rysasahrialEncountering 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
- 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.
- 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.
- 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
constructor() : this("", 0) // Default values
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")
}
plugins {
id "kotlin-noarg"
}
noArg {
annotation("androidx.room.Entity")
}
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.
