Develop Reference

What are dependencies in android?

What are dependencies ?
Why do we add dependencies ?
I searched a lot but could not find the answers to above questions.

In Android Studio, dependencies allows us to include external library or local jar files or other library modules in our Android project.
For example: Suppose I want to show some images in ImageView. But I'm using Glide Library to enhance the smoothness of application. So I have to add a dependency in the build.gradle(Module App) as:
compile 'com.github.bumptech.glide:glide:3.7.0'
So Now I can use Glide library :) and show my images.
Note: Glide library is the bumptech's library but still I can use it in my project from 1 line of code of dependency.

Whenever you add a dependency to your gradle file, it will download the added libraries, and add them to your project so that is available in your project. It makes it easy to manage external libraries in your project.
To study more , visit : https://developer.android.com/studio/build/dependencies.html

if you want to use external libraries or modules in your android
project you have to add the dependancies so that you may be given the
authority to use that particular library otherwise that will not be accessible to you inside the project.
so, its concluded that:
The Gradle build system in Android Studio makes it easy to include external binaries or other library modules to your build as dependencies. The dependencies can be located on your machine or in a remote repository, and any transitive dependencies they declare are automatically included as well
for further you can visit this link:
https://developer.android.com/studio/build/dependencies

Why does an Android app project have to include a package used by a library

An Android app uses a library (aar module) that uses "com.google.gson.Gson". The library has the following in its build.gradle:
compile 'com.google.code.gson:gson:2.6.2'
The app builds fine, but generates the following error when it starts:
Failed resolution of: Lcom/google/gson/Gson;
The only way to solve it is adding the same compile line to the app's build.gradle:
compile 'com.google.code.gson:gson:2.6.2'
Could anyone shed some light on this?
[Edit]
The library was added with the standard procedure that created a folder under the app called "androidLibrary-release". The following line has been added to the build.gradle of the app:
compile project(':androidLibrary-release')

Libraries don't include their dependencies. It is up to the developer to include them as necessary in the app modules that implement them. However, if this library comes from a Maven repo, it is possible to include the information about which dependencies the library uses and they will be fetched when your project is built.

How do I use another library in my app?

The title is a little misleading but I honestly don't know how to word it in any other way. This is my project structure:
I want to use the highlighted (fasteranimationscontainer-master) in my current app that I'm working on. I imported it by putting the jar file in my library folder then adding it to my library through Android Studio. But I try to create an object of that imported library, it doesn't show up/import.
I'm still learning how to use android studio so any help would be much appreciated!

1. Library with only the Source Code
To include a library with only the source code (like FasterAnimationsContainer) to your project, you only need to import it as a module from File -> New-> Import Module in Android Studio:
There should be a dialog for the project folder, enter the path where your library reside.
Then you need to add the module to your app build.gradle as a dependency:
android {
...
dependencies {
...
compile project(':fasteranimationscontainer')
...
}
}
Now you can use it in your project.
2. Library from Maven or JCenter
To add dependencies to your project where the library has uploaded to maven or jcenter, you need to modify your app build.gradle file and add extra lines configuring the packages you require. For example, for certain Google or Android, dependencies look like:
android {
...
dependencies {
// Google Play Services
compile 'com.google.android.gms:play-services:6.5.+'
// Support Libraries
compile 'com.android.support:support-v4:22.2.1'
}
}
Try to always read the library README first.
Suggestion:
If you still learning using Android Studio, you can read Using Android Studio. Then read Getting Started with Gradle, because Android Studio is tightly related with Gradle.

Sample app runs fine with library as a module, but not as an external dependency?

I have a library which itself has a few dependencies, namely Realm, Retrofit, as well as a native library. The native library is on github and I can successfully pull it into my project via jitpack.
I have a sample app which im using to test this library. In my sample apps 'app' module build.gradle i my dependencies block looks somewhat like the following:
dependencies {
compile project(':sdk')
...
//compile realm,rx,retrofit, etc..
}
When doing this, my sample app works correctly.
Now lets say I either:
Grab the sdk's generated .jar file and put it in my sample apps /libs
Get the .aar and do the same as above
Put the repo on jitpack and try to download it via compile 'xxxx'
Trying to include the sdk in my sample app any of these other ways does not seem to work and spits out unhelpful errors.
What could possibly be the issue? I got a hint that it may be an issue with 'transitive dependencies' but am not sure where to start.
Ideas?

How to insert github source code to my project

I'm new at GitHub. I found a library that I want to use in my Android project (Glide), but I don't know how.
After downloading the source code I'm stuck with a zip folder that I don't know how to import it into my project. I'm working with Android Studio.
Any help?
Thanks.

Unzip the downloaded project. Open YOUR project in Android studio. Click File -> Import module. Add this module as a dependency to your project. You should be good to go.
[EDIT]
BUT, since Glide has gradle/maven support, I can just simply modify your project's build.gradle file and add the following lines to the dependencies group:
compile 'com.github.bumptech.glide:glide:3.3.+'
compile 'com.android.support:support-v4:19.0.0' // You might need to increase the version numbers if the libraries have never versions