Android 7 steps to request/share a file to another app

Step 1: Request a file from appB

requestFileIntent = Intent(Intent.ACTION_PICK).apply {
    type = "image/png"
}startActivityForResult(requestFileIntent, 0)

Step 2: Get result

returnIntent?.data?.also { returnUri ->
    my_photo.setImageURI(returnUri)
    val mimeType: String? = returnIntent.data?.let { returnUri ->
        contentResolver.getType(returnUri)
    }
}

Copy file

private lateinit var inputPFD: ParcelFileDescriptor
inputPFD = try {
    contentResolver.openFileDescriptor(returnUri, "r") ?: kotlin.run { return }
} catch (e: FileNotFoundException) {
    e.printStackTrace()
    Log.e("MainActivity", "File not found.")
    return
}


FileInputStream(inputPFD.fileDescriptor).use { _in ->
    FileOutputStream(File(filesDir,"youFile.png")).use { _out ->
        try {
            val buff = ByteArray(1024)
            var read = 0

            while (_in.read(buff).also { read = it } > 0) {
                _out.write(buff, 0, read)
            }
        } catch (e: Exception) {
            e.printStackTrace()
        }
    }
}

Sharing a file from appA

The only secure way: send file’s content URI and grant temporary access permissions to that URI.

Step 1: Specify the FileProvider in appA

• add res/xml/filepaths.xml
• add provider in manifest.xml

<paths> element can have multiple children, each specifying a different directory to share. <files-path> shares directories within the files/ directory of your app's internal storage. <external-path> element to share directories in external storage, and the <cache-path>element to share directories in your internal cache directory.

Step 2: Add intent-filter in your provider activity

<action android:name="android.intent.action.PICK"/>
<category android:name="android.intent.category.DEFAULT"/>
<category android:name="android.intent.category.OPENABLE"/>
<data android:mimeType="text/plain"/>
<data android:mimeType="image/*"/>

Step 3: Make content URI

FileProvider.getUriForFile(
        this@MainActivity,
        "nj.f.njsharefile.fileprovider",
        imagePath)

Step 4: Grant permission and return the result

resultIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
resultIntent.setDataAndType(fileUri, contentResolver.getType(fileUri))
setResult(Activity.RESULT_OK, resultIntent)