The .gitignore file I use for every Android project, created by gitignore.io.

.gitignore

# Created by https://www.gitignore.io and updated by @markovicdev

### OSX ###
.DS_Store
.AppleDouble
.LSOverride

# Icon must end with two \r
Icon

# Thumbnails
._*

# Files that might appear in the root of a volume
.DocumentRevisions-V100
.fseventsd
.Spotlight-V100
.TemporaryItems
.Trashes
.VolumeIcon.icns

# Directories potentially created on remote AFP share
.AppleDB
.AppleDesktop
Network Trash Folder
Temporary Items
.apdisk


### Android ###
# Built application files
*.apk
*.ap_

# Files for the Dalvik VM
*.dex

# Java class files
*.class

# Generated files
bin/
gen/
captures/

# Keystores - comment if you want to keep keystores, but ignore any sensitive data like passwords
*.jks

## traces
*.trace

# Gradle files
.gradle/
build/
/*/build/
gradle/secrets.gradle

# Local configuration file (sdk path, etc)
local.properties

# Proguard folder generated by Eclipse
proguard/

# Log Files
*.log

### Android Patch ###
gen-external-apklibs


### Intellij ###
# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm

*.iml

## Directory-based project format:
.idea/
projectFilesBackup/
# if you remove the above rule, at least ignore the following:

# User-specific stuff:
# .idea/workspace.xml
# .idea/tasks.xml
# .idea/dictionaries

# Sensitive or high-churn files:
# .idea/dataSources.ids
# .idea/dataSources.xml
# .idea/sqlDataSources.xml
# .idea/dynamic.xml
# .idea/uiDesigner.xml

# Gradle:
# .idea/gradle.xml
# .idea/libraries

# Mongo Explorer plugin:
# .idea/mongoSettings.xml

## File-based project format:
*.ipr
*.iws

## Plugin-specific files:

# IntelliJ
/out/

# mpeltonen/sbt-idea plugin
.idea_modules/

# JIRA plugin
atlassian-ide-plugin.xml

# Crashlytics plugin (for Android Studio and IntelliJ)
com_crashlytics_export_strings.xml
crashlytics.properties
crashlytics-build.properties

# Proguard
app/class_files.txt
app/mapping.txt
app/seeds.txt
app/unused.txt

qaplug_result.html
*.hprof

.ruby-version