[Help Wanted] Using JNIGen to build a package

[Leylan24]

I have custom native java code that i interact with through a method channel from flutter. I reuse this plugin through multiple apps. I would like to use JNIGen to use this same java source code, however when trying to run it I get the error

(jnigen) INFO: trying to obtain gradle dependencies [getReleaseCompileClasspath]...
(jnigen) INFO: Restoring build scripts
Unhandled exception:


gradle exited with status 1
. This can be because the Android build is not yet cached. Please run `flutter build apk` in .\ and try again

#0      AndroidSdkTools._runGradleStub (package:jnigen/src/tools/android_sdk_tools.dart:207:7)
#1      AndroidSdkTools.getGradleClasspaths (package:jnigen/src/tools/android_sdk_tools.dart:144:7)
#2      getSummary (package:jnigen/src/summary/summary.dart:136:34)
#3      generateJniBindings (package:jnigen/src/generate_bindings.dart:31:21)
<asynchronous suspension>
#4      main (file:///D:/Pub/Cache/hosted/pub.dev/jnigen-0.12.0/bin/jnigen.dart:18:3)
<asynchronous suspension>

however I cannot run flutter build apk as its not yet in a example project. Would it be possible to have the java and bindings generated into a plugin/package that I can export into other applications and use it there ?

[HosseinYousefi]

If you have access to the source, you can pass the path to the source directly to JNIgen instead. If you want to use gradle, you should create an example app, pass in the path to it like https://github.com/dart-lang/http/blob/master/pkgs/cronet_http/jnigen.yaml#L3-L5 and run flutter build apk for the example app for gradle to download and cache the dependencies.

[Leylan24]

how would i pass it directily? My yaml file looks like this:

source_path:
  - 'android/src/main/java/za/co/scotchsoftware/asmart_v2_api/pay_api_driver/PayApiSystem.java'
classes:
  - 'za.co.scotchsoftware.asmart_v2_api.pay_api_driver.PayApiSystem'

output:
  dart:
    path: 'lib/jni_generated.dart'
    ## Output to single file instead of recreating source's file structure.
    ## This will be useful to reduce clutter when binding a small number of
    ## classes.
    structure: 'single_file'

I removed the lines:

android_sdk_config:
  add_gradle_deps: true
  add_gradle_sources: true

I get the error:

maven exited with 1
(jnigen) INFO: execute java -jar .dart_tool/jnigen/ApiSummarizer.jar -s "android\src\main\java\za\co\scotchsoftware\asmart_v2_api\pay_api_driver\PayApiSystem.java" za.co.scotchsoftware.asmart_v2_api.pay_api_driver.PayApiSystem
Error: Unable to access jarfile .dart_tool/jnigen/ApiSummarizer.jar

Fatal: Cannot generate summary: FormatException: Unexpected end of input (at character 1)

^

[HosseinYousefi]

Just provide the path to the java directory, jnigen will handle the rest from the package path:

source_path: 'android/src/main/java'

(Although it's usually android/app/src/main/java in case you missed that).

The error message needs to be better here though, I will fix this.

[Leylan24]

I have created an example app and have run the flutter build apk:

PS D:\Github\Api\asmart_v2_api\example_jni_gen> flutter build apk                    

You are applying Flutter's app_plugin_loader Gradle plugin imperatively using the apply script method, which is deprecated and will be removed in a future release. Migrate to applying Gradle plugins with the declarative plugins block: https://flutter.dev/to/flutter-gradle-plugin-apply

You are applying Flutter's main Gradle plugin imperatively using the apply script method, which is deprecated and will be removed in a future release. Migrate to applying Gradle plugins with the declarative plugins block: https://flutter.dev/to/flutter-gradle-plugin-apply

Running Gradle task 'assembleRelease'...                           70.5s
√ Built build\app\outputs\flutter-apk\app-release.apk (56.5MB)

I have then ran jnigen and get the following error:

gradle exited with status 1
. This can be because the Android build is not yet cached. Please run `flutter build apk` in example_jni_gen\ and try again

#0      AndroidSdkTools._runGradleStub (package:jnigen/src/tools/android_sdk_tools.dart:207:7)
#1      AndroidSdkTools.getGradleClasspaths (package:jnigen/src/tools/android_sdk_tools.dart:144:7)
#2      getSummary (package:jnigen/src/summary/summary.dart:136:34)
#3      generateJniBindings (package:jnigen/src/generate_bindings.dart:31:21)
<asynchronous suspension>
#4      main (file:///D:/Pub/Cache/hosted/pub.dev/jnigen-0.12.0/bin/jnigen.dart:18:3)
<asynchronous suspension>

here is the full log with the maven output

jnigenLog.txt

[Leylan24]

The fault was mine. There were conflicts with java jdk versioning, maven was using java8 but the project was using java11.

The errors are a bit misleading I had to run the mvn command with -e to find the error. It would be nice if we could print a verbose log ? or is there a way and I just dont know how to do it

[HosseinYousefi]

The errors are a bit misleading I had to run the mvn command with -e to find the error. It would be nice if we could print a verbose log ? or is there a way and I just dont know how to do it

You can find full logs in .dart_tool/jnigen/logs. However this is not well documented and not communicated in the actual logs which has to be improved. Thanks for reporting this.

I will improve this before 1.0 release.

[stuartmorgan-g]

You can find full logs in .dart_tool/jnigen/logs.

FYI no useful information is logged in this scenario. _runGradleStub throws on gradlew errors without ever recording the stdout/stderr anywhere.

I had a similar mismatch, and had to hack jnigen to get any useful information. The extremely helpful message from gradlew that jnigen was discarding was:

FAILURE: Build failed with an exception.

* Where:
Build file '/Users/stuartmorgan/src/packages/packages/video_player/video_player_android/example/android/app/build.gradle' line: 24

* What went wrong:
A problem occurred evaluating project ':app'.
> Failed to apply plugin 'com.android.internal.application'.
   > Android Gradle plugin requires Java 17 to run. You are currently using Java 11.
      Your current JDK is located in /Library/Java/JavaVirtualMachines/zulu-11.jdk/Contents/Home
      You can try some of the following options:
       - changing the IDE settings.
       - changing the JAVA_HOME environment variable.
       - changing `org.gradle.java.home` in `gradle.properties`.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
> Get more help at https://help.gradle.org.