File access and storage in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

Reading a file from internal storage

What will be the output shown in the TextView after running this code snippet that reads a file named "data.txt" from internal storage?

Android Kotlin

val fileInput = openFileInput("data.txt")
val content = fileInput.bufferedReader().use { it.readText() }
textView.text = content

A The exact text content stored inside "data.txt" is displayed in the TextView

B The TextView remains empty because openFileInput returns null

C The TextView shows the file path of "data.txt"

D The app crashes with FileNotFoundException if "data.txt" does not exist

💡 Hint

openFileInput reads the file content as a stream, which you convert to text.

openFileInput opens the file for reading. Using bufferedReader and readText() reads the entire file content as a string, which is then set to the TextView.

❓ lifecycle

intermediate

File writing in Activity lifecycle

If you write data to a file in the onPause() method of an Activity, what happens if the app is killed before onPause() is called?

A The data is saved in onCreate() instead

B The data will not be saved because onPause() was never called

C The data is saved only if onStop() is called

D The data is saved automatically by the system

💡 Hint

onPause() is called before the Activity goes to background, but not if the app is killed abruptly.

If the app is killed abruptly (e.g., by the system or user), onPause() may not be called, so any file writing code there will not run and data won't be saved.

📝 Syntax

advanced

Correct syntax for writing text to a file

Which Kotlin code snippet correctly writes the string "Hello World" to a file named "output.txt" in internal storage?

A File("output.txt").writeBytes("Hello World")

B openFileOutput("output.txt", Context.MODE_PRIVATE).writeText("Hello World")

C openFileOutput("output.txt", Context.MODE_PRIVATE).use { it.write("Hello World".toByteArray()) }

D openFileOutput("output.txt").write("Hello World")

💡 Hint

openFileOutput returns a FileOutputStream which you can write bytes to.

Option C correctly uses openFileOutput with mode and writes bytes using use block. Option C is invalid because FileOutputStream has no writeText method. Option C tries to write to a file without path and wrong method. Option C misses mode parameter and write method is invalid.

🔧 Debug

advanced

Diagnosing a FileNotFoundException

An app crashes with FileNotFoundException when trying to read "config.txt" using openFileInput("config.txt"). What is the most likely cause?

A "config.txt" does not exist in the app's internal storage

B The app lacks permission to read external storage

C The file path is incorrect because openFileInput requires absolute path

D The file is open in write mode elsewhere causing a lock

💡 Hint

openFileInput only reads files previously saved in internal storage by the app.

FileNotFoundException occurs if the file does not exist in internal storage. openFileInput does not require absolute paths and does not access external storage, so permissions or path are not the issue here.

🧠 Conceptual

expert

Choosing storage for sensitive data

Which storage option is best for saving sensitive user data like passwords in an Android app?

A External storage public directory

B SharedPreferences without encryption

C Cache directory accessible by other apps

D Internal storage files with MODE_PRIVATE access

💡 Hint

Sensitive data should be stored where only your app can access it.

Internal storage files with MODE_PRIVATE are only accessible by your app, making them suitable for sensitive data. External storage and cache directories can be accessed by other apps. SharedPreferences without encryption is not secure for sensitive data.