Spinner, AlertDialog

📖 Theory

A long list, then a final check

FestConnect needs two more things: a T-shirt size picker (S, M, L, XL, XXL) that does not eat the screen with five radio buttons, and a final 'Confirm registration?' box the student must answer before submitting.

Those are two widgets that often appear together: the Spinner (a compact dropdown) and the AlertDialog (a modal yes/no pop-up). One gathers a choice from a list; the other stops and asks a question. Learn them as a pair.

📖 Theory

A drop-down menu and a security gate

A Spinner is a restaurant menu on a rail: it stays folded showing your current pick, and drops open to reveal the full list when tapped. An AlertDialog is a security gate: it blocks the corridor and will not let you pass until you answer 'proceed?' yes or no. One is a tidy chooser; the other is a deliberate stop-and-decide.

📖 Theory

Spinner, then AlertDialog

Spinner (dropdown):

• Fill it with an ArrayAdapter (from a string array).
• React with setOnItemSelectedListener.
• Read with getSelectedItem() (or getSelectedItemPosition()).

AlertDialog (modal question):

• Build with new AlertDialog.Builder(this).
• setTitle, setMessage, setPositiveButton("OK", ...), setNegativeButton("Cancel", ...).
• Finish with create() then show() (or just .show()).

The dialog blocks until the user answers, unlike a Toast.

⌨️ Practical

Size Spinner, then confirm

// Spinner: feed it a list with an adapter
Spinner size = findViewById(R.id.size);
String[] sizes = {"S", "M", "L", "XL", "XXL"};
size.setAdapter(new ArrayAdapter<>(this,
        android.R.layout.simple_spinner_item, sizes));

register.setOnClickListener(v -> {
    String picked = size.getSelectedItem().toString();

    // AlertDialog: modal confirm before submitting
    new AlertDialog.Builder(this)
        .setTitle("Confirm")
        .setMessage("Register with size " + picked + "?")
        .setPositiveButton("Yes", (dialog, which) ->
            Toast.makeText(this, "Registered!", Toast.LENGTH_SHORT).show())
        .setNegativeButton("Cancel", null)
        .show();
});

💭 Think first

Toast or AlertDialog?

FestConnect could confirm the registration with a Toast ('Registered!') or an AlertDialog ('Register with size L? Yes/No'). Which fits a final confirmation the user must actively agree to, and why is the other wrong here?

🧩 Quiz

A Spinner shows nothing in its dropdown when tapped. What is the most likely missing step?

1. No adapter was set to supply the list of items
2. It needs a RadioGroup wrapper
3. The AlertDialog was not created
4. getSelectedItem() was never called

⚠️ Watch out

Spinner and dialog traps

1. Spinner with no adapter: it shows nothing. Populate it with an ArrayAdapter.

2. Building an AlertDialog but not showing it: like Toast, you must call show() (after create(), or directly). No show(), no dialog.

3. Using a Toast where a decision is required: a Toast cannot capture Yes/No. For a real choice, an AlertDialog with positive/negative buttons is correct.

📖 Theory

Next: the last widget, smart text

One widget remains: the AutoCompleteTextView, a text field that suggests matches as you type (great for FestConnect's college field), paired with a TextWatcher that reacts to every keystroke. It combines the adapter idea from the Spinner with live text events, a fitting finale that ties the unit together.

✅ Summary

Key takeaways

• A Spinner is a dropdown; populate it with an ArrayAdapter and read the choice with getSelectedItem().
• Use a Spinner for one choice from a longer list (RadioButtons suit a few options).
• An AlertDialog is a modal question built with AlertDialog.Builder: setTitle, setMessage, setPositiveButton/setNegativeButton, then show().
• An AlertDialog blocks until answered (a real decision); a Toast just flashes (passive feedback).
• A Spinner needs an adapter, and an AlertDialog needs show(), or nothing appears.
• Memory hook: a drop-down menu (Spinner) and a security gate (AlertDialog).