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)
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:
project(':ReactAndroid').projectDir = new File(rootProject.projectDir, '../node_modules/react-native/ReactAndroid')
...
```
4. 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')
...
}
...
```
5. If you use 3rd-party React Native modules, modify your `android/app/build.gradle` to override their dependencies so that they don't bundle the pre-compiled library, e.g. - replace `compile project(':react-native-custom-module')` with:
Building from source can take a long time, especially for the first build, as it needs to download ~200 MB of files and compile JSC etc. 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: