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BackHandler.kt
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BackHandler.kt
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/*
* Copyright 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.compose.jetchat.conversation
import androidx.activity.OnBackPressedCallback
import androidx.activity.OnBackPressedDispatcherOwner
import androidx.compose.runtime.Ambient
import androidx.compose.runtime.Composable
import androidx.compose.runtime.onCommit
import androidx.compose.runtime.remember
import androidx.compose.runtime.staticAmbientOf
/**
* This [Composable] can be used with a [BackPressedDispatcherAmbient] to intercept a back press (if
* [enabled]).
*/
@Composable
fun backPressHandler(onBackPressed: () -> Unit, enabled: Boolean = true) {
val dispatcher = BackPressedDispatcherAmbient.current.onBackPressedDispatcher
// This callback is going to be remembered only if onBackPressed is referentially equal.
val backCallback = remember(onBackPressed) {
object : OnBackPressedCallback(enabled) {
override fun handleOnBackPressed() {
onBackPressed()
}
}
}
// Using onCommit guarantees that failed transactions don't incorrectly toggle the
// remembered callback.
onCommit(enabled) {
backCallback.isEnabled = enabled
}
onCommit(dispatcher, onBackPressed) {
// Whenever there's a new dispatcher set up the callback
dispatcher.addCallback(backCallback)
onDispose {
backCallback.remove()
}
}
}
/**
* This [Ambient] is used to provide an [OnBackPressedDispatcherOwner]:
*
* ```
* Providers(BackPressedDispatcherAmbient provides requireActivity()) { }
* ```
*
* and setting up the callbacks with [backPressHandler].
*/
val BackPressedDispatcherAmbient =
staticAmbientOf<OnBackPressedDispatcherOwner> { error("Ambient used without Provider") }