Question description

I'm trying to use the url_launcher plugin in my Flutter project. To ensure version compatibility, I set the dependency version to any in pubspec.yml:

dependencies:
  url_launcher: any

The Gradle build succeeds when running ./gradlew clean build from the Android directory, but I get an error when running the Flutter project on an Android emulator. The console shows:

ERROR:D:\Workspace\Projects\trip\build\url_launcher_android\intermediates\runtime_library_classes_jar\debug\classes.jar: D8: java.lang.NullPointerException

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:mergeLibDexDebug'.
> Could not resolve all files for configuration ':app:debugRuntimeClasspath'.
   > Failed to transform classes.jar (project :url_launcher_android)...
      > Execution failed for DexingWithClasspathTransform: ...\classes.jar.
         > Error while dexing.

* Try: (Gradle troubleshooting steps)
...
BUILD FAILED in 1s
Error: Gradle task assembleDebug failed with exit code 1

Version

• Flutter 3.22.0
• Gradle 8.2.1
• Android SDK 35

Key Observations:

Build succeeds with ./gradlew clean build but fails at runtime NullPointerException during D8 dexing phase Error specifically occurs with url_launcher_android module

android/build.gradle file:

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

rootProject.buildDir = "../build"
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
}
subprojects {
    project.evaluationDependsOn(":app")
}

tasks.register("clean", Delete) {
    delete rootProject.buildDir
}

android/app/build.gradlefile:

plugins {
    id "com.android.application"
    id "kotlin-android"
    // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
    id "dev.flutter.flutter-gradle-plugin"
}

def localProperties = new Properties()
def localPropertiesFile = rootProject.file("local.properties")
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader("UTF-8") { reader ->
        localProperties.load(reader)
    }
}

def flutterVersionCode = localProperties.getProperty("flutter.versionCode")
if (flutterVersionCode == null) {
    flutterVersionCode = "1"
}

def flutterVersionName = localProperties.getProperty("flutter.versionName")
if (flutterVersionName == null) {
    flutterVersionName = "1.0"
}

android {
    namespace = "com.example.trip"
    compileSdk = flutterpileSdkVersion
    ndkVersion = flutter.ndkVersion

    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_1_8
        targetCompatibility = JavaVersion.VERSION_1_8
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (.html).
        applicationId = "com.example.trip"
        // You can update the following values to match your application needs.
        // For more information, see: /deployment/android#reviewing-the-gradle-build-configuration.
        minSdk = flutter.minSdkVersion
        targetSdk = flutter.targetSdkVersion
        versionCode = flutterVersionCode.toInteger()
        versionName = flutterVersionName
    }

    buildTypes {
        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig = signingConfigs.debug
        }
    }
}

flutter {
    source = "../.."
}

gradle-wrapper.propertiesfile:

distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https\://services.gradle/distributions/gradle-8.2.1-all.zip

Question description

I'm trying to use the url_launcher plugin in my Flutter project. To ensure version compatibility, I set the dependency version to any in pubspec.yml:

dependencies:
  url_launcher: any

The Gradle build succeeds when running ./gradlew clean build from the Android directory, but I get an error when running the Flutter project on an Android emulator. The console shows:

ERROR:D:\Workspace\Projects\trip\build\url_launcher_android\intermediates\runtime_library_classes_jar\debug\classes.jar: D8: java.lang.NullPointerException

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:mergeLibDexDebug'.
> Could not resolve all files for configuration ':app:debugRuntimeClasspath'.
   > Failed to transform classes.jar (project :url_launcher_android)...
      > Execution failed for DexingWithClasspathTransform: ...\classes.jar.
         > Error while dexing.

* Try: (Gradle troubleshooting steps)
...
BUILD FAILED in 1s
Error: Gradle task assembleDebug failed with exit code 1

Version

• Flutter 3.22.0
• Gradle 8.2.1
• Android SDK 35

Key Observations:

Build succeeds with ./gradlew clean build but fails at runtime NullPointerException during D8 dexing phase Error specifically occurs with url_launcher_android module

android/build.gradle file:

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

rootProject.buildDir = "../build"
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
}
subprojects {
    project.evaluationDependsOn(":app")
}

tasks.register("clean", Delete) {
    delete rootProject.buildDir
}

android/app/build.gradlefile:

plugins {
    id "com.android.application"
    id "kotlin-android"
    // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
    id "dev.flutter.flutter-gradle-plugin"
}

def localProperties = new Properties()
def localPropertiesFile = rootProject.file("local.properties")
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader("UTF-8") { reader ->
        localProperties.load(reader)
    }
}

def flutterVersionCode = localProperties.getProperty("flutter.versionCode")
if (flutterVersionCode == null) {
    flutterVersionCode = "1"
}

def flutterVersionName = localProperties.getProperty("flutter.versionName")
if (flutterVersionName == null) {
    flutterVersionName = "1.0"
}

android {
    namespace = "com.example.trip"
    compileSdk = flutterpileSdkVersion
    ndkVersion = flutter.ndkVersion

    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_1_8
        targetCompatibility = JavaVersion.VERSION_1_8
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android/studio/build/application-id.html).
        applicationId = "com.example.trip"
        // You can update the following values to match your application needs.
        // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
        minSdk = flutter.minSdkVersion
        targetSdk = flutter.targetSdkVersion
        versionCode = flutterVersionCode.toInteger()
        versionName = flutterVersionName
    }

    buildTypes {
        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig = signingConfigs.debug
        }
    }
}

flutter {
    source = "../.."
}

gradle-wrapper.propertiesfile:

distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https\://services.gradle./distributions/gradle-8.2.1-all.zip

• android
• flutter
• gradle
• dart-pub
• url-launcher

• Even though I was using the latest version of url_launcher, the problem persisted – Mingtiao Shiqi Commented yesterday
• provide some code that you have tried. – Ravindra S. Patil Commented yesterday
• Can you share the full stack trace when running flutter run -v to identify the root cause of the D8 NullPointerException? Also, you can check your android/build.gradle and gradle-wrapper.properties files and check the compatibility issue if any. – Kirtan Commented yesterday
• I have updated question with these files. – Mingtiao Shiqi Commented 13 hours ago

1 Answer 1

below could be the fixes you can do to resolve this issue,

1. Specify the stable version of url_launcher,

//Possibly
dependencies:
  url_launcher: ^6.3.1

2. You can explicitly specify AGP version in android/build.gradle.

dependencies {
    classpath 'com.android.tools.build:gradle:8.2.1'
}

3. Modify compileOptions to Java 17, if you're using the new java 23, it's too new for flutter dependency

android {
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_17
        targetCompatibility JavaVersion.VERSION_17
    }
}

4. clear your builds.

flutter clean
rm -rf ~/.gradle/caches
flutter pub get