Listview/arrayadapter OnItemClickevent error

Question

I'm working on a project in android studio that has a list with an array adapter. If i click on a list item you have to be send to the workshop page that show all the info for the workshop. I did this using a setOnItemClickListener but somehow it is not working. its throwing this error

Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference at com.example.jmuts.tikcitv2.scedule$1.onItemClick(scedule.java:68)*

I have no idea how to fix this, so im stuck now. i hope someone can help me.

Schedule.java (This is the code that has the Click event)

public class scedule extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

ListView lv;
ArrayAdapter<String> adapter;
String[] name, beginning, end;
String eventName;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_scedule);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    lv = findViewById(R.id.listView);

    Bundle bundle = getIntent().getExtras();
    if (bundle != null) {
        eventName = bundle.getString("eventname");
    }

    listner(eventName);

    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Intent intent = new Intent(scedule.this, workshop.class);
            intent.putExtra("eventname", lv.getItemAtPosition(position).toString());
            startActivity(intent);
        }
    });

}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.home, 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);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_Change) {
        Intent c = new Intent(scedule.this, MainActivity.class);
        c.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(c);
        finish();
    } else if (id == R.id.nav_home) {
        finish();
    } else if (id == R.id.nav_scedule) {
        //Intent intent = new Intent(scedule.this, scedule.class);
        //intent.putExtra("eventname", eventName);
        //startActivity(intent);
    } else if (id == R.id.nav_map) {
        Intent intent = new Intent(scedule.this, map.class);
        intent.putExtra("eventname", eventName);
        startActivity(intent);
        finish();
    } else if (id == R.id.nav_faq) {
        Intent intent = new Intent(scedule.this, faq.class);
        intent.putExtra("eventname", eventName);
        startActivity(intent);
        finish();
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}


private void listner(String item){
    String getData = null;
    String dbResult = "empty";
    dbConnect database = new dbConnect(this);

    try {
        Date c = Calendar.getInstance().getTime();
        System.out.println("Current time => " + c);

        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        String formattedDate = df.format(c);

        String query = "SELECT c.workshopname, b.starttime, b.endtime FROM events as a inner join scedules as b on a.eventid = b.eventid inner join workshops as c on b.workshopid = c.workshopid where b.workshopid = c.workshopid and b.eventid = (select eventid from events where eventname = '" + item + "') order by b.starttime;";
        getData = "?query=" + URLEncoder.encode(query, "UTF-8");
        //data += "&username=" + URLEncoder.encode(userName, "UTF-8");
        String link = "https://jackstest.000webhostapp.com/androiddbconnect.php" + getData;
        dbResult = database.execute(link).get();
    }
    catch (Exception e){
        e.printStackTrace();
    }

    try{
        JSONArray ja = new JSONArray(dbResult);
        JSONObject jo = null;
        name = new String[ja.length()];
        beginning = new String[ja.length()];
        end = new String[ja.length()];
        for(int i = 0; i < ja.length(); i++){
            jo = ja.getJSONObject(i);
            name[i] = jo.getString("workshopname");
            beginning[i] = "Start: " + jo.getString("starttime");
            end[i] = "end: " + jo.getString("endtime");
        }

        lv.setAdapter(new dataListAdapter(name, beginning, end));
    }
    catch (Exception e){
        e.printStackTrace();
    }
}

class dataListAdapter extends BaseAdapter {
    String[] name, beginning, end;

    dataListAdapter() {
        name = null;
        beginning = null;
        end = null;
    }

    public dataListAdapter(String[] text, String[] text1,String[] text3) {
        name = text;
        beginning = text1;
        end = text3;

    }

    public int getCount() {
        // TODO Auto-generated method stub
        return name.length;
    }

    public Object getItem(int arg0) {
        // TODO Auto-generated method stub
        return null;
    }

    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {

        LayoutInflater inflater = getLayoutInflater();
        View row;
        row = inflater.inflate(R.layout.list_view_scedule_layout, parent, false);
        TextView t1, t2, t3;
        t1 = (TextView) row.findViewById(R.id.list_item1);
        t2 = (TextView) row.findViewById(R.id.list_item2);
        t3 = (TextView) row.findViewById(R.id.list_item3);
        t1.setText(name[position]);
        t2.setText(beginning[position]);
        t3.setText(end[position]);

        return (row);
    }
}

}

Workshop.java (This is the activity that has to show the data)

public class workshop extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

String eventName;
TextView Header;
TextView Content;
TextView Time;
TextView Date;
TextView Location;
ImageView View;
ArrayAdapter<String> adapter;
String[] data;
String [] image;

private Bitmap bitmap;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_workshop);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    Header = (TextView) findViewById(R.id.header);
    Content = (TextView) findViewById(R.id.content);
    Time = (TextView) findViewById(R.id.start_end_time);
    Date = (TextView) findViewById(R.id.date);
    Location = (TextView) findViewById(R.id.location);
    View = (ImageView) findViewById(R.id.imageView3);

    Bundle bundle = getIntent().getExtras();
    if (bundle != null) {
        eventName = bundle.getString("eventname");
    }

    GetInfo(eventName);

}

private void GetInfo(String eventName) {
    String GetInfo = null;
    String dbResult = "empty";
    dbConnect database = new dbConnect(this);

    try{
        String query = "";
        GetInfo = "?query=" + URLEncoder.encode(query, "UTF-8");
        String link = "https://jackstest.000webhostapp.com/androiddbconnect.php" + GetInfo;
        dbResult = database.execute(link).get();
    }
    catch(Exception e){
        Header.setText("Workshop");
    }

    try{
        JSONArray ja = new JSONArray(dbResult);
        JSONObject jo = null;
        data = new String[ja.length()];
        image = new String[ja.length()];

        for (int i = 0;i < 1 ; i++){
            jo = ja.getJSONObject(i);
            data[i] = jo.getString("workshopname");
            image[i] = jo.getString("imagelink");


        }

        bitmap = getBitmapFromURL(image[0]);
        View.setImageBitmap(bitmap);

        Header.setText(data[0]);


    }
    catch(Exception e){
        e.printStackTrace();
    }
}

private Bitmap getBitmapFromURL(String src) {
    try {
        URL url = new URL(src);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setDoInput(true);
        connection.connect();
        InputStream input = connection.getInputStream();
        Bitmap myBitmap = BitmapFactory.decodeStream(input);
        return myBitmap;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.home, 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);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_Change) {
        Intent c = new Intent(workshop.this, MainActivity.class);
        c.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(c);
        finish();
    } else if (id == R.id.nav_home) {
        finish();
    } else if (id == R.id.nav_scedule) {
        Intent intent = new Intent(workshop.this, scedule.class);
        intent.putExtra("eventname", eventName);
        startActivity(intent);
        finish();
    } else if (id == R.id.nav_map) {
        Intent intent = new Intent(workshop.this, map.class);
        intent.putExtra("eventname", eventName);
        startActivity(intent);
        finish();
    } else if (id == R.id.nav_faq) {
        Intent intent = new Intent(workshop.this, faq.class);
        intent.putExtra("eventname", eventName);
        startActivity(intent);
        finish();
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}
 }

Possible duplicate of https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it — O.O.Balance, May 15 '18 at 13:41
i've already seen this article, but this didnt solve my problem. — acesteef, May 15 '18 at 13:50

score 0 · Answer 1 · answered May 15 '18 at 13:51

0

This line causes the error: scedule.java:68 because you are trying toString() for a null object. Just read the error and you'll know what to do. Probably because you didn't initialize your Strings?

answered May 15 '18 at 13:51

mafioso

1,630
4
25
45

score 0 · Answer 2 · answered May 15 '18 at 14:13

The getItemAtPosition function will call your adapter.getItem(position).

Your implementation for your adapter is:

public Object getItem(int arg0) {
    // TODO Auto-generated method stub
    return null;
}

You need to return some Object from this function in your implementation. I would suggest creating a class with your required fields(name,beginning,end), then an array of those in your adapter. Then you could do something like this:

public Object getItem(int arg0) {
    // TODO Auto-generated method stub
    return myDataObjectArray[arg0];
}

Listview/arrayadapter OnItemClickevent error

2 Answers2