FocusManager.kt
/*
* 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
*
* http://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 androidx.compose.ui.focus
import androidx.compose.ui.FocusModifier
import androidx.compose.ui.Modifier
import androidx.compose.ui.focus.FocusState.Active
import androidx.compose.ui.focus.FocusState.Inactive
import androidx.compose.ui.gesture.PointerInputModifierImpl
import androidx.compose.ui.gesture.TapGestureFilter
interface FocusManager {
/**
* Call this function to clear focus from the currently focused component, and set the focus to
* the root focus modifier.
*
* @param forcedClear: Whether we should forcefully clear focus regardless of whether we have
* any components that have [Captured][FocusState.Captured] focus.
*/
fun clearFocus(forcedClear: Boolean = false)
}
/**
* The focus manager is used by different [Owner][androidx.compose.ui.node.Owner] implementations
* to control focus.
*
* @param focusModifier The modifier that will be used as the root focus modifier.
*/
internal class FocusManagerImpl(
private val focusModifier: FocusModifier = FocusModifier(Inactive)
) : FocusManager {
private val passThroughClickModifier = PointerInputModifierImpl(
TapGestureFilter().apply {
onTap = { clearFocus() }
consumeChanges = false
}
)
/**
* A [Modifier] that can be added to the [Owners][androidx.compose.ui.node.Owner] modifier
* list that contains the modifiers required by the focus system. (Eg, a root focus modifier).
*/
val modifier: Modifier
// TODO(b/168831247): return an empty Modifier when there are no focusable children.
get() = passThroughClickModifier
.then(focusModifier)
/**
* The [Owner][androidx.compose.ui.node.Owner] calls this function when it gains focus. This
* informs the [focus manager][FocusManagerImpl] that the
* [Owner][androidx.compose.ui.node.Owner] gained focus, and that it should propagate this
* focus to one of the focus modifiers in the component hierarchy.
*/
fun takeFocus() {
// If the focus state is not Inactive, it indicates that the focus state is already
// set (possibly by dispatchWindowFocusChanged). So we don't update the state.
if (focusModifier.focusState == Inactive) {
focusModifier.focusState = Active
// TODO(b/152535715): propagate focus to children based on child focusability.
}
}
/**
* The [Owner][androidx.compose.ui.node.Owner] calls this function when it loses focus. This
* informs the [focus manager][FocusManagerImpl] that the
* [Owner][androidx.compose.ui.node.Owner] lost focus, and that it should clear focus from
* all the focus modifiers in the component hierarchy.
*/
fun releaseFocus() {
focusModifier.focusNode.clearFocus(forcedClear = true)
}
/**
* Call this function to set the focus to the root focus modifier.
*
* @param forcedClear: Whether we should forcefully clear focus regardless of whether we have
* any components that have [Captured][FocusState.Captured] focus.
*
* This could be used to clear focus when a user clicks on empty space outside a focusable
* component.
*/
override fun clearFocus(forcedClear: Boolean) {
if (focusModifier.focusNode.clearFocus(forcedClear)) {
focusModifier.focusState = Active
}
}
}