Question

我试图从这个JSON站点解析一些字符串：

Image of JSON table

我用asynctask写了这段代码：

package com.example.nortti.jsonexample;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

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

public class MainActivity extends Activity {
    TextView txView;

//URL to get JSON Array
private static String url = "http://localhost:10101/api/stats/1";

//JSON Node Names
private static final String TAG_USER = "";
private static final String TAG_NAME = "PersonName";
private static final String TAG_EMAIL = "Rank";


JSONArray user;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    user = null;
            new JSONParse().execute();



}

private class JSONParse extends AsyncTask<String, String, JSONObject> {
    private ProgressDialog pDialog;
    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        txView = (TextView)findViewById(R.id.txView);

        pDialog = new ProgressDialog(MainActivity.this);
        pDialog.setMessage("Getting Data ...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();

    }

    @Override
    protected JSONObject doInBackground(String... args) {
        JSONParser jParser = new JSONParser();

        // Getting JSON from URL
        JSONObject json = jParser.getJSONFromUrl(url);
        return json;
    }
    @Override
    protected void onPostExecute(JSONObject json) {
        pDialog.dismiss();
        try {
            // Getting JSON Array
            user = json.getJSONArray("ArrayOfCommonStatViewModel");
            Toast.makeText(getApplication(),user.toString(),Toast.LENGTH_SHORT).show();
            JSONObject c = user.getJSONObject(0);

            // Storing  JSON item in a Variable

            String name = c.getString(TAG_NAME);
            String email = c.getString(TAG_EMAIL);

            //Set JSON Data in TextView

            txView.setText(name+" " +email);


        } catch (JSONException e) {
            e.printStackTrace();
        }

    }
}

}

我还有另一个类：

import android.util.Log;

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

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

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();
        HttpGet httpPost = new HttpGet(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;

}
}

但它说我有NullPointerException

我想获取一个JSONArray来获取信息并将其放入ListView。

UPD：这是JSON截图

UPD2：完整日志

12-17 14:17:03.712 20308-20308/com.example.nortti.politrange E/AndroidRuntime: FATAL EXCEPTION: main
                                                                               Process: com.example.nortti.politrange, PID: 20308
                                                                               android.os.NetworkOnMainThreadException
                                                                                   at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1147)
                                                                                   at java.net.InetAddress.lookupHostByName(InetAddress.java:418)
                                                                                   at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252)
                                                                                   at java.net.InetAddress.getAllByName(InetAddress.java:215)
                                                                                   at org.apache.http.impl.conn.SystemDefaultDnsResolver.resolve(SystemDefaultDnsResolver.java:44)
                                                                                   at org.apache.http.impl.conn.HttpClientConnectionOperator.connect(HttpClientConnectionOperator.java:102)
                                                                                   at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:318)
                                                                                   at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:373)
                                                                                   at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:225)
                                                                                   at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:195)
                                                                                   at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:86)
                                                                                   at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:108)
                                                                                   at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:178)
                                                                                   at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
                                                                                   at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:106)
                                                                                   at com.example.nortti.politrange.utils.WebApiAdapter.select(WebApiAdapter.java:33)
                                                                                   at com.example.nortti.politrange.intefaces.impls.PersonCatalog.populateData(PersonCatalog.java:37)
                                                                                   at com.example.nortti.politrange.views.GeneralFragment.listData(GeneralFragment.java:65)
                                                                                   at com.example.nortti.politrange.views.GeneralFragment.onClick(GeneralFragment.java:88)
                                                                                   at android.view.View.performClick(View.java:4756)
                                                                                   at android.view.View$PerformClick.run(View.java:19761)
                                                                                   at android.os.Handler.handleCallback(Handler.java:739)
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                   at android.os.Looper.loop(Looper.java:135)
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:5253)
                                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                                   at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:900)
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:695)

Answer 1

您正在获取 NetworkOnMainThread 异常，因为您正在UI线程中实现网络操作，因此要从您的localhost加载json数据，您需要为其实现单独的线程

Answer 2

您正在尝试使用JSON Parser解析XML文档，但它无法正常工作。让我们看看this链接，它将向您展示如何以正确的方式解析XML文档（在Android环境中）：

Answer 3

您收到 NetworkOrMainThreadException 。

将以下代码放在 onCreate（）：

上

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);

希望这会对你有所帮助。

Answer 4

您尝试解析的内容实际上是xml而不是JSON。如果您需要执行网络请求，请解析JSON，您可以使用Retrofit库。它非常简单，无忧无虑。 Here是一个很好的教程。希望它有所帮助。

Answer 5

而不是开发整个解析代码，尝试使用Google的Volley库，它是asynchrone库，用于解析JSON。这是一个很好的tutorial。

Answer 6

enter code here

////在android studio中添加http客户端和http核心库/////

class mytask扩展了AsyncTask {

    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();


    }

    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub

        String url = "http://192.168.1.13/mywebservice/getbook.php";
        json = getJSONFromUrl(url);

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);

        Toast.makeText(ctx, json, Toast.LENGTH_LONG).show();
        parser_01();
    }

}

// from url to json object starts.......................................
public String 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");
            sb.append(line);
        }
        is.close();
        json = sb.toString();

    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    return json;

}

// from url to json object Ends.......................................

public void parser_01() {
    try {




        String jstring = json;



        JSONObject jobject = new JSONObject(jstring);

        JSONArray bookarray = jobject.getJSONArray("data");

        for (int i = 0; i < bookarray.length(); i++) {

            String isdn = bookarray.getJSONObject(i).getString("isdn") + "";
            String title = bookarray.getJSONObject(i).getString("title") + "";
            String author = bookarray.getJSONObject(i).getString("author") + "";
            String price = bookarray.getJSONObject(i).getString("price") + "";





        }



    } catch (Exception e) {
        // TODO: handle exception
    }

}

如何用AsyncTask解析JSON？

6 个答案: