package com.android.housingapp;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import com.android.housingapp.helper.JSONParser;
import com.android.housingapp.helper.ListViewAdapter;
import com.android.housingapp.helper.ListViewAdapterComplaints;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.Toast;
public class BillsandDuesSpinner extends Activity{
Button btnaddyear,btnnext;
String name_array[];
Spinner yearspinner, spmonth;
String year_id,year,month,own_id;
String url;
JSONParser jParser ;
JSONArray montharray= null;
Context context=this;
int success=0;
JSONObject json;
ArrayList<HashMap<String, String>> monthList;
List<NameValuePair> params = new ArrayList<NameValuePair>();
ProgressDialog pDialog;
private static final String TAG_SUCCESS = "success";
private static final String TAG_DUE_MAIN= "all_year_list";
private static final String TAG_DUE_ID = "year_id";
private static final String TAG_DUE_MON = "month";
private static final String TAG_DUE_YEAR = "year";
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.billsandduesspinner);
btnaddyear=(Button)findViewById(R.id.btnaddyear);
btnnext=(Button)findViewById(R.id.btnnext);
yearspinner=(Spinner)findViewById(R.id.spyear);
spmonth=(Spinner)findViewById(R.id.spmonth);
own_id=getIntent().getExtras().getString("own_id");
monthList =new ArrayList<HashMap<String, String>>();
new BindYear().execute();
ArrayAdapter<CharSequence> adapter=ArrayAdapter.createFromResource(this,R.array.month,android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spmonth.setAdapter(adapter);
url="http://10.0.2.2:80/Android/HousingApp/get_due_mon_spinner.php";
btnaddyear.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent i=new Intent(getApplicationContext(),NewYear.class);
startActivity(i);
}
});
btnnext.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent i=new Intent(BillsandDuesSpinner.this,TypesofBills.class);
startActivity(i);
}
});
}
class BindYear extends AsyncTask<String,String,String>{
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(BillsandDuesSpinner.this);
pDialog.setMessage("Loading complains. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected String doInBackground(String... params) {
// TODO Auto-generated method stub
// contactList = new ArrayList<HashMap<String, String>>()
// Creating JSON Parser instance
jParser = new JSONParser();
// getting JSON string from URL
try {
json = jParser.getJSONFromUrl(url);
if(json.has(TAG_DUE_MAIN))
{
// Getting Array of Contacts
montharray = json.getJSONArray(TAG_DUE_MAIN);
name_array = new String[montharray.length()];
// looping through All Contacts
for(int i = 0; i < montharray.length(); i++){
JSONObject c = montharray.getJSONObject(i);
// Storing each json item in variable
year_id=c.getString(TAG_DUE_ID);
month = c.getString(TAG_DUE_MON);
year = c.getString(TAG_DUE_YEAR);
name_array[i] = c.getString(TAG_DUE_YEAR);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_DUE_ID,year_id );
map.put(TAG_DUE_MON,month);
map.put(TAG_DUE_YEAR,year );
// adding HashList to ArrayList
monthList.add(map);
}
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_url) {
// Pass the results into ListViewAdapter.java
try{
if(json.has(TAG_DUE_MAIN))
{
ArrayAdapter<String> adapter = new ArrayAdapter<String> (BillsandDuesSpinner.this, android.R.layout.simple_spinner_item, name_array);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
yearspinner.setAdapter(adapter);
}
else{
Toast.makeText(BillsandDuesSpinner.this,"No year is available now.Please add one.",Toast.LENGTH_SHORT).show();
}
}catch(Exception e)
{
e.printStackTrace();
}
pDialog.dismiss();
}
}
}
这是一个在spinner中绑定json数据的简单代码。我的php代码用于获取json数据绝对没问题。问题是每当我尝试在微调器中绑定json数据时，首先应用程序崩溃（显示空指针）但是当我再次单击将json数据绑定到微调器（它驻留在另一个活动中）的按钮时，崩溃后（不再运行应用程序） ，然后数据成功绑定到微调器。所以问题是什么？为什么数据第一次没有绑定？
答案 0 :(得分：2)
试试这个..
在调用 BindYear BindYear
url="http://10.0.2.2:80/Android/HousingApp/get_due_mon_spinner.php";
new BindYear().execute();
因为第一次url是空的。那个时候Exception doInBackground json中的onPostExecute为空，那么json.has将从json作为{{1}}进入{{1}}那段时间运行的 NPE
答案 1 :(得分：1)
@Hariharan回答说，这是你第一次得到NPE的问题。所以最好的方法如下，
url="http://10.0.2.2:80/Android/HousingApp/get_due_mon_spinner.php";
new BindYear().execute(url);
并在doInBackground()中更改如下，
json = jParser.getJSONFromUrl(params[0]);