java.lang.NoClassDefFoundError: Failed resolution of: Landroidx/core/app/ActivityManagerCompat

java.lang.NoClassDefFoundError: Failed resolution of: Landroidx/core/app/ActivityManagerCompat

The error “java.lang.NoClassDefFoundError: Failed resolution of: Landroidx/core/app/ActivityManagerCompat” often occurs in Android development when the application cannot find the necessary class “ActivityManagerCompat” from the AndroidX Core library. This class provides helpful utilities for interacting with the Activity Manager.

Common Causes

This error can arise from a variety of issues, the most common being:

1. Missing Dependency

• The AndroidX Core library is not included as a dependency in your project’s build file (usually build.gradle).

2. Incorrect Dependency Version

• You might have a mismatch between the version of the AndroidX Core library included in your project and the version used by another library. This can lead to conflicts.

3. Incompatible Library Versions

• Different libraries in your project might rely on incompatible versions of AndroidX Core, leading to class loading issues.

4. Gradle Build Issues

• Issues with the Gradle build process, like corrupted cache files or incorrect configurations, could prevent the library from being downloaded and included properly.

Troubleshooting Steps

1. Verify the Dependency

Make sure your project’s build file (build.gradle) includes the AndroidX Core library dependency. Here’s an example using Gradle:

dependencies {
    implementation 'androidx.core:core-ktx:1.8.0' // Replace with the appropriate version
}

2. Check Dependency Versions

Use the ‘dependencies’ command in your terminal (while inside the project’s root directory) to view all dependencies. Ensure that all libraries using AndroidX Core are compatible.

./gradlew dependencies

3. Clean and Rebuild Project

Clean and rebuild your project to force Gradle to re-download and resolve dependencies:

./gradlew clean
./gradlew assembleDebug

4. Invalidate Caches/Restart IDE

Sometimes, invalid caches in your IDE can cause issues. Invalidate caches and restart your IDE (Android Studio) to refresh the project.

5. Ensure AndroidX Migration

If you’re using older support libraries (like “support-v4”), make sure you have properly migrated your project to AndroidX. This ensures consistency with modern libraries.

Resolution

The most effective way to resolve the “NoClassDefFoundError” is to follow the troubleshooting steps outlined above, focusing on:

• Adding the missing dependency (if it’s absent)
• Updating or aligning versions of AndroidX Core used across your project
• Cleaning and rebuilding your project to force Gradle to refresh dependencies
• Invalidating caches and restarting your IDE

If none of these steps resolve the issue, provide more context about your project setup and build environment for more tailored guidance.

Example: Using ActivityManagerCompat

import android.content.Context;
import androidx.core.app.ActivityManagerCompat;

public class MyActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Get the available memory in megabytes using ActivityManagerCompat
        ActivityManager activityManager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
        long availableMemory = ActivityManagerCompat.getMemoryClass(activityManager) * 1024 * 1024;
        Log.d("MyActivity", "Available memory: " + availableMemory + " bytes");
    }
}

D/MyActivity: Available memory: 209715200 bytes