Question

public void directionSpinner (String directions []) {
        //Does some stuff to assign namedDirections [0] and namedDirections[1] a value.

        dirSpinner = (Spinner) findViewById(R.id.route_direction_spinner); //THIS IS LINE 87
        dirSpinner.setOnItemSelectedListener(this);
        ArrayAdapter<CharSequence> adapter = new ArrayAdapter(this, android.R.layout.simple_spinner_item);

        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        adapter.add(namedDirections[0]);
        adapter.add(namedDirections[1]);
        dirSpinner.setAdapter(adapter);

        Log.i(TAG, "spinner populated");
}

LogCat:

12-09 20:50:13.497: E/AndroidRuntime(857): FATAL EXCEPTION: main
12-09 20:50:13.497: E/AndroidRuntime(857): java.lang.NullPointerException
12-09 20:50:13.497: E/AndroidRuntime(857):  at android.app.Activity.findViewById(Activity.java:1839)
12-09 20:50:13.497: E/AndroidRuntime(857):  at com.nicotera.colton.londontransitguide.RoutesActivity.directionSpinner(RoutesActivity.java:87)
12-09 20:50:13.497: E/AndroidRuntime(857):  at com.nicotera.colton.londontransitguide.MyInnerClass.onPostExecute(RoutesActivity.java:142)
12-09 20:50:13.497: E/AndroidRuntime(857):  at com.nicotera.colton.londontransitguide.MyInnerClass.onPostExecute(RoutesActivity.java:1)

Anyways, route_direction_spinner is defined correctly. directionSpinner() runs after an AsyncTask is completed.

Entire Code:

package com.nicotera.colton.londontransitguide;

import java.io.IOException;
import java.text.DecimalFormat;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.jsoup.*;
import org.jsoup.nodes.Attributes;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;

public class RoutesActivity extends Activity implements OnItemSelectedListener {
    Spinner dirSpinner;
    Spinner routeSpinner;


    static String [] namedDirections = new String [2];
    private static final String TAG = "RoutesActivity";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_routes);
        dirSpinner = (Spinner) findViewById(R.id.route_direction_spinner); // Create an ArrayAdapter using the string array and a default spinner layout
        routeSpinner = (Spinner) findViewById(R.id.route_name_spinner); // Create an ArrayAdapter using the string array and a default spinner layout
        routeSpinner.setOnItemSelectedListener(this);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.routes_array, android.R.layout.simple_spinner_item);
        // 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
        routeSpinner.setAdapter(adapter);
        Log.i(TAG, "second spinner populated");
    }

    public void onItemSelected(AdapterView<?> parent, View view, 
            int pos, long id) {
        Log.i(TAG, "Item selected");
        //DecimalFormat df = new DecimalFormat("00##");
        int tempPos = pos;
        Log.i(TAG, ("Position of selected item: " + tempPos));
        int routeSelected;
        if (tempPos < 17)
            routeSelected = (tempPos + 1);
        else if (tempPos >= 17 && tempPos < 29)
            routeSelected = (tempPos + 2);
        else
            routeSelected = (tempPos + 3);
        String temp;
        if (routeSelected < 10)
            temp = ("0") + routeSelected;
        else
            temp = ("") + routeSelected;
        String url = "http://www.ltconline.ca/WebWatch/MobileAda.aspx?r=" + temp;
        new MyInnerClass().execute(url);

    }

    public void directionSpinner (String directions []) {
        int temp;
        for (int i = 1; i <=2; i++)
        {
            temp = Integer.parseInt(directions[i]);
            if (temp == 1)
                namedDirections[(i-1)] = "Eastbound";
            else if (temp == 2)
                namedDirections[(i-1)] = "Northbound";
            else if (temp == 3)
                namedDirections[(i-1)] = "Southbound";
            else if (temp == 4)
                namedDirections[(i-1)] = "Westbound";               
        }
        //setContentView(R.layout.activity_routes);

        dirSpinner.setOnItemSelectedListener(this);
        ArrayAdapter<CharSequence> adapter = new ArrayAdapter(this, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        adapter.add(namedDirections[0]);
        adapter.add(namedDirections[1]);
        dirSpinner.setAdapter(adapter);
        Log.i(TAG, "spinner populated");
    }



    public void onNothingSelected(AdapterView<?> parent) {
        // Another interface callback
    }
}

class MyInnerClass extends AsyncTask<String, Void, String> {
    String [] directions = new String [3];
    String [] directionNames = new String [3];
    private static final String TAG = "RoutesActivity";
       @Override
       protected void onPreExecute() {
       super.onPreExecute();

       }

       @Override
       protected void onPostExecute(String result) {
       super.onPostExecute(result);
       RoutesActivity tc = new RoutesActivity();
       tc.directionSpinner(directions);
       }

    @Override
    protected String doInBackground(String... params) {
        try{
            Pattern routeDirPattern = Pattern.compile("\\&d=(\\d{1,2})");
            Connection conn = Jsoup.connect(params[0]);
            Document doc = conn.get();
            int i = 0;
            Elements routeLinks = doc.select("a[href]");
            for (Element routeLink : routeLinks) {
                i = (i + 1);
                String name = routeLink.text();
                Attributes attrs = routeLink.attributes();
                String href = attrs.get("href");
                Matcher m = routeDirPattern.matcher(href);
                if (m.find()) {
                        String number = m.group(1);
                        directions [i] = number;
                        directionNames [i] = name;
                        Log.i(TAG, directionNames [i]);
                }
            }
            }catch(Exception e){Log.d("doinbackground exception", e.toString());}
           return ("Done");
    }
}

Basically, this grabs some values from a transit website. This section of code so far just gets the direction of the route based off the route selected.

Answer 1

(Your directionSpinner() method is different in the two snippets you’ve posted, and I’m working using the one added later, but this solution should work for both snippets, assuming the problem is the same)

Your problem is that you’re not following the Activity lifecycle properly.

When you call:

RoutesActivity tc = new RoutesActivity();
tc.directionSpinner(directions);

You are actually creating a brand new instance of RoutesActivity. And since you’re calling it as a standard Java class, it never follows the Activity lifecycle, which means that onCreate() is never called, which in turn means that your two spinner objects remain null (as you assign values to them in onCreate()).

Due to this, when you use:

dirSpinner.setOnItemSelectedListener(this);

dirSpinner is actually null resulting in a NullPointerException.

Instead, try using:

RoutesActivity.this.directionSpinner(directions);

Instead of:

RoutesActivity tc = new RoutesActivity();
tc.directionSpinner(directions);