Create Free/Paid versions of Application from same code

Question

So I\'m coming down to release-time for my application. We plan on releasing two versions, a free ad-based play-to-unlock version, and a paid fully unlocked version. I have

Answer 1

The best way is to use "Android Studio" -> gradle.build -> [productFlavors + generate manifest file from template]. This combination allows to build free/paid versions and bunch of editions for different app markets from one source.

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This is a part of templated manifest file:

---

---

This is template "ProductInfo.template" for java file: ProductInfo.java

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    package com.packagename.generated;
    import com.packagename.R;
    public class ProductInfo {
        public static final boolean mIsPaidVersion = {f:PAID}true{/f}{f:FREE}false{/f};
        public static final int mAppNameId = R.string.app_name_{f:PAID}paid{/f}{f:FREE}free{/f};
        public static final boolean mIsDebug = {$DEBUG};
    }

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This manifest is processed by gradle.build script with productFlavors and processManifest task hook:

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import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.gradle.api.DefaultTask
import org.gradle.api.tasks.TaskAction  
...

android {
    ...
    productFlavors {
        free {
            packageName 'com.example.product.free'
        }
        paid {
            packageName 'com.example.product.paid'
        }
    }
    ...
}

afterEvaluate { project ->
    android.applicationVariants.each { variant ->

        def flavor = variant.productFlavors[0].name

        tasks['prepare' + variant.name + 'Dependencies'].doLast {
            println "Generate java files..."

            //Copy templated and processed by build system manifest file to filtered_manifests forder
            def productInfoPath = "${projectDir}/some_sourcs_path/generated/"
            copy {
                from(productInfoPath)
                into(productInfoPath)
                include('ProductInfo.template')
                rename('ProductInfo.template', 'ProductInfo.java')
            }

            tasks.create(name: variant.name + 'ProcessProductInfoJavaFile', type: processTemplateFile) {
                templateFilePath = productInfoPath + "ProductInfo.java"
                flavorName = flavor
                buildTypeName = variant.buildType.name
            }   
            tasks[variant.name + 'ProcessProductInfoJavaFile'].execute()
        }

        variant.processManifest.doLast {
            println "Customization manifest file..."

            // Copy templated and processed by build system manifest file to filtered_manifests forder
            copy {
                from("${buildDir}/manifests") {
                    include "${variant.dirName}/AndroidManifest.xml"
                }
                into("${buildDir}/filtered_manifests")
            }

            tasks.create(name: variant.name + 'ProcessManifestFile', type: processTemplateFile) {
                templateFilePath = "${buildDir}/filtered_manifests/${variant.dirName}/AndroidManifest.xml"
                flavorName = flavor
                buildTypeName = variant.buildType.name
            }
            tasks[variant.name + 'ProcessManifestFile'].execute()

        }
        variant.processResources.manifestFile = file("${buildDir}/filtered_manifests/${variant.dirName}/AndroidManifest.xml")
    }
}

---

This is separated task to process file

---

class processTemplateFile extends DefaultTask {
    def String templateFilePath = ""
    def String flavorName = ""
    def String buildTypeName = ""

    @TaskAction
    void run() {
        println templateFilePath

        // Load file to memory
        def fileObj = project.file(templateFilePath)
        def content = fileObj.getText()

        // Flavor. Find "{f:}...{/f}" pattern and leave only "==flavor"
        def patternAttribute = Pattern.compile("\\{f:((?!${flavorName.toUpperCase()})).*?\\{/f\\}",Pattern.DOTALL);
        content = patternAttribute.matcher(content).replaceAll("");

        def pattern = Pattern.compile("\\{f:.*?\\}");
        content = pattern.matcher(content).replaceAll("");
        pattern = Pattern.compile("\\{/f\\}");
        content = pattern.matcher(content).replaceAll("");

        // Build. Find "{$DEBUG}" pattern and replace with "true"/"false"
        pattern = Pattern.compile("\\{\\\$DEBUG\\}", Pattern.DOTALL);
        if (buildTypeName == "debug"){ 
            content = pattern.matcher(content).replaceAll("true");
        }
        else{
            content = pattern.matcher(content).replaceAll("false");
        }

        // Save processed manifest file
        fileObj.write(content)
    }
}

Updated: processTemplateFile created for code reusing purposes.