Add delegated property to automatically handle Fragment view unbinding (

closes #927) (#928) * Create delegated property to automatically handle Fragment view unbinding * Add new file at the end of file * Remove empty line * Update error message * Add missing imports for other flavors. Co-authored-by: darken <darken@darken.eu> Co-authored-by: Matthias Urhahn <matthias.urhahn@sap.com>
corona-warn-app · Sep 14, 2020 · 7f3b2b1 · 7f3b2b1
1 parent 0c598b1
commit 7f3b2b1
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Showing 34 changed files with 151 additions and 258 deletions.
diff --git a/Corona-Warn-App/build.gradle b/Corona-Warn-App/build.gradle
@@ -237,7 +237,8 @@ dependencies {
     implementation 'androidx.legacy:legacy-support-v4:1.0.0'
     implementation 'androidx.preference:preference:1.1.1'
     implementation 'androidx.work:work-runtime-ktx:2.3.4'
-    implementation 'android.arch.lifecycle:extensions:1.1.1'
+    implementation 'android.arch.lifecycle:extensions:2.2.0'
+    implementation 'androidx.lifecycle:lifecycle-common-java8:2.2.0'
     implementation 'androidx.annotation:annotation:1.1.0'
 
     // DAGGER
@@ -247,6 +248,7 @@ dependencies {
     kapt 'com.google.dagger:dagger-compiler:2.28.1'
     kapt 'com.google.dagger:dagger-android-processor:2.28.1'
 
+
     // QR
     implementation('com.journeyapps:zxing-android-embedded:4.1.0') { transitive = false }
     // noinspection GradleDependency - needed for SDK 23 compatibility, in combination with com.journeyapps:zxing-android-embedded:4.1.0

diff --git a/Corona-Warn-App/src/device/java/de.rki.coronawarnapp/ui/main/MainFragment.kt b/Corona-Warn-App/src/device/java/de.rki.coronawarnapp/ui/main/MainFragment.kt
@@ -16,6 +16,7 @@ import de.rki.coronawarnapp.risk.TimeVariables
 import de.rki.coronawarnapp.storage.LocalData
 import de.rki.coronawarnapp.timer.TimerHelper
 import de.rki.coronawarnapp.ui.doNavigate
+import de.rki.coronawarnapp.ui.viewLifecycle
 import de.rki.coronawarnapp.ui.viewmodel.SettingsViewModel
 import de.rki.coronawarnapp.ui.viewmodel.SubmissionViewModel
 import de.rki.coronawarnapp.ui.viewmodel.TracingViewModel
@@ -44,27 +45,21 @@ class MainFragment : Fragment() {
     private val tracingViewModel: TracingViewModel by activityViewModels()
     private val settingsViewModel: SettingsViewModel by activityViewModels()
     private val submissionViewModel: SubmissionViewModel by activityViewModels()
-    private var _binding: FragmentMainBinding? = null
-    private val binding: FragmentMainBinding get() = _binding!!
+    private var binding: FragmentMainBinding by viewLifecycle()
 
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
-        _binding = FragmentMainBinding.inflate(inflater)
+        binding = FragmentMainBinding.inflate(inflater)
         binding.tracingViewModel = tracingViewModel
         binding.settingsViewModel = settingsViewModel
         binding.submissionViewModel = submissionViewModel
         binding.lifecycleOwner = this
         return binding.root
     }
 
-    override fun onDestroyView() {
-        super.onDestroyView()
-        _binding = null
-    }
-
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
         setButtonOnClickListener()

diff --git a/Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/test/TestForAPIFragment.kt b/Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/test/TestForAPIFragment.kt
@@ -48,6 +48,7 @@ import de.rki.coronawarnapp.storage.ExposureSummaryRepository
 import de.rki.coronawarnapp.storage.LocalData
 import de.rki.coronawarnapp.storage.tracing.TracingIntervalRepository
 import de.rki.coronawarnapp.transaction.RiskLevelTransaction
+import de.rki.coronawarnapp.ui.viewLifecycle
 import de.rki.coronawarnapp.ui.viewmodel.TracingViewModel
 import de.rki.coronawarnapp.util.KeyFileHelper
 import kotlinx.android.synthetic.deviceForTesters.fragment_test_for_a_p_i.button_api_enter_other_keys
@@ -118,8 +119,7 @@ class TestForAPIFragment : Fragment(), InternalExposureNotificationPermissionHel
     private lateinit var qrPagerAdapter: RecyclerView.Adapter<QRPagerAdapter.QRViewHolder>
 
     // Data and View binding
-    private var _binding: FragmentTestForAPIBinding? = null
-    private val binding: FragmentTestForAPIBinding get() = _binding!!
+    private var binding: FragmentTestForAPIBinding by viewLifecycle()
 
     override fun onCreateView(
         inflater: LayoutInflater,
@@ -128,7 +128,7 @@ class TestForAPIFragment : Fragment(), InternalExposureNotificationPermissionHel
     ): View? {
 
         // get the binding reference by inflating it with the current layout
-        _binding = FragmentTestForAPIBinding.inflate(inflater)
+        binding = FragmentTestForAPIBinding.inflate(inflater)
 
         // set the viewmmodel variable that will be used for data binding
         binding.tracingViewModel = tracingViewModel
@@ -140,11 +140,6 @@ class TestForAPIFragment : Fragment(), InternalExposureNotificationPermissionHel
         return binding.root
     }
 
-    override fun onDestroyView() {
-        super.onDestroyView()
-        _binding = null
-    }
-
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 

diff --git a/...p/src/deviceForTesters/java/de/rki/coronawarnapp/test/TestRiskLevelCalculationFragment.kt b/...p/src/deviceForTesters/java/de/rki/coronawarnapp/test/TestRiskLevelCalculationFragment.kt
@@ -33,6 +33,7 @@ import de.rki.coronawarnapp.storage.LocalData
 import de.rki.coronawarnapp.storage.RiskLevelRepository
 import de.rki.coronawarnapp.transaction.RetrieveDiagnosisKeysTransaction
 import de.rki.coronawarnapp.transaction.RiskLevelTransaction
+import de.rki.coronawarnapp.ui.viewLifecycle
 import de.rki.coronawarnapp.ui.viewmodel.SettingsViewModel
 import de.rki.coronawarnapp.ui.viewmodel.SubmissionViewModel
 import de.rki.coronawarnapp.ui.viewmodel.TracingViewModel
@@ -59,8 +60,7 @@ class TestRiskLevelCalculationFragment : Fragment() {
     private val tracingViewModel: TracingViewModel by activityViewModels()
     private val settingsViewModel: SettingsViewModel by activityViewModels()
     private val submissionViewModel: SubmissionViewModel by activityViewModels()
-    private var _binding: FragmentTestRiskLevelCalculationBinding? = null
-    private val binding: FragmentTestRiskLevelCalculationBinding get() = _binding!!
+    private var binding: FragmentTestRiskLevelCalculationBinding by viewLifecycle()
 
     // reference to the client from the Google framework with the given application context
     private val exposureNotificationClient by lazy {
@@ -72,19 +72,14 @@ class TestRiskLevelCalculationFragment : Fragment() {
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
-        _binding = FragmentTestRiskLevelCalculationBinding.inflate(inflater)
+        binding = FragmentTestRiskLevelCalculationBinding.inflate(inflater)
         binding.tracingViewModel = tracingViewModel
         binding.settingsViewModel = settingsViewModel
         binding.submissionViewModel = submissionViewModel
         binding.lifecycleOwner = this
         return binding.root
     }
 
-    override fun onDestroyView() {
-        super.onDestroyView()
-        _binding = null
-    }
-
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 

diff --git a/Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/ui/main/MainFragment.kt b/Corona-Warn-App/src/deviceForTesters/java/de/rki/coronawarnapp/ui/main/MainFragment.kt
@@ -16,6 +16,7 @@ import de.rki.coronawarnapp.risk.TimeVariables
 import de.rki.coronawarnapp.storage.LocalData
 import de.rki.coronawarnapp.timer.TimerHelper
 import de.rki.coronawarnapp.ui.doNavigate
+import de.rki.coronawarnapp.ui.viewLifecycle
 import de.rki.coronawarnapp.ui.viewmodel.SettingsViewModel
 import de.rki.coronawarnapp.ui.viewmodel.SubmissionViewModel
 import de.rki.coronawarnapp.ui.viewmodel.TracingViewModel
@@ -44,27 +45,21 @@ class MainFragment : Fragment() {
     private val tracingViewModel: TracingViewModel by activityViewModels()
     private val settingsViewModel: SettingsViewModel by activityViewModels()
     private val submissionViewModel: SubmissionViewModel by activityViewModels()
-    private var _binding: FragmentMainBinding? = null
-    private val binding: FragmentMainBinding get() = _binding!!
+    private var binding: FragmentMainBinding by viewLifecycle()
 
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
-        _binding = FragmentMainBinding.inflate(inflater)
+        binding = FragmentMainBinding.inflate(inflater)
         binding.tracingViewModel = tracingViewModel
         binding.settingsViewModel = settingsViewModel
         binding.submissionViewModel = submissionViewModel
         binding.lifecycleOwner = this
         return binding.root
     }
 
-    override fun onDestroyView() {
-        super.onDestroyView()
-        _binding = null
-    }
-
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
         setButtonOnClickListener()

diff --git a/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/UIExtensions.kt b/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/UIExtensions.kt
@@ -1,7 +1,15 @@
 package de.rki.coronawarnapp.ui
 
+import android.os.Handler
+import android.os.Looper
+import androidx.fragment.app.Fragment
+import androidx.lifecycle.DefaultLifecycleObserver
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.Observer
 import androidx.navigation.NavController
 import androidx.navigation.NavDirections
+import kotlin.properties.ReadWriteProperty
+import kotlin.reflect.KProperty
 
 /**
  * Extends NavController to prevent navigation error when the user clicks on two buttons at almost
@@ -13,3 +21,47 @@ fun NavController.doNavigate(direction: NavDirections) {
     currentDestination?.getAction(direction.actionId)
         ?.let { navigate(direction) }
 }
+
+/**
+ * An extension to bind and unbind a value based on the view lifecycle of a Fragment.
+ * The binding will be unbound in onDestroyView.
+ *
+ * @throws IllegalStateException If the getter is invoked before the binding is set,
+ *                               or after onDestroyView an exception is thrown.
+ */
+fun <T> Fragment.viewLifecycle(): ReadWriteProperty<Fragment, T> {
+    return object : ReadWriteProperty<Fragment, T>, DefaultLifecycleObserver {
+
+        private var binding: T? = null
+
+        init {
+            this@viewLifecycle
+                .viewLifecycleOwnerLiveData
+                .observe(this@viewLifecycle, Observer { owner: LifecycleOwner? ->
+                    owner?.lifecycle?.addObserver(this)
+                })
+        }
+
+        override fun onDestroy(owner: LifecycleOwner) {
+            val handler = Handler(Looper.getMainLooper())
+            handler.post {
+                binding = null
+            }
+        }
+
+        override fun getValue(
+            thisRef: Fragment,
+            property: KProperty<*>
+        ): T {
+            return this.binding ?: error("Called before onCreateView or after onDestroyView.")
+        }
+
+        override fun setValue(
+            thisRef: Fragment,
+            property: KProperty<*>,
+            value: T
+        ) {
+            this.binding = value
+        }
+    }
+}
diff --git a/...na-Warn-App/src/main/java/de/rki/coronawarnapp/ui/information/InformationAboutFragment.kt b/...na-Warn-App/src/main/java/de/rki/coronawarnapp/ui/information/InformationAboutFragment.kt
@@ -11,6 +11,7 @@ import androidx.fragment.app.Fragment
 import de.rki.coronawarnapp.R
 import de.rki.coronawarnapp.databinding.FragmentInformationAboutBinding
 import de.rki.coronawarnapp.ui.main.MainActivity
+import de.rki.coronawarnapp.ui.viewLifecycle
 
 /**
  * Basic Fragment which only displays static content.
@@ -20,23 +21,17 @@ class InformationAboutFragment : Fragment() {
         private val TAG: String? = InformationAboutFragment::class.simpleName
     }
 
-    private var _binding: FragmentInformationAboutBinding? = null
-    private val binding: FragmentInformationAboutBinding get() = _binding!!
+    private var binding: FragmentInformationAboutBinding by viewLifecycle()
 
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
-        _binding = FragmentInformationAboutBinding.inflate(inflater)
+        binding = FragmentInformationAboutBinding.inflate(inflater)
         return binding.root
     }
 
-    override fun onDestroyView() {
-        super.onDestroyView()
-        _binding = null
-    }
-
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
         setButtonOnClickListener()

diff --git a/...-Warn-App/src/main/java/de/rki/coronawarnapp/ui/information/InformationContactFragment.kt b/...-Warn-App/src/main/java/de/rki/coronawarnapp/ui/information/InformationContactFragment.kt
@@ -9,6 +9,7 @@ import androidx.fragment.app.Fragment
 import de.rki.coronawarnapp.R
 import de.rki.coronawarnapp.databinding.FragmentInformationContactBinding
 import de.rki.coronawarnapp.ui.main.MainActivity
+import de.rki.coronawarnapp.ui.viewLifecycle
 import de.rki.coronawarnapp.util.ExternalActionHelper
 
 /**
@@ -19,23 +20,17 @@ class InformationContactFragment : Fragment() {
         private val TAG: String? = InformationContactFragment::class.simpleName
     }
 
-    private var _binding: FragmentInformationContactBinding? = null
-    private val binding: FragmentInformationContactBinding get() = _binding!!
+    private var binding: FragmentInformationContactBinding by viewLifecycle()
 
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
-        _binding = FragmentInformationContactBinding.inflate(inflater)
+        binding = FragmentInformationContactBinding.inflate(inflater)
         return binding.root
     }
 
-    override fun onDestroyView() {
-        super.onDestroyView()
-        _binding = null
-    }
-
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
         setButtonOnClickListener()

diff --git a/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/information/InformationFragment.kt b/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/information/InformationFragment.kt
@@ -12,6 +12,7 @@ import de.rki.coronawarnapp.R
 import de.rki.coronawarnapp.databinding.FragmentInformationBinding
 import de.rki.coronawarnapp.ui.doNavigate
 import de.rki.coronawarnapp.ui.main.MainActivity
+import de.rki.coronawarnapp.ui.viewLifecycle
 import de.rki.coronawarnapp.util.ExternalActionHelper
 
 /**
@@ -22,23 +23,17 @@ class InformationFragment : Fragment() {
         private val TAG: String? = InformationFragment::class.simpleName
     }
 
-    private var _binding: FragmentInformationBinding? = null
-    private val binding: FragmentInformationBinding get() = _binding!!
+    private var binding: FragmentInformationBinding by viewLifecycle()
 
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
-        _binding = FragmentInformationBinding.inflate(inflater)
+        binding = FragmentInformationBinding.inflate(inflater)
         return binding.root
     }
 
-    override fun onDestroyView() {
-        super.onDestroyView()
-        _binding = null
-    }
-
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
         setButtonOnClickListener()

diff --git a/...na-Warn-App/src/main/java/de/rki/coronawarnapp/ui/information/InformationLegalFragment.kt b/...na-Warn-App/src/main/java/de/rki/coronawarnapp/ui/information/InformationLegalFragment.kt
@@ -11,6 +11,7 @@ import de.rki.coronawarnapp.R
 import de.rki.coronawarnapp.databinding.FragmentInformationLegalBinding
 import de.rki.coronawarnapp.ui.main.MainActivity
 import de.rki.coronawarnapp.util.convertToHyperlink
+import de.rki.coronawarnapp.ui.viewLifecycle
 
 /**
  * Basic Fragment which only displays static content.
@@ -20,23 +21,17 @@ class InformationLegalFragment : Fragment() {
         private val TAG: String? = InformationLegalFragment::class.simpleName
     }
 
-    private var _binding: FragmentInformationLegalBinding? = null
-    private val binding: FragmentInformationLegalBinding get() = _binding!!
+    private var binding: FragmentInformationLegalBinding by viewLifecycle()
 
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
-        _binding = FragmentInformationLegalBinding.inflate(inflater)
+        binding = FragmentInformationLegalBinding.inflate(inflater)
         return binding.root
     }
 
-    override fun onDestroyView() {
-        super.onDestroyView()
-        _binding = null
-    }
-
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
         setButtonOnClickListener()