android-studio project, - What is Gradle in Android Studio?
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Gradle is bit confusing to me and also for new Android developer. Can anyone explain what gradle in Android Studio is and what its purpose is? Why is Gradle included in Android Studio?
It's the new build tool that Google wants to use for Android. It's being used due to it being more extensible, and useful than ant. It is meant to enhance developer experience.
You can view a talk by Xavier Ducrohet from the Android Developer Team on Google I/O here.
There is also another talk on Android Studio by Xavier and Tor Norbye, also during Google I/O here.
One Advantage of Gradle that I found is:
Gradle was designed for multi-project builds which can grow to be quite large, and supports incremental builds by intelligently determining which parts of the build tree are up-to-date, so that any task dependent upon those parts will not need to be re-executed.
DEFINITION:: Gradle can be described a structured building mechanism where it provides a developer the tools and flexibility to manage the resources of a project to create builds that are
smaller in size,
targeting specific requirements for certain devices of certain configurations
LIBRARIES:: We can add android libraries or any other third party libraries in addition as per requirements easy which was a tedious task earlier. If the library does not fit for the existing project, The developer is shown a log where the person can find a appropriate solution to make changes to the project so that the library can be added. Its just one line of dependency
GENERATING VARIETIES OF BUILDS
Combining build types with build flavours to get varities of build varients
==================== ==================== | BuildTypes | | ProductFlavours | -------------------- ====================== -------------------- | Debug,Production | || || | Paid,Free,Demo,Mock| ==================== || || ==================== || || VV VV ================================================================= | DebugPaid, DebugFree, DebugDemo, DebugMock | | ProductionPaid, ProductionFree, ProductionDemo, ProductionMock | =================================================================
Gradle helps in reducing the size of the generated build by removing the unused resources also unused things from integrated libraries
We can Specify certain permissions for certain builds by adding certain permissions in certain scenarios based on requirements
BUILDS FOR CERTAIN DEVICES
We can manage generating build for certain devices that include certain densities and certain api levels. This helps in product deployments in app store according to requirements across multiple types of devices
Here is a detailed explanation about what
Gradle is and how to use it in Android Studio.
Exploring the Gradle Files
- Whenever you create a project in Android Studio, the build system automatically generates all the necessary Gradle build files.
Gradle Build Files
Gradle build files use a
Domain Specific Language or DSLto define custom build logic and to interact with the Android-specific elements of the Android plugin for Gradle.
Android Studio projects consists of 1 or more modules, which are components that you can build, test, and debug independently. Each module has its own build file, so every Android Studio project contains 2 kinds of Gradle build files.
Top-Level Build File: This is where you'll find the configuration options that are common to all the modules that make up your project.
Module-Level Build File: Each module has its own Gradle build file that contains module-specific build settings. You'll spend most of your time editing module-level build file(s) rather than your project's top-level build file.
To take a look at these
build.gradle files, open Android Studio's Project panel (by selecting the Project tab) and expand the Gradle Scripts folder.
The first two items in the Gradle Scripts folder are the project-level and module-level Gradle build files
Top-Level Gradle Build File
Every Android Studio project contains a single, top-level Gradle build file. This
build.gradle file is the first item that appears in the Gradle Scripts folder and is clearly marked Project.
Most of the time, you won't need to make any changes to this file, but it's still useful to understand its contents and the role it plays within your project.
Module-Level Gradle Build Files
In addition to the project-level Gradle build file, each module has a Gradle build file of its own. Below is an annotated version of a basic, module-level Gradle build file.
Other Gradle Files
In addition to the build.gradle files, your Gradle Scripts folder contains some other Gradle files. Most of the time you won't have to manually edit these files as they'll update automatically when you make any relevant changes to your project. However, it's a good idea to understand the role these files play within your project.
gradle-wrapper.properties (Gradle Version)
This file allows other people to build your code, even if they don't have Gradle installed on their machine. This file checks whether the correct version of Gradle is installed and downloads the necessary version if necessary.
This file references all the modules that make up your project.
gradle.properties (Project Properties)
This file contains configuration information for your entire project. It's empty by default, but you can apply a wide range of properties to your project by adding them to this file.
local.properties (SDK Location)
This file tells the Android Gradle plugin where it can find your Android SDK installation.
local.properties contains information that's specific to the local installation of the Android SDK. This means that you shouldn't keep this file under source control.
I got clear understanding of gradle from this.
In plain terms, Gradle is a tool provided by Android Studio in order to implement two important processes:
- Build our projects
- Package AndroidManifest.xml,res folder,and binary code into a specially formatted zip file called APK
Gradle is an automated build toolkit that can integrate into lots of different environments not only for Android projects.
Here are few things that you can do with gradle.
Minimal Configuration Required for New Projects because Gradle has defaults configurations for your android studio projects.
Dependancy Declaration. You can declare dependency jar files or library files that is hosted in local or remote server.
Gradle automatically generates a test directory and a test APK from your project's source.
If you add all the necessary information, such as
keyAlias, to your Gradle build file, you can use Gradle to generate signed APKs.
Gradle can generate multiple APKs with different package and build configurations from a single module.
Gradle is to the Groovy JVM language what ant is to Java. Basically, it's Groovy's build tool. Unlike Ant, it's based on the full Groovy language. You can, for example, write Groovy script code in the Gradle script to do something rather than relying on a specific domain language.
I don't know IntelliJ's specific integration, but imagine you could "extend" Groovy such that you could write specific "build" language primitives and they just became part of the Groovy language. (Groovy's metaprogramming is a whole discussion unto itself.) IntelliJ/Google could use Gradle to build a very high-level build language, yet, it's a language build on an expandable, open standard.
In Android Studio, Gradle is a custom build tool used to build android packages (apk files) by managing dependencies and providing custom build logic.
APK file (Android Application package) is a specially formatted zip file which contains
- Byte code
- Resources (images, UI, xml etc)
- Manifest file
An apk file gets signed and pushed to the device using ADB(Android Debug Bridge) where it gets executed.
Gradle is a build tool custom and used for building APK or known as application package kit.
Gradle is a build system. Build systems are software tools designed to automate the process of program compilation. Build systems come in various forms, and are used for a variety of software build tasks. While their primary goal is to efficiently create executables.
Another related term is Build automation which is the process of automating the creation of a software build and the associated processes including: compiling computer source code into binary code, packaging binary code, and running automated tests.
Few similar build system for other languages are (see complete list here):
- Apache Ant & Apache Maven - Java
- sbt (Simple Build Tool) - for Scala (Play framework etc)
- A-A-P - Python based build tool
- Rake (Apache Builder) - Ruby
- Leiningen for Clojure
Gradle is an advanced build toolkit for android that manages dependencies and allows you to define custom build logic. features are like 1. Customize, configure, and extend the build process. 2. Create multiple APKs for your app with different features using the same project. 3. Reuse code and resources. refer this link http://developer.android.com/sdk/installing/studio-build.html
Gradle is what makes it possible to automate the building of complex Android projects that involve 10s of thousands of lines of code from multiple sources, projects, libraries etc. It can conditionally generate multiple optimised APKs based on a plethora of configuration specifications - if you are interested, the other answers provide more details of this aspect of Gradle.
However, if you're new to Android developing, Gradle in 99% of cases is what stops your project from building. It is an inscrutable, complex system that effectively obfuscates the Android build process and essentially renders it unavailable to inexperienced developers, ie in order to build a simple entry level Android App the unsuspecting newbie might need to study and understand many things that they didnt bargain for such as:
- Android APK structure and ecosystem
- Android Studio
- Java Classpaths and dependencies
- Gradle build scripts
- Many other complex and interesting technologies
All these things are interesting and useful for Android developers to know, but they are far from easy and present a formidable barrier to entry. I suspect that what inspired the OP to ask this question is the feeling of frustration that inevitably hits the neophyte developer after spending way too long trying to get a simple app to build and being continually thwarted by Gradle. The problem is perversely exacerbated by the overwhelming quantity of highly technical documentation that is available for all these technologies. Also for a large amount of development needs Gradle is overkill.
An alternative is to write a shell script that builds your project by automating the tools available in the android SDK. The virtues of this approach are many, for starters its probably the best way to study and understand the build process and the Android ecosystem, and it allows you to completely control how your app is built. However this approach is more suitable for deeply irredeemable tech-heads than it is to inexperienced noobs trying out android.
What is conspicuous by its absence (please inform me if there is such a thing) is an entry level, lightweight IDE with a reduced feature set that simultaneously simplifies the build process while not obscuring it (so not netbeans or eclipse) it could possibly still use Gradle (what was wrong with Ant). It should make it easy to generate APKs that conform to a few common configurations and use a project structure that can evolve to a full Android Studio project should you decide to take it that way.
Gradle is one type of build tool that builds the source code of the program. So it's an important part of Android Studio, and needs to be installed before starting developing your application.
We do not have to install it separately, because the Android Studio does it for us, when we make our first project.
At the risk of being discursive I think behind this is the question of why the Android Studio / Gradle experience is so bad.
Typical Clojure experience :
- download project with dependencies listed in project.clj.
- Leiningen gets the dependencies thanks to Clojars and Maven.
- Project compiles.
Typical Android Studio / Gradle experience :
- "Import my Eclipse project".
- OK project imported.
- Gradle is doing it's thang ... wait ... wait ... wait ... Gradle has finished.
- Compile ... can't compile because I don't know what an X is / can't find Y library.
I'm not sure this is Gradle's fault exactly. But the "import from Eclipse project" seems pretty flaky. For all of Gradle's alleged sophistication and the virtues of a build-system, Android Studio just doesn't seem to import the build dependencies or build-process from Eclipse very well.
It doesn't tell you when it's failed to import a complete dependency graph. The Android Studio gives no useful help or tips as to how to solve the problem. It doesn't tell you where you can manually look in the Eclipse folders. It doesn't tell you which library seems to be missing. Or help you search Maven etc. for them.
In 2016 things like Leiningen / Clojars, or node's npm, or Python's pip, or the Debian apkg (and I'm sure many similar package managers for other languages and systems) all work beautifully ... missing dependencies are thing of the past.
Except with Android. Android Studio is now the only place where I still seem to experience missing-dependency hell.
I'm inclined to say this is Google's fault. They broke the Android ecosystem (and thousands of existing Android projects / online tutorials) when they cavalierly decided to shift from Eclipse to Android Studio / Gradle without producing a robust conversion process. People whose projects work in Eclipse aren't adapting them to AS (presumably because it's a pain for them). And people trying to use those projects in AS are hitting the same issues.
And anyway, if Gradle is this super-powerful build system, why am I still managing a whole lot of other dependencies in the sdk manager? Why can't a project that needs, say, the ndk specify this in its Gradle file so that it gets automatically installed and built-against when needed? Why is NDK special? Similarly for target platforms? Why am I installing them explicitly in the IDE rather than just checking my project against them and having this all sorted for me behind the scenes?
Gradle = Groovy + Cradle Hans Dockter forum comment
The confusion is a bit unnecessary when it could have just been called "Build" or something in Android Studio.
We like to make things difficult for ourselves in the Development community.
The Gradle build system is designed to support complex scenarios in creating Android applications:
Multi-distribution: the same application must be customized for several clients or companies
Multi-apk: supporting the creation of multiple apk for different device types while reusing parts of the code
Gradel is a general purpose, declarative build tool. It is general purpose because it can be used to build pretty much anything you care to implement in the build script. It is declarative since you don't want to see lots of code in the build file, which is not readable and less maintainable. So, while Gradle provides the idea of conventions and a simple and declarative build, it also makes the tool adaptable and developers the ability to extend. It also provides an easy way to customize the default behavior and different hooks to add any third-party features.
Gradle combines the good parts of both tools and provides additional features and uses Groovy as a Domain Specific Language (DSL). It has power and flexibility of Ant tool with Maven features such as build life cycle and ease of use.
Why Gradle? Why Now?
The build tool's response is to add scripting functionality through nonstandard extension mechanisms. You end up mixing scripting code with XML or invoking external scripts from your build logic. It's easy to imagine that you'll need to add more and more custom code over time. As a result, you inevitably introduce accidental complexity, and maintainability goes out the window.
Let's say you want to copy a file to a specific location when you're building the release version of your project. To identify the version, you check a string in the metadata describing your project. If it matches a specific numbering scheme (for example, 1.0-RELEASE), you copy the file from point A to point B. From an outside perspective, this may sound like a trivial task. If you have to rely on XML, the build language of many traditional tools, expressing this simple logic becomes fairly difficult.
Evolution of Java Build Tools
Java build logic has to be described in XML. XML is great for describing hierarchical data but falls short on expressing program flow and conditional logic. As a build script grows in complexity, maintaining the building code becomes a nightmare.
In Ant, you make the JAR target depend on the compile target. Ant doesn't give any guidance on how to structure your project. Though it allows for maximum flexibility, Ant makes each build script unique and hard to understand. External libraries required by your project are usually checked into version control because there is no automated mechanism to pull them from a central location.
Maven 1, released in July 2004, tried to ease that process. It provided a standardized project and directory structure, as well as dependency management. Unfortunately, custom logic is hard to implement
Gradle fits right into that generation of build tools and satisfies many requirements of modern build tools (Figure 1). It provides an expressive DSL, a convention over configuration approach, and powerful dependency management. It makes the right move to abandon XML and introduce the dynamic language Groovy to define your build logic. Sounds compelling, doesn't it?
Gradle combines the best features of other build tools.
Gradle's Compelling Feature Set
Why Build Your Java Projects with Gradle Rather than Ant or Maven?
The default build tool for Android (and the new star of build tools on the JVM) is designed to ease scripting of complex, multi-language builds. Should you change to it, though, if you're using Ant or Maven?
Gradle can't know all the requirements specific to your enterprise build. By exposing hooks into lifecycle phases, Gradle allows for monitoring and configuring the build script's execution behavior.
Gradle establishes a vocabulary for its model by exposing a DSL implemented in Groovy. When dealing with a complex problem domain, in this case, the task of building software, being able to use a common language to express your logic can be a powerful tool.
Another example is the way you can express dependencies to external libraries, a very common problem solved by build tools. Out-of-the-box Gradle provides you with two configuration blocks for your build script that allow you to define the dependencies and repositories that you want to retrieve them from. If the standard DSL elements don't fit your needs, you can even introduce your own vocabulary through Gradle's extension mechanism.
Integration with Other Build Tools
Gradle plays well with its predecessors' Ant, Maven, and Ivy, as shown in the image below.
Automating Your Project from Build to Deployment
In image: Stages of a deployment pipeline.
Compiling the code
Running unit and integration tests
Performing static code analysis and generating test coverage
Creating the distribution
Provisioning the target environment
Deploying the deliverable
Performing smoke and automated functional tests
Gradle is an advanced build system as well as an advanced build toolkit allowing to create custom build logic through plugins!
- Dsl - Domain specific language, based on groovy
- DAG - Directed Acyclic Graph
- Incremental builds
- Extensible domain model
- Gradle is always up to date
- Before a task is being execute, Gradle takes a snapshot of its task’s input and output.
- In case the snapshot has changed or it doesn’t exists, Gralde will re- execute this task.
Through the DSL it is possible to configure the following manifest entries:
By default, the Android plugin automatically sets up the project to build both a debug and a release version of the application.
- Local Dependencies:
If you have binary archives in your local filesystem that a module depends on, such as JAR files, you can declare these dependencies in the build file for that module.
- Remote Dependencies:
First the repository must be added to the list, and then the dependency must be declared in a way that Maven or Ivy declare their artifacts.
select the package will be refactored, refactor->move ->"move xxx to new package"