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Hooking onto tasks

info

This guide was written for flutter_rust_bridge v1, thus some content may be outdated. The quickest approach to integrate is to follow the one-click approach in flutter_rust_bridge's quickstart page.

This is the same method used by the app template and also the easier one. Go ahead and install cargo-ndk if you have not already done so:

cargo install cargo-ndk

Next, add these lines1 near the bottom of android/app/build.gradle:

[
    new Tuple2('Debug', ''),
    new Tuple2('Profile', '--release'),
    new Tuple2('Release', '--release')
].each {
    def taskPostfix = it.first
    def profileMode = it.second
    tasks.whenTaskAdded { task ->
        if (task.name == "javaPreCompile$taskPostfix") {
            task.dependsOn "cargoBuild$taskPostfix"
        }
    }
    tasks.register("cargoBuild$taskPostfix", Exec) {
        // Until https://github.com/bbqsrc/cargo-ndk/pull/13 is merged,
        // this workaround is necessary.

        def ndk_command = """cargo ndk \
            -t armeabi-v7a -t arm64-v8a -t x86_64 -t x86 \
            -o ../android/app/src/main/jniLibs build $profileMode"""

        workingDir "../../$crate"
        environment "ANDROID_NDK_HOME", "$ANDROID_NDK"
        if (org.gradle.nativeplatform.platform.internal.DefaultNativePlatform.currentOperatingSystem.isWindows()) {
            commandLine 'cmd', '/C', ndk_command
        } else {
            commandLine 'sh', '-c', ndk_command
        }
    }
}

Note the ANDROID_NDK variable, this is a Gradle property that points to your installation of the Android NDK. If you don't rely on portability, you can hardcode this value, but note that it can be supplied by one of the many gradle.properties scattered throughout your filesystem. The most reliable way is to create a file at ~/.gradle/gradle.properties and fill it with this:

ANDROID_NDK=(path to NDK)

Note the ABIs x86_64 and x86 in ndk_command are usually used for Android simulators. Feel free to remove them as needed.

  1. This excerpt might be outdated, please check out the source file at the template repository.↩