How to import the sources to Android Studio / IntelliJ

Install Android Studio

Go to the Download page and download the package for your OS.

Unpack the downloaded file to a destination of your choice, then follow the instructions described in Install-Linux-tar.txt file which is in the extracted folder.

Prepare a project file

Open a shell and navigate to the root folder of your Android sources, e.g. ~/android/lineage. In case environment functions and variables are not yet loaded, type:

source build/envsetup.sh

Tip: You can always check this by executing croot (go to your Android root dir) and see if it gives an error. If not, you have already executed the source command.

Now execute:

make idegen && development/tools/idegen/idegen.sh

Note: This can take some time while it goes through your tree and generates an Android Studio project based on it.

In case you are developing on multiple branches or plan to do so (otherwise skip the next step), do the following (replace every occurrence of lineage with your desired naming scheme):

mv android.ipr lineage.ipr
mv android.iml lineage.iml && ln -s lineage.iml android.iml

Prepare Android Studio

Android Studio struggles to parse the huge LineageOS / Android sources and requires some different settings than the defaults. Therefore, before starting actual development, it is necessary to change some of those.

Configure memory

Navigate to the bin folder from the install directory of Android Studio (e.g. ~/android-studio/bin), open the files studio.vmoptions and studio64.vmoptions with a text editor and include the following:

-Xms748m
-Xmx748m

This will set the initial allocated (Xms parameter) and maximum usable (Xmx parameter) RAM to 748MB each. You can also use higher numbers but should not go below that to ensure usablility. You can find more information of these and other parameters in the official documentation

Increase the file parsing limit

Again, navigate to the bin folder and open the file idea.properties with a text editor. Look for the line idea.max.intellisense.filesize= and change its value to 5000 (or higher, if you wish).

This is required so Android Studio can parse very large files to properly provide the auto-complete features (Android Studio calls this IntelliSense).

Note: If the line is missing (it should already be inside the file with current Android Studio versions), append it to the end of the file.

Start working with Android Studio

Open Android Studio and click on Open existing project.

Then navigate to your Android source directory and open the .ipr file.

Note: Opening the project the first time or after a fresh sync can take a while. You should wait until any indexing of files is done to be sure that every IDE feature is ready to use.

Configure the project

After opening the project, navigate to File -> Project Structure -> SDKs (this might be disabled until the indexing has finished) and set up a JDK (version 1.8 for LineageOS 14.1 branch) where you remove all libraries (.jar files).

Then, on the left side of the settings panel, choose Project Settings -> Modules and mark the folder out/target/common/R as Sources (you can also select it and press [ALT]+[S]).

Press Apply and close the settings.

Start developing

Now, after all the previous steps are done, you can actually start developing and exploring the sources. The Find in path function (Edit -> Find -> Find in path) can be a good start to find a file you want to modify. Just search for a known string among all source files and then dive in deeper until you actually found the function you want to modify.

Contribute!

After you have modified the sources and tested your change, you can contribute to LineageOS by submitting your work.