| /* |
| * 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.ui.layout |
| |
| import androidx.compose.Composable |
| import androidx.compose.Immutable |
| import androidx.compose.Stable |
| import androidx.ui.core.Alignment |
| import androidx.ui.core.Measured |
| import androidx.ui.core.Modifier |
| import androidx.ui.core.VerticalAlignmentLine |
| import androidx.ui.layout.ColumnScope.alignWithSiblings |
| import androidx.ui.layout.RowScope.alignWithSiblings |
| import androidx.ui.util.annotation.FloatRange |
| |
| /** |
| * A layout composable that places its children in a vertical sequence. For a layout composable |
| * that places its children in a horizontal sequence, see [Row]. |
| * |
| * The layout model is able to assign children heights according to their weights provided |
| * using the [ColumnScope.weight] modifier. If a child is not provided a weight, it will be |
| * asked for its preferred height before the sizes of the children with weights are calculated |
| * proportionally to their weight based on the remaining available space. |
| * |
| * When none of its children have weights, a [Column] will be as small as possible to fit its |
| * children one on top of the other. In order to change the height of the [Column], use the |
| * [Modifier.height] modifiers; e.g. to make it fill the available height [Modifier.fillMaxHeight] |
| * can be used. If at least one child of a [Column] has a [weight][ColumnScope.weight], |
| * the [Column] will fill the available height, so there is no need for [Modifier.fillMaxHeight]. |
| * However, if [Column]'s size should be limited, the [Modifier.height] or [Modifier.size] layout |
| * modifiers should be applied. |
| * |
| * When the size of the [Column] is larger than the sum of its children sizes, a |
| * [verticalArrangement] can be specified to define the positioning of the children inside the |
| * [Column]. See [Arrangement] for available positioning behaviors; a custom arrangement can also |
| * be defined using the constructor of [Arrangement]. |
| * |
| * Example usage: |
| * |
| * @sample androidx.ui.layout.samples.SimpleColumn |
| * |
| * @param modifier The modifier to be applied to the Column. |
| * @param verticalArrangement The vertical arrangement of the layout's children. |
| * @param horizontalGravity The horizontal gravity of the layout's children. |
| * |
| * @see Column |
| */ |
| @Composable |
| fun Column( |
| modifier: Modifier = Modifier, |
| verticalArrangement: Arrangement.Vertical = Arrangement.Top, |
| horizontalGravity: Alignment.Horizontal = Alignment.Start, |
| children: @Composable ColumnScope.() -> Unit |
| ) { |
| RowColumnImpl( |
| orientation = LayoutOrientation.Vertical, |
| modifier = modifier, |
| arrangement = { totalSize, size, _ -> |
| verticalArrangement.arrange(totalSize, size) |
| }, |
| crossAxisAlignment = CrossAxisAlignment.horizontal(horizontalGravity), |
| crossAxisSize = SizeMode.Wrap, |
| children = { ColumnScope.children() } |
| ) |
| } |
| |
| /** |
| * Scope for the children of [Column]. |
| */ |
| @LayoutScopeMarker |
| @Immutable |
| object ColumnScope { |
| /** |
| * Position the element horizontally within the [Column] according to [align]. |
| * |
| * Example usage: |
| * @sample androidx.ui.layout.samples.SimpleGravityInColumn |
| */ |
| @Stable |
| fun Modifier.gravity(align: Alignment.Horizontal) = this + HorizontalGravityModifier(align) |
| |
| /** |
| * Position the element horizontally such that its [alignmentLine] aligns with sibling elements |
| * also configured to [alignWithSiblings]. [alignWithSiblings] is a form of [gravity], |
| * so both modifiers will not work together if specified for the same layout. |
| * Within a [Column], all components with [alignWithSiblings] will align horizontally using |
| * the specified [VerticalAlignmentLine]s or values provided using the other |
| * [alignWithSiblings] overload, forming a sibling group. |
| * At least one element of the sibling group will be placed as it had [Alignment.Start] gravity |
| * in [Column], and the alignment of the other siblings will be then determined such that |
| * the alignment lines coincide. Note that if only one element in a [Column] has the |
| * [alignWithSiblings] modifier specified the element will be positioned |
| * as if it had [Alignment.Start] gravity. |
| * |
| * Example usage: |
| * @sample androidx.ui.layout.samples.SimpleRelativeToSiblingsInColumn |
| */ |
| @Stable |
| fun Modifier.alignWithSiblings(alignmentLine: VerticalAlignmentLine) = |
| this + SiblingsAlignedModifier.WithAlignmentLine(alignmentLine) |
| |
| /** |
| * Size the element's height proportional to its [weight] relative to other weighted sibling |
| * elements in the [Column]. The parent will divide the vertical space remaining after measuring |
| * unweighted child elements and distribute it according to this weight. |
| * When [fill] is true, the element will be forced to occupy the whole height allocated to it. |
| * Otherwise, the element is allowed to be smaller - this will result in [Column] being smaller, |
| * as the unused allocated height will not be redistributed to other siblings. |
| * |
| * @sample androidx.ui.layout.samples.SimpleColumn |
| */ |
| @Stable |
| fun Modifier.weight( |
| @FloatRange(from = 0.0, to = 3.4e38 /* POSITIVE_INFINITY */, fromInclusive = false) |
| weight: Float, |
| fill: Boolean = true |
| ): Modifier { |
| require(weight > 0.0) { "invalid weight $weight; must be greater than zero" } |
| return this + LayoutWeightImpl(weight, fill) |
| } |
| |
| /** |
| * Position the element horizontally such that the alignment line for the content as |
| * determined by [alignmentLineBlock] aligns with sibling elements also configured to |
| * [alignWithSiblings]. [alignWithSiblings] is a form of [gravity], so both modifiers |
| * will not work together if specified for the same layout. |
| * Within a [Column], all components with [alignWithSiblings] will align horizontally using |
| * the specified [VerticalAlignmentLine]s or values obtained from [alignmentLineBlock], |
| * forming a sibling group. |
| * At least one element of the sibling group will be placed as it had [Alignment.Start] gravity |
| * in [Column], and the alignment of the other siblings will be then determined such that |
| * the alignment lines coincide. Note that if only one element in a [Column] has the |
| * [alignWithSiblings] modifier specified the element will be positioned |
| * as if it had [Alignment.Start] gravity. |
| * |
| * Example usage: |
| * @sample androidx.ui.layout.samples.SimpleRelativeToSiblings |
| */ |
| @Stable |
| fun Modifier.alignWithSiblings( |
| alignmentLineBlock: (Measured) -> Int |
| ) = this + SiblingsAlignedModifier.WithAlignmentLineBlock(alignmentLineBlock) |
| } |