`KeyboardAvoidingView` — `behavior` chọn `padding` hay `height`?

<KeyboardAvoidingView> đẩy nội dung lên khi keyboard mở để không che TextInput. Prop behavior:

• padding (recommend cho iOS): thêm padding bottom = chiều cao keyboard. Children giữ nguyên, chỉ vùng dưới được "đẩy" lên. Mượt và predictable.
• height: shrink chiều cao container = screenHeight - keyboardHeight. Hữu ích khi container có background image — tránh image bị resize.
• position: dịch toàn bộ container lên trên. Dễ gây content bị cắt nếu không có ScrollView ngoài.
• undefined (Android): default Android có windowSoftInputMode="adjustResize" trong AndroidManifest.xml xử lý việc này tự động.

Pattern thực tế cross-platform:

<KeyboardAvoidingView
  behavior={Platform.OS === 'ios' ? 'padding' : undefined}
  style={{ flex: 1 }}
  keyboardVerticalOffset={headerHeight}
>
  <ScrollView keyboardShouldPersistTaps="handled">{...}</ScrollView>
</KeyboardAvoidingView>

keyboardVerticalOffset cần khi có header navigation bên trên — bù phần header để keyboard đẩy đúng vị trí.

<KeyboardAvoidingView> pushes content up so the keyboard does not cover a TextInput. The behavior prop:

• padding (recommended for iOS): adds bottom padding equal to keyboard height. Children stay put, only the bottom area is pushed up. Smooth and predictable.
• height: shrinks container height to screenHeight - keyboardHeight. Useful when the container has a background image you do not want resized.
• position: shifts the whole container up. Easy to crop content if there is no outer ScrollView.
• undefined (Android): the platform default with windowSoftInputMode="adjustResize" in AndroidManifest.xml already handles this.

Practical cross-platform pattern:

<KeyboardAvoidingView
  behavior={Platform.OS === 'ios' ? 'padding' : undefined}
  style={{ flex: 1 }}
  keyboardVerticalOffset={headerHeight}
>
  <ScrollView keyboardShouldPersistTaps="handled">{...}</ScrollView>
</KeyboardAvoidingView>

keyboardVerticalOffset is needed when a navigation header is above — it accounts for the header so the keyboard pushes by the right amount.