File access and storage in Android Kotlin - Mini App: Build & Ship

Build: Simple File Storage

This screen lets the user write text to a file and read it back to display on screen.

Target UI

-------------------------
| Simple File Storage    |
|-----------------------|
| Enter text:           |
| [___________________] |
|                       |
| [Save]   [Load]       |
|                       |
| File content:         |
| ____________________  |
|                       |
-------------------------

A TextField for user to enter text

A Save button that writes the text to a file in internal storage

A Load button that reads the text from the file and shows it below

Show the loaded file content in a TextView

Handle exceptions gracefully with Toast messages

Starter Code

Android Kotlin

package com.example.filestorage

import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.io.File

class MainActivity : AppCompatActivity() {
    private lateinit var inputEditText: EditText
    private lateinit var saveButton: Button
    private lateinit var loadButton: Button
    private lateinit var contentTextView: TextView

    private val filename = "myfile.txt"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        inputEditText = findViewById(R.id.inputEditText)
        saveButton = findViewById(R.id.saveButton)
        loadButton = findViewById(R.id.loadButton)
        contentTextView = findViewById(R.id.contentTextView)

        // TODO: Add click listeners for saveButton and loadButton
    }
}

Task 1

Task 2

Task 3

Solution

Android Kotlin

package com.example.filestorage

import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.io.File
import java.io.IOException

class MainActivity : AppCompatActivity() {
    private lateinit var inputEditText: EditText
    private lateinit var saveButton: Button
    private lateinit var loadButton: Button
    private lateinit var contentTextView: TextView

    private val filename = "myfile.txt"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        inputEditText = findViewById(R.id.inputEditText)
        saveButton = findViewById(R.id.saveButton)
        loadButton = findViewById(R.id.loadButton)
        contentTextView = findViewById(R.id.contentTextView)

        saveButton.setOnClickListener {
            val textToSave = inputEditText.text.toString()
            try {
                openFileOutput(filename, MODE_PRIVATE).use { output ->
                    output.write(textToSave.toByteArray())
                }
                Toast.makeText(this, "File saved", Toast.LENGTH_SHORT).show()
                inputEditText.text.clear()
            } catch (e: IOException) {
                Toast.makeText(this, "Error saving file", Toast.LENGTH_SHORT).show()
            }
        }

        loadButton.setOnClickListener {
            try {
                val file = File(filesDir, filename)
                if (file.exists()) {
                    val content = file.readText()
                    contentTextView.text = content
                    Toast.makeText(this, "File loaded", Toast.LENGTH_SHORT).show()
                } else {
                    Toast.makeText(this, "File not found", Toast.LENGTH_SHORT).show()
                    contentTextView.text = ""
                }
            } catch (e: IOException) {
                Toast.makeText(this, "Error loading file", Toast.LENGTH_SHORT).show()
            }
        }
    }
}

This app uses Android internal storage to save and load a simple text file named myfile.txt.

When the user taps Save, the app writes the text from the input field to the file using openFileOutput with MODE_PRIVATE, which means only this app can access the file.

When the user taps Load, the app checks if the file exists in the internal files directory, reads its content as text, and shows it in the TextView below.

Toast messages inform the user about success or errors during file operations.

This approach keeps file access simple and secure inside the app's private storage.

Final Result

Completed Screen

-------------------------
| Simple File Storage    |
|-----------------------|
| Enter text:           |
| [Hello world       ]  |
|                       |
| [Save]   [Load]       |
|                       |
| File content:         |
| Hello world           |
|                       |
-------------------------

User types text in the input field.

User taps Save: text is saved to internal file, input clears, Toast shows 'File saved'.

User taps Load: file content is read and displayed below, Toast shows 'File loaded'.

If file missing or error, Toast shows appropriate message.

Stretch Goal

Add a Clear button that deletes the saved file and clears the displayed content.

💡 Hint

Use File.delete() on the internal file and clear the TextView text.