DroidMatt
Reputation: 183
Android: JSON to ListView
I am trying to pass a JSON from my PHP to my Android app. Then the Android will populate the JSON into a ListView. The JSON has successfully been passed to my Android app. But the problem is, it keeps on throwing NullPointerException to me. Im all stressed out as I've been spending a lot of times looking for the error I've done. Below are the codes:
import java.util.ArrayList;
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 android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class PlacesActivity extends Activity {
List<Places> model = new ArrayList<Places>();
PlacesAdapter adapter = new PlacesAdapter();
@SuppressWarnings("static-access")
@Override
public void onCreate(Bundle savedInstanceState) {
ListView lv = (ListView) findViewById(R.id.placesListView);
super.onCreate(savedInstanceState);
setContentView(R.layout.places);
ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>();
postParameters.add(new BasicNameValuePair("request","request_for_places"));
String response = null;
try{
response = CustomHttpClient.executeHttpPost("http://www.test.com/requestPlaces.php", postParameters);
String res = response;
try{
JSONArray arr = new JSONArray(res);
for(int i = 0; i < arr.length(); i++)
{
JSONObject jsonObj = arr.getJSONObject(i);
Places newPlace = new Places();
newPlace.setPlace(jsonObj.optString("placeID"),jsonObj.optString("placeName"),jsonObj.optString("placeType"),jsonObj.optString("placeLat"),jsonObj.optString("placeLng"),jsonObj.optString("placePict"));
model.add(newPlace);
}
}catch(JSONException e){
Toast.makeText(getApplicationContext(), "Error : JSONException!", Toast.LENGTH_LONG).show();
}
lv.setAdapter(adapter);
}catch(Exception e){
Toast.makeText(getApplicationContext(), e+"", Toast.LENGTH_LONG).show();
}
}
class PlacesAdapter extends ArrayAdapter<Places>
{
PlacesAdapter()
{
super(PlacesActivity.this,android.R.layout.simple_list_item_1,model);
}
public View getView(int position, View convertView, ViewGroup parent)
{
View row = convertView;
PlaceHolder holder = null;
if(row == null)
{
LayoutInflater inflater = getLayoutInflater();
row = inflater.inflate(R.layout.row, parent,false);
holder = new PlaceHolder(row);
}
else
{
holder = (PlaceHolder)row.getTag();
}
holder.populateFrom(model.get(position));
return row;
}
}
static class PlaceHolder{
private TextView placeName = null;
private TextView placeType = null;
private ImageView icon = null;
PlaceHolder(View row){
placeName = (TextView)row.findViewById(R.id.placeName);
placeType = (TextView)row.findViewById(R.id.placeType);
icon = (ImageView)row.findViewById(R.id.icon);
}
void populateFrom(Places p){
placeName.setText(p.getPlaceName());
placeType.setText(p.getType());
if(p.getType().equals("Education")){
icon.setImageResource(R.drawable.ball_red);
}
else if (p.getType().equals("Leisure")){
icon.setImageResource(R.drawable.ball_yellow);
}
else{
icon.setImageResource(R.drawable.ball_green);
}
}
}
}
This is the JSON returned from PHP:
[{"placeID":"p0001","placeName":"INTI International University","placeType":"Education","placeLat":"2.813997","placeLng":"101.758229","placePict":"http:\/\/test.com\/placesImage\/inti_iu.JPG"},
{"placeID":"p0002","placeName":"Nilai International College","placeType":"Education","placeLat":"2.814179","placeLng":"101.7700107","placePict":"http:\/\/test.com\/placesImage\/nilai_uc.jpg"}]
This is my Places.java
public class Places{
private static String placeName;
private static String placeImg;
private static String placeLat;
private static String placeLng;
private static String placeType;
private static String placeID;
public Places()
{
placeID = "";
}
//set method
public static void setPlace(String place_id, String place_name, String place_type, String place_lat, String place_lng, String place_img) {
Places.placeName = place_name;
Places.placeID = place_id;
Places.placeImg = place_img;
Places.placeLat = place_lat;
Places.placeLng = place_lng;
Places.placeType = place_type;
}
//get methods
public static String getPlaceName(){
return placeName;
}
public static String getPlaceID(){
return placeID;
}
public static String getImg(){
return placeImg;
}
public static String getLat(){
return placeLat;
}
public static String getLng(){
return placeLng;
}
public static String getType(){
return placeType;
}
}
edit:logcat below
02-17 17:10:03.595: W/System.err(1994): java.lang.NullPointerException
02-17 17:10:03.615: W/System.err(1994): at com.application.fyp.PlacesActivity.onCreate(PlacesActivity.java:50)
02-17 17:10:03.615: W/System.err(1994): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
02-17 17:10:03.615: W/System.err(1994): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1836)
02-17 17:10:03.615: W/System.err(1994): at android.app.ActivityThread.startActivityNow(ActivityThread.java:1692)
02-17 17:10:03.625: W/System.err(1994): at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
02-17 17:10:03.625: W/System.err(1994): at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
02-17 17:10:03.625: W/System.err(1994): at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:656)
02-17 17:10:03.625: W/System.err(1994): at android.widget.TabHost.setCurrentTab(TabHost.java:326)
02-17 17:10:03.625: W/System.err(1994): at android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:132)
02-17 17:10:03.625: W/System.err(1994): at android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:458)
02-17 17:10:03.625: W/System.err(1994): at android.view.View.performClick(View.java:2533)
02-17 17:10:03.625: W/System.err(1994): at android.view.View$PerformClick.run(View.java:9320)
02-17 17:10:03.635: W/System.err(1994): at android.os.Handler.handleCallback(Handler.java:587)
02-17 17:10:03.635: W/System.err(1994): at android.os.Handler.dispatchMessage(Handler.java:92)
02-17 17:10:03.635: W/System.err(1994): at android.os.Looper.loop(Looper.java:150)
02-17 17:10:03.635: W/System.err(1994): at android.app.ActivityThread.main(ActivityThread.java:4385)
02-17 17:10:03.635: W/System.err(1994): at java.lang.reflect.Method.invokeNative(Native Method)
02-17 17:10:03.635: W/System.err(1994): at java.lang.reflect.Method.invoke(Method.java:507)
02-17 17:10:03.635: W/System.err(1994): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
02-17 17:10:03.635: W/System.err(1994): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
02-17 17:10:03.645: W/System.err(1994): at dalvik.system.NativeStart.main(Native Method)
Upvotes: 0
Views: 2198
Answers (4)
steevoo
Reputation: 631
your exception come from this
holder = (PlaceHolder)row.getTag();
cos u didn't initialize tag and is return null so in
if(row == null)
{
LayoutInflater inflater = getLayoutInflater();
row = inflater.inflate(R.layout.row, parent,false);
holder = new PlaceHolder(row);
}
change it and make it like that
if(row == null)
{
LayoutInflater inflater = getLayoutInflater();
row = inflater.inflate(R.layout.row, parent,false);
holder = new PlaceHolder(row);
row.setTag(holder);}
and than it will work
Upvotes: 0
DroidMatt
Reputation: 183
I've given up this way of doing what I'm suppose to do and end up trying the alternative way of doing it.
The tutorial on : Creating ListView based on JSON Object is a good tutorial.
Finally, thanks to those who helped me, and sorry for the trouble.
Upvotes: 0
just_user
Reputation: 12059
I changed your code a little bit, but I got it to work with this code.
public class MainActivity extends Activity {
List<Places> model;
PlacesAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ListView lv = (ListView) findViewById(R.id.listView1);
model = new ArrayList<Places>();
adapter = new PlacesAdapter();
try {
List<NameValuePair> pairs = new ArrayList<NameValuePair>();
pairs.add(new BasicNameValuePair("whatever", "XXXX"));
JSONArray jArray = connectToServer("http://www.example.com/get.php", pairs);
try {
for (int i = 0; i < jArray.length(); i++) {
JSONObject jsonObj = jArray.getJSONObject(i);
Places newPlace = new Places();
Places.setPlace(jsonObj.optString("name"),
jsonObj.optString("name"),
jsonObj.optString("name"),
jsonObj.optString("name"),
jsonObj.optString("name"),
jsonObj.optString("name"));
model.add(newPlace);
}
} catch (JSONException e) {
Toast.makeText(getApplicationContext(),
"Error : JSONException!", Toast.LENGTH_LONG).show();
}
lv.setAdapter(adapter);
} catch (Exception e) {
Toast.makeText(getApplicationContext(), e + "", Toast.LENGTH_LONG)
.show();
}
}
class PlacesAdapter extends ArrayAdapter<Places> {
PlacesAdapter() {
super(MainActivity.this, android.R.layout.simple_list_item_1, model);
}
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
PlaceHolder holder = null;
if (row == null) {
LayoutInflater inflater = getLayoutInflater();
row = inflater.inflate(R.layout.row, parent, false);
holder = new PlaceHolder(row);
} else {
holder = (PlaceHolder) row.getTag();
}
holder.populateFrom(model.get(position));
return row;
}
}
static class PlaceHolder {
private TextView placeName = null;
private TextView placeType = null;
private ImageView icon = null;
PlaceHolder(View row) {
placeName = (TextView) row.findViewById(R.id.textView1);
placeType = (TextView) row.findViewById(R.id.textView1);
icon = (ImageView) row.findViewById(R.id.imageView1);
}
void populateFrom(Places p) {
placeName.setText(Places.getPlaceName());
placeType.setText(Places.getType());
if (Places.getType().equals("Education")) {
icon.setImageResource(R.drawable.ic_launcher);
} else if (Places.getType().equals("Leisure")) {
icon.setImageResource(R.drawable.ic_launcher);
} else {
icon.setImageResource(R.drawable.ic_launcher);
}
}
}
public static JSONArray connectToServer(String address, List<NameValuePair> valuePairs) {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(address);
try {
httppost.setEntity(new UrlEncodedFormEntity(valuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
InputStream is = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"UTF8"),8);
StringBuilder sb = new StringBuilder();
sb.append(reader.readLine() + "\n");
String line="0";
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
String result = sb.toString();
JSONArray array = new JSONArray(result);
return array;
} catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
return null;
}
}
}
Hope this helps!
EDIT: Changed to ListView instead of ListActivity!
Upvotes: 1
user370305
Reputation: 109237
I think this line cause NPE..
adapter.add(newPlace);
You missed to initialize PlacesAdapter adapter;
adapter = new PlacesAdapter();
Updated:
So many mistakes,
First: I mentioned above,
Second:
List<Places> model = new ArrayList<Places>();
So, adapter.add(newPlace); this line should be, model.add(newPlace);
Third:
Whats the use of Adapter? means where you set adapter? Any ListView or GridView?
Question looks basic, you have to take a look at some basic tutorial about display json data on list..
EDIT:
1.
List<Places> model = new ArrayList<Places>();
PlacesAdapter adapter = new PlacesAdapter();
it should be
List<Places> model = new ArrayList<Places>();
PlacesAdapter adapter;
2.
ListView lv = (ListView) findViewById(R.id.placesListView);
super.onCreate(savedInstanceState);
setContentView(R.layout.places);
it should be
super.onCreate(savedInstanceState);
setContentView(R.layout.places);
ListView lv = (ListView) findViewById(R.id.placesListView);
3.
lv.setAdapter(adapter);
it should be,
adapter = new PlacesAdapter();
lv.setAdapter(adapter);
Thanks..
Upvotes: 3