使用 Jetpack Compose 進行主題設定

git clone https://github.com/googlecodelabs/android-compose-codelabs.git
cd android-compose-codelabs/ThemingCodelabM2

@Composable
fun MaterialTheme(
    colors: Colors,
    typography: Typography,
    shapes: Shapes,
    content: @Composable () -> Unit
) { ...

@Composable
fun Home() {
  ...
  MaterialTheme {
    Scaffold(...

@Composable
fun JetnewsTheme(content: @Composable () -> Unit) {
  MaterialTheme(content = content)
}

-  MaterialTheme {
+  JetnewsTheme {
    ...

@Preview("Featured Post")
@Composable
private fun FeaturedPostPreview() {
  val post = remember { PostRepo.getFeaturedPost() }
+ JetnewsTheme {
    FeaturedPost(post = post)
+ }
}

val Red700 = Color(0xffdd0d3c)
val Red800 = Color(0xffd00036)
val Red900 = Color(0xffc20029)

private val LightColors = lightColors(
    primary = Red700,
    primaryVariant = Red900,
    onPrimary = Color.White,
    secondary = Red700,
    secondaryVariant = Red900,
    onSecondary = Color.White,
    error = Red800
)

@Composable
fun JetnewsTheme(content: @Composable () -> Unit) {
  MaterialTheme(
+   colors = LightColors,
    content = content
  )
}

data class TextStyle(
    val color: Color = Color.Unset,
    val fontSize: TextUnit = TextUnit.Inherit,
    val fontWeight: FontWeight? = null,
    val fontStyle: FontStyle? = null,
    val fontFamily: FontFamily? = null,
    val letterSpacing: TextUnit = TextUnit.Inherit,
    val background: Color = Color.Unset,
    val textAlign: TextAlign? = null,
    val textDirection: TextDirection? = null,
    val lineHeight: TextUnit = TextUnit.Inherit,
    ...
)

private val Montserrat = FontFamily(
    Font(R.font.montserrat_regular),
    Font(R.font.montserrat_medium, FontWeight.W500),
    Font(R.font.montserrat_semibold, FontWeight.W600)
)

private val Domine = FontFamily(
    Font(R.font.domine_regular),
    Font(R.font.domine_bold, FontWeight.Bold)
)

val JetnewsTypography = Typography(
    h4 = TextStyle(
        fontFamily = Montserrat,
        fontWeight = FontWeight.W600,
        fontSize = 30.sp
    ),
    h5 = TextStyle(
        fontFamily = Montserrat,
        fontWeight = FontWeight.W600,
        fontSize = 24.sp
    ),
    h6 = TextStyle(
        fontFamily = Montserrat,
        fontWeight = FontWeight.W600,
        fontSize = 20.sp
    ),
    subtitle1 = TextStyle(
        fontFamily = Montserrat,
        fontWeight = FontWeight.W600,
        fontSize = 16.sp
    ),
    subtitle2 = TextStyle(
        fontFamily = Montserrat,
        fontWeight = FontWeight.W500,
        fontSize = 14.sp
    ),
    body1 = TextStyle(
        fontFamily = Domine,
        fontWeight = FontWeight.Normal,
        fontSize = 16.sp
    ),
    body2 = TextStyle(
        fontFamily = Montserrat,
        fontSize = 14.sp
    ),
    button = TextStyle(
        fontFamily = Montserrat,
        fontWeight = FontWeight.W500,
        fontSize = 14.sp
    ),
    caption = TextStyle(
        fontFamily = Montserrat,
        fontWeight = FontWeight.Normal,
        fontSize = 12.sp
    ),
    overline = TextStyle(
        fontFamily = Montserrat,
        fontWeight = FontWeight.W500,
        fontSize = 12.sp
    )
)

@Composable
fun JetnewsTheme(content: @Composable () -> Unit) {
  MaterialTheme(
    colors = LightColors,
+   typography = JetnewsTypography,
    content = content
  )
}

val JetnewsShapes = Shapes(
    small = CutCornerShape(topStart = 8.dp),
    medium = CutCornerShape(topStart = 24.dp),
    large = RoundedCornerShape(8.dp)
)

@Composable
fun JetnewsTheme(content: @Composable () -> Unit) {
  MaterialTheme(
    colors = LightColors,
    typography = JetnewsTypography,
+   shapes = JetnewsShapes,
    content = content
  )
}

val Red200 = Color(0xfff297a2)
val Red300 = Color(0xffea6d7e)

private val DarkColors = darkColors(
    primary = Red300,
    primaryVariant = Red700,
    onPrimary = Color.Black,
    secondary = Red300,
    onSecondary = Color.Black,
    error = Red200
)

@Composable
fun JetnewsTheme(
+ darkTheme: Boolean = isSystemInDarkTheme(),
  content: @Composable () -> Unit
) {
  MaterialTheme(
+   colors = if (darkTheme) DarkColors else LightColors,
    typography = JetnewsTypography,
    shapes = JetnewsShapes,
    content = content
  )
}

@Preview("Featured Post • Dark")
@Composable
private fun FeaturedPostDarkPreview() {
    val post = remember { PostRepo.getFeaturedPost() }
    JetnewsTheme(darkTheme = true) {
        FeaturedPost(post = post)
    }
}

@Composable
fun FloatingActionButton(
  backgroundColor: Color = MaterialTheme.colors.secondary,
  ...
) {

Surface(color = Color.LightGray) {
  Text(
    text = "Hard coded colors don't respond to theme changes :(",
    textColor = Color(0xffff00ff)
  )
}

Surface(color = MaterialTheme.colors.primary)

val derivedColor = MaterialTheme.colors.onSurface.copy(alpha = 0.1f)

Surface(
  color: Color = MaterialTheme.colors.surface,
  contentColor: Color = contentColorFor(color),
  ...

TopAppBar(
  backgroundColor: Color = MaterialTheme.colors.primarySurface,
  contentColor: Color = contentColorFor(backgroundColor),
  ...

Surface(color = MaterialTheme.colors.primary) {
  Text(...) // default text color is 'onPrimary'
}
Surface(color = MaterialTheme.colors.error) {
  Icon(...) // default tint is 'onError'
}

BottomNavigationItem(
  unselectedContentColor = LocalContentColor.current ...

-Row(Modifier.background(MaterialTheme.colors.primary)) {
+Surface(color = MaterialTheme.colors.primary) {
+  Row(
...

+ Surface(
+   color = MaterialTheme.colors.onSurface.copy(alpha = 0.1f),
+   contentColor = MaterialTheme.colors.primary,
+   modifier = modifier
+ ) {
  Text(
    text = text,
    modifier = Modifier
      .fillMaxWidth()
-     .background(Color.LightGray)
      .padding(horizontal = 16.dp, vertical = 8.dp)
  )
+ }

// By default, both Icon & Text use the combination of LocalContentColor &
// LocalContentAlpha. De-emphasize content by setting a different content alpha
CompositionLocalProvider(LocalContentAlpha provides ContentAlpha.medium) {
    Text(...)
}
CompositionLocalProvider(LocalContentAlpha provides ContentAlpha.disabled) {
    Icon(...)
    Text(...)
}

+ CompositionLocalProvider(LocalContentAlpha provides ContentAlpha.medium) {
  Text(
    text = text,
    modifier = modifier
  )
+ }

val isLightTheme = MaterialTheme.colors.isLight

Surface(
  elevation = 2.dp,
  color = MaterialTheme.colors.surface, // color will be adjusted for elevation
  ...

@Composable
private fun AppBar() {
  TopAppBar(
    ...
-   backgroundColor = MaterialTheme.colors.primary
+   backgroundColor = MaterialTheme.colors.primarySurface
  )
}

Button(...) {
  Text("This text will use MaterialTheme.typography.button style by default")
}

@Composable
fun Button(
    // many other parameters
    content: @Composable RowScope.() -> Unit
) {
  ...
  ProvideTextStyle(MaterialTheme.typography.button) { //set the "current" text style
    ...
    content()
  }
}

@Composable
fun Text(
    // many, many parameters
    style: TextStyle = LocalTextStyle.current // get the value set by ProvideTextStyle
) { ...

Text(
  style = MaterialTheme.typography.subtitle2
)

Text(
  text = "Hello World",
  style = MaterialTheme.typography.body1.copy(
    background = MaterialTheme.colors.secondary
  )
)

Text(
  text = "Hello World",
  style = MaterialTheme.typography.subtitle2,
  fontSize = 22.sp // explicit size overrides the size in the style
)

@Composable
fun Header(...) {
  ...
  Text(
    text = text,
+   style = MaterialTheme.typography.subtitle2

val text = buildAnnotatedString {
  append("This is some unstyled text\n")
  withStyle(SpanStyle(color = Color.Red)) {
    append("Red text\n")
  }
  withStyle(SpanStyle(fontSize = 24.sp)) {
    append("Large text")
  }
}

+ val tagStyle = MaterialTheme.typography.overline.toSpanStyle().copy(
+   background = MaterialTheme.colors.primary.copy(alpha = 0.1f)
+ )
post.tags.forEachIndexed { index, tag ->
  ...
+ withStyle(tagStyle) {
    append(" ${tag.toUpperCase()} ")
+ }
}

@Composable
fun Button( ...
  shape: Shape = MaterialTheme.shapes.small
) {

@Composable
fun FilledTextField(
  // other parameters
  shape: Shape = MaterialTheme.shapes.small.copy(
    bottomStart = ZeroCornerSize, // overrides small theme style
    bottomEnd = ZeroCornerSize // overrides small theme style
  )
) {

@Composable
fun UserProfile(
  ...
  shape: Shape = MaterialTheme.shapes.medium
) {
  Surface(shape = shape) {
    ...
  }
}

@Composable
fun PostItem(...) {
  ...
  Image(
    painter = painterResource(post.imageThumbId),
+   modifier = Modifier.clip(shape = MaterialTheme.shapes.small)
  )

@Composable
fun Header(
  text: String,
  modifier: Modifier = Modifier
) {
  Surface(
    color = MaterialTheme.colors.onSurface.copy(alpha = 0.1f),
    contentColor = MaterialTheme.colors.primary,
    modifier = modifier.semantics { heading() }
  ) {
    Text(
      text = text,
      style = MaterialTheme.typography.subtitle2,
      modifier = Modifier
        .fillMaxWidth()
        .padding(horizontal = 16.dp, vertical = 8.dp)
    )
  }
}

@Composable
fun LoginButton(
    onClick: () -> Unit,
    modifier: Modifier = Modifier,
    content: @Composable RowScope.() -> Unit
) {
    Button(
        colors = ButtonConstants.defaultButtonColors(
            backgroundColor = MaterialTheme.colors.secondary
        ),
        onClick = onClick,
        modifier = modifier
    ) {
        ProvideTextStyle(...) { // set our own text style
            content()
        }
    }
}

@Composable
fun AcmeButton(
  // expose Button params consumers should be able to change
) {
  val acmeButtonShape: Shape = ...
  Button(
    shape = acmeButtonShape,
    // other params
  )
}