Get all child views inside LinearLayout at once

((ViewGroup) findViewById(android.R.id.content));// you can use this in an Activity to get your layout root view, then pass it to findAllEdittexts() method below.

Here I am iterating only EdiTexts, if you want all Views you can replace EditText with View.

SparseArray<EditText> array = new SparseArray<EditText>();

private void findAllEdittexts(ViewGroup viewGroup) {

    int count = viewGroup.getChildCount();
    for (int i = 0; i < count; i++) {
        View view = viewGroup.getChildAt(i);
        if (view instanceof ViewGroup)
            findAllEdittexts((ViewGroup) view);
        else if (view instanceof EditText) {
            EditText edittext = (EditText) view;
            array.put(editText.getId(), editText);
        }
    }
}

Use getChildCount() and getChildAt(int index).

Example:

LinearLayout ll = …
final int childCount = ll.getChildCount();
for (int i = 0; i < childCount; i++) {
      View v = ll.getChildAt(i);
      // Do something with v.
      // …
}

use this

    final int childCount = mainL.getChildCount();
    for (int i = 0; i < childCount; i++) {
          View element = mainL.getChildAt(i);

        // EditText
        if (element instanceof EditText) {
            EditText editText = (EditText)element;
            System.out.println("ELEMENTS EditText getId=>"+editText.getId()+ " getTag=>"+element.getTag()+
            " getText=>"+editText.getText());
        }

        // CheckBox
        if (element instanceof CheckBox) {
            CheckBox checkBox = (CheckBox)element;
            System.out.println("ELEMENTS CheckBox getId=>"+checkBox.getId()+ " getTag=>"+checkBox.getTag()+
            " getText=>"+checkBox.getText()+" isChecked=>"+checkBox.isChecked());
        }

        // DatePicker
        if (element instanceof DatePicker) {
            DatePicker datePicker = (DatePicker)element;
            System.out.println("ELEMENTS DatePicker getId=>"+datePicker.getId()+ " getTag=>"+datePicker.getTag()+
            " getDayOfMonth=>"+datePicker.getDayOfMonth());
        }

        // Spinner
        if (element instanceof Spinner) {
            Spinner spinner = (Spinner)element;
            System.out.println("ELEMENTS Spinner getId=>"+spinner.getId()+ " getTag=>"+spinner.getTag()+
            " getSelectedItemId=>"+spinner.getSelectedItemId()+
            " getSelectedItemPosition=>"+spinner.getSelectedItemPosition()+
            " getTag(key)=>"+spinner.getTag(spinner.getSelectedItemPosition()));
        }

    }