Fix Kotlin “No Suitable Constructor Found” in Android

Encountering the “No Suitable Constructor Found” error in Kotlin while building Android applications can be frustrating, especially for beginners. This error typically occurs when the system cannot find a constructor that matches the parameters you’ve provided. Understanding the root cause can save hours of debugging.

Common Causes

1. Missing No-Arg Constructor: If you’re using libraries like Room, Gson, or Firebase, they often rely on reflection and expect a zero-argument constructor.
2. Incorrect Data Class Usage: Kotlin’s data classes generate constructors automatically, but if used improperly in serialization/deserialization (like in Room or Gson), this error can appear.
3. Incompatibility with Java Libraries: Java-based libraries may not recognize Kotlin-specific features like default parameters or secondary constructors.

How to Fix It

• Add an empty constructor: Manually define a constructor without parameters.

constructor() : this("", 0) // Default values

Use @Keep Annotation: Prevent code shrinking from removing constructors during ProGuard or R8 processing.

Enable Kotlin No-Arg Plugin: For frameworks like Room, add the kotlin-noarg plugin to your build.gradle:

plugins {
    id "kotlin-noarg"
}

noArg {
    annotation("androidx.room.Entity")
}

• Double-check @Entity, @SerializedName, or @Inject usage to make sure dependencies are correctly initialized.

📚 Additional Tips

• Always keep your dependencies updated.
• Use reflection-based libraries cautiously, and understand their expectations.

For a deeper dive into Kotlin constructor behaviors and compatibility with serialization libraries, this article from Kotlinlang.org offers excellent insight.