setAdapter is showing NullPointerException

Question

I want to open a dialog for user to choose from multiple items but I get an error when setAdapter() was going to execute...

button.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                Dialog cd = new Dialog(Main1.this);

                String[] mobileArray = {"Android","IPhone","WindowsMobile","Blackberry","WebOS","Ubuntu","Windows7","Max OS X"};

                ArrayAdapter adapter = new ArrayAdapter<String>(cd.getContext(), R.layout.lvlayout, mobileArray);

                 ListView listView = (ListView) findViewById(R.id.listviewID);

                 listView.setAdapter(adapter);


                cd.setContentView(R.layout.dialogLayout);
                cd.setTitle("MEOW");
                cd.show();

            }
        });

ListView is in Dialog layout. whats Wrong here?

then use `ListView listView = (ListView) cd.findViewById(R.id.listviewID);` — Shree Krishna, Mar 27 '16 at 07:02
can you check this [listview with in alert dialog](http://stackoverflow.com/a/15762955/5955593) — Kathi, Mar 27 '16 at 07:05
adding listview in your `dialogLayout` will work as suggested by @ShreeKrishna — Kathi, Mar 27 '16 at 07:09

score 1 · Accepted Answer · answered Mar 27 '16 at 07:12

Simply there are two mistakes in your code, you are calling this line without prefixing it with cd. so that you have to do it like this,

ListView listView = (ListView) cd.findViewById(R.id.listviewID);

Another mistake you are doing is calling findViewById before calling setContentView(), This may also raise NPE.

So I suggest you to move this up and re-arrange like this

cd.setContentView(R.layout.dialogLayout);
ListView listView = (ListView) cd.findViewById(R.id.listviewID);

score 0 · Answer 2 · answered Mar 27 '16 at 07:15

0

The problem is that your variable listView null is when you call setAdapter() on it. So the call to findViewById() returns null. Maybe you just used a wrong ID.

answered Mar 27 '16 at 07:15

Micha F.

634
4
17

Reaz Murshed · Answer 3 · 2016-03-27T09:20:43.817

You have some basic mistakes here. The major mistake is calling the cd.setContentView(R.layout.dialogLayout); at the end of your code. You need to call before you want to find something in that content layout.

And the other mistake is trying to find the list. You need to get a view to find the list in that view. This might be something like this.

ListView listView = (ListView) cd.getView().findViewById(R.id.listviewID);

However, I do prefer the following solution for your problem. This might be an easier way for what you're trying to achieve.

Here's a nice example of implementing a custom dialogue. You can have a look here. https://github.com/afollestad/material-dialogs

So, now as you're getting NullPointerException, findViewById is not returning any reference of your ListView I guess. So here by using the library mentioned above you can achieve this quite easily.

// Initialize your dialogue
MaterialDialog dialog = new MaterialDialog.Builder(getActivity())
                .title("MEOW")
                .customView(R.layout.dialogLayout, true)
                .positiveText(R.string.ok)
                .negativeText(R.string.cancel)
                .onNegative(new MaterialDialog.SingleButtonCallback() {
                    @Override
                    public void onClick(@NonNull MaterialDialog dialog, @NonNull DialogAction which) {
                        dialog.dismiss();
                    }
                })
                .show();

// Now get the view of that dialogue. 
View view = dialog.getCustomView();

// Initialize the array adapter
String[] mobileArray = {"Android","IPhone","WindowsMobile","Blackberry","WebOS","Ubuntu","Windows7","Max OS X"};
ArrayAdapter adapter = new ArrayAdapter<String>(cd.getContext(), R.layout.lvlayout, mobileArray);

// Get the list view and set the adapter 
ListView listView = (ListView) view.findViewById(R.id.listviewID);
listView.setAdapter(adapter);

score 0 · Answer 4 · answered Mar 27 '16 at 08:09

Just initialize your listview outside of onClick listener. Initializing it in onCreate() is more preferable.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout);
    // initialize
    ListView listView = (ListView) findViewById(R.id.listviewID);
}

setAdapter is showing NullPointerException

4 Answers4