MaterialTheme.kt
/*
* Copyright 2019 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.material
import androidx.compose.foundation.Indication
import androidx.compose.foundation.AmbientIndication
import androidx.compose.foundation.ProvideTextStyle
import androidx.compose.material.ripple.RippleIndication
import androidx.compose.runtime.Composable
import androidx.compose.runtime.ComposableContract
import androidx.compose.runtime.Providers
import androidx.compose.runtime.remember
/**
* A MaterialTheme defines the styling principles from the Material design specification.
*
* Material components such as [Button] and [Checkbox] use values provided here when retrieving
* default values.
*
* It defines colors as specified in the [Material Color theme creation spec](https://material.io/design/color/the-color-system.html#color-theme-creation),
* typography defined in the [Material Type Scale spec](https://material.io/design/typography/the-type-system.html#type-scale),
* and shapes defined in the [Shape scheme](https://material.io/design/shape/applying-shape-to-ui.html#shape-scheme).
*
* All values may be set by providing this component with the [colors][Colors],
* [typography][Typography], and [shapes][Shapes] attributes. Use this to configure the overall
* theme of elements within this MaterialTheme.
*
* Any values that are not set will inherit the current value from the theme, falling back to the
* defaults if there is no parent MaterialTheme. This allows using a MaterialTheme at the top
* of your application, and then separate MaterialTheme(s) for different screens / parts of your
* UI, overriding only the parts of the theme definition that need to change.
*
* @sample androidx.compose.material.samples.MaterialThemeSample
*
* @param colors A complete definition of the Material Color theme for this hierarchy
* @param typography A set of text styles to be used as this hierarchy's typography system
* @param shapes A set of shapes to be used by the components in this hierarchy
*/
@Composable
fun MaterialTheme(
colors: Colors = MaterialTheme.colors,
typography: Typography = MaterialTheme.typography,
shapes: Shapes = MaterialTheme.shapes,
content: @Composable () -> Unit
) {
val rememberedColors = remember {
// TODO: b/162450508 remove the unnecessary .copy() here when it isn't needed to ensure that
// we don't skip the updateColorsFrom call
colors.copy()
}.apply { updateColorsFrom(colors) }
val indicationFactory: @Composable () -> Indication = remember { { RippleIndication() } }
Providers(
AmbientColors provides rememberedColors,
AmbientIndication provides indicationFactory,
AmbientTypography provides typography,
AmbientShapes provides shapes
) {
ProvideTextStyle(value = typography.body1, children = content)
}
}
/**
* Contains functions to access the current theme values provided at the call site's position in
* the hierarchy.
*/
object MaterialTheme {
/**
* Retrieves the current [Colors] at the call site's position in the hierarchy.
*
* @sample androidx.compose.material.samples.ThemeColorSample
*/
@Composable
@ComposableContract(readonly = true)
val colors: Colors
get() = AmbientColors.current
/**
* Retrieves the current [Typography] at the call site's position in the hierarchy.
*
* @sample androidx.compose.material.samples.ThemeTextStyleSample
*/
@Composable
@ComposableContract(readonly = true)
val typography: Typography
get() = AmbientTypography.current
/**
* Retrieves the current [Shapes] at the call site's position in the hierarchy.
*/
@Composable
@ComposableContract(readonly = true)
val shapes: Shapes
get() = AmbientShapes.current
}