Namespace not specified. Specify a namespace in the module's build file Flutter Android Studio

Read what the error tells you.

In newer versions of AGP, the declaration of namespace/package was moved from AndroidManifest and to build script.

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    <!-- package="com.example.app" POOF! -->
>

and

android {
    namespace = "com.example.app"

This worked for me. Include this in your project level build.gradle file:

subprojects {
    afterEvaluate { project ->
        if (project.hasProperty('android')) {
            project.android {
                if (namespace == null) {
                    namespace = project.group.toString()  // Set namespace as fallback
                }
                project.tasks.whenTaskAdded { task ->
                    if (task.name.contains('processDebugManifest') || task.name.contains('processReleaseManifest')) {
                        task.doFirst {
                            File manifestFile = file("${projectDir}/src/main/AndroidManifest.xml")
                            if (manifestFile.exists()) {
                                String manifestContent = manifestFile.text
                                if (manifestContent.contains('package=')) {
                                    manifestContent = manifestContent.replaceAll(/package="[^"]*"/, "")
                                    manifestFile.write(manifestContent)
                                    println "Removed 'package' attribute from ${manifestFile}"
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

Source on medium

compileOptions
{
    sourceCompatibility JavaVersion.VERSION_17
    targetCompatibility JavaVersion.VERSION_17
}

kotlinOptions
{
    jvmTarget = '17'
}

Upgrade the Java version to 17 in the app-level build.gradle file. This adjustment should resolve the issue in my scenario.[1]: https://i.sstatic.net/8zRn6.png

I encountered the same error you described while using the flutter_login_facebook package version 2.0.1. The error you're seeing is likely related to namespace conflicts.

To resolve this, I added the following namespace declaration:

android {
    namespace "ru.innim.flutter_login_facebook"
}

This was added to the build.gradle file of the flutter_login_facebook module. In my case, the file was located at:

/Users/mac/.pub-cache/hosted/pub.dev/flutter_login_facebook-2.0.1/android/build.gradle

After modifying the build.gradle file, I performed the following steps:

1. Remove or comment out the package name from pubspec.yaml: This is to ensure a clean slate.

2. Run flutter clean: This clears the build artifacts.

3. Add the package name back to pubspec.yaml and Run flutter pub get: This re-installs the package with the namespace fix.

4. Run the Flutter project again: This rebuilds the app with the changes.

This process resolved the error for me without requiring an upgrade of the flutter_login_facebook package (as there was no update) or reverting to an older Flutter version.

I hope this solution is helpful.

Just add the namespace in build.gradle file
app/build.gralde

android {
    namespace "com.android.example"
}

Note: Namespace get from main/kotlin/MainActivity Check package com.android.example