Android Jetpack Compose 中如何使用字符串资源？

Question

Let's I have the following strings.xml resource file:

<resources>
    <!-- basic string -->
    <string name="app_name">My Playground</string>

    <!-- basic string with an argument -->
    <string name="greeting">Hello %!</string>

    <!-- plural string -->
    <plurals name="likes">
        <item quantity="one">%1d like</item>
        <item quantity="other">%1d likes</item>
    </plurals>

    <!-- string array -->
    <string-array name="planets">
        <item>Earth</item>
        <item>Mars</item>
    </string-array>
</resources>

How can I use these resources in Jetpack Compose?

Answer 1

There's androidx.compose.ui.res package containing functions for loading string resources as well as other resource types.

string

You can get a string using stringResource() function, for example:

...
import androidx.compose.ui.res.stringResource

@Composable
fun StringResourceExample() {
  Text(
    // a string without arguments
    text = stringResource(R.string.app_name)
  )

  Text(
    // a string with arguments
    text = stringResource(R.string.greeting, "World")
  )
}

string array

Can be obtained using stringArrayResource() function:

val planets = stringArrayResource(R.array.planets_array)

plural (quantity string)

As of compose 1.0.0-alpha10 there's no build-in function for obtaining a plural resource, but you can get the android context via LocalContext and use it the same way as you do it in a view-based app. Even better if you create your own function similar to other resource functions (like Jetcaster compose sample does for example):

// PluralResources.kt

package com.myapp.util

import androidx.annotation.PluralsRes
import androidx.compose.runtime.Composable
import androidx.compose.ui.platform.LocalContext

@Composable
fun quantityStringResource(@PluralsRes id: Int, quantity: Int, vararg formatArgs: Any): String {
    return LocalContext.current.resources.getQuantityString(id, quantity, *formatArgs)
}

so you can use it the same way:

val likes = quantityStringResource(R.plurals.likes, 10, 10)

a note about recomposition

As you know, in compose a composable function might be re-executed up to hundreds of times per second during recomposition . If the string you build isn't trivial and requires some calculation, it's better to remember the calculation result, so it won't be re-executed on each recomposition. For example:

...

import androidx.compose.runtime.remember

@Composable
fun BirthdayDateComposable(username: String, dateMillis: Long) {
  // formatDate() function will be executed only if dateMillis value 
  // is changed, otherwise the remembered value will be used
  val dateStr = remember(dateMillis) {
    formatDate(dateMillis)
  }

  Text(
    text = stringResource(R.string.birthday_date, dateStr)
  )
}

Answer 2

This is now supported as of compose 1.2.0-alpha06 :

val likes = pluralStringResource(R.plurals.likes, 10, 10)

Answer 3

Here is an example;

Text(text = stringResource(id = R.string.myString)