Jetpack Compose主题切换

时间:2022-05-23 九狼人气:0

前言

新建的Compose项目默认的 Material 主题为我们提供了一些颜色，但对我这种花里胡哨的人来说根本不够呀。所以系统提供的主题不能满足需求时候可以自己配置主题

compose 实现换肤很简单

之前xml方法可复杂了

通过LayoutInflater调用inflate方法加载XML布局，在inflate方法中有一个createViewFromTag，再根据LayoutInflater当中Factory的接口类型（Factory or Factory2）调用CreateView方法加载，其中通过“name”可以得到加载的控件Tag，再通过AttributeSet得到控件的全部属性最后再切换背景颜色

这是默认的代码，我们要改造一下

color.kt

先是用全局静态变量写一套颜色变量

val statusBarColorLight = Color(0xFFFFFFFF)
val statusBarColorDark = Color(0xFF1C1C28)

val backgroundColorLight = Color(0xFFF2F2F6)
val backgroundColorDark = Color(0xFF1C1C28)

val textPrimaryLight = Color(0xFF333333)
val textPrimaryDark = Color(0xFFE8E8F0)

val textSecondaryLight = Color(0xFF999999)
val textSecondaryDark = Color(0xFF999999)

...此处省略500字哈哈

Theme.kt

定义各种各样的颜色名称

@Stable
class AppColors(
    statusBarColor: Color,
    themeUi: Color,
    background: Color,
    listItem: Color,
    divider: Color,
    textPrimary: Color,
    textSecondary: Color,
    mainColor: Color,
    card: Color,
    icon: Color,
    info: Color,
    warn: Color,
    success: Color,
    error: Color,
    primaryBtnBg: Color,
    secondBtnBg: Color,
    hot: Color,
    placeholder: Color,
)

接着引入mutableStateOf，来标明这个Color是有状态的，如果状态发生了改变，所有引用这个颜色的控件都发生了改变，都需要重新绘制！

var statusBarColor: Color by mutableStateOf(statusBarColor)
    internal set
var themeUi: Color by mutableStateOf(themeUi)
    internal set
var background: Color by mutableStateOf(background)
    private set
var listItem: Color by mutableStateOf(listItem)
    private set
var divider: Color by mutableStateOf(divider)
    private set
var textPrimary: Color by mutableStateOf(textPrimary)
    internal set
var textSecondary: Color by mutableStateOf(textSecondary)
    private set
var mainColor: Color by mutableStateOf(mainColor)
    internal set
var card: Color by mutableStateOf(card)
    private set
var icon: Color by mutableStateOf(icon)
    private set
var info: Color by mutableStateOf(info)
    private set
var warn: Color by mutableStateOf(warn)
    private set
var success: Color by mutableStateOf(success)
    private set
var error: Color by mutableStateOf(error)
    private set
var primaryBtnBg: Color by mutableStateOf(primaryBtnBg)
    internal set
var secondBtnBg: Color by mutableStateOf(secondBtnBg)
    private set
var hot: Color by mutableStateOf(hot)
    private set
var placeholder: Color by mutableStateOf(placeholder)
    private set

复制粘贴就行啦

接着定义两套主题白天和黑夜

你永远不懂我伤悲

像白天不懂夜的黑

//夜色主题
private val DarkColorPalette = AppColors(
    statusBarColor = statusBarColorDark,
    themeUi = themeColor,
    background = backgroundColorDark,
    listItem = listItemDark,
    divider = dividerDark,
    textPrimary = textPrimaryDark,
    textSecondary = textSecondaryDark,
    mainColor = black3,
    card = black3,
    icon = grey1,
    info = info,
    warn = warn,
    success = green3,
    error = red2,
    primaryBtnBg = backgroundColorDark,
    secondBtnBg = black3,
    hot = red,
    placeholder = grey1,
)

//白天主题
private val LightColorPalette = AppColors(
    statusBarColor = statusBarColorLight,
    themeUi = themeColor,
    background = backgroundColorLight,
    listItem = listItemLight,
    divider = dividerLight,
    textPrimary = textPrimaryLight,
    textSecondary = textSecondaryLight,
    mainColor = white,
    card = white1,
    icon = inonGary,
    info = info,
    warn = warn,
    success = green3,
    error = red2,
    primaryBtnBg = themeColor,
    secondBtnBg = white3,
    hot = red,
    placeholder = white3,
)

接着重要的一步来了，如何应用这些颜色配色呢？

@Composable
fun AppTheme(
    content: @Composable () -> Unit
)

就是这样

只需要在使用的时候把控件装在里面就行了

应用之前我们要判断使用哪个主题

这里我用深色模式来演示

在Composable下可以用这行代码判断当前系统处于深色模式

isSystemInDarkTheme()

var LocalAppColors = compositionLocalOf {
    LightColorPalette
}
//主题配置单例
@Stable
object CustomTheme {
    val colors: AppColors
        @Composable
        get() = LocalAppColors.current

  //创建主题枚举
    enum class Theme {
        Light, Dark
    }
}

关于compositionLocalOf

官方解释如下: Compose 将数据通过组合树显式地通过参数传递给可组合函数。这通常是让数据流过树的最简单和最好的方法。

有时，对于许多组件需要的数据，或者当组件需要在彼此之间传递数据但保持该实现细节私有时，此模型可能很麻烦或分解。对于这些情况，CompositionLocal 可以用作让数据流过组合的隐式方式。

CompositionLocal本质上是分层的。当CompositionLocal需要将的值限定为组合的特定子层次结构时，它们是有意义的。

必须创建一个CompositionLocal实例，该实例可以被消费者静态引用。CompositionLocal实例本身不持有任何数据，可以将其视为传递到树中的数据的类型安全标识符。CompositionLocal工厂函数采用单个参数：在CompositionLocal没有提供程序的情况下使用a 的情况下创建默认值的工厂。如果这是您不想处理的情况，则可以在此工厂中引发错误。

在树上的某个地方，CompositionLocalProvider可以使用一个组件，它为CompositionLocal. 这通常位于树的“根”，但也可以在任何地方，也可以在多个位置使用以覆盖子树的提供值。中间组件不需要知道该CompositionLocal值，并且可以对其具有零依赖关系

完整代码

@Composable
fun AppTheme(
    isDark :Boolean = isSystemInDarkTheme(),
    content: @Composable () -> Unit
) {

    val targetColors = if (isDark) DarkColorPalette else LightColorPalette

    val statusBarColor = animateColorAsState(targetColors.statusBarColor, TweenSpec(600))
    val themeUi = animateColorAsState(targetColors.themeUi, TweenSpec(600))
    val background = animateColorAsState(targetColors.background, TweenSpec(600))
    val listItem = animateColorAsState(targetColors.listItem, TweenSpec(600))
    val divider = animateColorAsState(targetColors.divider, TweenSpec(600))
    val textPrimary = animateColorAsState(targetColors.textPrimary, TweenSpec(600))
    val textSecondary = animateColorAsState(targetColors.textSecondary, TweenSpec(600))
    val mainColor = animateColorAsState(targetColors.mainColor, TweenSpec(600))
    val card = animateColorAsState(targetColors.card, TweenSpec(600))
    val icon = animateColorAsState(targetColors.icon, TweenSpec(600))
    val info = animateColorAsState(targetColors.info, TweenSpec(600))
    val warn = animateColorAsState(targetColors.warn, TweenSpec(600))
    val success = animateColorAsState(targetColors.success, TweenSpec(600))
    val error = animateColorAsState(targetColors.error, TweenSpec(600))
    val primaryBtnBg = animateColorAsState(targetColors.primaryBtnBg, TweenSpec(600))
    val secondBtnBg = animateColorAsState(targetColors.secondBtnBg, TweenSpec(600))
    val hot = animateColorAsState(targetColors.hot, TweenSpec(600))
    val placeholder = animateColorAsState(targetColors.placeholder, TweenSpec(600))

    val appColors = AppColors(
        statusBarColor = statusBarColor.value,
        themeUi = themeUi.value,
        background = background.value,
        listItem = listItem.value,
        divider = divider.value,
        textPrimary = textPrimary.value,
        textSecondary = textSecondary.value,
        mainColor = mainColor.value,
        card = card.value,
        icon = icon.value,
        primaryBtnBg = primaryBtnBg.value,
        secondBtnBg = secondBtnBg.value,
        info = info.value,
        warn = warn.value,
        success = success.value,
        error = error.value,
        hot = hot.value,
        placeholder = placeholder.value
    )

    ProvideWindowInsets {
        CompositionLocalProvider(LocalAppColors provides appColors) {
            MaterialTheme(
                shapes = shapes
            ) {
                ProvideWindowInsets(content = content)
            }
        }
    }
}

用TweenSpec创建配置了给定持续时间、延迟和缓和曲线的效果反正就是可以在换肤的时候不会一闪，会慢慢切换

最后放在AppTheme下面使用就可以啦

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