尝试使用名称字段从数据库获取数据时，应用程序无响应，然后崩溃

Question

Im trying to create an app that gets a json object from a url. This is proving to be unnecessarily frustrating as it keeps crashing on the activity that is supposed to load and parse the json object. It just pops up the message "Unfortunately, (AppName) has stopped." and then exits the application. The data from the JSON is never shown on the screen. Here is the code with the activity and the JSON parsing

JSONParser.class

    package com.example.android.andrtest1;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
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() {

    }

    // function get json from url
    // by making HTTP POST or GET mehtod
    public JSONObject makeHttpRequest(String url, String method,
                                      List<NameValuePair> params) {

        // Making HTTP request
        try {

            // check for request method
            if(method.equals("POST")){
                // request method is POST
                // defaultHttpClient
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params));

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

            }else if(method.equals("GET")){
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
                HttpGet httpGet = new HttpGet(url);

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


        } 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).append("\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;

    }

    public JSONObject getJSONFromUrl(String url_create_product,
                                     List<NameValuePair> params) {
        // TODO Auto-generated method stub
        return null;
    }
}

Error in Logcat

    06-11 15:18:32.448 17200-17200/com.example.android.andrtest1 E/Buffer Error: Error converting result java.lang.NullPointerException: lock == null
06-11 15:18:32.451 17200-17200/com.example.android.andrtest1 E/JSON Parser: Error parsing data org.json.JSONException: End of input at character 0 of 
06-11 15:18:32.456 17200-17200/com.example.android.andrtest1 D/AndroidRuntime: Shutting down VM
06-11 15:18:32.457 17200-17200/com.example.android.andrtest1 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.android.andrtest1, PID: 17200
    java.lang.NullPointerException: Attempt to invoke virtual method 'int org.json.JSONObject.getInt(java.lang.String)' on a null object reference
        at com.example.android.andrtest1.NameSearchDisplayActivity$GetProductDetails$1.run(NameSearchDisplayActivity.java:91)
        at android.os.Handler.handleCallback(Handler.java:815)
        at android.os.Handler.dispatchMessage(Handler.java:104)
        at android.os.Looper.loop(Looper.java:194)
        at android.app.ActivityThread.main(ActivityThread.java:5651)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)

NameSearchDisplayActivity.class

    package com.example.android.andrtest1;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.StrictMode;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.view.Window;
import android.widget.TextView;

import junit.framework.Assert;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;

public class NameSearchDisplayActivity extends Activity {
    TextView empnameview;
    TextView empcugview;
    TextView emprailphnview;
    TextView empdesigview;
    TextView empresipnview;
    String empname;
    ProgressDialog pDialog;
    JSONParser jsonParser=new JSONParser();

    private static final String url_product_details = "http://192.168.116.1/serdb1.0/get_employee_details.php";
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_PRODUCT = "product";
    //private static final String TAG_ID = "id";
    private static final String TAG_NAME = "name";
    private static final String TAG_CUG = "CUG";
    private static final String TAG_RAILWAY_PHN = "railway_phone";
    private static final String TAG_DESIGNATION = "designation";
    private static final String TAG_RESIDENCE_PN = "residence_pn";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.namesearch_display);

        // getting product details from intent
        Intent i = getIntent();

        // getting name from intent
        empname = i.getStringExtra(NameSearchDisplayActivity.TAG_NAME);

        // Getting complete product details in background thread
        new GetProductDetails().execute();
    }

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

            pDialog = new ProgressDialog(NameSearchDisplayActivity.this);
            pDialog.setMessage("Loading employee details. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }

        protected JSONObject doInBackground(String... args) {
                    if(pDialog!=null)
                        pDialog.dismiss();

                    // Check for success tag
                    JSONObject product=null;
                    int success;
                    try {
                        // Building Parameters
                        List<NameValuePair> params = new ArrayList<NameValuePair>();
                        params.add(new BasicNameValuePair("name", empname));

                        // getting product details by making HTTP request
                        // Note that product details url will use GET request
                        JSONObject json;
                        json = jsonParser.makeHttpRequest(
                                url_product_details, "GET", params);


                        // check your log for json response

                            Log.d("Single Product Details", json.toString());

                        // json success tag

                        success = json.getInt(TAG_SUCCESS);
                        if (success == 1) {
                            // successfully received product details
                            JSONArray productObj = json
                                    .getJSONArray(TAG_PRODUCT); // JSON Array

                            // get first product object from JSON Array
                            product = productObj.getJSONObject(0);

                        }
                        else {

                        }// product with pid not found

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

                }


        protected void onPostExecute(JSONObject product) {
            // Edit Text
            try{
            empnameview = (TextView) findViewById(R.id.namevalueview);
            empcugview = (TextView) findViewById(R.id.cugvalueview);
            emprailphnview = (TextView) findViewById(R.id.railphnvalueview);
            empdesigview = (TextView) findViewById(R.id.desigvalueview);
            empresipnview = (TextView) findViewById(R.id.resipnvalueview);

            // display product data in EditText

            empcugview.setText(product.getString(TAG_CUG));
            emprailphnview.setText(product.getString(TAG_RAILWAY_PHN));
            empdesigview.setText(product.getString(TAG_DESIGNATION));
            empresipnview.setText(product.getString(TAG_RESIDENCE_PN));}
            catch (JSONException e) {
                e.printStackTrace();
            }
            // dismiss the dialog once got all details
            if(pDialog != null)
                pDialog.dismiss();
        }


    }

}

Answer 1

Check whether the method is POST or GET using Postman extension in Chrome. and Use the specific method to get the data.

Link for Postman Extension