnMainThreadException

任何人都可以帮我解决这个问题吗？感谢。

JSONPaser

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.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 JSONObject getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();           

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

MainActivity

import android.view.Menu;

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

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

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


public class MainActivity extends ListActivity{
    // url to make request
        private static String url = "http://api.androidhive.info/contacts/";

        // JSON Node names
        private static final String TAG_CONTACTS = "contacts";
        private static final String TAG_ID = "id";
        private static final String TAG_NAME = "name";
        private static final String TAG_EMAIL = "email";
        private static final String TAG_ADDRESS = "address";
        private static final String TAG_GENDER = "gender";
        private static final String TAG_PHONE = "phone";
        private static final String TAG_PHONE_MOBILE = "mobile";
        private static final String TAG_PHONE_HOME = "home";
        private static final String TAG_PHONE_OFFICE = "office";

        // contacts JSONArray
        JSONArray contacts = null;

    @Override
    protected 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>>();

                // Creating JSON Parser instance
                JSONParser jParser = new JSONParser();

                // getting JSON string from URL
                JSONObject json = jParser.getJSONFromUrl(url);

                try {
                    // Getting Array of Contacts
                    contacts = json.getJSONArray(TAG_CONTACTS);

                    // looping through All Contacts
                    for(int i = 0; i < contacts.length(); i++){
                        JSONObject c = contacts.getJSONObject(i);

                        // Storing each json item in variable
                        String id = c.getString(TAG_ID);
                        String name = c.getString(TAG_NAME);
                        String email = c.getString(TAG_EMAIL);
                        String address = c.getString(TAG_ADDRESS);
                        String gender = c.getString(TAG_GENDER);

                        // Phone number is agin JSON Object
                        JSONObject phone = c.getJSONObject(TAG_PHONE);
                        String mobile = phone.getString(TAG_PHONE_MOBILE);
                        String home = phone.getString(TAG_PHONE_HOME);
                        String office = phone.getString(TAG_PHONE_OFFICE);

                        // creating new HashMap
                        HashMap<String, String> map = new HashMap<String, String>();

                        // adding each child node to HashMap key => value
                        map.put(TAG_ID, id);
                        map.put(TAG_NAME, name);
                        map.put(TAG_EMAIL, email);
                        map.put(TAG_PHONE_MOBILE, mobile);

                        // adding HashList to ArrayList
                        contactList.add(map);
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }


                /**
                 * Updating parsed JSON data into ListView
                 * */
                ListAdapter adapter = new SimpleAdapter(this, contactList,
                        R.layout.list_item,
                        new String[] { TAG_NAME, TAG_EMAIL, TAG_PHONE_MOBILE }, new int[] {
                                R.id.name, R.id.email, R.id.mobile });

                setListAdapter(adapter);

                // selecting single ListView item
                ListView lv = getListView();

                // Launching new screen on Selecting Single ListItem
                lv.setOnItemClickListener(new OnItemClickListener() {

                    @Override
                    public void onItemClick(AdapterView<?> parent, View view,
                            int position, long id) {
                        // getting values from selected ListItem
                        String name = ((TextView) view.findViewById(R.id.name)).getText().toString();
                        String cost = ((TextView) view.findViewById(R.id.email)).getText().toString();
                        String description = ((TextView) view.findViewById(R.id.mobile)).getText().toString();

                        // Starting new intent
                        Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
                        in.putExtra(TAG_NAME, name);
                        in.putExtra(TAG_EMAIL, cost);
                        in.putExtra(TAG_PHONE_MOBILE, description);
                        startActivity(in);

                    }
                });


            }

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

}

<uses-permission android:name="android.permission.INTERNET" />用于清单

如何使用AsyncTask或Thread with Handler来解决错误？我需要删除我的JSON Parser类吗？

到目前为止我尝试过的事情：

我切换了我的目标SDK版本以适应我的模拟器，但它仍然不起作用
我在手机（三星）和模拟器（Genymotion）上运行项目它显示相同的错误

我试图测试没有JSON数组的另一种方法

导入android.os.Bundle; import android.app.Activity; import android.view.Menu; import android.widget.TextView; import android.util.Log;

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

import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpPost; import org.apache.http.impl.client.DefaultHttpClient;

public class Main扩展Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    try{ //try1 start
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // this is our TextView element, obtained by id from our XML layout
    TextView myListView = (TextView)findViewById(R.id.netResult);

    //lets try to connect
        try{ //try2 start

        //create a new client object
        HttpClient httpclient = new DefaultHttpClient();

        HttpPost httppost = new HttpPost("http://ephemeraltech.com/demo/android_tutorial20.php");

        //execute the post and get the response object
        HttpResponse response = httpclient.execute(httppost);

        //get the message from the response 
        HttpEntity entity = response.getEntity();

        //get the content of the message
        InputStream webs = entity.getContent();

        //convert response to string
                try{ //try3 start
                BufferedReader reader = new BufferedReader(new InputStreamReader(webs,"utf-8"),8);

                //read one line of the response
                myListView.setText(reader.readLine());

                //slow our inputStream
                webs.close();
                }//try3 end
        catch (Exception e){//catch 3 start 
            Log.e("log_result", "Error converting result "+e.toString());
        }//catch 3 end

        } //try2 end
        catch (Exception e){//catch 2 start
            Log.e("log_connect", "Error in http connection "+e.toString());
        }
    }//try1 end
    catch (Exception e){ //catch 1 start
        //this is the lie of code that sends a real error message to the log
        Log.e("ERROR", "ERROR IN CODE: "+e.toString());
        e.printStackTrace();
    }//catch 1 end
}

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

}

在此代码中，LogCat捕获我的第二次尝试并打印log_connect，http连接中的错误

Answer 1

您有 NetworkOnMainThreadException 错误。

这意味着您已在 onCreate 方法上直接运行代码：

但您无法直接在 MainUI 主题上更新您的数据。

为此，您必须使用 AsyncTask 或带处理程序的主题，或使用 runOnUiThread（）

更新您的用户界面

你可以这样做： http://www.vogella.com/articles/AndroidBackgroundProcessing/article.html

Answer 2

您是否完全阅读了堆栈跟踪？

引起：android.os.NetworkOnMainThreadException

如果您使用“NetworkOnMainThreadException”进行了Google搜索，那么您就可以得到答案。

简而言之，原因是您在主线程上执行HTTP请求，这实际上是一种不好的做法。 Android最近变得更加严格，并引发异常。

你需要的是这样的东西：

new AsyncTask<CustomParamClass, Void, String>() {
    @Override
    protected String doInBackground(final CustomerParamClass... params) {
        //use params to get the data and make an HHTP Request.
    }

    @Override
    protected void onPostExecute(final String params) {
        // This is invoked on the main thread. Communicate here.
    }
}.execute(<pass some params here>);

JSON分析器错误：http客户端失败

2 个答案: