In an android ListView, how can I iterate/manipulate all the child views, not just the visible ones?-ThrowExceptions

Exception or error:

The code below does NOT change the text of all of a ListView's rows because getChildCount() does not get all of a ListView's rows, but just the rows that are visible.

for (int i = 0; i < listView.getChildCount(); i++)
{
    View v = listView.getChildAt(i);
    TextView tx = (TextView) v.findViewById(R.id.mytext);
    tx.setTextSize(newTextSize);
}

So, what SHOULD I do?

Is there code for getting a notification when a ListView's row becomes visible, so I can set its text size then?

How to solve:

List13 from the API Demos does something similar using OnScrollStateChanged. There may be a better way, though:

public void onScrollStateChanged(AbsListView view, int scrollState) {
    switch (scrollState) {
    case OnScrollListener.SCROLL_STATE_IDLE:
        mBusy = false;

        int first = view.getFirstVisiblePosition();
        int count = view.getChildCount();
        for (int i=0; i<count; i++) {
            TextView t = (TextView)view.getChildAt(i);
            if (t.getTag() != null) {
                t.setText(mStrings[first + i]);
                t.setTag(null);
            }
        }

        mStatus.setText("Idle");
        break;

.
.
.

EDIT BY Corey Trager:

The above definitely pointed me in the right direction. I found handling OnScrollListener.onScroll worked better than onScrollStateChanged. Even if I removed the case statement in onScrollSgtaetChanged and handled every state change, some text wasn’t getting resized. But with onScroll, things seem to work.

So, my seemingly working code looks like this:

public void onScroll(AbsListView v, int firstVisibleItem, int visibleCount, int totalItemCount)
{
    ListView lv = this.getListView();
    int childCount = lv.getChildCount();

    for (int i = 0; i < childCount; i++)
    {
        View v = lv.getChildAt(i);
        TextView tx = (TextView) v.findViewById(R.id.mytext);
        tx.setTextSize(textSize);
    }
}

###

In a ListView the only children are the visible ones. If you want to do something with “all the children,” do it in the adapter. That’s the best place.

###

Not so sure about the performace effect but u can try this.

//declare the list
ListView list = (ListView)findViewById(R.id.yourListID);

// in my case i have spinners and made a test just to know if this works
 Spinner spnWhatever;
 View view;
 int i =0;


       do{

           view =list.getAdapter().getView(i,null,null);
           //get the spinners from each row
           spnWhatever =(Spinner)view.findViewById(R.id.spnTarifas);

        i++;

       }while(list.getAdapter().getCount() !=i);

###

//Create layout file containing views you want to read input from
//layout/gen_edt_layout.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/parLay"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <com.google.android.material.textfield.TextInputEditText
        android:id="@+id/edtGName"
        android:layout_width = "match_parent"
        android:layout_height ="wrap_content"
        android:hint="Name"
        android:inputType="text" />


    <com.google.android.material.textfield.TextInputEditText
        android:id="@+id/edtGIdPass"
        style="@style/edt"
        android:hint="Id number"
        android:inputType="number" />


</LinearLayout>

//Create Empty Activity -> MultipleInput

//layout/activity_multiple_input.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".OpenAccount">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent">


      <ListView
            android:id="@+id/inputLView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginBottom="60dp" />

    </LinearLayout>

    <Button
        android:layout_width="wrap_content
        android:layout_height="wrap_content"
        android:text="Read"
        android:onClick="readInput"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent>

</androidx.constraintlayout.widget.ConstraintLayout>

public class MultipleInput extends AppCompatActivity {

    //Declare and intialize arrays to store input fields as public modifiers
    ArrayList<TextInputEditText> edtNameArr = new ArrayList<>();
    ArrayList<TextInputEditText> edtIdsArr = new ArrayList<>();

    //Intialize arrays to store input values as public modifiers
    ArrayList<String> arr0 = new ArrayList<>();
    ArrayList<String> arr1 = new ArrayList<>();

    ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {


        listView = findViewById(R.id.listView);

        edtNameArr.clear();
        edtIdsArr.clear();

        arr0.clear();
        arr1.clear();

        //set number of group fields to be generated
        int members = 4;

        //initialize class passing fields number and context
        edtAdapter = new EdtAdapter(members, getApplicationContext());

        //Set retured fields in listView
        listView.setAdapter(edtAdapter);


    }

    public class EdtAdapter extends BaseAdapter {

        class ViewHolder {

            TextInputEditText edtGName, edtGIdPass;
        }

        public Context context;

        ArrayList<EdtClass> edtArrayList;
        int members;

        EdtAdapter(int members, Context context) {

            this.members = members;
            this.context = context;

        }

        @Override
        public int getCount() {
            return members;
        }

        @Override
        public Object getItem(int position) {
            return position;
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(final int position, View contentView, ViewGroup parent) {

            View rowView = contentView;

            if (rowView == null) {

                viewHolder = new ViewHolder();

                LayoutInflater inflater = getLayoutInflater();
                rowView = inflater.inflate(R.layout.gen_edt_layout, parent, false);
                viewHolder.edtGName = rowView.findViewById(R.id.edtGName);
                viewHolder.edtGIdPass = rowView.findViewById(R.id.edtGIdPass);

                viewPosition = position;

                //loop adding input fields in arrays
                for (int i = 0; i < members; i++) {
                    edtNameArr.add(viewHolder.edtGName);
                    edtIdsArr.add(viewHolder.edtGIdPass);
                }


            } else {
                viewHolder = (ViewHolder) contentView.getTag();
            }

            return rowView;

        }

    }


    //Read input when button clicked
    public void readInput(View view){


        for(int edt = 0; edt<edtNameArr.size(); edt++){

            String name = Objects.requireNonNull(edtNameArr.get(edt).getText()).toString();

            if(!arr0.contains(name)) {
                arr0.add(name);
            }

            String ids = Objects.requireNonNull(edtIdsArr.get(edt).getText()).toString();

            if(!arr1.contains(ids)) {
                arr1.add(ids);
            }

        }

        StringBuilder name = new StringBuilder();
        StringBuilder idno = new StringBuilder();

        //loop through arrays with input, reading and appending values in StringBuilder
        for (int m = 0; m < arr0.size(); m++) {

            name.append(arr0.get(m)).append(",");

            idno.append(arr1.get(m)).append(",");

        }

        //Show input values in logcat/Toast
        Log.e("Names ", name.toString());
        Log.e("Ids ", idno.toString());
        Toast.makeText(MultipleInput.this, "Names "+ name.toString(), Toast.LENGTH_LONG).show();

    }

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