FocusRequester.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.runtime.collection.ExperimentalCollectionApi
import androidx.compose.runtime.collection.MutableVector
import androidx.compose.runtime.collection.mutableVectorOf
import androidx.compose.ui.node.ModifiedFocusRequesterNode
private val focusRequesterNotInitialized = "FocusRequester is not initialized. One reason for " +
"this is that you requesting focus changes during composition. Focus requests should " +
"not be made during composition, but should be made in response to some event."
/**
* The [FocusRequester] is used in conjunction with
* [Modifier.focusRequester][androidx.compose.ui.focusRequester] to send requests for focus state
* change.
*
* @see androidx.compose.ui.focusRequester
*/
@OptIn(ExperimentalCollectionApi::class)
@ExperimentalFocus
class FocusRequester {
internal val focusRequesterNodes: MutableVector<ModifiedFocusRequesterNode> = mutableVectorOf()
/**
* Use this function to request focus. If the system grants focus to a component associated
* with this [FocusRequester], its [state][FocusState] will be set to
* [Active][FocusState.Active].
*/
fun requestFocus() {
check(focusRequesterNodes.isNotEmpty()) { focusRequesterNotInitialized }
focusRequesterNodes.forEach { it.findFocusNode()?.requestFocus(propagateFocus = false) }
}
/**
* Deny requests to clear focus.
*
* Use this function to send a request to capture the focus. If a component is captured, it's
* [state][FocusState] will be set to [Captured][FocusState.Captured]. When a
* component is in this state, it holds onto focus until [freeFocus] is called. When a
* component is in the [Captured][FocusState.Captured] state, all focus requests from
* other components are declined.
*
* @return true if the focus was successfully captured by one of the
* [focus][androidx.compose.ui.focus] modifiers associated with this [FocusRequester].
* false otherwise.
*/
fun captureFocus(): Boolean {
check(focusRequesterNodes.isNotEmpty()) { focusRequesterNotInitialized }
var success = false
focusRequesterNodes.forEach {
it.findFocusNode()?.apply {
if (captureFocus()) {
success = true
}
}
}
return success
}
/**
* Use this function to send a request to release focus when one of the components associated
* with this [FocusRequester] is in a [Captured][FocusState.Captured] state.
*
* When the node is in the [Captured][FocusState.Captured] state, it rejects all requests to clear focus. Calling
* [freeFocus] puts the node in the [Active][FocusState.Active] state, where it is no longer
* preventing other
* nodes from requesting focus.
*
* @return true if the focus was successfully released. i.e. At the end of this operation,
* one of the components associated with this
* [focusRequester][androidx.compose.ui.focusRequester] is in the [Active][FocusState.Active]
* state. false otherwise.
*/
fun freeFocus(): Boolean {
check(focusRequesterNodes.isNotEmpty()) { focusRequesterNotInitialized }
var success = false
focusRequesterNodes.forEach {
it.findFocusNode()?.apply {
if (freeFocus()) {
success = true
}
}
}
return success
}
}