Android String XML Reference

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Language
Kotlin
Version
2.0.0 (Feb 19, 2022)
Created
Oct 22, 2019
Updated
Feb 19, 2022
Owner
LikeTheSalad
Contributor
LikeTheSalad
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Android Stem

Table of Contents

What is it

Android Stem is a Gradle plugin that resolves placeholders of XML strings referenced into other XML strings at build time. You won't have to write any Java or Kotlin code into your project to make it work, and you will still be able to access to the 'resolved' strings the same way as with any other manually added string to your XML files.

In other words, if you're looking to do something like this:

Input:

<resources>
    <string name="app_name">My App Name</string>
    <string name="welcome_message">Welcome to ${app_name}</string>
</resources>

Output:

<!-- Auto generated during compilation -->
<resources>
    <string name="welcome_message">Welcome to My App Name</string>
</resources>

Without having to write any Java or Kotlin code, then Android Stem might help you.

How to use

1.- Templates

All you have to do is to define string templates inside your XML values' files, the file to add these templates to can be any file inside your values folders, not necessarily the "strings.xml" file but any other XML file within the same directory will work too.

In order to create a template all you need to do is to add references to other strings in the form of "placeholders" into the string you want to use as template, the placeholder format is ${another_string_name} where "another_string_name" will be the name of any other string you have in your project or in a library of yours that serves as a "Stem provider" one, more on it below.

Following our example above for our "my_message" template, let's say that we have another string in our project named "app_name" (which content is "My app name") and we want to place it inside our "my_message" template, we can do it like so:

<string name="my_message">Welcome to ${app_name}</string>

A template can contain from one to any amount of placeholders. Any string within your values' folder (even other templates) can be referenced inside a placeholder. And that's it, we've defined a template. Meaning that when we compile, we'll get as a result the following "resolved" string:

<!-- Auto generated during compilation -->
<string name="my_message">Welcome to My app name</string>

2.- Running it

The process that resolves the string templates will run during your app's compilation process, based on that, there's many ways of running it, some of those could be:

  • By pressing on the "play" button of Android Studio:
  • Or, by pressing on the "make" button on Android Studio:
  • Or, if you prefer command line, then you can run it by calling the build command: ./gradlew build or the assemble command: ./gradlew assemble or by calling the specific task to resolve the strings which has the following format: ./gradlew resolve[BUILD_VARIANT]Placeholders more info on this command below under "Running it manually".

2.1- How to know if it worked?

After the task has run, now you will be able to access to the "resolved" strings where you'll see that your placeholders have been replaced by the actual referenced values.

2.2- Where can I find the resolved strings in my project?

The resolved strings go into your app's build folder, specifically under the build/generated/resolved path. That's where Android Stem places them into when it is run.

The following cases are supported:

  • Regular main strings.
  • Localized (language-specific) strings.
  • Flavor specific strings.
  • Flavor specific with localized strings.

Both values and templates can be overridden for a different language and also for a different flavor. So if for example you have templates in your project which contain the app name placeholder (e.g. ${app_name}) then if you need to create a flavor with a different app name value, you just have to override the 'app_name' string inside the flavor's 'values' folder and that's it, now for this flavor you'll get all the old strings but with the new app_name.

Same for languages, based on the example above, if you need to translate your 'my_message' string to spanish for example, you just have to override the template 'my_message', inside the 'values-es' folder, and you'll get the translated 'my_message' string in the 'resolved.xml' file inside the 'values-es' folder.

Use case examples

Here's a couple of examples for some of the use cases supported by Android Stem

1.- Simple use case

Within our app/main/res/values folder, we have the following file:

<!--strings.xml-->
<resources>
    <string name="app_name">Test</string>
    <string name="welcome_message">Welcome to ${app_name}</string>
</resources>

After building our project we get:

<!--Auto generated during compilation-->
<resources>
    <string name="welcome_message">Welcome to Test</string>
</resources>

2.- Multi files use case

Within our app/main/res/values folder, we have the following files:

<!--strings.xml-->
<resources>
    <string name="app_name">Test</string>
    <string name="welcome_message">Welcome to ${app_name}</string>
    <string name="app_version_name">The version for ${app_name} is ${my_version}</string>
</resources>
<!--my_configs.xml-->
<resources>
    <string name="my_version">1.0.0</string>
</resources>

After building our project we get:

<!--Auto generated during compilation-->
<resources>
    <string name="app_version_name">The version for Test is 1.0.0</string>
    <string name="welcome_message">Welcome to Test</string>
</resources>

So no matter which file contains a template or a value used in a template, as long as it's within your app's values folders, then the plugin will find it.

3.- Multi languages use case

Within our app/main/res/values folder, we have the following file:

<!--strings.xml-->
<resources>
    <string name="app_name">Test</string>
    <string name="welcome_message">Welcome to ${app_name}</string>
</resources>

Then, Within our app/main/res/values-es folder, we have the following file:

<!--any_file.xml-->
<resources>
    <string name="welcome_message">Bienvenido a ${app_name}</string>
</resources>

After building our project, what we get for our default values folder is:

<!--Auto generated during compilation-->
<resources>
    <string name="welcome_message">Welcome to Test</string>
</resources>

And then what we get for our spanish values-es folder is:

<!--Auto generated during compilation-->
<resources>
    <string name="welcome_message">Bienvenido a Test</string>
</resources>

4.- Flavors use case

Let's say we've defined a flavor in our project, named demo, then:

Within our app/main/res/values folder, we have the following files:

<!--strings.xml-->
<resources>
    <string name="app_name">Test</string>
    <string name="welcome_message">Welcome to ${app_name}</string>
    <string name="app_version_name">The version for ${app_name} is ${my_version}</string>
</resources>
<!--my_configs.xml-->
<resources>
    <string name="my_version">1.0.0</string>
</resources>

And for our app/demo/res/values folder we add the following file:

<!--any_file.xml-->
<resources>
    <string name="app_name">Demo app</string>
</resources>

After building the demo variant of our project, we'll get for such variant:

<!--Auto generated during compilation-->
<resources>
    <string name="app_version_name">The version for Demo app is 1.0.0</string>
    <string name="welcome_message">Welcome to Demo app</string>
</resources>

So we see that the app_name value has been overridden by the demo's app_name, this doesn't only happen for values but also for templates, we can also override templates within our demo's resources.

Those were some of the use cases that you can achieve using Android Stem, there's more of them such as overriding flavors' multi languages from the base values folder and also working with multi-dimension flavors. You can play around with it, it all should work the way you'd expect it to work.

Adding it to your project

We're going to need to modify two build.gradle files in our project in order to make Android Stem work, those are:

  • Root's build.gradle
  • App's build.gradle
  • Android libraries build.gradle (Optional - If you want to define templates in your own android libraries)

1.- Where to find the build.gradle files

To get a better idea of where you can find these files, take a look at this Android Studio screenshot below:

  • The number 1 selection is to make sure that you've selected the "Project" view in order to see the build.gradle files as shown on this image.
  • The number 2 selection represents your App's build.gradle file, and it should look similar for Android libraries, if you happen to have any in your project.
  • The number 3 selection represents your Root's build.gradle file.

2.- What to add to the build.gradle files

2.1- Changes to your Root's build.gradle file

First, in your Root's build.gradle file, you'll need to add this line into your buildscript dependencies block:

classpath "com.likethesalad.android:stem-plugin:2.0.0"

Example:

// Root's build.gradle file
buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        //...
        classpath "com.likethesalad.android:stem-plugin:2.0.0"

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

Please note that you must also add (if not there already) mavenCentral() to your buildscript's repositories block as shown above.

2.2- Changes to your App's build.gradle file

In your App's build.gradle file you have to add the following line below the apply plugin: 'com.android.application' one:

apply plugin: 'com.likethesalad.stem'

Example:

// App's build.gradle file
apply plugin: 'com.android.application'
apply plugin: 'com.likethesalad.stem'

android {
  //...
}

2.3- Adding it to your own Android Libraries (Optional)

If you have parts of your project split into multiple android libraries where you'd like to define templates, you can do so by applying a "producer" version of Stem into them like so:

// App's build.gradle file
apply plugin: 'com.android.library'
apply plugin: 'com.likethesalad.stem-library'

android {
    //...
}

Please bear in mind that the "producer" plugin doesn't resolve templates, it only provides them along with values needed to resolve those, so that the "consumer" (application) can use them later on when building the final app.

2.4- Sync your project

After your changes to the build.gradle files are done, you should see the above message in Android Studio that has a "Sync Now" button. You have to click on that button for the changes to take effect. After the sync is done, you'll be ready to go! you can start adding your string templates to your app's resources.

Running it manually

If you want to just run the gradle task that resolves the templates without having to build your project, you can do so by running: resolve[BUILD_VARIANT]Placeholders depending on your build configuration. For example, to run it for the debug variant, you'll have to run: resolveDebugPlaceholders, or if you have flavors set up in your application, e.g. say you have 'demo' as a flavor defined, then you can run resolveDemoDebugPlaceholders to generate the strings for the demo flavor on the debug variant and so on.

Donations

If this plugin is useful for you, and if it's within your possibilities, please consider making a one-off donation that will help keeping the development of new features and bug support. And if you can't make a donation right now, you could also support this plugin by sharing it with your dev friends and colleagues!

<string>"Thanks for your support, ${your_beautiful_name}!"</string>

License

MIT License

Copyright (c) 2019 LikeTheSalad.

Permission is hereby granted, free of charge, to any person obtaining a copy
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copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.