Whats wrong with my code? Android simple list view example

Question

I am creating simple listview from string array. i watched many tutorials all are saying the same just 3 lines enough to make it work.I am doing the same but still getting NPE , almost frustrated with this issue. Could not figure out whats went wrong please help me.

My code is here:

Mainfiest:

   <uses-sdk
    android:minSdkVersion="16"
    android:targetSdkVersion="18" />

MainActivity.java

public class MainActivity extends Activity {
    ListView lv;
    String[] days = new String[] { "Sunday", "Monday", "Tuesday",
        "Wednesday", "Thursday", "Friday"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView) findViewById(R.id.listView1);

        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction().add(R.id.container, new PlaceholderFragment()).commit();
        }

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, days);
        lv.setAdapter(adapter);
    }

    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            return rootView;
        }
    }
}

you know what,absence of logcat frustrate people at SO,when SOMEONE ask question about NPE or ANR — nobalG, Jul 28 '14 at 06:50
This question appears to be off-topic because it is about an error which is not included in the question. — Nanne, Jul 28 '14 at 06:55
Check this your **listView1** is belong to your **activity_main layout**. — M D, Jul 28 '14 at 06:55
i have strongly doubt that you are using wrong XML file....... So check it first... — Pragnesh Ghoda シ, Jul 28 '14 at 06:56
its a common prob with beginners..i have faced it too.. so no worries.. — Pragnesh Ghoda シ, Jul 28 '14 at 06:58
possible duplicate of [NullPointerException accessing views in onCreate()](http://stackoverflow.com/questions/23653778/nullpointerexception-accessing-views-in-oncreate) — Haresh Chhelana, Jul 28 '14 at 07:29

score 1 · Accepted Answer · answered Jul 28 '14 at 06:58

Hey are you wrong configure code. here you are put listview in fragment xml and write your code in mainactivity class so you have to either remove your fragment xml and Replace your fragment xml code to mainactivity xml and Remove below code

if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }

from onCreate()

OR

Just Initialize your Listview in OnCreateView of Fragment Class

public static class PlaceholderFragment extends Fragment {
    ListView lv;
String[] days = new String[] { "Sunday", "Monday", "Tuesday",
    "Wednesday", "Thursday", "Friday"};

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
            lv = (ListView) view.findViewById(R.id.listView1);
            ArrayAdapter<String> adapter = new ArrayAdapter<String>(GetActivity(),
            android.R.layout.simple_list_item_1, days);

            lv.setAdapter(adapter);
        return rootView;
    }
}

Thats it...

score 0 · Answer 2 · answered Jul 28 '14 at 06:56

0

change

setContentView(R.layout.activity_main);

to

setContentView(R.layout.fragment_main);

answered Jul 28 '14 at 06:56

Pragnesh Ghoda シ

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score 0 · Answer 3 · answered Jul 28 '14 at 07:02

Your showing new fragment in your activity.

if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
}

But listview is declared in main activity layout. So to view your list view just comment above code and see.

score 0 · Answer 4 · answered Jul 28 '14 at 07:09

You need to add items in your "String[] days" to your "adapter" you can use the methods adapter.add or adapter.addAll for adding items to your ArrayAdapter.for more details here is an example of simple listView

http://windrealm.org/tutorials/android/android-listview.php

Whats wrong with my code? Android simple list view example

4 Answers4