Chapter 11 Update Genders
In the last chapter we covered the Create-part of our CRUD app for genders. In this chapter we now want to enable the user to update existing genders (for example to correct a typo). Let’s start with a view model for our update page:
11.1 UpdateGenderViewModel.kt
package app.gedama.tutorial.cruddiary.viewmodel
import android.database.sqlite.SQLiteConstraintException
import androidx.lifecycle.ViewModel
import androidx.lifecycle.ViewModelProvider
import androidx.lifecycle.viewModelScope
import app.gedama.tutorial.cruddiary.dao.GenderDao
import kotlinx.coroutines.launch
class UpdateGenderViewModel(genderId: Long, val genderDao: GenderDao) : BaseViewModel() {
var gender = genderDao.get(genderId)
fun updateGender() {
_doValidation.value = true
}
override fun updateEntryAfterValidation() {
viewModelScope.launch {
if ( deactivateSuccess.value!! || gender.value!!.inactive ) {
gender.value!!.inactive = true
} else {
gender.value!!.inactive = false
}
try {
genderDao.update(gender.value!!)
_navigateToList.value = true
} catch(sqlExc: SQLiteConstraintException) {
_deactivateSuccess.value = false
_insertSuccess.value = false
}
}
}
fun deactivateGender() {
_deactivateSuccess.value = true
_doValidation.value = true
}
}
class UpdateGenderViewModelFactory(private val genderId: Long, private val genderDao: GenderDao) : ViewModelProvider.Factory {
override fun <T : ViewModel> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(UpdateGenderViewModel::class.java)) {
return UpdateGenderViewModel(genderId, genderDao) as T
}
throw java.lang.IllegalArgumentException("Unknown ViewModel")
}
}
As with our view models from the previous chapters, we have a separate Factory-class which is passed a GenderDao object at initialization. However, in this case we additionally pass the ID of the gender item that gets updated. The variable gender gets our existing gender object from the database. As with our view model for adding new gender items, we have to validate the user input and check for database constraint violations.
11.2 string.xml (English)
For our user interface, we have to add a couple of string values to our string.xml files:
<resources>
<string name="app_name">CrudDiary</string>
<string name="nothing_selected" translatable="false">---</string>
<string name="male_gender">male</string>
<string name="female_gender">female</string>
<string name="diverse_gender">diverse</string>
<string name="main_menu_title">Home</string>
<string name="persons_list_menu_title">Persons</string>
<string name="tags_list_menu_title">Tags</string>
<string name="diary_entries_list_menu_title">Diary entries</string>
<string name="genders_list_menu_title">Genders</string>
<string name="genders_add_menu_title">Add gender</string>
<string name="genders_update_menu_title">Update gender</string>
<string name="help_menu_title">Help</string>
<string name="support_section">Support</string>
<string name="preferences_menu_title">Preferences</string>
<string name="import_export_menu_title">Import/Export</string>
<string name="search_view_hint">Search entries</string>
<string name="fab_add_description">Add entry</string>
<string name="fab_filter_description">Filter entries</string>
<string name="fab_csv_description">Export entries to CSV file</string>
<string name="name_label">Name</string>
<string name="save_button">Save</string>
<string name="deactivate_button">Deactivate</string>
<string name="delete_button">Delete</string>
<string name="update_button">Update</string>
<string name="unique_gender_violation">This gender name already exists!</string>
<string name="validation_no_name">Name is required</string>
<string name="validation_no_title">Title is required</string>
<string name="inactive_label">Inactive</string>
</resources>
Since we want a consistent look across our app, we add a new style definition for inactive items to our themes.xml file:
11.3 themes.xml (Light-Mode)
...
<style name="CrudDiary_LinearLayoutCompat_CardView_Single_Text" parent="Theme.CrudDiary">
<item name="android:layout_width">match_parent</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:minHeight">50dp</item>
<item name="android:gravity">center_vertical</item>
<item name="android:textStyle">bold</item>
<item name="android:padding">8dp</item>
<item name="android:textSize">16sp</item>
</style>
<style name="CrudDiary_InactivityCheckbox" parent="Theme.CrudDiary">
<item name="android:layout_width">wrap_content</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:layout_gravity">center</item>
<item name="android:text">@string/inactive_label</item>
<item name="android:visibility">gone</item>
</style>
<style name="CrudDiary_Button" parent="Widget.MaterialComponents.Button.OutlinedButton">
<item name="android:minHeight">60dp</item>
<item name="android:layout_width">wrap_content</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:layout_gravity">center</item>
</style>
...
11.4 checkbox_inactive.xml
<?xml version="1.0" encoding="utf-8"?>
<layout
xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="viewModelValue"
type="String" />
</data>
<merge>
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/nameLayout"
style="@style/CrudDiary_TextInputLayout"
android:hint="@string/name_label">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="textCapWords"
android:text="@={viewModelValue}" />
</com.google.android.material.textfield.TextInputLayout>
</merge>
</layout>
11.5 fragment_update_gender.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".framgent.UpdateGenderFragment">
<data>
<variable
name="viewModel"
type="app.gedama.tutorial.cruddiary.viewmodel.UpdateGenderViewModel" />
</data>
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.appcompat.widget.LinearLayoutCompat
style="@style/CrudDiary_LinearLayoutCompat">
<include
android:id="@+id/title_text_field_binding"
app:viewModelValue="@={viewModel.gender.name}"
layout="@layout/text_input_name" />
<include
android:id="@+id/check_box_binding"
app:viewModelValue="@={viewModel.gender.inactive}"
layout="@layout/checkbox_inactive" />
<include
app:viewModelFunc="@{ () -> viewModel.updateGender() }"
android:id="@+id/crud_buttons"
layout="@layout/crud_buttons" />
</androidx.appcompat.widget.LinearLayoutCompat>
</ScrollView>
</layout>
Next we have to extend our navigation graph with our new fragment:
11.6 nav_graph.xml
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/nav_graph"
app:startDestination="@id/homeFragment">
<fragment
android:id="@+id/homeFragment"
android:name="app.gedama.tutorial.cruddiary.fragment.HomeFragment"
android:label="@string/main_menu_title" >
<action
android:id="@+id/action_homeFragment_to_gendersListFragment"
app:destination="@id/gendersListFragment" />
</fragment>
<fragment
android:id="@+id/gendersListFragment"
android:name="app.gedama.tutorial.cruddiary.fragment.GendersListFragment"
android:label="@string/genders_list_menu_title"
tools:layout="@layout/fragment_genders_list" >
<action
android:id="@+id/action_gendersListFragment_to_homeFragment"
app:destination="@id/homeFragment" />
<action
android:id="@+id/action_gendersListFragment_to_addGenderFragment"
app:destination="@id/addGenderFragment" />
<action
android:id="@+id/action_gendersListFragment_to_updateGenderFragment"
app:destination="@id/updateGenderFragment" />
</fragment>
<fragment
android:id="@+id/addGenderFragment"
android:name="app.gedama.tutorial.cruddiary.fragment.AddGenderFragment"
android:label="@string/genders_add_menu_title" >
<action
android:id="@+id/action_addGenderFragment_to_gendersListFragment"
app:destination="@id/gendersListFragment"
app:popUpTo="@id/homeFragment" />/>
</fragment>
<fragment
android:id="@+id/updateGenderFragment"
android:name="app.gedama.tutorial.cruddiary.fragment.UpdateGenderFragment"
android:label="@string/genders_update_menu_title" >
<action
android:id="@+id/action_updateGenderFragment_to_gendersListFragment"
app:destination="@id/gendersListFragment"
app:popUpTo="@id/homeFragment" />/>
<argument
android:name="genderId"
app:argType="long" />
</fragment>
</navigation>
Note that we added the argument genderId to our new fragment because we have to pass the ID so we know which gender item gets updated. Next we add new methods to our BaseFragment class. Method saveToUpdateButton() simply changes the text of our CRUD-button in the UI from ’save’ to ’update’. Method setInactivityButton() is used to change the visibility of the inactivity button in the UI. And method setDeactivateButton() presents a safety check dialog to the user asking if she really wants to deactivate the given object.
11.7 BaseFragment.kt
package app.gedama.tutorial.cruddiary.fragment
import android.view.View
import android.widget.Button
import android.widget.CheckBox
import androidx.appcompat.app.AlertDialog
import app.gedama.tutorial.cruddiary.R
import androidx.core.view.isVisible
import androidx.fragment.app.Fragment
import androidx.lifecycle.lifecycleScope
import app.gedama.tutorial.cruddiary.ui.formfields.FormFieldText
import app.gedama.tutorial.cruddiary.ui.formfields.validate
import app.gedama.tutorial.cruddiary.viewmodel.BaseViewModel
import com.google.android.material.button.MaterialButton
import com.google.android.material.floatingactionbutton.FloatingActionButton
import kotlinx.coroutines.launch
abstract class BaseFragment: Fragment() {
val TAG = this::class.simpleName
fun saveToUpdateButton(saveButton: Button) {
saveButton.text = resources.getString(R.string.update_button)
}
fun setDeactivateButton(deactivateButton: MaterialButton, viewModelFunc: () -> Unit ) {
deactivateButton.setOnClickListener {
val builder = AlertDialog.Builder(this.requireContext())
builder.setTitle(resources.getText(R.string.inactivity_safety_dialog_title))
builder.setMessage(resources.getText(R.string.inactivity_safety_check))
builder.setPositiveButton(R.string.yes) { _, _ ->
viewModelFunc()
}
builder.setNegativeButton(R.string.no) { _, _ ->
// do nothing, but we need this statement to show the No-Button
}
builder.show()
}
}
fun setInactivityButton(inactive: Boolean, deactivateButton: MaterialButton, checkBoxInactive: CheckBox) {
if ( inactive ) {
deactivateButton.visibility = View.GONE
checkBoxInactive.isVisible = true
}
}
fun activateAddFAB(viewModelFunc: () -> Unit ) {
val fab = this.requireActivity().findViewById<FloatingActionButton>(R.id.add_floating_action_button)
fab.isVisible = true
fab.setOnClickListener { viewModelFunc() }
}
fun deactivateAddFAB() {
val fab = this.requireActivity().findViewById<FloatingActionButton>(R.id.add_floating_action_button)
fab.isVisible = false
}
fun formValidation(actionButton: Button, formFields: List<FormFieldText>, viewModel: BaseViewModel) = lifecycleScope.launch {
actionButton.isEnabled = false
// formFields.disable()
if (formFields.validate(validateAll = true)) {
viewModel.updateEntryAfterValidation()
viewModel.onValidatedAndUpdated()
} else {
viewModel._deactivateSuccess.value = false
}
// formFields.enable()
actionButton.isEnabled = true
}
}
Now it is time to present our UpdateGenderFragment class:
11.8 UpdateGenderFragment.kt
package app.gedama.tutorial.cruddiary.fragment
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProvider
import androidx.lifecycle.lifecycleScope
import androidx.navigation.findNavController
import app.gedama.tutorial.cruddiary.R
import app.gedama.tutorial.cruddiary.data.Validation
import app.gedama.tutorial.cruddiary.database.CrudDiaryDatabase
import app.gedama.tutorial.cruddiary.databinding.FragmentUpdateGenderBinding
import app.gedama.tutorial.cruddiary.ui.formfields.FormFieldText
import app.gedama.tutorial.cruddiary.viewmodel.UpdateGenderViewModel
import app.gedama.tutorial.cruddiary.viewmodel.UpdateGenderViewModelFactory
import com.google.android.material.snackbar.Snackbar
class UpdateGenderFragment: BaseFragment() {
private var _binding: FragmentUpdateGenderBinding? = null
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentUpdateGenderBinding.inflate(inflater, container, false)
val view = binding.root
val vaccinationTypeId = UpdateGenderFragmentArgs.fromBundle(requireArguments()).genderId
val application = requireNotNull(this.activity).application
val genderDao = CrudDiaryDatabase.getInstance(application).genderDao
val viewModelFactory = UpdateGenderViewModelFactory(vaccinationTypeId,genderDao)
val viewModel = ViewModelProvider(this, viewModelFactory)[UpdateGenderViewModel::class.java]
binding.viewModel = viewModel
binding.lifecycleOwner = viewLifecycleOwner
val fieldTitle = FormFieldText(
scope = lifecycleScope,
textInputLayout = binding.titleTextFieldBinding.nameLayout,
textInputEditText = binding.titleTextFieldBinding.name,
Validation.nameValidation
)
val formFields = listOf(fieldTitle)
saveToUpdateButton(binding.crudButtons.actionButton)
viewModel.navigateToList.observe(viewLifecycleOwner, Observer { navigate ->
if (navigate) {
view.findNavController()
.navigate(R.id.action_updateGenderFragment_to_gendersListFragment)
viewModel.onNavigatedToList()
}
})
viewModel.gender.observe(viewLifecycleOwner, Observer { item ->
setInactivityButton(item.inactive,binding.crudButtons.deactivateButton,binding.checkBoxBinding.checkBoxInactive)
})
viewModel.doValidation.observe(viewLifecycleOwner, Observer { doValidate ->
if (doValidate) {
formValidation(binding.crudButtons.actionButton, formFields, viewModel)
}
})
viewModel.insertSuccess.observe(viewLifecycleOwner, Observer { isSuccess ->
if (isSuccess != null && !isSuccess ) {
Snackbar.make(binding.crudButtons.actionButton,resources.getText(R.string.unique_gender_violation),
Snackbar.LENGTH_INDEFINITE).show()
Log.d(TAG,"There was a problem when updating gender data in the database ...")
}
})
setDeactivateButton(binding.crudButtons.deactivateButton, { viewModel.deactivateGender() } )
return view
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
Once again, for getting from the genders list page to the ’Update gender’ page, we have to extend our existing GendersListFragment:
11.9 GendersListFragment.kt
...
viewModel.navigateToAddItem.observe(viewLifecycleOwner, Observer { navigate ->
if (navigate) {
val action = GendersListFragmentDirections
.actionGendersListFragmentToAddGenderFragment()
this.findNavController().navigate(action)
viewModel.onItemAddNavigated()
}
})
viewModel.navigateToEditItem.observe(viewLifecycleOwner, Observer { genderId ->
genderId?.let {
val action = GendersListFragmentDirections
.actionGendersListFragmentToUpdateGenderFragment(genderId)
this.findNavController().navigate(action)
viewModel.onItemEditNavigated()
}
})
return view
...
With all these new files and extensions of existing files, the code should now rebuild and run on a (virtual) device. If you tap on one of the items in the genders list, you get to the input mask for updating the selected gender (see Figure 11.1). If the validation of our updated gender was successful, the logic returns to the genders list and displays the updated gender value (see Figure 11.2).
Have you noticed the ’Deactivate’ button below the ’Save’ button? It already works, but please ignore this button for now since we have to tackle the settings menu first in a later chapter (see Chapter 16) so you can actually see the effects of deactivating database items!