Build Level Variables And Methods Using Gradle

This topic written about build environment of an android studio application. It will discuss on how to write variables and methods at build configuration level. Such variables and functions, they will be independent of build variants and able to provide information about build variant to the application.

During our development of an android application we create multiple build variants eg, debug, release. Each build variant may have different values and each time when we build variant we are manually changing the values. Have you ever thought of something which can detect the build variant at application level
and leaving the overhead of switching the entire configuration values on each build variants to build system?

The the solution to the above mentioned question is going to explained in this article.

The solution is a single word, Gradle, is a intelligent build tool used by android studio IDE, which comes as a plugin. By default all android applications are gradle based. There will be build.gradle file which is the entry point to the build configuration of the application.

Create 2 Build Variants

app/build.gradle

buildTypes {

        debug {
            buildConfigField "String", "API_KEY", "\"hkjdbfkujfdbkbfsd\""
            buildConfigField "String", "API_URL", '\"http://api.example.com/dev\"'
            buildConfigField "boolean", "LOG", "true"
        }

        release {
            buildConfigField "String", "API_KEY", "\"dfskdhfskdskfsdk\""
            buildConfigField "String", "API_URL", '\"http://api.example.com/live\"'
            buildConfigField "boolean", "LOG", "false"


            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

The script taken from the build.gradle file of an android studio project. Where we have two build variants, debug and release. In both variants there are 3 variables declared,

• API_KEY – is a string variable
• API_URL – is a string variable
• LOG – is a boolean variable

Define Methods

Here we define two methods, getMyVersionCodeValue() and getMyVersionCodeNameValue()

android {
.....

 def versionCodeValue = 1;
 def versionCodeNameValue = "1.0";


 ext.getMyVersionCodeValue = {
   return versionCodeValue;
 }

 ext.getMyVersionCodeNameValue = {
   return versionCodeNameValue;
 }


defaultConfig {
        applicationId "gradlevars.devdeeds.com.gradlevariables"
        minSdkVersion 16
        targetSdkVersion 23
        versionCode versionCodeValue
        versionName versionCodeNameValue
}

.....
}

Call the Methods

Now we can the above defined method from tasks. Here we have two tasks, assembleDebug will be called when you are building debug variant and getMyVersionCodeNameValue will be called when you are building release variant.

assembleDebug << {
  getMyVersionCodeValue()
  getMyVersionCodeNameValue()
}

assembleRelease << {
   getMyVersionCodeValue()
   getMyVersionCodeNameValue()
}

Choosing the build variant

Debug Build

Go to Build > Select Build Variant... > select debug > rebuild the app

Release Build

Go to Build > Select Build Variant... > select release > rebuild the app

Generated Java File

This is the generated java class file when we built the application in debug mode.

/**
 * Automatically generated file. DO NOT MODIFY
 */
package gradlevars.devdeeds.com.gradlevariables;

public final class BuildConfig {
  public static final boolean DEBUG = Boolean.parseBoolean("true");
  public static final String APPLICATION_ID = "gradlevars.devdeeds.com.gradlevariables";
  public static final String BUILD_TYPE = "debug";
  public static final String FLAVOR = "";
  public static final int VERSION_CODE = 1;
  public static final String VERSION_NAME = "1.0";
  // Fields from build type: debug
  public static final String API_KEY = "hkjdbfkujfdbkbfsd";
  public static final String API_URL = "http://api.example.com/dev";
  public static final boolean LOG = true;
}

MainActivity.java

Let's see how to access these build variables through Activity class.

package gradlevars.devdeeds.com.gradlevariables;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toast.makeText(getApplicationContext(), BuildConfig.API_KEY + "\n" + BuildConfig.API_URL + "\n" + Boolean.toString(BuildConfig.LOG), Toast.LENGTH_SHORT).show();

    }
}

Output

Debug Variant

Download Source Code