How to get element of listview row using getChildAt

Question

I have a custom view (which has checkbox) for listview. I also added a checkbox in activity layout to select all checkboxes. I'm getting all the listview items when I select the activity checkbox but I'm unable to make all the checkboxes in listview as checked. When I tried to use getChildAt() in for loop, I'm getting a Null Pointer .

// row layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:id="@+id/rootlay">

    <CheckBox
        android:id="@+id/cbBox"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical" >
    </CheckBox>

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp"
        android:orientation="vertical"
        android:layout_weight="1" >

        <TextView
            android:id="@+id/tvDescr"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="5dp"
            android:text=""
            android:textSize="20sp" >
        </TextView>

        <TextView
            android:id="@+id/tvPrice"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:text="" >
        </TextView>
    </LinearLayout>


</LinearLayout>

public class ContactsPickerActivity extends AppCompatActivity{

    ArrayList<Model> arrayList = new ArrayList<>();
    ListView list;
    CustomAdapter adapter;
    CheckBox selectall;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_contact);

        list = (ListView)findViewById(R.id.list);
        Button loadbtn = (Button)findViewById(R.id.loadbtn);
        loadbtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M ){
                    askForPermission(Manifest.permission.READ_CONTACTS,1100);
                }else{
                    new LoadContactsAyscn().execute();
                }

            }
        });

        Button getbtn = (Button)findViewById(R.id.getbtn);
        getbtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String result = "Selected Product are :";
                for (Model p : adapter.getBox()) {
                    if (p.box){
                        result += "\n" + p.price;
                    }
                }
                Toast.makeText(ContactsPickerActivity.this, result, Toast.LENGTH_LONG).show();
            }
        });

        adapter = new CustomAdapter(ContactsPickerActivity.this, arrayList);
        list.setAdapter(adapter);

        selectall = (CheckBox)findViewById(R.id.selectall);
        selectall.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
                if(b){
                    int count = list.getAdapter().getCount();
                    System.out.println("sammy_total_count "+count);
                    for(int i=0; i<count; i++){
                        adapter.getProduct(i).box=true;
                        LinearLayout itemlay = (LinearLayout)list.getChildAt(i);
                        CheckBox checkBox = (CheckBox)itemlay.findViewById(R.id.cbBox);
                        checkBox.setTag(i);
                        checkBox.setChecked(adapter.getProduct(i).box);
                    }
                }else{
                    int count = list.getAdapter().getCount();
                    System.out.println("sammy_total_count "+count);
                    for(int i=0; i<count; i++){
                        adapter.getProduct(i).box=false;
                        LinearLayout itemlay = (LinearLayout)list.getChildAt(i);
                        CheckBox checkBox = (CheckBox)itemlay.findViewById(R.id.cbBox);
                        checkBox.setTag(i);
                        checkBox.setChecked(adapter.getProduct(i).box);
                    }
                }

            }
        });
    }

    private void askForPermission(String permission, Integer requestCode) {
        System.out.println("sammy_reached_askForPermission");
        if (ContextCompat.checkSelfPermission(ContactsPickerActivity.this, permission) != PackageManager.PERMISSION_GRANTED) {

            if(ActivityCompat.shouldShowRequestPermissionRationale(ContactsPickerActivity.this, permission)) {
                // if (shouldShowRequestPermissionRationale(permission)) {  // for fragment

                ActivityCompat.requestPermissions(ContactsPickerActivity.this, new String[]{permission}, requestCode);
                // requestPermissions(new String[]{permission}, requestCode);  // for fragment

            } else {

                ActivityCompat.requestPermissions(ContactsPickerActivity.this, new String[]{permission}, requestCode);
                // requestPermissions(new String[]{permission}, requestCode); // for fragment
            }
        } else {
            new LoadContactsAyscn().execute();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        System.out.println("sammy_reached_onRequestPermissionsResult");
        if(ActivityCompat.checkSelfPermission(ContactsPickerActivity.this, permissions[0]) == PackageManager.PERMISSION_GRANTED){
            if(requestCode==1100){
                new LoadContactsAyscn().execute();
            }
            Toast.makeText(ContactsPickerActivity.this, "Permission granted", Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(ContactsPickerActivity.this, "Permission denied", Toast.LENGTH_SHORT).show();
        }
    }

    class LoadContactsAyscn extends AsyncTask<Void, Void, ArrayList<Model>> {
        ProgressDialog pd;

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();

            pd = ProgressDialog.show(ContactsPickerActivity.this, "Loading Contacts",
                    "Please Wait");
        }

        @Override
        protected ArrayList<Model> doInBackground(Void... params) {


            Cursor c = getContentResolver().query(
                    ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null,
                    null, null, null);
            while (c.moveToNext()) {

                String contactName = c.getString(c.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
                String phNumber = c.getString(c.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));


                arrayList.add(new Model(contactName,phNumber, false));

            }
            c.close();

            return arrayList;
        }

        @Override
        protected void onPostExecute(ArrayList<Model> contacts) {
            // TODO Auto-generated method stub
            super.onPostExecute(contacts);

            pd.cancel();
            adapter.notifyDataSetChanged();


        }

    }
}

where do you initialize adapter? – Randyka Yudhistira Dec 27 '16 at 07:32 — Randyka Yudhistira, Dec 27 '16 at 07:32
What is list and where you initialized it ? – Surabhi Singh Dec 27 '16 at 07:36 — Surabhi Singh, Dec 27 '16 at 07:36
in Activty. @RandykaYudhistira – Somnath Pal Dec 27 '16 at 07:37 — Somnath Pal, Dec 27 '16 at 07:37

score 1 · Answer 1 · answered Dec 27 '16 at 07:44

Better you can define one

      ArrayList<ViewHolder> holders = new ArrayList<>();

and in your adapter just add your holders into list like

          holders.add(holder);

and whenever you are pressing checkbox just get the holder and get the checkbox and set the checkbox state like following

  (holders.get(POSITION)).checkbox.setChecked(boolean);

it ll be simple and easy one to do....

Hope it helps!!!

Exigente05 · Answer 2 · 2016-12-27T08:09:45.550

0

Change like this,

for(int i=0; i<count; i++){
                    adapter.getProduct(i).box=true;
                    View rowView = list.getChildAt(i);
                    LinearLayout itemlay = (LinearLayout)rowView.findViewById(R.id.id);
                    CheckBox checkBox = (CheckBox)rowView.findViewById(R.id.cbBox);
                    checkBox.setTag(i);
                    checkBox.setChecked(adapter.getProduct(i).box);
                }

Here is an issue of visible items and total items. NPE is getting because not all items are in view. So you need to change like this,

for(int i=0; i<count; i++){
                    adapter.getProduct(i).box=true;
                    notifyDataSetChanged();
                }

And inside list adapter getView() method

checkBox.setChecked(adapter.getProduct(i).box);

Make sure getProduct(i).box value is not null

edited Dec 27 '16 at 08:09

answered Dec 27 '16 at 07:42

Exigente05

2,161
3
22
42

I used the above code but still its giving NPE @Exigente05 – Somnath Pal Dec 27 '16 at 07:54
what id you are using to get LinearLayout? – Exigente05 Dec 27 '16 at 07:57
R.id.rootlay @Exigente05 – Somnath Pal Dec 27 '16 at 08:03
Thanks for the answer. I got it working by passing the checkbox into adapter constructor and then using this check box in adapter. – Somnath Pal Dec 27 '16 at 08:20

score 0 · Answer 3 · answered Dec 27 '16 at 07:46

0

I think you should change "box" property in your models and use notifyDataSetChanged().

ListView will be refreshed and the CheckBoxes will be updated by your boolean field.

answered Dec 27 '16 at 07:46

oyenigun

587
6
15

How to get element of listview row using getChildAt

3 Answers3