Crash when on click button

Question

The folllowing is the error:java.lang.ClassCastException: com.example.myhouse.MainActivity cannot be cast to com.example.myhouse.TasklistFragment$Callbacks at com.example.myhouse.TasklistFragment.onAttach(TasklistFragment.kt:50)

Where the code for tasklist at line 50 is

  interface Callbacks{
        fun addTaskToViewModel(task: Task, destinationTasklistType: Int)
        fun deleteTaskFromViewModel(tasklistType: Int, adapterPosition: Int)
        fun getTaskListFromViewModel(tasklistType: Int) : LinkedList<Task>
    }

override fun onAttach(context: Context) {
        super.onAttach(context)
        callbacks = context as Callbacks?
    }

Answer 1

Always use safe casting to avoid class cast exception which is causing the crash in this case. Like this

override fun onAttach(context: Context) {
        super.onAttach(context)
        callbacks = context as? Callbacks?
    }

Other than this, the context you are passing is not of type Callbacks which is causing the casting to fail. Maybe provide some more info to solve this issue.