How to use termux-ndk to build android app

Download the android-ndk and android-sdk from release

# install openjdk-17
pkg install openjdk-17

# install gradle
pkg install gradle

Add a local.properties file to the root of the project as below

# modify the local.properties file
# although ndk.dir has been deprecated, but it still works
sdk.dir=/path/to/android-sdk
ndk.dir=/path/to/android-ndk
cmake.dir=/path/to/cmake
# for example:
sdk.dir=/data/data/com.termux/files/home/opt/android-sdk
ndk.dir=/data/data/com.termux/files/home/opt/android-ndk-r27b
cmake.dir=/data/data/com.termux/files/home/opt/android-sdk/cmake

Modify the project/build.gradle.kts file

// set the Android gradle plugin version 
plugins {
    id("com.android.application") version "8.6.0" apply false
    id("com.android.library") version "8.6.0" apply false
    id("org.jetbrains.kotlin.android") version "2.0.20" apply false
}

Modify the project app/build.gradle.kts file

android {
    // set the build tools version
    buildToolsVersion = "35.0.0"
    
    externalNativeBuild {
        cmake {
            path("src/main/cpp/CMakeLists.txt")
            // If your cmake version >= 3.21, you must specify a version
            // 3.18.5+ or 3.25.1 and so on
            version = "3.25.1"
        }
    }
}

Execute the gradle build command to start building the android app, when building for the first time, the exec format error will occur, because the aapt2 is x86_64 architecture not aarch64, so we need to replace it

# replace the aapt2 with your own
# note: it's /path/to not /path/to/aapt2
find ~/.gradle -name 'aapt2-*-linux.jar' -type f | xargs -I{} jar -uvf {} -C /path/to aapt2

If an error occurs during the build app, this may be a network problem, please execute the gradle build again or execute the gradle build --info for more information.

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Building termux-app with termux

# clone the termux-app
git clone --depth=1 https://github.com/termux/termux-app

# add a local.properties file
sdk.dir=/path/to/android-sdk 
ndk.dir=/path/to/android-ndk 
cmake.dir=/path/to/cmake

# modify gradle.properties file 
minSdkVersion=24
targetSdkVersion=28
ndkVersion=27.1.12297006
compileSdkVersion=35
buildToolsVersion=35.0.0

# modify the build.gradle file
# termux-app/app/build.gradle 
# terminal-emulator/build.gradle 
# terminal-view/build.gradle 
# termux-shared/build.gradle
# set the buildToolsVersion
android {
    ...
    compileSdkVersion project.properties.compileSdkVersion.toInteger()
    // set the build tools version
    buildToolsVersion project.properties.buildToolsVersion.toString()
    ...
}

# start building
gradle assembleDebug

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Building example

# GL2
cd GL2 && gradle installDebug

# GL3
cd GL3 && gradle installDebug

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Known issues

Using proot or chroot linux is not recommended, this may have some problems, the building speed is much slower than the native Termux.