refactor: use a ViewModel to pass around decryption passphrase

app/src/main/java/app/passwordstore/ui/autofill/AutofillDecryptActivity.kt

@@ -11,6 +11,7 @@ import android.content.IntentSender
 import android.os.Build
 import android.os.Bundle
 import android.view.autofill.AutofillManager
+import androidx.activity.viewModels
 import androidx.annotation.RequiresApi
 import androidx.appcompat.app.AppCompatActivity
 import androidx.lifecycle.lifecycleScope
@@ -21,6 +22,7 @@ import app.passwordstore.util.autofill.AutofillPreferences
 import app.passwordstore.util.autofill.AutofillResponseBuilder
 import app.passwordstore.util.autofill.DirectoryStructure
 import app.passwordstore.util.extensions.asLog
+import app.passwordstore.util.viewmodel.PasswordViewModel
 import com.github.androidpasswordstore.autofillparser.AutofillAction
 import com.github.androidpasswordstore.autofillparser.Credentials
 import com.github.michaelbull.result.getOrElse
@@ -77,6 +79,7 @@ class AutofillDecryptActivity : AppCompatActivity() {
     }
   }
 
+  private val viewModel: PasswordViewModel by viewModels()
   @Inject lateinit var passwordEntryFactory: PasswordEntry.Factory
   @Inject lateinit var repository: CryptoRepository
 
@@ -105,10 +108,8 @@ class AutofillDecryptActivity : AppCompatActivity() {
     val dialog = PasswordDialog()
     lifecycleScope.launch {
       withContext(Dispatchers.Main) {
-        dialog.password.collectLatest { value ->
-          if (value != null) {
-            decrypt(File(filePath), clientState, action, value)
-          }
+        viewModel.password.collectLatest { value ->
+          decrypt(File(filePath), clientState, action, value)
         }
       }
     }

app/src/main/java/app/passwordstore/ui/crypto/DecryptActivity.kt

@@ -9,6 +9,7 @@ import android.content.Intent
 import android.os.Bundle
 import android.view.Menu
 import android.view.MenuItem
+import androidx.activity.viewModels
 import androidx.lifecycle.lifecycleScope
 import app.passwordstore.R
 import app.passwordstore.data.crypto.CryptoRepository
@@ -22,6 +23,7 @@ import app.passwordstore.util.extensions.unsafeLazy
 import app.passwordstore.util.extensions.viewBinding
 import app.passwordstore.util.settings.Constants
 import app.passwordstore.util.settings.PreferenceKeys
+import app.passwordstore.util.viewmodel.PasswordViewModel
 import com.github.michaelbull.result.Err
 import com.github.michaelbull.result.Ok
 import com.github.michaelbull.result.runCatching
@@ -45,6 +47,7 @@ import logcat.logcat
 @AndroidEntryPoint
 class DecryptActivity : BasePgpActivity() {
 
+  private val viewModel: PasswordViewModel by viewModels()
   private val binding by viewBinding(DecryptLayoutBinding::inflate)
   private val relativeParentPath by unsafeLazy { getParentPath(fullPath, repoPath) }
   @Inject lateinit var passwordEntryFactory: PasswordEntry.Factory
@@ -67,7 +70,7 @@ class DecryptActivity : BasePgpActivity() {
         true
       }
     }
-    askPassphrase(isError = false)
+    askPassphrase()
   }
 
   override fun onCreateOptionsMenu(menu: Menu): Boolean {
@@ -138,34 +141,36 @@ class DecryptActivity : BasePgpActivity() {
     )
   }
 
-  private fun askPassphrase(isError: Boolean) {
+  private fun askPassphrase() {
     if (retries < MAX_RETRIES) {
       retries += 1
     } else {
       finish()
     }
-    val dialog = PasswordDialog()
-    if (isError) {
-      dialog.setError()
-    }
+    showPasswordDialog(isError = false)
     lifecycleScope.launch(dispatcherProvider.main()) {
-      dialog.password.collectLatest { value ->
-        if (value != null) {
-          when (val result = decryptWithPassphrase(value)) {
-            is Ok -> {
-              val entry = passwordEntryFactory.create(result.value.toByteArray())
-              passwordEntry = entry
-              createPasswordUI(entry)
-              startAutoDismissTimer()
-            }
-            is Err -> {
-              logcat(ERROR) { result.error.stackTraceToString() }
-              askPassphrase(isError = true)
-            }
+      viewModel.password.collectLatest { value ->
+        when (val result = decryptWithPassphrase(value)) {
+          is Ok -> {
+            val entry = passwordEntryFactory.create(result.value.toByteArray())
+            passwordEntry = entry
+            createPasswordUI(entry)
+            startAutoDismissTimer()
+          }
+          is Err -> {
+            logcat(ERROR) { result.error.stackTraceToString() }
+            showPasswordDialog(isError = true)
           }
         }
       }
     }
+  }
+
+  private fun showPasswordDialog(isError: Boolean) {
+    val dialog = PasswordDialog()
+    if (isError) {
+      dialog.setError()
+    }
     dialog.show(supportFragmentManager, "PASSWORD_DIALOG")
   }
 

app/src/main/java/app/passwordstore/ui/crypto/PasswordDialog.kt

@@ -12,22 +12,20 @@ import android.view.KeyEvent
 import android.view.WindowManager
 import androidx.core.widget.doOnTextChanged
 import androidx.fragment.app.DialogFragment
+import androidx.fragment.app.activityViewModels
 import app.passwordstore.R
 import app.passwordstore.databinding.DialogPasswordEntryBinding
 import app.passwordstore.util.extensions.finish
 import app.passwordstore.util.extensions.unsafeLazy
+import app.passwordstore.util.viewmodel.PasswordViewModel
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
-import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.asStateFlow
-import kotlinx.coroutines.flow.update
 
 /** [DialogFragment] to request a password from the user and forward it along. */
 class PasswordDialog : DialogFragment() {
 
+  private val viewModel: PasswordViewModel by activityViewModels()
   private val binding by unsafeLazy { DialogPasswordEntryBinding.inflate(layoutInflater) }
   private var isError: Boolean = false
-  private val _password = MutableStateFlow<String?>(null)
-  val password = _password.asStateFlow()
 
   override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
     val builder = MaterialAlertDialogBuilder(requireContext())
@@ -66,7 +64,7 @@ class PasswordDialog : DialogFragment() {
   }
 
   private fun setPasswordAndDismiss() {
-    _password.update { binding.passwordEditText.text.toString() }
+    viewModel.setPassword(binding.passwordEditText.text.toString())
     dismissAllowingStateLoss()
   }
 }

app/src/main/java/app/passwordstore/util/viewmodel/PasswordViewModel.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright © 2014-2022 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package app.passwordstore.util.viewmodel
+
+import androidx.lifecycle.ViewModel
+import app.passwordstore.ui.crypto.PasswordDialog
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.dropWhile
+import kotlinx.coroutines.flow.update
+
+/**
+ * ViewModel for classes that use [PasswordDialog] for getting user input. [PasswordDialog] will
+ * ensure that it retrieves an instance of this [ViewModel] from the Activity scope and will post
+ * values into [PasswordViewModel.password].
+ */
+class PasswordViewModel : ViewModel() {
+  private val _password = MutableStateFlow("")
+  val password = _password.asStateFlow().dropWhile(String::isBlank)
+
+  fun setPassword(pass: String) {
+    _password.update { pass }
+  }
+}