AsyncTask and MainActivity in separated files

AsyncTask and MainActivity in separated files - java

I'm trying to separate my AsyncTask class and MainActivity class by putting them in other files.
Here is my fully-working program:
package com.example.kamilh.pierwsza;
import android.location.Address;
import android.location.Criteria;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.List;
import java.util.Locale;
public class MainActivity extends ActionBarActivity {
String region = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private void getRegion()
{
TextView textView = (TextView) findViewById(R.id.textView3);
Criteria cr = new Criteria();
LocationManager lm = (LocationManager) getSystemService(LOCATION_SERVICE);
Location loc = lm.getLastKnownLocation(lm.getBestProvider(cr, true));
double lat = loc.getLatitude();
double lon = loc.getLongitude();
new Region().execute(lat, lon);
textView.setText(region);
}
public void count(View view) throws IOException {
EditText editText = (EditText) findViewById(R.id.editText);
EditText editText2 = (EditText) findViewById(R.id.editText2);
double cost = 5.25;
double petrol = Double.valueOf(editText.getText().toString());
double distance = Double.valueOf(editText2.getText().toString());
double result = Math.round(cost*(distance/100)*petrol);
//textView.setText("The cost of your trip is: "+String.valueOf(result)+" zĹ‚");
getRegion();
}
private class Region extends AsyncTask<Double, Void, String> {
#Override
public String doInBackground(Double... params) {
URL url = null;
BufferedReader in = null;
try {
url = new URL("https://maps.googleapis.com/maps/api/geocode/json?latlng="+params[0]+","+params[1]);
} catch (MalformedURLException e) {
e.printStackTrace();
}
try {
if (url != null) {
in = new BufferedReader(new InputStreamReader(url.openStream()));
}
} catch (IOException e) {
e.printStackTrace();
}
String line = null;
String x = null;
for (int i = 0; i<31; i++){
if (in != null) {
try {
line = in.readLine();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return line;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
region = result;
}
}
Now, I'd like to be able to clean up a bit my code, so I decided to separate those two classes. I saw this example (above) and I tried to implement this solution in my project, but i failed.
Android: How to run asynctask from different class file?
Here are my MainActivity class:
package com.example.kamilh.pierwsza;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import java.io.IOException;
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public void getRegion(String result)
{
TextView textView = (TextView) findViewById(R.id.textView3);
textView.setText(result);
}
public void count(View view) throws IOException {
EditText editText = (EditText) findViewById(R.id.editText);
EditText editText2 = (EditText) findViewById(R.id.editText2);
double cost = 5.25;
double petrol = Double.valueOf(editText.getText().toString());
double distance = Double.valueOf(editText2.getText().toString());
double result = Math.round(cost*(distance/100)*petrol);
//textView.setText("The cost of your trip is: "+String.valueOf(result)+" zł");
Criteria cr = new Criteria();
LocationManager lm = (LocationManager) getSystemService(LOCATION_SERVICE);
Location loc = lm.getLastKnownLocation(lm.getBestProvider(cr, true));
double lat = loc.getLatitude();
double lon = loc.getLongitude();
new Region(this).execute(lat, lon);
}
}
Here is my Region class:
package com.example.kamilh.pierwsza;
import android.content.Context;
import android.os.AsyncTask;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
/**
* Created by KamilH on 2015-02-19.
*/
class Region extends AsyncTask<Double, Void, String> {
private Context context;
MainActivity activity;
public Region (Context context){
this.context = context;
}
#Override
public String doInBackground(Double... params) {
URL url = null;
BufferedReader in = null;
try {
url = new URL("https://maps.googleapis.com/maps/api/geocode/json?latlng="+params[0]+","+params[1]);
} catch (MalformedURLException e) {
e.printStackTrace();
}
try {
if (url != null) {
in = new BufferedReader(new InputStreamReader(url.openStream()));
}
} catch (IOException e) {
e.printStackTrace();
}
String line = null;
String x = null;
for (int i = 0; i<31; i++){
if (in != null) {
try {
line = in.readLine();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return line;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
activity.getRegion(result);
}
}
After I run the app with separated files I get those errors:
02-19 14:42:39.793 13842-13842/com.example.kamilh.pierwsza E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.kamilh.pierwsza, PID: 13842
java.lang.NullPointerException
at com.example.kamilh.pierwsza.Region.onPostExecute(Region.java:57)
at com.example.kamilh.pierwsza.Region.onPostExecute(Region.java:15)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:157)
at android.app.ActivityThread.main(ActivityThread.java:5867)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:674)
at dalvik.system.NativeStart.main(Native Method)
Could you please, tell me how to fix it?

Change your Region class to this:
package com.example.kamilh.pierwsza;
import android.os.AsyncTask;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
/**
* Created by KamilH on 2015-02-19.
*/
class Region extends AsyncTask<Double, Void, String> {
private MainActivity activity;
public Region (MainActivity activity){
this.activity = activity;
}
#Override
public String doInBackground(Double... params) {
URL url = null;
BufferedReader in = null;
try {
url = new URL("https://maps.googleapis.com/maps/api/geocode/json?latlng="+params[0]+","+params[1]);
} catch (MalformedURLException e) {
e.printStackTrace();
}
try {
if (url != null) {
in = new BufferedReader(new InputStreamReader(url.openStream()));
}
} catch (IOException e) {
e.printStackTrace();
}
String line = null;
String x = null;
for (int i = 0; i<31; i++){
if (in != null) {
try {
line = in.readLine();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return line;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
activity.getRegion(result);
}
}
Why? Well. You call getRegion on activity in the onPostExecute. But activity is never initialised. And since you want it to call that method in the MainActivity where you did new Region(this), the constructor has to be changed. Since you don't use the Context, we remove that and replace it by MainActivity and make sure it gives the value to the activity field in your class.
Note that an Activity is a subclass of Context. And that this in the activity is the activity and thus a context. Not that you need it here.
It could also be good to look into callback routines. It is what you're doing here, but it can be done by using an interface. And then re-using your code will be easier.

You are not initializing activity in Region constructor, so activity is null when you try to call getRegion in asyncTask postExecute. You should init activity in Region constructor.

Your activity is null
public Region (Context context, MainActivity act){
this.context = context;
this.activity = act;
}

You're getting NullPointerException, because your Region class does not find getRegion() method which is inside your MainActivity.
Provide the activity to the constructor of Region class.

Related

Accessing the searchview query text from mainactivity

I am planning to make a news app. I have created a simple search view inside the action bar of my app.
This is the Main activity
package com.example.hp.simplenews;
import android.app.Activity;
import android.app.LoaderManager;
import android.app.SearchManager;
import android.content.Context;
import android.content.Intent;
import android.content.Loader;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SearchView;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<List<News>> {
private int Newsloaderid = 1;
private Newsadapter newslistadapter;
private String search_query_input = "";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView newslistview = findViewById(R.id.list);
newslistadapter = new Newsadapter(this, new ArrayList<News>());
newslistview.setAdapter(newslistadapter);
LoaderManager loaderManager = getLoaderManager();
loaderManager.initLoader(Newsloaderid, null, MainActivity.this);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the options menu from XML
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.options_menu, menu);
// Get the SearchView and set the searchable configuration
SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
SearchView searchView = (SearchView) menu.findItem(R.id.search).getActionView();
// Assumes current activity is the searchable activity
searchView.setSearchableInfo(searchManager.getSearchableInfo(getComponentName()));
searchView.setIconifiedByDefault(false); // Do not iconify the widget; expand it by default
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
#Override
public boolean onQueryTextSubmit(String newtext) {
search_query_input = newtext;
return true;
}
#Override
public boolean onQueryTextChange(String query) {
return true;
}
});
return true;
}
#Override
public Loader<List<News>> onCreateLoader(int i, Bundle bundle) {
return new NewsLoader(this, search_query_input);
}
#Override
public void onLoadFinished(Loader<List<News>> loader, List<News> news) {
newslistadapter.clear();
if (news != null && !news.isEmpty()) {
newslistadapter.addAll(news);
}
}
#Override
public void onLoaderReset(Loader loader) {
newslistadapter.clear();
}
}
The SearchResultsActivity handles the HTTP request and JSON parsing.
This is the SearchResultsActivity
package com.example.hp.simplenews;
import android.app.Activity;
import android.app.LoaderManager;
import android.app.SearchManager;
import android.content.Context;
import android.content.Intent;
import android.content.Loader;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.text.TextUtils;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.widget.SearchView;
import android.widget.TextView;
import android.widget.Toast;
import org.json.JSONArray;
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.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
public class SearchResultsActivity extends Activity{
String query_string = "";
private static final String LOG_TAG = SearchResultsActivity.class.getName();
public static URL createUrl(String query_url) throws MalformedURLException {
URL url = null;
String APIKey = "apiKey";
String query = "q";
try {
final String base_url = "https://newsapi.org/v2/everything?";
Uri final_url = Uri.parse(base_url).buildUpon()
.appendQueryParameter(query, query_url)
.appendQueryParameter(APIKey, "48f67c1e66994aa8a92f92a48b5f6581")
.build();
url = new URL(final_url.toString());
Log.i(LOG_TAG, "THE FINAL URL IS" + final_url);
} catch (MalformedURLException e) {
e.printStackTrace();
Log.e(LOG_TAG, "the url couldn't be made");
}
return url;
}
private static final String HTTPREQUEST(URL url) throws IOException {
String jsonresponse = "";
if (jsonresponse == null) {
return null;
}
HttpURLConnection httpURLConnection = null;
InputStream inputStream = null;
try {
httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("GET");
httpURLConnection.setReadTimeout(10000);
httpURLConnection.setConnectTimeout(150000);
httpURLConnection.connect();
if (httpURLConnection.getResponseCode() == 200) {
inputStream = httpURLConnection.getInputStream();
jsonresponse = readfromstream(inputStream);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (inputStream != null) {
inputStream.close();
}
if (httpURLConnection != null) {
httpURLConnection.disconnect();
}
}
return jsonresponse;
}
private static final String readfromstream(InputStream inputStream) throws IOException {
StringBuilder output = new StringBuilder();
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String urlline = bufferedReader.readLine();
while (urlline != null) {
output.append(urlline);
urlline = bufferedReader.readLine();
}
return output.toString();
}
private static List<News> JSONParser(String NewsJSON) throws JSONException {
if (TextUtils.isEmpty(NewsJSON)) {
return null;
}
List<News> news = new ArrayList<>();
try {
JSONObject basejson = new JSONObject(NewsJSON);
JSONArray articles = basejson.getJSONArray("articles");
for (int i = 0; i < articles.length(); i++) {
News newss = new News();
JSONObject c = articles.getJSONObject(i);
JSONObject source = c.getJSONObject("source");
newss.setMsource(source.getString("name"));
newss.setMtitle(c.getString("title"));
newss.setMdescription(c.getString("description"));
newss.setMtime(c.getString("publishedAt"));
String image = c.getString("urlToImage");
if (image != null) {
newss.setmImage(c.getString("urlToImage"));
}
newss.setNewsURL(c.getString("url"));
news.add(newss);
}
} catch (JSONException j) {
Log.e(LOG_TAG, "couldn't parse jSON");
}
return news;
}
public static List<News> fetchnews(String search_query) throws IOException, JSONException {
URL url = createUrl(search_query);
String JSONRESPONSE = null;
try {
JSONRESPONSE = HTTPREQUEST(url);
} catch (IOException j) {
j.printStackTrace();
}
List<News> news = JSONParser(JSONRESPONSE);
return news;
}
#Override
protected void onNewIntent(Intent intent) {
setIntent(intent);
try {
handleIntent(intent);
} catch (MalformedURLException e) {
e.printStackTrace();
}
}
private void handleIntent(Intent intent) throws MalformedURLException {
if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
query_string = intent.getStringExtra(SearchManager.QUERY);
Log.i(LOG_TAG, "The querytext is" + query_string);
}
}
}
This whole process of refreshing the list view is done by a AsyncTaskLoader
The custom Asyntaskloader class is copied below:
public class NewsLoader extends AsyncTaskLoader<List<News>> {
private String mUrl;
private static String LOG_TAG = NewsLoader.class.getName();
public NewsLoader(Context context, String url) {
super(context);
mUrl = url;
}
#Override
protected void onStartLoading() {
forceLoad();
}
#Override
public List<News> loadInBackground() {
if (mUrl == null) {
return null;
}
List<News> news = null;
try {
news = SearchResultsActivity.fetchnews(mUrl);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return news;
}
}
Now I have the search query entered by the user stored in the search_query_input variable in the MainActivity.
But the app just gets stuck when I press the submit button. The override methods for the asynctaskloader are not getting executed at all.
What is happening? Any help will be much appreciated.

searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener(){
onQueryTextChange(String newText){
//when user type in searchview get string as newText parameter
asynTaskMethod(newText);
}
onQueryTextSubmit(String query){
//when user press submit button in searchview get string as query parameter
asynTaskMethod(query);
}
});

Populate list outside of async task

I'm trying to populate a listview with json data (from the web) through an aSync task. I have created a list called myCars earlier on in the script and am having trouble populating it from inside the async thread.
package com.*****.complexlistview;
import android.app.Activity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
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;
import org.json.JSONArray;
import org.json.JSONObject;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends Activity {
private List<Car> myCars = new ArrayList<Car>();
protected String[] mBlogPostTitles;
public static final int NUMBER_OF_POSTS = 20; //caps indicate constants
public static final String TAG = MainActivity.class.getSimpleName();//prints name of class without package name
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(isNetworkAvailable()) {
GetBlogPostsTask getBlogPostsTask = new GetBlogPostsTask(); // new thread
getBlogPostsTask.execute();// don't call do in background directly
populateListView();
}else{
Toast.makeText(this, "Network is unavailable", Toast.LENGTH_LONG).show();
}
}
public boolean isNetworkAvailable() {
ConnectivityManager manager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = manager.getActiveNetworkInfo();
boolean isAvailable = false;
if(networkInfo != null && networkInfo.isConnected()){
isAvailable = true;
}
return isAvailable;
}
private class GetBlogPostsTask extends AsyncTask<Object, Void, String> {
#Override
protected String doInBackground(Object[] params) {
int responseCode = -1;//need to have this variable outside scope of try/catch block
try {
URL blogFeedUrl = new URL("http://blog.teamtreehouse.com/api/get_recent_summary/?count=" + NUMBER_OF_POSTS);
HttpURLConnection connection = (HttpURLConnection) blogFeedUrl.openConnection();
connection.connect();
responseCode = connection.getResponseCode();
if(responseCode == HttpURLConnection.HTTP_OK){ //could have used just 200 value
InputStream inputStream = connection.getInputStream();
Reader reader = new InputStreamReader(inputStream);
int contentLength = connection.getContentLength();
char[] charArray = new char[contentLength];
reader.read(charArray);
String responseData = new String(charArray);
JSONObject jsonResponse = new JSONObject(responseData);
String status = jsonResponse.getString("status");
Log.v(TAG, status);
JSONArray jsonPosts = jsonResponse.getJSONArray("posts");
for(int i=0; i < jsonPosts.length(); i++ ){
JSONObject jsonPost = jsonPosts.getJSONObject(i);
String title = jsonPost.getString("title");
Log.v(TAG, "Post " + i + ": " + title);
myCars.add(new Car(title, 1994, R.drawable.kanye8080s, "Lovable"));
/*myCars.add(new Car("Ford", 1940, R.drawable.stadiumarcadium, "Needing work"));
myCars.add(new Car("Toyota", 1994, R.drawable.kanye8080s, "Lovable"));
myCars.add(new Car("Honda", 1999, R.drawable.meteora, "Great condition"));
myCars.add(new Car("Porsche", 2005, R.drawable.olp, "Awesome"));
myCars.add(new Car("Jeep", 2010, R.drawable.yeezus, "Out of this world"));
myCars.add(new Car("Honda", 1999, R.drawable.meteora, "Great condition"));
myCars.add(new Car("Porsche", 2005, R.drawable.olp, "Awesome"));
myCars.add(new Car("Jeep", 2010, R.drawable.yeezus, "Out of this world"));*/
}
}else{
Log.i(TAG, "Unsuccessful HTTP Response Code: " + responseCode);
}
}
catch (MalformedURLException e){
Log.e(TAG, "Exception caught");
}
catch (IOException e){
Log.e(TAG, "Exception caught");
}
catch (Exception e){//must be in this order, this is the last, general catch
Log.e(TAG, "Exception caught");
}
return "Code: " + responseCode;
}
}
private void populateListView() {
ArrayAdapter<Car> adapter = new MyListAdapter();
ListView list = (ListView) findViewById(R.id.carsListView);
list.setAdapter(adapter);
}
private class MyListAdapter extends ArrayAdapter<Car>{
public MyListAdapter() {
super(MainActivity.this, R.layout.item_view, myCars);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
// make sure we have a view to work with
View itemView = convertView;
if (itemView == null) {
itemView = getLayoutInflater().inflate(R.layout.item_view, parent,false);
}
//find the car to work with
Car currentCar = myCars.get(position);
//fill the view
ImageView imageView = (ImageView) itemView.findViewById(R.id.item_icon);
imageView.setImageResource(currentCar.getIconID());
//Make:
TextView makeText = (TextView) itemView.findViewById(R.id.item_txtMake);
makeText.setText(currentCar.getMake());
//Year
TextView yearText = (TextView) itemView.findViewById(R.id.item_txtYear);
yearText.setText("" + currentCar.getYear());
//Condition
TextView conditionText = (TextView) itemView.findViewById(R.id.item_txtCondition);
conditionText.setText(currentCar.getCondition());
return itemView;
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
The myCars list is supposed to get populated inside of the doInBackground function. After, inside of the main activity function, it should call the populateListView function which ties it all together. I'm having difficulty though getting the data out.
Any help would be greatly appreciated, thanks,
-- 24x7

Populate data in Listview using AsyncTask you should override onPostExecute method of AsyncTask to call populateListView() method.do it as:
Override onPostExecute in GetBlogPostsTask class :
#Override
protected void onPostExecute(Void result) {
// call populateListView method here
populateListView();
super.onPostExecute(result);
}

Failing onPostExecute

I have an app I am trying to pass data through an ASYNC task but am getting a null pointer error in my onPosteExecute method. Seems like no matter how I change my code I still get this same fatal error:
10-31 18:43:56.517 1253-1253/com.brianstacks.project1 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.brianstacks.project1, PID: 1253
java.lang.NullPointerException
at com.brianstacks.project1.MainActivity$MyTask.onPostExecute(MainActivity.java:277)
at com.brianstacks.project1.MainActivity$MyTask.onPostExecute(MainActivity.java:247)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Here is my code:
MainActivity.java
public class MainActivity extends ListActivity implements MasterFragment.OnListItemClickListener {
final String Tag = "Project 1 test";
EditText myEdit;
Button myButton;
ProgressBar pb;
SerialCustomObject myObject;
// create a reference to the list's needed for data
List<MyTask> tasks;
ArrayList<Places> placeList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if ((savedInstanceState != null)&& (savedInstanceState.getSerializable("name") != null)) {
Places name = (Places) savedInstanceState.getSerializable("name");
Log.v("name:",name.getName());
}
//initiate my tasks
tasks = new ArrayList<>();
pb = (ProgressBar)findViewById(R.id.progressBar);
myEdit = (EditText)findViewById(R.id.myEditText);
myButton = (Button)findViewById(R.id.myButton);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
return id == R.id.action_settings || super.onOptionsItemSelected(item);
}
public void findAndRemoveFragment() {
FragmentManager mgr = getFragmentManager();
DetailFragment frag =
(DetailFragment) mgr.findFragmentByTag(DetailFragment.TAG);
if (frag == null) {
// No fragment found, possibly because the transaction
// hasn't completed yet.
} else {
// Fragment found. You can use it here.
FragmentTransaction trans = mgr.beginTransaction();
trans.remove(frag);
trans.commit();
// When the main thread runs, the fragment will be
// removed from the activity.
}
}
public void deviceStorage() {
// Read in a private file
try {
FileInputStream fis = this.openFileInput("some_file.txt");
} catch (FileNotFoundException e) {
e.printStackTrace();
}
// Create new or open existing private file
try {
FileOutputStream fos = this.openFileOutput("some_other_file.txt", Context.MODE_PRIVATE);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
private void writeToFile(Context _c, String _filename, String _data) {
File external = _c.getExternalFilesDir(null);
File file = new File(external, _filename);
try {
FileOutputStream fos = new FileOutputStream(file);
ObjectOutputStream oos = new ObjectOutputStream(fos);
if(myObject == null) {
myObject = new SerialCustomObject();
}
myObject.setData(_data);
oos.writeObject(myObject);
oos.close();
// Write bytes to the stream
fos.write(_data.getBytes());
// Close the stream to save the file.
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private String readFromFile(String _filename) {
File external = getExternalFilesDir(null);
File file = new File(external, _filename);
try {
FileInputStream fin = new FileInputStream(file);
InputStreamReader inReader = new InputStreamReader(fin);
BufferedReader reader = new BufferedReader(inReader);
// Reading data from our file using the reader
// and storing it our string buffer.
StringBuffer buffer = new StringBuffer();
String text = null;
// Make sure a line of text is available to be read.
while((text = reader.readLine()) != null) {
buffer.append(text + "\n");
}
// Close the reader and underlying stream.
reader.close();
// Convert the buffer to a string.
return buffer.toString();
} catch(IOException e) {
e.printStackTrace();
}
return null;
}
#Override
public void displayText(String myText) {
DetailFragment frag = (DetailFragment) getFragmentManager().findFragmentByTag(DetailFragment.TAG);
if (frag == null){
frag = DetailFragment.newInstance(myText);
getFragmentManager().beginTransaction()
.replace(R.id.container2,frag,DetailFragment.TAG)
.commit();
}else {
frag.setDisplayInfo(myText);
}
}
//#Override
public void onClick(View _v){
myEdit = (EditText)findViewById(R.id.myEditText);
String newString = myEdit.getText().toString();
Log.v(Tag,newString);
}
// the method for when the button is clicked
public void myClick(View _v){
// create a string to grab the text of the edit text
String myString = myEdit.getText().toString();
// replace the spaces with + to encode into the url
String encodedString = myString.replace(" ","+");
//check to see if online and if so continue to get the JSON data if not toast a message telling the user no connection
if (isOnline()){
requestData("https://maps.googleapis.com/maps/api/place/textsearch/json?query="+encodedString+"&key=AIzaSyB9iOw6wF4FwbOdUTZYiU_MxsbfWM5iMOI");
}else Toast.makeText(this, "Network isn't available", Toast.LENGTH_SHORT).show();
}
// method to get the data from ASYNC task
private void requestData(String uri) {
MyTask task = new MyTask();
task.execute(uri);
}
// method to check internet connectivity
protected boolean isOnline(){
ConnectivityManager cm =(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
return netInfo != null && netInfo.isConnectedOrConnecting();
}
protected void updateDisplay(ArrayList<Places> placeList){
// get instance of the Master List fragment then replaces container1 and commits it to the activity
MasterFragment frag = MasterFragment.newInstance(placeList);
getFragmentManager().beginTransaction()
.replace(R.id.container1, frag, MasterFragment.TAG).commit();
}
// Async task method to do network action in
private class MyTask extends AsyncTask<String ,String ,String>{
#Override
protected void onPreExecute() {
// add this to the task
tasks.add(this);
}
#Override
protected String doInBackground(String... params) {
return HttpManager.getData(params[0]);
}
#Override
protected void onPostExecute(String result) {
tasks.remove(this);
if(null != result && !result.isEmpty()) {
placeList = JSONParser.parseFeed(result);
updateDisplay(placeList);
}else {
Toast.makeText(MainActivity.this, "Can't connect to API", Toast.LENGTH_SHORT).show();
}
}
#Override
protected void onProgressUpdate(String... values) {
}
}
}
DetailFragment.java
package com.brianstacks.project1.fragments;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import com.brianstacks.project1.R;
/**
* Created by Brian Stacks
* on 10/27/14
* for FullSail.edu.
*/
public class DetailFragment extends Fragment {
public static final String TAG = "DetailFragment.TAG";
public static final String ARG_TAG = "DetailFragment.TAG";
public static DetailFragment newInstance(String myString) {
DetailFragment frag = new DetailFragment();
Bundle args = new Bundle();
args.putString(ARG_TAG, myString);
frag.setArguments(args);
return frag;
}
#Override
public View onCreateView(LayoutInflater _inflater, ViewGroup _container,
Bundle _savedInstanceState) {
// Create and return view for this fragment.
return _inflater.inflate(R.layout.detail_layout, _container, false);
}
#Override
public void onActivityCreated(Bundle _savedInstanceState) {
super.onActivityCreated(_savedInstanceState);
Bundle args = getArguments();
if(args != null && args.containsKey(ARG_TAG)){
setDisplayInfo(args.getString(ARG_TAG));
}
}
public void setDisplayInfo(String myText){
getArguments().putString(ARG_TAG,myText);
// Get our TextView and set some text to it.
TextView tv;
tv = (TextView)getView().findViewById(R.id.detailText);
tv.setText(myText);
}
}
MasterFragment.java
package com.brianstacks.project1.fragments;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.ListFragment;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import com.brianstacks.project1.JSONParser;
import com.brianstacks.project1.MainActivity;
import com.brianstacks.project1.Places;
import com.brianstacks.project1.PlacesAdapter;
import com.brianstacks.project1.R;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Brian Stacks
* on 10/27/14
* for FullSail.edu.
*/
public class MasterFragment extends ListFragment{
public static final String TAG = "MasterFragment.TAG";
public static final String KEY = "places";
private OnListItemClickListener mListener;
private ArrayList<Places> placeList2;
public static MasterFragment newInstance(ArrayList<Places> placeList) {
MasterFragment masterFragment = new MasterFragment();
Bundle args = new Bundle();
args.putSerializable("places", placeList);
masterFragment.setArguments(args);
return masterFragment;
}
public interface OnListItemClickListener{
public void displayText(String myText);
}
#Override
public void onAttach(Activity activity){
super.onAttach(activity);
if (activity instanceof OnListItemClickListener){
mListener = (OnListItemClickListener) activity;
}else {
throw new IllegalArgumentException("Containing Activity must implement the OnListItemClicked");
}
}
#Override
public void onActivityCreated(Bundle _savedInstanceState) {
super.onActivityCreated(_savedInstanceState);
if (_savedInstanceState == null){
Bundle args = getArguments();
String myStrings=args.getString("places");
Log.v("Places",myStrings);
/*String[] presidents = getResources().getStringArray(R.array.presidents);
//ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, presidents);
//PlacesAdapter adapter2 = new PlacesAdapter(this.getActivity(),R.layout.item_place,placeList);
//setListAdapter(adapter2);
}
#Override
public void onListItemClick(ListView _l, View _v, int _position, long _id) {
String president = (String)_l.getItemAtPosition(_position);
mListener.displayText(president);
*/
}
}
}
HTTPManager.java
package com.brianstacks.project1;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
/**
* Created by Brian Stacks
* on 10/20/14
* for FullSail.edu.
*/
public class HttpManager {
public static String getData(String uri){
BufferedReader reader = null;
try {
URL url = new URL(uri);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
StringBuilder sb = new StringBuilder();
reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String line;
while ((line = reader.readLine()) != null){
sb.append(line).append("");
}
return sb.toString();
}catch (Exception e){
e.printStackTrace();
return null;
}finally {
if (reader!=null) {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
JSONParser.java
package com.brianstacks.project1;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Brian Stacks
* on 10/20/14
* for FullSail.edu.
*/
public class JSONParser {
public static ArrayList<Places> parseFeed(String content) {
JSONObject myObj;
try {
myObj = new JSONObject(content);
JSONArray result = myObj.getJSONArray("results");
ArrayList<Places> placeList = new ArrayList<>();
for (int i = 0; i < result.length(); i++) {
JSONObject obj = result.getJSONObject(i);
Places place = new Places();
place.setName(obj.getString("name"));
place.setFormatted_address(obj.getString("formatted_address"));
place.setTypes(obj.getString("types"));
//place.setPhotos(obj.getString("photos"));
placeList.add(place);
}
return placeList;
} catch (JSONException e) {
e.printStackTrace();
return null;
}
}
}
Places.java
import java.io.Serializable;
/**
* Created by Brian Stacks
* on 10/22/14
* for FullSail.edu.
*/
public class Places implements Serializable {
private String pName;
private String pTypes;
private String pFormatted_address;
public Places(){
pName ="";
pTypes ="";
pFormatted_address = "";
}
public String getName() {
return pName;
}
public void setName(String name) {
pName = name;
}
public String getTypes() {
return pTypes;
}
public void setTypes(String types) {
pTypes= types;
}
public String getFormatted_address() {
return pFormatted_address;
}
public void setFormatted_address(String formatted_address) {
pFormatted_address=formatted_address;
}
}
Any help is much appreciated
ALSO was reading this post but to no avail LINK!

I found my solution to this problem, it was I was trying to cast my Objectin my MasterFragment.java as a String when the code was expecting an ArrayList<Places> changed that bit of code and pow there it was, no error.
Old Code
Bundle args = getArguments();
String myStrings=args.getString("places");
New Code
Bundle args = getArguments();
ArrayList myStrings = args.getParcelableArrayList("places");

Android: how to restart a method with a button click

I have a button that gets month and year from spinners then calls an Async task, which read json data. That part works fine But if I try and change the month and year then click the button again it does nothing. I have to press back to reload the page to click the button again to get different results.
Here is my code. Can any of you smart folks please help me.
package com.app.simplictyPortal;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import com.app.simplicityPortal.adapter.InvoiceAdapter;
import android.app.Fragment;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Spinner;
public class InvoiceFragment extends Fragment {
public InvoiceFragment(){}
Button load;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_invoice, container, false);
ArrayList<String> years = new ArrayList<String>();
int thisYear = Calendar.getInstance().get(Calendar.YEAR);
int currentMonth = Calendar.getInstance().get(Calendar.MONTH);
for (int i = 2013; i <= thisYear; i++)
{
years.add(Integer.toString(i));
}
//String tmonth = Integer.toString(currentMonth);
String tyear = Integer.toString(thisYear);
final Spinner year = (Spinner)rootView.findViewById(R.id.spinner1);
final Spinner month = (Spinner)rootView.findViewById(R.id.spinner2);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),
android.R.layout.simple_spinner_item, years);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
year.setAdapter(adapter);
year.setSelection(adapter.getPosition(tyear));
ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(getActivity(),
R.array.month, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
month.setAdapter(adapter2);
month.setSelection(currentMonth);
load=(Button)rootView.findViewById(R.id.button1);
load.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
String y = (String) year.getSelectedItem();
int im = month.getSelectedItemPosition();
String m = Integer.toString(im +1);
final GlobalClass globalVariable = (GlobalClass) getActivity().getApplicationContext();
final String Compid = globalVariable.getCompid();
new InvoiceAsyncTask().execute("http://dev-sql1:8080/api/invoice/getall/"+Compid+"?m="+m+"&y="+y);
}
});
return rootView;
}
public void invoice(JSONArray jArray) {
ListView lv = (ListView) getView().findViewById(R.id.listView1);
List<ListViewItem> items = new ArrayList<InvoiceFragment.ListViewItem>();
try {
for (int i = 0; i <jArray.length(); i++) {
final JSONObject json_data = jArray.getJSONObject(i);
items.add(new ListViewItem()
{{
Vendor= json_data.optString("CarrierName");
Bill = "$ " + json_data.optString("BillAmount");
Serviceacct = json_data.optString("ServiceAccountNumber");
Date = json_data.optString("ReceivedDate");
}});
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
InvoiceAdapter adapter = new InvoiceAdapter(getActivity(), items);
lv.setAdapter(adapter);
// TODO Auto-generated method stub
}
public class ListViewItem
{
public String Vendor;
public String Bill;
public String Serviceacct;
public String Date;
} public static String GET(String url){
InputStream inputStream = null;
String result = "";
try {
// create HttpClient
HttpClient httpclient = new DefaultHttpClient();
// make GET request to the given URL
HttpResponse httpResponse = httpclient.execute(new HttpGet(url));
// receive response as inputStream
inputStream = httpResponse.getEntity().getContent();
// convert inputstream to string
if(inputStream != null)
result = convertInputStreamToString(inputStream);
else
result = "Did not work!";
} catch (Exception e) {
Log.d("InputStream", e.getLocalizedMessage());
}
return result;
}
private static String convertInputStreamToString(InputStream inputStream) throws IOException{
BufferedReader bufferedReader = new BufferedReader( new InputStreamReader(inputStream));
String line = "";
String result = "";
while((line = bufferedReader.readLine()) != null)
result += line;
inputStream.close();
return result;
}
public class InvoiceAsyncTask extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
return GET(urls[0]);
}
// onPostExecute displays the results of the AsyncTask.
#Override
protected void onPostExecute(String result) {
try {
JSONArray jArray = new JSONArray(result);
invoice(jArray);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}

How do you process results of your InvoiceAsyncTask? Do you implement a callback from your AsyncTask's onPostExecute() to the activity?
Maybe the sample below will help you.
First, implement AsyncTask class with callback interface:
public class ServerRequestAsyncTask extends AsyncTask<String, Void, ServerResponseDetails> {
public ServerRequestAsyncTask(Fragment fragment, ServerRequestDetails request) {
mFragment = fragment;
mRequest = request;
}
public interface OnServerRequestAsyncTaskCompletedListener {
void onServerRequestAsyncTaskCompleted(ServerResponseDetails response);
}
public void cancel() {
if (mHttpGet != null && !mHttpGet.isAborted()) mHttpGet.abort();
cancel(true);
}
And also add onPostExecute():
#Override
protected void onPostExecute(ServerResponseDetails response) {
if (mFragment != null) mFragment.onServerRequestAsyncTaskCompleted(response);
}
I call AsyncTask from Fragment, but you can use it with Activity instead.
Then, in your Activity you implement interface:
#Override
public void onServerRequestAsyncTaskCompleted(ServerResponseDetails response) {
// do what you need here, then 'finish' task by setting mServerRequest to null
mServerRequest = null;
}
And to execute AsyncTask:
protected ServerRequestAsyncTask mServerRequest = null;
public boolean isServerRequestRunning() {
return (mServerRequest != null);
}
public void cancelServerRequest() {
mServerRequest.cancel();
}
public void sendServerRequest(Fragment fragment, ServerRequestDetails request) {
if (Application.isNetworkAvailable()) {
if (!isServerRequestRunning()) {
mServerRequest = new ServerRequestAsyncTask(fragment, request);
mServerRequest.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,
{params});
}
}
}
mServerRequest variable holds reference to currently executed task. You can call mServerRequest.cancel() if need to abort.

Thanks Everyone But I have figured it out. I needed to cancel the Async task in the post execute method.
#Override
protected void onPostExecute(String result) {
try {
JSONArray jArray = new JSONArray(result);
invoice(jArray);
cancel(true);
isCancelled();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

Null Pointer Exception after some code moved to a custom Application class

Getting NullPointerException after I moved some of the code to a separate, custom application class called YambaApplication. This application posts to a Twitter enabled service. I checked the code 3 times, and cleaned the project 5 times:
Exception:
06-16 14:08:22.723: E/AndroidRuntime(392): Caused by:
java.lang.NullPointerException 06-16 14:08:22.723:
E/AndroidRuntime(392): at
com.user.yamba.StatusActivity$PostToTwitter.doInBackground(StatusActivity.java:70)
YambaApplication.java (here we initialize and return a twitter object):
package com.user.yamba;
import winterwell.jtwitter.Twitter;
import android.app.Application;
import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.preference.PreferenceManager;
import android.text.TextUtils;
import android.util.Log;
public class YambaApplication extends Application implements
OnSharedPreferenceChangeListener {
private static final String TAG = YambaApplication.class.getSimpleName();
public Twitter twitter;
private SharedPreferences prefs;
#Override
public void onCreate() {
super.onCreate();
this.prefs = PreferenceManager.getDefaultSharedPreferences(this);
this.prefs.registerOnSharedPreferenceChangeListener(this);
Log.i(TAG, "onCreated");
}
#Override
public void onTerminate() {
super.onTerminate();
Log.i(TAG, "onTerminated");
}
#Override
public synchronized void onSharedPreferenceChanged(
SharedPreferences sharedPreferences, String key) {
this.twitter = null;
}
public synchronized Twitter getTwitter() {
if (this.twitter == null) {
String username, password, apiRoot;
username = this.prefs.getString("username", "");
password = this.prefs.getString("password", "");
apiRoot = this.prefs.getString("apiRoot",
"http://yamba.marakana.com/api");
if (!TextUtils.isEmpty(username) && !TextUtils.isEmpty(password)
&& !TextUtils.isEmpty(apiRoot)) {
this.twitter = new Twitter(username, password);
this.twitter.setAPIRootUrl(apiRoot);
}
}
return this.twitter;
}
}
StatusActivity.java (the first activity user sees with an EditText and an update button. Most of the code from YambaApplication class was inside this class.):
package com.user.yamba;
import winterwell.jtwitter.Twitter;
import winterwell.jtwitter.TwitterException;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class StatusActivity extends Activity implements OnClickListener,
TextWatcher {
private static final String TAG = "StatusActivity";
EditText editTextStatusUpdate;
Button buttonStatusUpdate;
TextView textViewCharacterCounter;
//SharedPreferences prefs;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_status);
// Find views
editTextStatusUpdate = (EditText) findViewById(R.id.editStatus);
buttonStatusUpdate = (Button) findViewById(R.id.buttonUpdate);
buttonStatusUpdate.setOnClickListener(this);
textViewCharacterCounter = (TextView) findViewById(R.id.editTextUpdateStatusCounter);
textViewCharacterCounter.setText(Integer.toString(140));
textViewCharacterCounter.setTextColor(Color.GREEN);
editTextStatusUpdate.addTextChangedListener(this);
//prefs = PreferenceManager.getDefaultSharedPreferences(this);
//prefs.registerOnSharedPreferenceChangeListener(this);
// Initialize twitter
// twitter = new Twitter("student", "password");
// twitter.setAPIRootUrl("http://yamba.marakana.com/api");
}
#Override
public void onClick(View v) {
String statusUpdate = editTextStatusUpdate.getText().toString();
new PostToTwitter().execute(statusUpdate);
Log.d(TAG, "onClicked");
}
// Async class to post of twitter
class PostToTwitter extends AsyncTask<String, Integer, String> {
// Async post status to twitter
#Override
protected String doInBackground(String... params) {
try {
YambaApplication yamba = ((YambaApplication) getApplication());
Twitter.Status status = yamba.getTwitter().updateStatus(params[0]); // EXCEPTION FIRED HERE
return status.text;
} catch (TwitterException e) {
Log.e(TAG, "Failed to connect to twitter service");
return "Failed to post";
}
}
// Called when there's status to be updated
#Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
// Not used
}
// Called once async task completed
#Override
protected void onPostExecute(String result) {
Toast.makeText(StatusActivity.this, result, Toast.LENGTH_LONG)
.show();
}
}
#Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
// Not in use
}
#Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// Not in use
}
// Update characters counter after text
// is changed(entered or deleted)
#Override
public void afterTextChanged(Editable statusText) {
int count = 140 - statusText.length();
textViewCharacterCounter.setText(Integer.toString(count));
textViewCharacterCounter.setTextColor(Color.GREEN);
if (count < 10) {
textViewCharacterCounter.setTextColor(Color.YELLOW);
}
if (count < 0) {
textViewCharacterCounter.setTextColor(Color.RED);
}
}
// When user taps on the menu hardware button inflate
// the menu resource
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return true;
}
// Determine what item user tapped on the menu
// and start the item's activity
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.itemPrefs:
startActivity(new Intent(this, PrefsActivity.class));
break;
}
return true;
}
// private Twitter getTwitter() {
// if (twitter == null) {
// String username, password, apiRoot;
// username = prefs.getString("username", "");
// password = prefs.getString("password", "");
// apiRoot = prefs.getString("apiRoot",
// "http://yamba.marakana.com/api");
//
// // Connect to twitter
// twitter = new Twitter(username, password);
// twitter.setAPIRootUrl(apiRoot);
// }
// return twitter;
// }
// #Override
// public void onSharedPreferenceChanged(SharedPreferences sharedPreferences,
// String key) {
// // invalidate twitter
// twitter = null;
//
// }
}
Manifest (added this line to the application tag in the manifest):
android:name=".YambaApplication"

The first thing I saw were the new checks for the username and password to contain text.
Maybe try to debug if they both are set correctly and if a Twitter Object is returned from the Application, or simply null, because of those checks.

Null is because in YambaApplication you check:
if (!TextUtils.isEmpty(username) && !TextUtils.isEmpty(password)
&& !TextUtils.isEmpty(apiRoot)) {
...
}
If any field is empty you get twiter == null.

Develop Reference

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

AsyncTask and MainActivity in separated files - java

You are not initializing activity in Region constructor, so activity is null when you try to call getRegion in asyncTask postExecute. You should init activity in Region constructor.

Your activity is null public Region (Context context, MainActivity act){ this.context = context; this.activity = act; }

You're getting NullPointerException, because your Region class does not find getRegion() method which is inside your MainActivity. Provide the activity to the constructor of Region class.

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