saving viewModel state, saving fragment arguments, completed readme

README.md

@@ -114,22 +114,20 @@ As you can see, the codes for the Fragment and for the View are completely ident
 
 **Note:** you may need to build the project twice so that the binding adapters and component classes are generated correctly.
 
-Also, in the case of a View, you can set `Prop.twoWay = true`, and then a two-way binding adapter will be generated for the View. It will send the value back when the annotated property changes.
+Also, in the case of a View:
+- You can set `Prop.twoWay = true`, and then a two-way binding adapter will be generated for the View. It will send the value back when the annotated property changes.
 ```kotlin
 @Prop(twoWay = true)
 var twoWayText: String? = null //a two-way binding adapter will be generated
 ```
-
-And in the case of Fragments, you can pass callbacks to them:
+- You can bind xml attribute to your state property:
 ```kotlin
-// ChildFragmentViewModel.kt
-@Prop
-var callback: (() -> Unit)? = null
-
-// ChildFragment's parent Fragment
-showFragment(ChildFragmentComponent().apply { callback = this@ParentFragment.viewModel.childFragmentCallback })
+var picture by state<Drawable?>(null, attr = R.styleable.MyViewComponent_picture)
+```
+```xml
+<MyViewComponent
+	app:picture="@drawable/myPicture"/>
 ```
-But keep in mind that the source value of the callback must be in the ViewModel  so that the callback does not refer to a Fragment or View.
 
 ### 2. Observable state
 
@@ -182,6 +180,8 @@ class MyTextView : ComponentScheme<TextView, MyTextViewModel>({
 
 ### 5. Coroutine support
 
+#### suspend funs
+
 Suppose that before you display some data, you need to load it first. Here's how you do it:
 ```kotlin
 var greeting: String? by state({
@@ -212,4 +212,20 @@ fun reloadGreeting() {
 }
 ```
 
+#### Flows
+
+Suppose you need to subscribe to the Flow and display all its elements. Here's how you do it:
+```kotlin
+var countDown: Int? by state(flow {
+    delay(1000)
+        emit(3)
+        delay(1000)
+        emit(2)
+        delay(1000)
+        emit(1)
+        delay(1000)
+        emit(0)
+})
+```
+
 ***For detailed examples see module `app`.***

ui-generator-base/src/main/java/ru/impression/ui_generator_base/ComponentViewModel.kt

@@ -2,6 +2,7 @@ package ru.impression.ui_generator_base
 
 import android.os.Handler
 import android.os.Looper
+import android.os.Parcelable
 import androidx.annotation.CallSuper
 import androidx.lifecycle.*
 import kotlin.reflect.KMutableProperty0
@@ -107,6 +108,10 @@ abstract class ComponentViewModel(val attrs: IntArray? = null) : ViewModel(), St
 
     protected open fun onLifecycleEvent(event: Lifecycle.Event) = Unit
 
+    open fun onSaveInstanceState(): Parcelable? = null
+
+    open fun onRestoreInstanceState(savedInstanceState: Parcelable?) = Unit
+
     public override fun onCleared() = Unit
 
     protected fun <T> KMutableProperty0<T>.set(value: T, renderImmediately: Boolean = false) {

ui-generator-base/src/main/java/ru/impression/ui_generator_base/Ext.kt

@@ -3,11 +3,13 @@ package ru.impression.ui_generator_base
 import android.content.Context
 import android.content.ContextWrapper
 import android.graphics.drawable.Drawable
+import android.os.Bundle
 import android.util.AttributeSet
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.appcompat.app.AppCompatActivity
+import androidx.core.os.bundleOf
 import androidx.databinding.ViewDataBinding
 import androidx.fragment.app.Fragment
 import androidx.lifecycle.Lifecycle
@@ -30,6 +32,11 @@ val View.activity: AppCompatActivity?
         return contextWrapper
     }
 
+fun Fragment.putArgument(key: String, value: Any?) {
+    val arguments = arguments ?: Bundle().also { arguments = it }
+    arguments.putAll(bundleOf(key to value))
+}
+
 fun <T, VM : ComponentViewModel> T.resolveAttrs(attrs: AttributeSet?) where T : Component<*, VM>, T : View {
     with(context.theme.obtainStyledAttributes(attrs, viewModel.attrs ?: return, 0, 0)) {
         try {

ui-generator-base/src/main/java/ru/impression/ui_generator_base/SavedViewState.kt

@@ -0,0 +1,7 @@
+package ru.impression.ui_generator_base
+
+import android.os.Parcelable
+import kotlinx.android.parcel.Parcelize
+
+@Parcelize
+class SavedViewState(val superState: Parcelable?, val viewModelState: Parcelable?): Parcelable

ui-generator-base/src/main/java/ru/impression/ui_generator_base/StateDelegate.kt

@@ -60,7 +60,6 @@ open class StateDelegate<R : StateOwner, T>(
         (parent as? ComponentViewModel)?.initSubscriptions(::collect) ?: collect()
     }
 
-    @Synchronized
     override fun getValue(thisRef: R, property: KProperty<*>) = value
 
     @Synchronized

ui-generator-processor/src/main/java/ru/impression/ui_generator_processor/ComponentClassBuilder.kt

@@ -93,5 +93,7 @@ abstract class ComponentClassBuilder(
         val type: TypeMirror,
         val twoWay: Boolean,
         val attrChangedPropertyName: String
-    )
+    ) {
+        val kotlinType = type.asTypeName().javaToKotlinType().copy(true)
+    }
 }

ui-generator-processor/src/main/java/ru/impression/ui_generator_processor/FragmentComponentClassBuilder.kt

@@ -33,6 +33,7 @@ class FragmentComponentClassBuilder(
                     propProperties.forEach {
                         add(
                             """
+                                val ${it.name} = ${it.name}
                                 if (${it.name} != null && ${it.name} !== viewModel.${it.name})
                                   viewModel::${it.name}.%M(${it.name})
                                   viewModel.onStateChanged(renderImmediately = true)
@@ -73,19 +74,51 @@ class FragmentComponentClassBuilder(
 
     override fun TypeSpec.Builder.addRestMembers() {
         propProperties.forEach { addProperty(buildPropWrapperProperty(it)) }
+        addFunction(buildOnCreateFunction())
         addFunction(buildOnCreateViewFunction())
         addFunction(buildOnActivityCreatedFunction())
+        addFunction(buildOnSaveInstanceStateFunction())
         addFunction(buildOnDestroyViewFunction())
     }
 
     private fun buildPropWrapperProperty(propProperty: PropProperty) = with(
         PropertySpec.builder(
             propProperty.name,
-            propProperty.type.asTypeName().javaToKotlinType().copy(true)
+            propProperty.kotlinType
         )
     ) {
         mutable(true)
         initializer("null")
+        getter(
+            FunSpec.getterBuilder()
+                .addCode(
+                    """
+                        return field ?: arguments?.get("${propProperty.name}") as? ${propProperty.kotlinType}
+                    
+                    """.trimIndent()
+                )
+                .build()
+        )
+        setter(
+            FunSpec.setterBuilder().addParameter("value", propProperty.kotlinType).addCode(
+                """
+                    field = value
+                    %M("${propProperty.name}", value)
+                """.trimIndent(),
+                MemberName("ru.impression.ui_generator_base", "putArgument")
+            ).build()
+        )
+        build()
+    }
+
+    private fun buildOnCreateFunction() = with(FunSpec.builder("onCreate")) {
+        addModifiers(KModifier.OVERRIDE)
+        addParameter("savedInstanceState", ClassName("android.os", "Bundle").copy(true))
+        addCode(
+            """
+                super.onCreate(savedInstanceState)
+                viewModel.onRestoreInstanceState(savedInstanceState?.getParcelable("viewModelState"))""".trimIndent()
+        )
         build()
     }
 
@@ -110,10 +143,21 @@ class FragmentComponentClassBuilder(
         addCode(
             """
                 super.onActivityCreated(savedInstanceState)
-        
-        """.trimIndent()
+                viewModel.setComponent(this)
+                """.trimIndent()
+        )
+        build()
+    }
+
+    private fun buildOnSaveInstanceStateFunction() = with(FunSpec.builder("onSaveInstanceState")) {
+        addModifiers(KModifier.OVERRIDE)
+        addParameter("outState", ClassName("android.os", "Bundle"))
+        addCode(
+            """
+                super.onSaveInstanceState(outState)
+                outState.putParcelable("viewModelState", viewModel.onSaveInstanceState())
+                """.trimIndent()
         )
-        addCode("viewModel.setComponent(this)")
         build()
     }
 

ui-generator-processor/src/main/java/ru/impression/ui_generator_processor/ViewComponentClassBuilder.kt

@@ -62,6 +62,8 @@ class ViewComponentClassBuilder(
             addFunction(buildOnTwoWayPropChangedFunction())
         addFunction(buildOnAttachedToWindowFunction())
         addFunction(buildOnDetachedFromWindowFunction())
+        addFunction(buildOnSaveInstanceStateFunction())
+        addFunction(buildOnRestoreInstanceStateFunction())
         addType(buildCompanionObject())
     }
 
@@ -191,6 +193,34 @@ class ViewComponentClassBuilder(
             build()
         }
 
+    private fun buildOnSaveInstanceStateFunction() = with(FunSpec.builder("onSaveInstanceState")) {
+        addModifiers(KModifier.OVERRIDE)
+        returns(ClassName("android.os", "Parcelable").copy(true))
+        addCode(
+            """
+                return %T(super.onSaveInstanceState(), viewModel.onSaveInstanceState())
+                
+                """.trimIndent(),
+            ClassName("ru.impression.ui_generator_base", "SavedViewState")
+        )
+        build()
+    }
+
+    private fun buildOnRestoreInstanceStateFunction() =
+        with(FunSpec.builder("onRestoreInstanceState")) {
+            addModifiers(KModifier.OVERRIDE)
+            addParameter("state", ClassName("android.os", "Parcelable").copy(true))
+            addCode(
+                """
+                super.onRestoreInstanceState((state as? %T)?.superState)
+                viewModel.onRestoreInstanceState((state as? %T)?.viewModelState)
+                """.trimIndent(),
+                ClassName("ru.impression.ui_generator_base", "SavedViewState"),
+                ClassName("ru.impression.ui_generator_base", "SavedViewState")
+            )
+            build()
+        }
+
     private fun buildCompanionObject(): TypeSpec = with(TypeSpec.companionObjectBuilder()) {
         propProperties.forEach {
             addFunction(buildPropSetter(it))