# How to ask for confirmation with Alert

> Open a modal confirmation dialog with Cancel/OK buttons and react to the choice.

Source: https://crossfly.dev/docs/cookbook/ui/confirmar-com-alert — CrossFly documentation. Full docs as one file: https://crossfly.dev/llms-full.txt

# How to ask for confirmation with Alert

**Purpose.** Show a modal dialog with a title, a message and one or more buttons, and
run an action depending on the button pressed. Use it for destructive confirmations
("Delete?"), warnings that require the user's acknowledgment, or simple choices.

## APIs used
- `new Alert(String title, String message, String... buttonTexts)` — creates the alert. The button texts are passed **in the constructor** (index 0, 1, 2...). If none is given, it uses `"OK"`.
- `alert.buttonAction(int index, Component.Action action)` — registers the callback for the button at that index. **There is no `addButton`**; the buttons were already declared in the constructor.
- `alert.show()` — displays the dialog (inherited from `Window`).
- `alert.getStyle().fadeBackground(int alpha)` — darkens the background behind the alert (0–255). `getStyle()` returns the alert's `WindowStyle`.
- `alert.getButton(int index)` — returns the `Button` at that index (available after `show()`).

> Non-obvious behavior: if you **don't** register a `buttonAction` for a button,
> it just closes the alert (`hide()`) when tapped. So, for "Cancel", you often
> don't even need a callback.

## Complete example (copy, paste and run)
```java
package com.exemplo;

import dev.crossfly.ui.*;
import dev.crossfly.ui.layout.*;

/** Runnable main screen. Point the launcher (classname) and run: gradlew :lwjgl3:run */
public class MainWindow extends Window
{
   @Override
   public void onShow() throws Exception
   {
      super.onShow();
      setLayout(new VerticalLayout());

      // Trigger button: opens the Alert when tapped
      Button btn = new Button("Excluir registro");
      btn.onAction(origin ->
      {
         Alert alert = new Alert(
            "Excluir registro",
            "Esta ação não pode ser desfeita. Deseja continuar?",
            "Cancelar",   // index 0
            "Excluir");   // index 1

         // Darkens the background (optional, but recommended for destructive modals)
         alert.getStyle().fadeBackground(150);

         // Button 0 (Cancel) with no callback → just closes.
         // Button 1 (Delete) runs the action and closes:
         alert.buttonAction(1, o ->
         {
            excluirRegistro();
            alert.hide();
         });

         alert.show();
      });
      add(LAY_FILL, btn);
   }

   private void excluirRegistro()
   {
      // ... your deletion logic ...
   }
}
```

> The snippet below shows **just the core**. To run it, place it in the `MainWindow` skeleton above.

## Minimal snippet
```java
Alert alert = new Alert(
   "Excluir registro",
   "Esta ação não pode ser desfeita. Deseja continuar?",
   "Cancelar",   // index 0
   "Excluir");   // index 1

// Darkens the background (optional, but recommended for destructive modals)
alert.getStyle().fadeBackground(150);

// Button 0 (Cancel) with no callback → just closes.
// Button 1 (Delete) runs the action and closes:
alert.buttonAction(1, origin ->
{
   excluirRegistro();
   alert.hide();
});

alert.show();
```

> **Verification note (2026 code).** Confirmed in source: constructor
> `Alert(title, message, String... buttonTexts)` + `buttonAction(int, Action)`.
> The button layout (iOS/Material/Flutter) is decided by the active `Skin`'s `AlertStyle` —
> switch the `Skin` (or use `alert.skin(new IOSSkin())`) to change the look
> without changing the logic code. The alert's width/height is auto-computed from
> the title, message and buttons.

## Dig deeper
- Widget page: [Alert](/docs/ui/widgets/alert) · Canonical source: Chapter 16
- Sister recipes: [Actions menu (ActionSheet)](/docs/cookbook/ui/menu-de-acoes) · [Show a Hint](/docs/cookbook/ui/mostrar-um-hint)