Kotlin, how can I base64Encode the file I get back from the OnActivityResult - file

Question

I need to make the logic to add attachments to a email client.
I have all the needed permissions and I create a intent for files:
val intent = Intent(Intent.ACTION_GET_CONTENT)
intent.type = "*/*"
activity?.startActivityForResult(intent, ActivityResultHandler.PICK_FILE)
I choose a file, and I get result ok in my onActivityResult:
public override fun onActivityResult(reqCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(reqCode, resultCode, data)
ActivityResultHandler().onActivityResult(this, reqCode, resultCode, data)
if (reqCode == REQUEST_CODE_SET_DEFAULT_DIALER) {
activityToFragmentCommunicationCallback?.sendData("refresh")
} else if (reqCode == ActivityResultHandler.PICK_FILE && resultCode == RESULT_OK && data != null) {
val uri = data.data
val cr = this.contentResolver
val mime = cr.getType(uri)
var file = uri.toFile()
if (file.exists()) {
var base64 = convertToBase64(file)
DialogFullScreenEmailComposer.addAttachment()
}
}
}
But then it crashes at this: var file = uri.toFile()
Telling me that:
2019-09-18 16:12:12.300 20608-20608/com.xelion.android.debug E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.xelion.android.debug, PID: 20608
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=3, result=-1, data=Intent { dat=content://com.android.providers.downloads.documents/document/raw:/storage/emulated/0/Download/106.apk flg=0x1 }} to activity {com.xelion.android.debug/com.xelion.android.activity.MainActivity}: java.lang.IllegalArgumentException: Uri lacks 'file' scheme: content://com.android.providers.downloads.documents/document/raw%3A%2Fstorage%2Femulated%2F0%2FDownload%2F106.apk
at android.app.ActivityThread.deliverResults(ActivityThread.java:4398)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4440)
at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:49)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1816)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6718)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.IllegalArgumentException: Uri lacks 'file' scheme: content://com.android.providers.downloads.documents/document/raw%3A%2Fstorage%2Femulated%2F0%2FDownload%2F106.apk
at androidx.core.net.UriKt.toFile(Uri.kt:40)
at com.xelion.android.activity.MainActivity.onActivityResult(MainActivity.kt:312)
at android.app.Activity.dispatchActivityResult(Activity.java:7462)
at android.app.ActivityThread.deliverResults(ActivityThread.java:4391)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4440) 
at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:49) 
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1816) 
at android.os.Handler.dispatchMessage(Handler.java:106) 
at android.os.Looper.loop(Looper.java:193) 
at android.app.ActivityThread.main(ActivityThread.java:6718) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
What can be done so that it can create my file? Or can I skip that and just create the base64Encoded directly?

Answer 1

The error message states that the Uri isn't pointing to a file (it doesn't start with file://). In newer Android versions you don't have direct access to the file you are requesting, but you can read its content through the ContentResolver. You can do that by opening an InputStream with cr.openInputStream(uri). When you have it you can read from that stream and convert the result to Base64.
Here's an example on how to read the entire content of the file into a ByteArray:
private fun readFile(cr: ContentResolver, uri: Uri): ByteArray {
val inStream = cr.openInputStream(uri) ?: return ByteArray(0)
val outStream = ByteArrayOutputStream()
val buffer = ByteArray(32)
while (inStream.read(buffer) > 0) {
outStream.write(buffer)
}
return outStream.toByteArray()
}