# Handling input

> onAction vs onActionThread, focus, TextField/TextArea and the touch/gesture handlers.

Source: https://crossfly.dev/docs/learn/handling-input — CrossFly documentation. Full docs as one file: https://crossfly.dev/llms-full.txt

# 6. Handling input

> **What you'll learn:** reacting to touches, keys, and gestures, and reading text input.
> **Prerequisites:** [Styling and themes](/docs/learn/styling-and-themes).

## Complete example (copy, paste, and run)
An add-task form: field + button with validation, reading the text on submit, and feedback with
`Hint`. It adds the tasks to an output `Label`. Compiles as is.
```java
package com.exemplo;

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

public class MainWindow extends Window
{
   private final TextField campo = new TextField().caption("Nova tarefa");
   private final Label saida = new Label("Nenhuma tarefa ainda");

   @Override
   public void onShow() throws Exception
   {
      super.onShow();
      setLayout(new VerticalLayout());

      add(LAY_AUTO, campo);

      Button add = new Button("Adicionar");
      add.onAction(c -> {                                 // runs on the paint thread
         String texto = campo.getText().trim();
         if (texto.isEmpty()) { Hint.show("Digite algo", 2000); return; }   // validation (2 args)
         adicionarTarefa(texto);
         campo.clearText();
      });
      add(LAY_AUTO, add);

      add(LAY_AUTO, saida);
   }

   private void adicionarTarefa(String texto)
   {
      saida.setText("Adicionada: " + texto);
      saida.repaint();
   }
}
```
> The snippets below show **only the core** (what goes inside `onShow()`). To run them, put them in the `MainWindow` skeleton above.

## `onAction` vs `onActionThread`
```java
botao.onAction(c -> salvar());          // runs on the paint thread (fast, touches the UI)
botao.onActionThread(c -> {             // runs on a background thread (heavy work)
   var dados = baixar();
   c.onUI(() -> mostrar(dados));         // back to the UI
});
```

## Text input — read it on submit
There's no per-key event: read `getText()` when you need it (e.g., in the button).
```java
TextField campo = new TextField().caption("Nova tarefa");
Button add = new Button("Adicionar");
add.onAction(c -> {
   String texto = campo.getText().trim();
   if (texto.isEmpty()) { Hint.show("Digite algo", 2000); return; }   // validation
   adicionarTarefa(texto);
   campo.clearText();
});
```
Focus: override `onFocus()`/`onBlur()` in a subclass when you need to react to gaining/losing focus.

## Touch gestures (overridable)
In a custom component, override the handlers for gestures:
```java
@Override public void onLongTouch(float x, float y) throws Exception { abrirDetalhe(); }
// also: onTouchDown/onTouchUp/onPan
```
> Exceptions in callbacks go to `Debug.handle` (they don't bubble up to bring down the frame).

## What you build in this step
The **add-task form** (field + button + validation) and the **gesture** to open the detail.

## Recap
`onAction` (UI) / `onActionThread` (background); read text with `getText()` on submit; gestures via
overridable handlers; errors go to `Debug.handle`.

## Next steps
→ [Managing state](/docs/learn/managing-state)

## See also
- [Forms and input (ui)](/docs/ui/forms-and-input) · Canonical source: Chapter 6 · Chapter 14