type mismatch when trying to read List from internal Storage-CodePudding

I am new to Kotlin so please excuse this question, as it is probably pretty stupid...

So I followed the tutorial by Philipp Lackner to create a Todo-List as an android app if any of you know that. Now I tried to add a read and write functionality to this app by saving into a simple .txt-file for now. For that I tried to follow this tutorial as much as possible, but now I am running into Problems when writing code to load the Todo-Items from a file.

I wrote this function to load Todo-Items from the .txt-file:

private suspend fun loadTodoItemsFromInternalStorage(): List<Todo> {
    return withContext(Dispatchers.IO) {
        val todoItemList: MutableList<Todo> = mutableListOf<Todo>()
        var isEven = true
        val files = filesDir.listFiles()
        files?.filter { it.canRead() && it.isFile && it.name.endsWith(".txt") }?.map {
            val lines = it.bufferedReader().readLines()
            for (i in lines.indices) {
                isEven = if(isEven) {
                    todoItemList.add(Todo(lines[i], lines[i 1].toBoolean()))
                    !isEven
                } else {
                    !isEven
                }
            }
            todoItemList
        } ?: mutableListOf<Todo>()
    }
}

Why do I get that type mismatch? I even initialize the list I want to return as a MutableList of type Todo, but I guess the type inference of Kotlin turns it into a MutableList of type Any?

So how do I fix this? And if you want to you could tell me better ways to do what I did (e.g. saving Todo-items (which consist of title and a boolean whether they are checked or not) to a file)

My plan to keep this as simple as possible as this is my first Kotlin project was to just use 2 lines for a Todo-item, where the first line is the title and the second line is the status whether it has been checked or not. I hope that makes my code easier to understand.

Thank you so much for your help in advance! I appreciate it a lot, as I have been struggling with coding in the past and really want to improve my coding skills.

CodePudding user response：

If you cast your return statement, the code should work. Taking your code as a basis:

private suspend fun loadTodoItemsFromInternalStorage(): List<Todo> {
    return withContext(Dispatchers.IO) {
        ...
        } ?: mutableListOf<Todo>()
    } as MutableList<Todo>
}

Some additional suggestions:

when dealing with file handling in general: error handling, check for correct format, empty entries, ...
the check for isEven/isOdd is obsolete and the code can be shortened to great extent when you use the step-option within the for-loop

for (i in lines.indices step 2) {
    todoItemList.add(Todo(lines[i], lines[i 1].toBoolean()))
}