Android Jetpack Compose External Storage
Android device provides us with various options to store the data of the application. We can use shared preferences, external storage, and internal storage to store our data. In this article, we will take a look at How to use External storage to store the data within our android application. We will be creating a simple application to save data to the device external storage.
Step by Step Implementation
Step 1: Create a New Project in Android Studio
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. While choosing the template, select Empty Compose Activity. If you do not find this template, try upgrading the Android Studio to the latest version. We demonstrated the application in Kotlin, so make sure you select Kotlin as the primary language while creating a New Project.
Step 2: Adding a new color in the Color.kt file
Navigate to app > java > your appâs package name > ui.theme > Color.kt file and add the below code to it.
Kotlin
package com.example.newcanaryproject.ui.theme import androidx.compose.ui.graphics.Color val Purple200 = Color( 0xFF0F9D58 ) val Purple500 = Color( 0xFF0F9D58 ) val Purple700 = Color( 0xFF3700B3 ) val Teal200 = Color( 0xFF03DAC5 ) // on below line we are adding different colors. val greenColor = Color( 0xFF0F9D58 ) |
Step 3: Adding permissions to read and write data to External Storage
Navigate to app > AndroidManifest.xml file and add the below permissions to it to read and write data.
XML
< uses-permission android:name = "android.permission.WRITE_EXTERNAL_STORAGE" /> < uses-permission android:name = "android.permission.READ_EXTERNAL_STORAGE" /> |
Step 4: Working with the MainActivity.kt file
Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.
Kotlin
package com.example.newcanaryproject import android.Manifest import android.app.Activity import android.content.* import android.os.Bundle import android.os.Environment import android.widget.Toast import androidx.activity.ComponentActivity import androidx.activity.compose.setContent import androidx.compose.foundation.layout.* import androidx.compose.material.* import androidx.compose.runtime.Composable import androidx.compose.runtime.mutableStateOf import androidx.compose.runtime.remember import androidx.compose.ui.Alignment import androidx.compose.ui.Modifier import androidx.compose.ui.graphics.Color import androidx.compose.ui.platform.LocalContext import androidx.compose.ui.text.TextStyle import androidx.compose.ui.text.font.FontWeight import androidx.compose.ui.text.style.TextAlign import androidx.compose.ui.unit.dp import androidx.compose.ui.unit.sp import androidx.core.app.ActivityCompat import com.example.newcanaryproject.ui.theme.NewCanaryProjectTheme import com.example.newcanaryproject.ui.theme.greenColor import java.io.File import java.io.FileInputStream import java.io.FileOutputStream import java.io.IOException class MainActivity : ComponentActivity() { var message = "" override fun onCreate(savedInstanceState: Bundle?) { super .onCreate(savedInstanceState) setContent { NewCanaryProjectTheme { // on below line we are specifying // background color for our application Surface( // on below line we are specifying modifier and color for our app modifier = Modifier.fillMaxSize(), color = MaterialTheme.colors.background ) { // on the below line we are specifying // the theme as the scaffold. Scaffold( // in scaffold we are specifying the top bar. topBar = { // inside top bar we are specifying // background color. TopAppBar(backgroundColor = greenColor, // along with that we are // specifying title for our top bar. title = { // in the top bar we are specifying tile as a text Text( // on below line we are specifying // text to display in top app bar. text = "GFG" , // on below line we are specifying // modifier to fill max width. modifier = Modifier.fillMaxWidth(), // on below line we are specifying // text alignment. textAlign = TextAlign.Center, // on below line we are specifying // color for our text. color = Color.White ) }) }) { // on below line we are calling method to display UI saveDataToExternalStorage(context = LocalContext.current, message) } } } } } } @Composable fun saveDataToExternalStorage(context: Context, msg: String) { // on below line creating a variable for message. val message = remember { mutableStateOf( "" ) } val txtMsg = remember { mutableStateOf( "" ) } val activity = context as Activity // on below line we are creating a column, Column( // on below line we are adding a modifier to it, modifier = Modifier .fillMaxSize() // on below line we are adding a padding. .padding(all = 30 .dp), horizontalAlignment = Alignment.CenterHorizontally, verticalArrangement = Arrangement.Center, ) { // on below line we are adding a text for heading. Text( // on below line we are specifying text text = "External Storage in Android" , // on below line we are specifying text color, // font size and font weight color = greenColor, textAlign = TextAlign.Center, fontSize = 20 .sp, fontWeight = FontWeight.Bold ) // on below line adding a spacer. Spacer(modifier = Modifier.height( 10 .dp)) // on below line we are creating a text field for our message number. TextField( // on below line we are specifying value for our message text field. value = message.value, // on below line we are adding on value change for text field. onValueChange = { message.value = it }, // on below line we are adding place holder as text as "Enter your email" placeholder = { Text(text = "Enter your message" ) }, // on below line we are adding modifier to it // and adding padding to it and filling max width modifier = Modifier .padding( 16 .dp) .fillMaxWidth(), // on below line we are adding text style // specifying color and font size to it. textStyle = TextStyle(color = Color.Black, fontSize = 15 .sp), // on below line we are adding single line to it. singleLine = true , ) // on below line adding a spacer. Spacer(modifier = Modifier.height( 10 .dp)) Row( modifier = Modifier .fillMaxWidth() .padding(all = 10 .dp), horizontalArrangement = Arrangement.Center ) { // on below line adding a button. Button( onClick = { // Requesting Permission to access External Storage // Requesting Permission to access External Storage ActivityCompat.requestPermissions( activity, arrayOf(Manifest.permission.READ_EXTERNAL_STORAGE), 23 ) // getExternalStoragePublicDirectory() represents root of external storage, we are using DOWNLOADS // We can use following directories: MUSIC, PODCASTS, ALARMS, RINGTONES, NOTIFICATIONS, PICTURES, MOVIES val folder: File = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) // Storing the data in file with name as BeginnerData.txt val file = File(folder, "BeginnerData.txt" ) writeTextData(file, message.value, context) message.value = "" // displaying a toast message Toast.makeText(context, "Data saved publicly.." , Toast.LENGTH_SHORT).show() }, // on below line adding a modifier for our button. modifier = Modifier .padding( 5 .dp) .width( 120 .dp) ) { // on below line adding a text for our button. Text(text = "Save Publicly" , textAlign = TextAlign.Center) } // on below line adding a spacer Spacer(modifier = Modifier.width( 10 .dp)) // on below line creating a button Button( onClick = { // Creating folder with name GeekForBeginner val folder: File? = context.getExternalFilesDir( "w3wiki" ) // Creating file with name gfg.txt // Creating file with name gfg.txt val file = File(folder, "gfg.txt" ) writeTextData(file, message.value, context) message.value = "" // displaying a toast message Toast.makeText(context, "Data saved privately" , Toast.LENGTH_SHORT).show() }, // on below line adding a modifier for our button. modifier = Modifier .padding( 5 .dp) .width( 120 .dp) ) { // on below line adding a text for our button. Text(text = "Save Privately" , textAlign = TextAlign.Center) } } // adding spacer on below line. Spacer(modifier = Modifier.height( 100 .dp)) // on below line adding a text view to display our data. Text( // on below line we are specifying text text = "Data will appear below : \n" + txtMsg.value, // on below line we are specifying text color, // font size and font weight color = greenColor, textAlign = TextAlign.Center, fontSize = 20 .sp, fontWeight = FontWeight.Bold ) // on below line adding a Spacer. Spacer(modifier = Modifier.height( 10 .dp)) Row( modifier = Modifier .fillMaxWidth() .fillMaxSize() .padding(all = 20 .dp), horizontalArrangement = Arrangement.Center ) { // on below line adding a button. Button( onClick = { // Accessing the saved data from the downloads folder val folder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) // BeginnerData represent the file data that is saved publicly val file = File(folder, "BeginnerData.txt" ) val data: String = getdata(file) if (data != null && data != "" ) { txtMsg.value = data } else { txtMsg.value = "No Data Found" } }, // on below line adding a modifier for our button. modifier = Modifier .padding( 5 .dp) .width( 120 .dp) ) { // on below line adding a text for our button. Text(text = "View\nPublic" , textAlign = TextAlign.Center) } // on below line adding a spacer Spacer(modifier = Modifier.width( 10 .dp)) // on below line creating a button Button( onClick = { // w3wiki represent the folder name to access privately saved data val folder: File? = context.getExternalFilesDir( "w3wiki" ) // gft.txt is the file that is saved privately val file = File(folder, "gfg.txt" ) val data = getdata(file) if (data != null ) { txtMsg.value = data } else { txtMsg.value = "No Data Found" } }, // on below line adding a modifier for our button. modifier = Modifier .padding( 5 .dp) .width( 120 .dp) ) { // on below line adding a text for our button. Text(text = "View\nPrivate" , textAlign = TextAlign.Center) } } } } // on below line creating get data method to get data from file. private fun getdata(myfile: File): String { // on below line creating a variable for file input stream. var fileInputStream: FileInputStream? = null // on below line reading data from file and returning it. try { fileInputStream = FileInputStream(myfile) var i = - 1 val buffer = StringBuffer() while (fileInputStream.read().also { i = it } != - 1 ) { buffer.append(i.toChar()) } return buffer.toString() } catch (e: java.lang.Exception) { e.printStackTrace() } finally { if (fileInputStream != null ) { try { fileInputStream.close() } catch (e: IOException) { e.printStackTrace() } } } return "" } // on below line creating a method to write data to txt file. private fun writeTextData(file: File, data: String, context: Context) { var fileOutputStream: FileOutputStream? = null try { fileOutputStream = FileOutputStream(file) fileOutputStream.write(data.toByteArray()) } catch (e: Exception) { e.printStackTrace() } finally { if (fileOutputStream != null ) { try { fileOutputStream.close() } catch (e: IOException) { e.printStackTrace() } } } } |
Now run your application to see the output of it.
Output:
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