Mobile Kotlin resources

This is a Kotlin MultiPlatform library that provides access to the resources on macOS, iOS, Android the JVM and JS/Browser with the support of the default system localization.

Table of Contents

• Features
• Requirements
• Versions
• Installation
• Usage
• Samples
• Set Up Locally
• Contributing
• License

Features

• Strings, Plurals, Images, Fonts, Files to access the corresponding resources from common code;
• Colors with light/dark mode support;
• StringDesc for lifecycle-aware access to resources and unified localization on both platforms;
• Static iOS frameworks support;
• Fat and XC frameworks support.

Requirements

• Gradle version 6.8.3+
• Android API 16+
• iOS version 11.0+

Installation

root build.gradle

buildscript {
    repositories {
        gradlePluginPortal()
    }

    dependencies {
        classpath "dev.icerock.moko:resources-generator:0.20.1"
    }
}


allprojects {
    repositories {
        mavenCentral()
    }
}

project build.gradle

apply plugin: "dev.icerock.mobile.multiplatform-resources"

dependencies {
    commonMainApi("dev.icerock.moko:resources:0.20.1")
    androidMainApi("dev.icerock.moko:resources-compose:0.20.1")
    jvmMainApi("dev.icerock.moko:resources-compose:0.20.1")
    commonTestImplementation("dev.icerock.moko:resources-test:0.20.1")
}

multiplatformResources {
    multiplatformResourcesPackage = "org.example.library" // required
    multiplatformResourcesClassName = "SharedRes" // optional, default MR
    multiplatformResourcesVisibility = MRVisibility.Internal // optional, default Public
    iosBaseLocalizationRegion = "en" // optional, default "en"
    multiplatformResourcesSourceSet = "commonClientMain"  // optional, default "commonMain"
}

To use toUIColor(), toUIImage(), desc() and other iOS extensions from Swift - you should add export declarations:

framework {
    export("dev.icerock.moko:resources:0.20.1")
    export("dev.icerock.moko:graphics:0.9.0") // toUIColor here
}

If your project includes a build type, for example staging which isn't in moko-resources. That isn't an issue. Use matchingFallbacks to specify alternative matches for a given build type, as shown below

buildTypes {
    staging {
        initWith debug
        matchingFallbacks = ['debug']
    }
}

ios-app Info.plist:

<key>CFBundleLocalizations</key>
<array>
<string>en</string>
<string>ru</string>
</array>

in array should be added all used languages.

JS/Browser generates json files which is included in webpack by default. For more details about JS see this example

Static kotlin frameworks support

If project configured with static framework output (for example by org.jetbrains.kotlin.native.cocoapods plugin) in Xcode project should be added Build Phase (at end of list) with script:

"$SRCROOT/../gradlew" -p "$SRCROOT/../" :yourframeworkproject:copyFrameworkResourcesToApp \
    -Pmoko.resources.PLATFORM_NAME=$PLATFORM_NAME \
    -Pmoko.resources.CONFIGURATION=$CONFIGURATION \
    -Pmoko.resources.BUILT_PRODUCTS_DIR=$BUILT_PRODUCTS_DIR \
    -Pmoko.resources.CONTENTS_FOLDER_PATH=$CONTENTS_FOLDER_PATH

Please replace :yourframeworkproject to kotlin project gradle path, and set correct relative path ($SRCROOT/../ in example).
This phase will copy resources into application, because static frameworks can't have resources.

To disable warnings about static framework in gradle set flag:

multiplatformResources {
    disableStaticFrameworkWarning = true
}

With Pods dependencies in Kotlin

When you use org.jetbrains.kotlin.native.cocoapods plugin and also kotlin module depends to Pods - you also need to pass extra properties:

"$SRCROOT/../gradlew" -p "$SRCROOT/../" :shared:copyFrameworkResourcesToApp \
    -Pmoko.resources.PLATFORM_NAME=$PLATFORM_NAME \
    -Pmoko.resources.CONFIGURATION=$CONFIGURATION \
    -Pmoko.resources.BUILT_PRODUCTS_DIR=$BUILT_PRODUCTS_DIR \
    -Pmoko.resources.CONTENTS_FOLDER_PATH=$CONTENTS_FOLDER_PATH\
    -Pkotlin.native.cocoapods.platform=$PLATFORM_NAME \
    -Pkotlin.native.cocoapods.archs="$ARCHS" \
    -Pkotlin.native.cocoapods.configuration=$CONFIGURATION 

iOS executable

When you use executable kotlin target you should add custom build phase to xcode, after kotlin compilation:

"$SRCROOT/../gradlew" -p "$SRCROOT/../" :shared:copyResourcesDebugExecutableIosSimulatorArm64 \
    -Pmoko.resources.BUILT_PRODUCTS_DIR=$BUILT_PRODUCTS_DIR \
    -Pmoko.resources.CONTENTS_FOLDER_PATH=$CONTENTS_FOLDER_PATH

copyResourcesDebugExecutableIosSimulatorArm64 should be configured depends on target.

Configured sample you can see in sample/ios-app - TestKotlinApp target

Usage

Example 1 - simple localization string

The first step is a create a file strings.xml in commonMain/resources/MR/base with the following content:

<?xml version="1.0" encoding="UTF-8" ?>
<resources>
    <string name="my_string">My default localization string</string>
</resources>

Next - create a file strings.xml with localized strings in commonMain/resource/MR/<languageCode>. Here's an example of creating commonMain/resource/MR/ru for a Russian localization:

<?xml version="1.0" encoding="UTF-8" ?>
<resources>
    <string name="my_string">Моя строка локализации по умолчанию</string>
</resources>

After adding the resources we can call a gradle sync or execute a gradle task generateMRcommonMain. This will generate a MR class containing MR.strings.my_string, which we can use in commonMain:

fun getMyString(): StringDesc {
    return StringDesc.Resource(MR.strings.my_string)
}

After this we can use our functions on the platform side:
Android:

val string = getMyString().toString(context = this)

iOS:

let string = getMyString().localized()

JS:

val strings = MR.stringsLoader.getOrLoad() // loading localization from a remote file
val string = getMyString().localized(strings)

Note: StringDesc is a multiple-source container for Strings: in StringDesc we can use a resource, plurals, formatted variants, or raw string. To convert StringDesc to String on Android call toString(context) (a context is required for the resources usage), on iOS - call localized().

MR directly from native side

Android:

val string = MR.strings.my_string.desc().toString(context = this)

iOS:

let string = MR.strings().my_string.desc().localized()

Get resourceId for Jetpack Compose / SwiftUI

Android:

val resId = MR.strings.my_string.resourceId

for example in Compose:

text = stringResource(id = MR.strings.email.resourceId)

iOS:

LocalizedStringKey(MR.strings().email.resourceId)

Note: more info in issue #126.

Example 2 - formatted localization string

In commonMain/resources/MR/base/strings.xml add:

<?xml version="1.0" encoding="UTF-8" ?>
<resources>
    <string name="my_string_formatted">My format \'%s\'</string>
</resources>

Then add the localized values for other languages like in example #1. Now create the following function in commonMain:

fun getMyFormatDesc(input: String): StringDesc {
    return StringDesc.ResourceFormatted(MR.strings.my_string_formatted, input)
}

To create formatted strings from resources you can also use extension format:

fun getMyFormatDesc(input: String): StringDesc {
    return MR.strings.my_string_formatted.format(input)
}

Now add support on the platform side like in example #1:
Android:

val string = getMyFormatDesc("hello").toString(context = this)

iOS:

let string = getMyFormatDesc(input: "hello").localized()

Warning: Do no mix positioned placeholders with unpositioned ones within a string, as this may lead to different behaviour on different platforms. Stick to one style for each string.

Example 3 - plural string

The first step is to create a file plurals.xml in commonMain/resources/MR/base with the following content:

<?xml version="1.0" encoding="UTF-8" ?>
<resources>
    <plural name="my_plural">
        <item quantity="zero">zero</item>
        <item quantity="one">one</item>
        <item quantity="two">two</item>
        <item quantity="few">few</item>
        <item quantity="many">many</item>
        <item quantity="other">other</item>
    </plural>
</resources>

Then add the localized values for other languages like in example #1.
Next, create a function in commonMain:

fun getMyPluralDesc(quantity: Int): StringDesc {
    return StringDesc.Plural(MR.plurals.my_plural, quantity)
}

Now add support on the platform side like in example #1:
Android:

val string = getMyPluralDesc(10).toString(context = this)

iOS:

let string = getMyPluralDesc(quantity: 10).localized()

Example 4 - plural formatted string

The first step is to create file plurals.xml in commonMain/resources/MR/base with the following content:

<?xml version="1.0" encoding="UTF-8" ?>
<resources>
    <plural name="my_plural">
        <item quantity="zero">no items</item>
        <item quantity="one">%d item</item>
        <item quantity="two">%d items</item>
        <item quantity="few">%d items</item>
        <item quantity="many">%d items</item>
        <item quantity="other">%d items</item>
    </plural>
</resources>

Then add the localized values for other languages like in example #1.
Next, create a function in commonMain:

fun getMyPluralFormattedDesc(quantity: Int): StringDesc {
    // we pass quantity as selector for correct plural string and for pass quantity as argument for formatting
    return StringDesc.PluralFormatted(MR.plurals.my_plural, quantity, quantity)
}

To create formatted plural strings from resources you can also use extension format:

fun getMyPluralFormattedDesc(quantity: Int): StringDesc {
    // we pass quantity as selector for correct plural string and for pass quantity as argument for formatting
    return MR.plurals.my_plural.format(quantity, quantity)
}

And like in example #1, add the platform-side support:
Android:

val string = getMyPluralFormattedDesc(10).toString(context = this)

iOS:

let string = getMyPluralFormattedDesc(quantity: 10).localized()

Example 5 - pass raw string or resource

If we already use some resources as a placeholder value, we can use StringDesc to change the string source:

fun getUserName(user: User?): StringDesc {
    if(user != null) {
        return StringDesc.Raw(user.name)
    } else {
        return StringDesc.Resource(MR.strings.name_placeholder)
    }
}

And just like in example 1 usage on platform side:
Android:

val string1 = getUserName(user).toString(context = this) // we got name from User model
val string2 = getUserName(null).toString(context = this) // we got name_placeholder from resources

iOS:

let string1 = getUserName(user: user).localized() // we got name from User model
let string2 = getUserName(user: null).localized() // we got name_placeholder from resources

Example 6 - Select localization in runtime

You can force StringDesc to use preferred localization in common code:

StringDesc.localeType = StringDesc.LocaleType.Custom("es")

and return to system behaviour (when localization depends on device settings):

StringDesc.localeType = StringDesc.LocaleType.System()

Example 7 - pass image

Image resources directory is commonMain/resources/MR/images with support of nested directories.
Image name should be end with one of:

• @0.75x - android ldpi;
• @1x - android mdpi, ios 1x;
• @1.5x - android hdpi;
• @2x - android xhdpi, ios 2x;
• @3x - android xxhdpi, ios 3x;
• @4x - android xxxhdpi. Supported png and jpg resources for now.

If we add to commonMain/resources/MR/images files:

• home_black_18@1x.png
• home_black_18@2x.png

We got autogenerated MR.images.home_black_18 ImageResource in code, that we can use:

• Android: imageView.setImageResource(image.drawableResId)
• iOS: imageView.image = image.toUIImage()

You can get images by their name too

in commonMain create a Resources.kt file with the content below

fun getImageByFileName(name: String): ImageResource {
    val fallbackImage = MR.images.transparent
    return MR.images.getImageByFileName(name) ?: fallbackImage
}

• Android: imageView.setImageResource(getDrawableByFileName("image_name"))
• iOS: imageView.image = ResourcesKt.getDrawableByFileName(name: "image_name").toUIImage()!

Example 8 - pass font

Fonts resources directory is commonMain/resources/MR/fonts.
Font name should be this pattern: <fontFamily>-<fontStyle> like:

• Raleway-Bold.ttf
• Raleway-Regular.ttf
• Raleway-Italic.ttf Supports ttf and otf resources.

If we add to commonMain/resources/MR/fonts files:

• Raleway-Bold.ttf
• Raleway-Regular.ttf
• Raleway-Italic.ttf

We got autogenerated MR.fonts.Raleway.italic, MR.fonts.Raleway.regular, MR.fonts.Raleway.bold FontResource in code, that we can use:

• Android: textView.typeface = font.getTypeface(context = this)
• iOS: textView.font = font.uiFont(withSize: 14.0)

Example 9 - pass colors

Colors resources directory is commonMain/resources/MR/colors.
Colors files is xml with format:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- format: #RRGGBB[AA] or 0xRRGGBB[AA] or RRGGBB[AA] where [AA] - optional -->
    <color name="valueColor">#B02743FF</color>
    <color name="referenceColor">@color/valueColor</color>
    <color name="themedColor">
        <light>0xB92743FF</light>
        <dark>7CCFEEFF</dark>
    </color>
    <color name="themedReferenceColor">
        <light>@color/valueColor</light>
        <dark>@color/referenceColor</dark>
    </color>
</resources>

If you want use one color without light/dark theme selection:

<color name="valueColor">#B02743FF</color>

If you want use value of other color - use references:

<color name="referenceColor">@color/valueColor</color>

If you want different colors in light/dark themes:

<color name="themedColor">
    <light>0xB92743FF</light>
    <dark>7CCFEEFF</dark>
</color>

Also themed colors can be referenced too:

<color name="themedReferenceColor">
    <light>@color/valueColor</light>
    <dark>@color/referenceColor</dark>
</color>

Colors available in common code insode MR.colors.** as ColorResource.
ColorResource can be ColorResource.Single - simple color without theme selection.
And can be ColorResource.Themed with colors for each mode.

You can read colors value from common code:

val color: Color = MR.colors.valueColor.color

but if you use ColorResource.Themed you can get current theme color only from platfrom side. Android:

val color: Color = MR.colors.valueColor.getColor(context = this)

iOS:

val color: UIColor = MR.colors.valueColor.getColor(UIScreen.main.traitCollection.userInterfaceStyle)

// If your SwiftUI View can not handle the run time dark/light mode changes for colors
// add this line on top of the View it will make it aware of dark/light mode changes 
@Environment(\.colorScheme) var colorScheme

You can get Color from resource on IOS with toUIColor For use it you should export moko-resources library to IOS

framework {
    export(libs.mokoResources)
}

Example 10 - plain file resource access

The first step is a create a resource file test.txt for example, in commonMain/resources/MR/files After gradle sync we can get file by id MR.files.test Moko-resources has out of box implementation function for read text files from common code - readText()

Usage on Android:

val text = MR.files.test.getText(context = this)

Usage on Apple:

val text = MR.files.test.readText()

If you want to read files not as text, add your own implementation to expect/actual FileResource

Example 11 - assets access

Assets allow you save directories hierarchy (in files structure is plain). Locate files to commonMain/resources/MR/assets and access to it by MR.assets.*

Creating Fat Framework with resources

Just use FatFrameworkTask from kotlin plugin .

Creating XCFramework with resources

Just use XCFramework from kotlin plugin .

But if you use static frameworks required additional setup - add to Xcode build phase (at end):

"$SRCROOT/../gradlew" -p "$SRCROOT/../" :shared:copyResourcesMPLReleaseXCFrameworkToApp \
    -Pmoko.resources.BUILT_PRODUCTS_DIR=$BUILT_PRODUCTS_DIR \
    -Pmoko.resources.CONTENTS_FOLDER_PATH=$CONTENTS_FOLDER_PATH

Details you can check in sample TestStaticXCFramework in ios-app. In this sample used mpp-hierarhical kotlin module with XCFramework.

Samples

Please see more examples in the sample directory.

Sample mpp-hierarhical contains usage of org.jetbrains.kotlin.native.cocoapods plugin and unit tests with resources usage. Jvm-sample to run it you should use IntelliJ IDEA.
macOS-sample it contains two schemes. TestProj is the sample app and TestHierarchical is a splash-screen.
android-sample TestHierarchical creates two launchers, the first one starts the sample-app at once, the second one allows to choose language before starting the sample.

Set Up Locally

• The resources directory contains the resources library;
• The gradle-plugin directory contains a gradle plugin with a MR class generator;
• The sample directory contains sample apps for Android and iOS; plus the mpp-library connected to the apps.

Contributing

All development (both new features and bug fixes) is performed in the develop branch. This way master always contains the sources of the most recently released version. Please send PRs with bug fixes to the develop branch. Documentation fixes in the markdown files are an exception to this rule. They are updated directly in master.

The develop branch is pushed to master on release.

For more details on contributing please see the contributing guide.

License

Copyright 2019 IceRock MAG Inc.

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.