In this post i want to explain you how i use Gradle variables to keep my buildscript clearer.
DefaultConfig and Dependencies
The problem
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dependencies { ... implementation 'com.android.support:appcompat-v7:27.0.2' implementation 'com.android.support:recyclerview-v7:27.0.2' implementation "com.jakewharton:butterknife:8.8.1" annotationProcessor "com.jakewharton:butterknife-compiler:8.8.1" } |
By default you add your dependencies under dependencies in your build.gradle . But the more dependencies your app has, the more confusing it can get if you want to check which version of a dependency you are using or when you want to update a specific one. For example all the google support libraries need the same version number. If you use hardcoded version numbers you need to update every single support library.
My solution
I saw this solution in an example project from google. I keep all variables in dedicated file called constants.gradle
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project.ext { applicationId = "jensklingenberg.de.exampleexoplayer" compileSdk = 27 targetSdk = 27 minSdk = 21 versionCode = 1 versionName = "1.0" buildTools = '27.0.1' junitVersion = '4.12' appVersion = '1.0' butterknifeVersion = '8.8.1' supportLibVersion = '27.0.2' exoplayerVersion = '2.6.0' } |
To use these variables i add
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apply from: 'constants.gradle' |
on the top of my build.gradle.
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dependencies { ... implementation "com.android.support:appcompat-v7:${supportLibVersion}" implementation "com.google.android.exoplayer:exoplayer:${exoplayerVersion}" implementation "com.jakewharton:butterknife:${butterknifeVersion}" annotationProcessor "com.jakewharton:butterknife-compiler:${butterknifeVersion}"} |
Now i can use these variables instead of hard coded values. When using variables in a String you need to use double quotes instead of single qoutes.
As you can see i also used variables for things like applicationId or compileSdk. To use these variables you just use the variable name:
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compileSdkVersion compileSdk defaultConfig { applicationId applicationId ... } |
BuildConfigField
A different kind of variables or respectively constants are buildConfigField’s. You can use these fields to generate the value of a constant depending on your Gradle buildtype.
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buildTypes { debug { buildConfigField "String", "API_BASE_URL", '"https://test.de/testing/api/v1/"' ... } release { buildConfigField "String", "API_BASE_URL", '"https://test.de/prod/api/v1/"' ... } } |
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new Retrofit.Builder().addConverterFactory(MoshiConverterFactory.create(moshi)) .addCallAdapterFactory(new LiveDataCallAdapterFactory()) .baseUrl(BuildConfig.API_BASE_URL) .client(App.getInstance().getOkHttpClient()) .build(); |
In this example i have two different base urls for every buildtype. To use the value of API_BASE_URL in my java code i just use BuildConfig.API_BASE_URL.
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