Saving ViewModel state in Android, #3

Miha-x64 · Feb 8, 2018 · b3668ba · b3668ba
1 parent fbb89b9
commit b3668ba
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Showing 3 changed files with 24 additions and 9 deletions.
diff --git a/README.md b/README.md
@@ -28,20 +28,17 @@ verticalLayout {
     padding = dip(16)
 
     editText {
-        id = 1
         hint = "Email"
         bindTextBidirectionally(vm.emailProp)
         bindErrorMessageTo(vm.emailValidProp.map { if (it) null else "E-mail is invalid" })
     }
 
     editText {
-        id = 2
         hint = "Name"
         bindTextBidirectionally(vm.nameProp)
     }
 
     editText {
-        id = 3
         hint = "Surname"
         bindTextBidirectionally(vm.surnameProp)
     }

diff --git a/android-sample/src/main/kotlin/net/aquadc/properties/android/sample/MainActivity.kt b/android-sample/src/main/kotlin/net/aquadc/properties/android/sample/MainActivity.kt
@@ -2,6 +2,7 @@ package net.aquadc.properties.android.sample
 
 import android.app.Activity
 import android.os.Bundle
+import net.aquadc.properties.android.ParcelPropertiesMemento
 import net.aquadc.properties.android.bindings.*
 import net.aquadc.properties.map
 import net.aquadc.properties.sample.logic.MainVm
@@ -17,26 +18,27 @@ class MainActivity : Activity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
-        vm = MainVm(app.userProp)
+        // create or restore ViewModel
+        vm = (lastNonConfigurationInstance as MainVm?) ?: MainVm(app.userProp)
+
+        // restore ViewModel's state in case of process death
+        savedInstanceState?.getParcelable<ParcelPropertiesMemento>("vm")?.restoreTo(vm)
 
         verticalLayout {
             padding = dip(16)
 
             editText {
-                id = 1
                 hint = "Email"
                 bindTextBidirectionally(vm.emailProp)
                 bindErrorMessageTo(vm.emailValidProp.map { if (it) null else "E-mail is invalid" })
             }
 
             editText {
-                id = 2
                 hint = "Name"
                 bindTextBidirectionally(vm.nameProp)
             }
 
             editText {
-                id = 3
                 hint = "Surname"
                 bindTextBidirectionally(vm.surnameProp)
             }
@@ -56,4 +58,11 @@ class MainActivity : Activity() {
         }
     }
 
+    override fun onSaveInstanceState(outState: Bundle) {
+        super.onSaveInstanceState(outState)
+        outState.putParcelable("vm", ParcelPropertiesMemento(vm))
+    }
+
+    override fun onRetainNonConfigurationInstance(): Any? = vm
+
 }
diff --git a/logic-sample/src/main/kotlin/net/aquadc/properties/sample/logic/MainVm.kt b/logic-sample/src/main/kotlin/net/aquadc/properties/sample/logic/MainVm.kt
@@ -1,22 +1,31 @@
 package net.aquadc.properties.sample.logic
 
 import net.aquadc.properties.*
+import net.aquadc.properties.persistence.PersistableProperties
+import net.aquadc.properties.persistence.PropertyIo
+import net.aquadc.properties.persistence.x
 
 /**
  * This ViewModel can be used both in Android and on JVM.
- * In ansroid-sample it is used in Android Activity,
+ * In android-sample it is used in Android Activity,
  * and in fx-sample it is in JavaFX view.
  */
 class MainVm(
         private val userProp: MutableProperty<InMemoryUser>
-) {
+) : PersistableProperties {
 
     // todo: find a shorter way to create single-threaded properties
     val emailProp = unsynchronizedMutablePropertyOf(userProp.value.email)
     val nameProp = unsynchronizedMutablePropertyOf(userProp.value.name)
     val surnameProp = unsynchronizedMutablePropertyOf(userProp.value.surname)
     val buttonClickedProp = unsynchronizedMutablePropertyOf(false)
 
+    override fun saveOrRestore(d: PropertyIo) {
+        d x emailProp
+        d x nameProp
+        d x surnameProp
+    }
+
     val emailValidProp = unsynchronizedMutablePropertyOf(false)
     val buttonEnabledProp = unsynchronizedMutablePropertyOf(false)
     val buttonTextProp = unsynchronizedMutablePropertyOf("")