pythonnative/src/pythonnative/native_modules/app_state.py at main · andevsr/pythonnative · GitHub

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"""Foreground / background app lifecycle state.

[`AppState`][pythonnative.AppState] exposes the current lifecycle phase

(``"active"``, ``"inactive"``, or ``"background"``) and lets you

subscribe to transitions. The native host (the iOS app delegate /

Android ``Activity``) forwards lifecycle callbacks by calling

[`dispatch_app_state`][pythonnative.native_modules.app_state.dispatch_app_state],

so the same listener machinery works on every platform and in tests.

Prefer the [`use_app_state`][pythonnative.use_app_state] hook inside

components; use the imperative API for non-UI code.

Example:

```python

import pythonnative as pn

@pn.component

def Banner():

state = pn.use_app_state()

return pn.Text(f"App is {state}")

```

"""

from __future__ import annotations

from typing import Callable, List

from .. import diagnostics

from ..hooks import use_effect, use_state

AppStateStatus = str # "active" | "inactive" | "background"

_VALID = ("active", "inactive", "background")

_current: AppStateStatus = "active"

_listeners: List[Callable[[AppStateStatus], None]] = []

class AppState:

"""App lifecycle state interface."""

@staticmethod

def current_state() -> AppStateStatus:

"""Return the current lifecycle phase."""

return _current

@staticmethod

def add_listener(callback: Callable[[AppStateStatus], None]) -> Callable[[], None]:

"""Subscribe to lifecycle changes.

Returns:

A zero-arg function that unsubscribes when called.

"""

_listeners.append(callback)

def _unsubscribe() -> None:

try:

_listeners.remove(callback)

except ValueError:

pass

return _unsubscribe

def dispatch_app_state(state: AppStateStatus) -> None:

"""Update the current state and notify every listener.

Called by the native host on lifecycle transitions. Unknown values

are ignored so a misbehaving host can't push garbage into the tree.

"""

global _current

if state not in _VALID or state == _current:

return

_current = state

for listener in list(_listeners):

try:

listener(state)

except Exception:

diagnostics.swallowed("app_state.dispatch_app_state")

def use_app_state() -> AppStateStatus:

"""Subscribe a component to [`AppState`][pythonnative.AppState].

Returns:

The current lifecycle phase; the component re-renders whenever

it changes.

"""

state, set_state = use_state(_current)

def _subscribe() -> Callable[[], None]:

set_state(_current)

return AppState.add_listener(set_state)

use_effect(_subscribe, [])

return state

pythonnative/src/pythonnative/native_modules/app_state.py at main · andevsr/pythonnative · GitHub

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