我是开发android应用程序的新手。我已经阅读了很多关于我所问问题的相关帖子，但帖子中的提示或解决方案并没有解决我的问题。当我运行我的应用程序时出现此错误
03-11 11:52:39.115 3209-3236/com.example.blue_sky.store E/JSON Parser: Error parsing data org.json.JSONException: End of input at character 0 of
03-11 11:52:39.116 3209-3236/com.example.blue_sky.store E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.example.blue_sky.store, PID: 3209
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:304)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:818)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'org.json.JSONArray org.json.JSONObject.getJSONArray(java.lang.String)' on a null object reference
at com.example.blue_sky.store.MainActivity$Store.doInBackground(MainActivity.java:76)
at com.example.blue_sky.store.MainActivity$Store.doInBackground(MainActivity.java:53)
at android.os.AsyncTask$2.call(AsyncTask.java:292)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:818)
听到的是我的 MainAcivity：
package com.example.blue_sky.store;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class MainActivity extends ListActivity {
private ProgressDialog pd;
//jparser
JSONparser jsoNparser = new JSONparser();
ArrayList<HashMap<String,String>> p;
//s
static JSONArray jsonArray ;
String Url="http://127.0.0.1/store.php";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
p = new ArrayList<HashMap<String, String>>();
new Store().execute();
/* Store s =new Store();
s.execute();*/
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
String code = ((TextView)v.findViewById(R.id.tvPid)).getText().toString();
Intent i = new Intent(MainActivity.this,ADD.class);
i.putExtra("pid",code);
startActivity(i);
}
class Store extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(MainActivity.this);
pd.setMessage("LogIn");
pd.show();
//pd.dismiss();
}
@Override
protected String doInBackground(String... params) {
List <NameValuePair> parms = new ArrayList<>(); // Building Parameters
//json
JSONObject jsonObject = jsoNparser.makeHttpRequest(Url,"GET",parms);
try {
// int t =jsonObject.getInt("t");
int t =1;
if (t==1){
jsonArray = jsonObject.getJSONArray("Store");
for(int i = 0; i<jsonArray.length(); i++){
//c
JSONObject jObject = jsonArray.getJSONObject(i);
String pid = jObject.getString("pid");
String name = jObject.getString("name");
String price = jObject.getString("price");
String description = jObject.getString("description");
HashMap<String,String> hashMap = new HashMap<String, String>();
hashMap.put("pid",pid);
hashMap.put("name",name);
hashMap.put("price",price);
hashMap.put("description",description);
p.add(hashMap);
}
}else {
Toast.makeText(MainActivity.this,"اطلاعاتی یافت نشد!!",Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
// e.printStackTrace();
System.out.println("Error " + e.getMessage());
return null;
}
return null;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
pd.cancel();
runOnUiThread(new Runnable() {
@Override
public void run() {
ListAdapter listAdapter = new SimpleAdapter(MainActivity.this,p,R.layout.item_list,
new String[]{"pid","name","price","description","store"},
new int[]{R.id.tvPid,R.id.tvName,R.id.tvPrice,R.id.tvDisc});
setListAdapter(listAdapter);
}
});
}
}
@Override
public void onDestroy() {
super.onDestroy();
if (pd != null) {
pd.dismiss();
pd = null;
}
}
}
这是我的 ADD 类：
package com.example.blue_sky.store;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Blue_Sky on 3/11/2017.
*/
public class ADD extends Activity {
private String cod;
private ProgressDialog pd;
EditText InputName,InputCode,InputNumber;
Button Send;
JSONparser jparser = new JSONparser();
private String url;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
InputName = (EditText)findViewById(R.id.edInputName);
InputCode = (EditText)findViewById(R.id.edInputCode);
InputNumber = (EditText)findViewById(R.id.edInputNumber);
Send = (Button)findViewById(R.id.btnSend);
setContentView(R.layout.add);
Bundle input = getIntent().getExtras();
cod = input.getString("pid");
Send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new load().execute();
}
});
}
class load extends AsyncTask<String,String,String>{
public void AttemptLogin(String name, String code, String number){
name = InputName.getText().toString();
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(ADD.this);
pd.setMessage("LogIn");
pd.show();
}
String code = InputCode.getText().toString();
String name = InputName.getText().toString();
String number = InputNumber.getText().toString();
@Override
protected String doInBackground(String... params) {
List<NameValuePair> parms = new ArrayList<NameValuePair>();
parms.add(new BasicNameValuePair("name",name));
parms.add(new BasicNameValuePair("code",code));
parms.add(new BasicNameValuePair("number",number));
parms.add((new BasicNameValuePair("cod",cod)));
JSONObject Json = jparser.makeHttpRequest(url,"POST",parms);
try {
int t = Json.getInt("t");
if(t == 1){
Intent in = new Intent(ADD.this,MainActivity.class);
startActivity(in);
}else {
Toast.makeText(getApplicationContext(),"خطایی رخ داده!!",Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
pd.dismiss();
}
}
}
和 JSONParser 类：
package com.example.blue_sky.store;
import android.util.Log;
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 java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;
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 == "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 == "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 (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;
}
}