Squashed commit of the following:

commit ff0a46aefcc6a918ec349608f21613c71605eefe
Author: Jonas L <jonas@determapp.de>
Date:   Mon Apr 8 00:00:00 2019 +0000

    Skip asking for password if only one parent and password is empty

commit c2ca7bd177806f99a3db49528a35de3b8a06782e
Author: Jonas L <jonas@determapp.de>
Date:   Mon Apr 8 00:00:00 2019 +0000

    Allow setting password to empty

commit 218f0fc94047593ff9cb083ce1eefa48e69c8e6d
Author: Jonas L <jonas@determapp.de>
Date:   Mon Apr 8 00:00:00 2019 +0000

    Extend set password view

app/src/main/java/io/timelimit/android/ui/login/LoginPasswordDialogFragmentModel.kt

@@ -23,6 +23,7 @@ import io.timelimit.android.coroutines.executeAndWait
 import io.timelimit.android.coroutines.runAsync
 import io.timelimit.android.crypto.PasswordHashing
 import io.timelimit.android.livedata.castDown
+import io.timelimit.android.livedata.waitForNonNullValue
 import io.timelimit.android.livedata.waitForNullableValue
 import io.timelimit.android.logic.AppLogic
 import io.timelimit.android.logic.DefaultAppLogic
@@ -40,6 +41,25 @@ class LoginPasswordDialogFragmentModel(application: Application): AndroidViewMod
 
     val status = statusInternal.castDown()
 
+    fun tryDefaultLogin(model: ActivityViewModel) {
+        runAsync {
+            loginLock.withLock {
+                logic.database.user().getParentUsersLive().waitForNonNullValue().singleOrNull()?.let { user ->
+                    val emptyPasswordValid = Threads.crypto.executeAndWait { PasswordHashing.validateSync("", user.password) }
+
+                    if (emptyPasswordValid) {
+                        model.setAuthenticatedUser(AuthenticatedUser(
+                                userId = user.id,
+                                passwordHash = user.password
+                        ))
+
+                        statusInternal.value = LoginPasswordDialogFragmentStatus.Success
+                    }
+                }
+            }
+        }
+    }
+
     fun tryLogin(userId: String, password: String, model: ActivityViewModel) {
         runAsync {
             loginLock.withLock {

app/src/main/java/io/timelimit/android/ui/login/NewLoginFragment.kt

@@ -56,6 +56,10 @@ class NewLoginFragment: DialogFragment() {
         if (savedInstanceState?.containsKey(SELECTED_USER_ID) == true) {
             selectedUserId.value = savedInstanceState.getString(SELECTED_USER_ID)
         }
+
+        if (savedInstanceState == null) {
+            model.tryDefaultLogin(getActivityViewModel(activity!!))
+        }
     }
 
     override fun onCreateDialog(savedInstanceState: Bundle?) = object: BottomSheetDialog(context!!, theme) {

app/src/main/java/io/timelimit/android/ui/manage/parent/password/change/ChangeParentPasswordFragment.kt

@@ -67,7 +67,7 @@ class ChangeParentPasswordFragment : Fragment(), FragmentWithCustomTitle {
             model.changePassword(
                     parentUserId = params.parentUserId,
                     oldPassword = binding.oldPassword.text.toString(),
-                    newPassword = binding.newPassword.password.value!!
+                    newPassword = binding.newPassword.readPassword()
             )
         }
 
@@ -109,6 +109,8 @@ class ChangeParentPasswordFragment : Fragment(), FragmentWithCustomTitle {
             }.let {  }
         })
 
+        binding.newPassword.allowNoPassword.value = true
+
         return binding.root
     }
 

app/src/main/java/io/timelimit/android/ui/setup/SetupLocalModeFragment.kt

@@ -61,10 +61,12 @@ class SetupLocalModeFragment : Fragment() {
 
         binding.nextBtn.setOnClickListener {
             model.trySetupWithPassword(
-                    set_password_view.password.value!!
+                    binding.setPasswordView.readPassword()
             )
         }
 
+        binding.setPasswordView.allowNoPassword.value = true
+
         return binding.root
     }
 }

app/src/main/java/io/timelimit/android/ui/user/create/AddUserFragment.kt

@@ -75,6 +75,8 @@ class AddUserFragment : Fragment() {
 
         val isPasswordOk = binding.password.passwordOk.or(isPasswordRequired.invert())
 
+        binding.password.allowNoPassword.value = true
+
         // username
 
         val username = binding.name.getTextLive()
@@ -94,7 +96,7 @@ class AddUserFragment : Fragment() {
                         name = binding.name.text.toString(),
                         type = userType.value!!,
                         password = when (userType.value!!) {
-                            UserType.Parent -> binding.password.password.value!!
+                            UserType.Parent -> binding.password.readPassword()
                             UserType.Child -> ""
                         },
                         model = auth

app/src/main/java/io/timelimit/android/ui/view/SetPasswordView.kt

@@ -25,6 +25,8 @@ import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.Transformations
 import io.timelimit.android.databinding.ViewSetPasswordBinding
+import io.timelimit.android.livedata.and
+import io.timelimit.android.livedata.or
 import io.timelimit.android.util.PasswordValidator
 
 class SetPasswordView(context: Context, attributeSet: AttributeSet): FrameLayout(context, attributeSet) {
@@ -36,6 +38,14 @@ class SetPasswordView(context: Context, attributeSet: AttributeSet): FrameLayout
 
     val password = MutableLiveData<String>()
     val passwordRepeat = MutableLiveData<String>()
+    val allowNoPassword = MutableLiveData<Boolean>().apply { value = false }
+    val noPasswordChecked = MutableLiveData<Boolean>().apply { value = false }
+    val useEmptyPassword = allowNoPassword.and(noPasswordChecked)
+
+    fun readPassword() = if (useEmptyPassword.value!! == true)
+        ""
+    else
+        password.value!!
 
     init {
         password.value = ""
@@ -71,6 +81,20 @@ class SetPasswordView(context: Context, attributeSet: AttributeSet): FrameLayout
 
         password.observeForever { binding.password = it!! }
         passwordRepeat.observeForever() { binding.passwordRepeat = it!! }
+        allowNoPassword.observeForever { binding.allowNoPassword = it }
+        noPasswordChecked.observeForever {
+            binding.noPasswordChecked = it
+
+            if (binding.noPasswordCheckbox.isChecked != it) {
+                binding.noPasswordCheckbox.isChecked = it
+            }
+        }
+
+        binding.noPasswordCheckbox.setOnCheckedChangeListener { _, isChecked ->
+            if (isChecked != noPasswordChecked.value) {
+                noPasswordChecked.value = isChecked
+            }
+        }
     }
 
     private val passwordQualityProblem: LiveData<String?> = Transformations.map(password) {
@@ -87,7 +111,7 @@ class SetPasswordView(context: Context, attributeSet: AttributeSet): FrameLayout
             (passwordValue.isNotEmpty() && it.isNotEmpty()) && passwordValue != it
         }
     }
-    val passwordOk: LiveData<Boolean> = Transformations.switchMap(password) {
+    val passwordOk: LiveData<Boolean> = useEmptyPassword.or(Transformations.switchMap(password) {
         val password1 = it
 
         Transformations.map(passwordRepeat) {
@@ -96,7 +120,7 @@ class SetPasswordView(context: Context, attributeSet: AttributeSet): FrameLayout
             password1.isNotEmpty() && password2.isNotEmpty() && (password1 == password2) &&
                     (PasswordValidator.validate(password1, context) == null)
         }
-    }
+    })
 
     init {
         passwordQualityProblem .observeForever { binding.passwordProblem = it }