Platform & Accessibility¶
Platform¶
Platform is the canonical way to write
platform-aware code:
import pythonnative as pn
font = pn.Platform.select(
{"ios": "Helvetica", "android": "Roboto", "default": None}
)
if pn.Platform.is_ios:
margin = 16
else:
margin = 12
Platform.select looks up the current platform first, then "native"
(matches iOS and Android), then "default", then the explicit
default= argument. Platform.OS is "test" when running off-device,
which is useful for skipping native-only code paths in tests.
Window dimensions, safe area, keyboard¶
PythonNative ships three reactive hooks that subscribe to the
platform-published metrics in pythonnative.platform_metrics:
@pn.component
def Responsive():
dims = pn.use_window_dimensions()
insets = pn.use_safe_area_insets()
keyboard = pn.use_keyboard_height()
return pn.Column(
pn.Text(f"{dims['width']:.0f} × {dims['height']:.0f}"),
pn.Text(f"Bottom inset: {insets['bottom']:.0f}"),
pn.Text(f"Keyboard: {keyboard:.0f}"),
style={"padding": 16, "spacing": 8},
)
The component re-renders whenever the underlying value actually
changes (no spurious renders on no-op updates). For most apps,
KeyboardAvoidingView handles
the keyboard case for you and you won't need
use_keyboard_height directly.
Status bar¶
Mount StatusBar anywhere in the tree (it
renders nothing visible) to control style and visibility:
style is "light" (light icons, dark background), "dark" (dark
icons, light background), or "default".
Alerts and pickers¶
Alert.show is the imperative way
to present a dialog.
Alert.confirm wraps the common
confirm/cancel case. The Picker component is
implemented on top of Alert.show(style="action_sheet").
Accessibility props¶
Every interactive component (Text, Button, Pressable,
TextInput, Image, container views) accepts the same set of
accessibility kwargs:
| Prop | Purpose |
|---|---|
accessibility_label |
Short spoken description for screen readers |
accessibility_hint |
Extra detail (iOS only) |
accessibility_role |
Semantic role ("button", "link", "image", ...) |
accessible |
Override whether the element is exposed to assistive tech |
accessibility_state |
Dict of state flags announced with the element |
accessibility_live_region |
Announce content changes: "polite" or "assertive" |
test_id |
Stable identifier for UI test frameworks |
Components like Button supply a sensible
default accessibility_role for you.
State flags¶
accessibility_state mirrors React Native's prop of the same name.
Supported keys are disabled, selected, checked, busy, and
expanded; they map to UIAccessibilityTraits on iOS and to
AccessibilityNodeInfo state on Android:
pn.Pressable(
pn.Text("Inbox"),
on_press=select_inbox,
accessibility_role="button",
accessibility_state={"selected": current_tab == "inbox"},
)
Live regions¶
Set accessibility_live_region="polite" on a status line so screen
readers announce its text when it changes without moving focus (use
"assertive" only for content the user must hear immediately):
Test identifiers¶
test_id gives UI-test frameworks (Maestro, Appium, XCUITest,
Espresso) a stable handle that is independent of visible text. It
maps to accessibilityIdentifier on iOS and to the accessibility
node's viewIdResourceName (resource-id) on Android: