react-native/docs/AndroidBuildingFromSource.md

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---
id: android-building-from-source
title: Building React Native from source
layout: docs
category: Guides (Android)
permalink: docs/android-building-from-source.html
next: activityindicatorios
---
You will need to build React Native from source if you want to work on a new feature/bug fix, try out the latest features which are not released yet, or maintain your own fork with patches that cannot be merged to the core.
## Prerequisites
Assuming you have the Android SDK installed, run `android` to open the Android SDK Manager.
Make sure you have the following installed:
1. Android SDK version 23 (compileSdkVersion in [`build.gradle`](https://github.com/facebook/react-native/blob/master/ReactAndroid/build.gradle))
2. SDK build tools version 23.0.1 (buildToolsVersion in [`build.gradle`](https://github.com/facebook/react-native/blob/master/ReactAndroid/build.gradle))
3. Android Support Repository >= 17 (for Android Support Library)
4. Android NDK (download & extraction instructions [here](http://developer.android.com/ndk/downloads/index.html))
Point Gradle to your Android SDK: either have `$ANDROID_SDK` and `$ANDROID_NDK ` defined, or create a local.properties file in the root of your react-native checkout with the following contents:
```
sdk.dir=absolute_path_to_android_sdk
ndk.dir=absolute_path_to_android_ndk
```
Example:
```
sdk.dir=/Users/your_unix_name/android-sdk-macosx
ndk.dir=/Users/your_unix_name/android-ndk/android-ndk-r10e
```
## Building the source
#### 1. Installing the fork
First, you need to install `react-native` from your fork. For example, to install the master branch from the official repo, run the following:
```sh
npm install --save github:facebook/react-native#master
```
Alternatively, you can clone the repo to your `node_modules` directory and run `npm install` inside the cloned repo.
#### 2. Adding gradle dependencies
Add `gradle-download-task` as dependency in `android/build.gradle`:
```gradle
...
dependencies {
classpath 'com.android.tools.build:gradle:1.3.1'
classpath 'de.undercouch:gradle-download-task:2.0.0'
// NOTE: Do not place your application dependencies here; they belong
// in the individual module build.gradle files
}
...
```
#### 3. Adding the `:ReactAndroid` project
Add the `:ReactAndroid` project in `android/settings.gradle`:
```gradle
...
include ':ReactAndroid'
project(':ReactAndroid').projectDir = new File(
rootProject.projectDir, '../node_modules/react-native/ReactAndroid')
...
```
Modify your `android/app/build.gradle` to use the `:ReactAndroid` project instead of the pre-compiled library, e.g. - replace `compile 'com.facebook.react:react-native:0.16.+'` with `compile project(':ReactAndroid')`:
```gradle
...
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:23.0.1'
compile project(':ReactAndroid')
...
}
...
```
#### 4. Making 3rd-party modules use your fork
If you use 3rd-party React Native modules, you need to override their dependencies so that they don't bundle the pre-compiled library. Otherwise you'll get an error while compiling - `Error: more than one library with package name 'com.facebook.react'`.
Modify your `android/app/build.gradle` and replace `compile project(':react-native-custom-module')` with:
```gradle
compile(project(':react-native-custom-module')) {
exclude group: 'com.facebook.react', module: 'react-native'
}
```
## Building from Android Studio
From the Welcome screen of Android Studio choose "Import project" and select the `android` folder of your app.
You should be able to use the _Run_ button to run your app on a device. Android Studio won't start the packager automatically, you'll need to start it by running `npm start` on the command line.
## Additional notes
Building from source can take a long time, especially for the first build, as it needs to download ~200 MB of artifacts and compile the native code. Every time you update the `react-native` version from your repo, the build directory may get deleted, and all the files are re-downloaded. To avoid this, you might want to change your build directory path by editing the `~/.gradle/init.gradle ` file:
```gradle
gradle.projectsLoaded {
rootProject.allprojects {
buildDir = "/path/to/build/directory/${rootProject.name}/${project.name}"
}
}
```
## Troubleshooting
Gradle build fails in `ndk-build`. See the section about `local.properties` file above.