# [Android Product Flavor](https://developer.android.com/studio/build/build-variants.html#product-flavors)

###### tags: `Android Gradle`


[TOC]

# Introduction
With **Product Flavor**, we can have **many versions of the same app** with slightly different variables/aspects in each.

# Where to use it?
All Product Flavor settings are set in **build.gradle** file , which is located in **app/build.gradle**.

We can also put it in an apart .gradle file, while applying the file in the same **build.gradle (app/build.gradle)**.

**Example:**

apply from: '../variant.gradle'

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# How to set up?
Having **build.gradle (app/build.gradle)** opened, we can either set it up on the **same file** or get a **separated .gradle file**

## Things to take into account before set up
No matter either set up in build.gradle or separated .gradle file, all set ups must:
1. **be enclosed by android {}**
2. **specify flavorDimension "inputName"

**Example:**

android {
    flavorDimensions "productFlavor"
    productFlavors {
        flavor {

        }

        flavor1 {

        }
    }
}

After **sync** you will see that **Build Variant** window will have more options in **Active Build Variant**.

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## Set up in build.gradle (app/build.gradle)
1. Open build.gradle(app/build.gradle)
2. Inside Android {} set up the product flavors
3. Sync Gradle
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## Set up in separated .gradle file
1. New > File
2. Name the file with **.gradle extension**
3. Open build.gradle(app/build.gradle)
4. Link build.gradle to the newFile.gradle by using **apply from: 'location'**
5. Go to newFile.gradle
6. Set up product flavor

**Note:** Remember to add **android {}** by yourself
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# Product Flavor Information
Profuct Flavor information can be set up by 3 methods:
1. **buildConfigField:** Values are shown in BuildConfig file.
2. **resValue:** Values are shown in res(generated) > values > gradleResValues.
3. **manifestPlaceholders:** Values can be used in manifest directly.

## **buildConfigField**
This one will generate a file called **BuildConfig**, which will set up all constants set in gradle.

### **How to set up?**
Just put **buildConfigField "type", "FieldName", "FieldValue"**
Note: For String FieldValue a **\ (slash)** must be used.

As we can see below, we can also set up **applicationId, versionCode, versionName** for each of our product flavor.

**Example:**

flavorDimensions "productFlavor"

def BASE_URL = "BASE_URL"
def APP_NAME = "APP_NAME"

productFlavors {
    flavor {
        applicationId "com.zc.learngradle0"
        versionCode 2
        buildConfigField "String", BASE_URL, "\"FieldValue\""
        buildConfigField "String", APP_NAME, "\"AppName\""
        buildConfigField "int", "FieldInt0", "0"
    }

}

### **BuildConfig File**
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>**Note:** Sync may not be enough for it to appear, you may need to run the project once.

### **What if your applicationId, versionCode, versionName did not change?**
If you are **using another .gradle file** check the import place in build.gradle.

As shown in the image below, check **build.gradle (app/build.gradle)** whether you have set up **defaultConfig** with the same fields as the one you have wrong in BuildConfig.

If you did, check:
* Whether you have really stated the variables in your variant.
* Close BuildConfig, ReSync and Rebuild to check again

If not, then it may be another issue.

**Note:**
DefaultConfig acts as default state when you did not specify the variables for any variant.

## **resValue**
This one will show its values in **res(generated) > values > gradleResValues**.

### **How to set up?**

flavorDimensions "productFlavor"

productFlavors {
    flavor {
        // Will be put in res(generated) > values > gradleResValues
        // Note: res > values > strings.xml must not have same string id (Error: Duplicate resources)
        resValue "string", "base_url_base", "www.example.com"

    }

}

### **Output location: gradleResValues**
**res(generated) > values > gradleResValues**
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## **manifestPlaceholders**
Values generated can be used directly by **manifest by using ${constantName}**.

### **How to set up?**
By setting an **array for manifestPlaceholders** we can set up **key-value** for each constant/variable we want.

**Example:**

flavorDimensions "productFlavor"

productFlavors {
    flavor {
        manifestPlaceholders = [
            "app_name": "FlavorApp",
            "app_icon": "@mipmap/ic_launcher",
            "app_round_icon": "@mipmap/ic_launcher_round"
        ]
    }

}

### **How to use the values set up in the manifestPlaceholder?**
#### **In Manifest file**
By using **${keyName}** we can call out the value set up in the manifestPlaceholder without any problem.

#### **In Project**
If we want to retrive **manifestPlaceholder' values** in our project too, we have to use **meta-data** in manifest.

>Be aware to put meta-data inside the Application section. [color=red]
>**Note:** the meta-data name cannot use manifestPlaceholder values as name, meaning we cannot use name = ${...}
>

**In Activity Retrive Example:**

try{
    PackageManager packageManager = getApplicationContext().getPackageManager();
    ApplicationInfo appInfo = packageManager.getApplicationInfo(this.getPackageName(), PackageManager.GET_META_DATA);
    Log.d("manifestPlaceholder", appInfo.metaData.getString("app_icon"));
} catch (PackageManager.NameNotFoundException e) {
    e.printStackTrace();
}

# Reference
https://medium.com/stepstone-tech/how-to-build-17-apps-with-a-single-android-project-and-not-go-crazy-91d025adf0f0