iserbin · April 7, 2021 08:46 · Apr 1, 2021 · Mar 25, 2021 · Mar 25, 2021 · Jan 17, 2021
diff --git a/FragmentViewBindingDelegate.kt b/FragmentViewBindingDelegate.kt
@@ -58,4 +58,7 @@ class FragmentViewBindingDelegate<T : ViewBinding>(
         binding = bindMethod.invoke(null, thisRef.requireView()).cast<T>()
         return binding!!
     }
-}
+}
+
+@Suppress("UNCHECKED_CAST")
+private fun <T> Any.cast(): T = this as T
diff --git a/ViewViewBindingDelegate.kt b/ViewViewBindingDelegate.kt
@@ -22,3 +22,6 @@ class ViewBindingDelegate<T : ViewBinding>(
 
     override fun getValue(thisRef: ViewGroup, property: KProperty<*>): T = binding
 }
+
+@Suppress("UNCHECKED_CAST")
+private fun <T> Any.cast(): T = this as T
diff --git a/ViewViewBindingDelegate.kt b/ViewViewBindingDelegate.kt
@@ -9,7 +9,7 @@ inline fun <reified T : ViewBinding> ViewGroup.viewBinding() = ViewBindingDelega
 
 class ViewBindingDelegate<T : ViewBinding>(
     private val bindingClass: Class<T>,
-    val view: ViewGroup
+    private val view: ViewGroup
 ) : ReadOnlyProperty<ViewGroup, T> {
     private val binding: T = try {
         val inflateMethod = bindingClass.getMethod("inflate", LayoutInflater::class.java, ViewGroup::class.java, Boolean::class.javaPrimitiveType)

diff --git a/ViewViewBindingDelegate.kt b/ViewViewBindingDelegate.kt
@@ -1,10 +1,3 @@
-import android.view.LayoutInflater
-import android.view.ViewGroup
-import androidx.viewbinding.ViewBinding
-import com.tonal.trainer.utils.cast
-import kotlin.properties.ReadOnlyProperty
-import kotlin.reflect.KProperty
-
 /**
  * Create bindings for a view similar to bindView.
  *
@@ -16,21 +9,16 @@ inline fun <reified T : ViewBinding> ViewGroup.viewBinding() = ViewBindingDelega
 
 class ViewBindingDelegate<T : ViewBinding>(
     private val bindingClass: Class<T>,
-    val fragment: ViewGroup
+    val view: ViewGroup
 ) : ReadOnlyProperty<ViewGroup, T> {
-    private var binding: T? = null
-
-    override fun getValue(thisRef: ViewGroup, property: KProperty<*>): T {
-        binding?.let { return it }
-
-        try {
-            val inflateMethod = bindingClass.getMethod("inflate", LayoutInflater::class.java, ViewGroup::class.java, Boolean::class.javaPrimitiveType)
-            binding = inflateMethod.invoke(null, LayoutInflater.from(thisRef.context), thisRef, true).cast<T>()
-        } catch (e: NoSuchMethodException) {
-            // <merge> tags don't have the boolean parameter.
-            val inflateMethod = bindingClass.getMethod("inflate", LayoutInflater::class.java, ViewGroup::class.java)
-            binding = inflateMethod.invoke(null, LayoutInflater.from(thisRef.context), thisRef).cast<T>()
-        }
-        return binding!!
+    private val binding: T = try {
+        val inflateMethod = bindingClass.getMethod("inflate", LayoutInflater::class.java, ViewGroup::class.java, Boolean::class.javaPrimitiveType)
+        inflateMethod.invoke(null, LayoutInflater.from(view.context), view, true).cast<T>()
+    } catch (e: NoSuchMethodException) {
+        // <merge> tags don't have the boolean parameter.
+        val inflateMethod = bindingClass.getMethod("inflate", LayoutInflater::class.java, ViewGroup::class.java)
+        inflateMethod.invoke(null, LayoutInflater.from(view.context), view).cast<T>()
     }
-}
+
+    override fun getValue(thisRef: ViewGroup, property: KProperty<*>): T = binding
+}
diff --git a/FragmentA.kt b/FragmentA.kt
@@ -1,4 +1,5 @@
 class WifiNetworksFragment : TonalFragment(R.layout.wifi_networks_fragment) {
+    // This automatically creates and clears the binding in a lifecycle-aware way.
     private val binding: WifiNetworksFragmentBinding by viewBinding()
 
   ...

diff --git a/FragmentViewBindingDelegate.kt b/FragmentViewBindingDelegate.kt
@@ -10,6 +10,15 @@ import com.tonal.trainer.utils.cast
 import kotlin.properties.ReadOnlyProperty
 import kotlin.reflect.KProperty
 
+/**
+ * Create bindings for a view similar to bindView.
+ *
+ * To use, just call
+ * private val binding: FHomeWorkoutDetailsBinding by viewBinding()
+ * with your binding class and access it as you normally would.
+ */
+inline fun <reified T : ViewBinding> Fragment.viewBinding() = FragmentViewBindingDelegate(T::class.java, this)
+
 class FragmentViewBindingDelegate<T : ViewBinding>(
     private val bindingClass: Class<T>,
     val fragment: Fragment
@@ -49,13 +58,4 @@ class FragmentViewBindingDelegate<T : ViewBinding>(
         binding = bindMethod.invoke(null, thisRef.requireView()).cast<T>()
         return binding!!
     }
-}
-
-/**
- * Create bindings for a view similar to bindView.
- *
- * To use, just call
- * private val binding: FHomeWorkoutDetailsBinding by viewBinding()
- * with your binding class and access it as you normally would.
- */
-inline fun <reified T : ViewBinding> Fragment.viewBinding() = FragmentViewBindingDelegate(T::class.java, this)
+}
diff --git a/ViewViewBindingDelegate.kt b/ViewViewBindingDelegate.kt
@@ -5,6 +5,15 @@ import com.tonal.trainer.utils.cast
 import kotlin.properties.ReadOnlyProperty
 import kotlin.reflect.KProperty
 
+/**
+ * Create bindings for a view similar to bindView.
+ *
+ * To use, just call:
+ * private val binding: FHomeWorkoutDetailsBinding by viewBinding()
+ * with your binding class and access it as you normally would.
+ */
+inline fun <reified T : ViewBinding> ViewGroup.viewBinding() = ViewBindingDelegate(T::class.java, this)
+
 class ViewBindingDelegate<T : ViewBinding>(
     private val bindingClass: Class<T>,
     val fragment: ViewGroup
@@ -24,13 +33,4 @@ class ViewBindingDelegate<T : ViewBinding>(
         }
         return binding!!
     }
-}
-
-/**
- * Create bindings for a view similar to bindView.
- *
- * To use, just call:
- * private val binding: FHomeWorkoutDetailsBinding by viewBinding()
- * with your binding class and access it as you normally would.
- */
-inline fun <reified T : ViewBinding> ViewGroup.viewBinding() = ViewBindingDelegate(T::class.java, this)
+}
diff --git a/FragmentA.kt b/FragmentA.kt
@@ -0,0 +1,17 @@
+class WifiNetworksFragment : TonalFragment(R.layout.wifi_networks_fragment) {
+    private val binding: WifiNetworksFragmentBinding by viewBinding()
+
+  ...
+}
+
+class WifiNetworkView @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null,
+    defStyleAttr: Int = 0,
+    defStyleRes: Int = 0
+) : FrameLayout(context, attrs, defStyleAttr, defStyleRes) {
+    // This does the inflate too.
+    private val binding: WifiNetworkViewBinding by viewBinding()
+
+  ...
+}
diff --git a/FragmentViewBindingDelegate.kt b/FragmentViewBindingDelegate.kt
@@ -0,0 +1,61 @@
+import android.os.Handler
+import android.os.Looper
+import android.view.View
+import androidx.fragment.app.Fragment
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleObserver
+import androidx.lifecycle.OnLifecycleEvent
+import androidx.viewbinding.ViewBinding
+import com.tonal.trainer.utils.cast
+import kotlin.properties.ReadOnlyProperty
+import kotlin.reflect.KProperty
+
+class FragmentViewBindingDelegate<T : ViewBinding>(
+    private val bindingClass: Class<T>,
+    val fragment: Fragment
+) : ReadOnlyProperty<Fragment, T> {
+    private val clearBindingHandler by lazy(LazyThreadSafetyMode.NONE) { Handler(Looper.getMainLooper()) }
+    private var binding: T? = null
+
+    private val bindMethod = bindingClass.getMethod("bind", View::class.java)
+
+    init {
+        fragment.viewLifecycleOwnerLiveData.observe(fragment) { viewLifecycleOwner ->
+            viewLifecycleOwner.lifecycle.addObserver(object : LifecycleObserver {
+                @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
+                fun onDestroy() {
+                    // Lifecycle listeners are called before onDestroyView in a Fragment.
+                    // However, we want views to be able to use bindings in onDestroyView
+                    // to do cleanup so we clear the reference one frame later.
+                    clearBindingHandler.post { binding = null }
+                }
+            })
+        }
+    }
+
+    override fun getValue(thisRef: Fragment, property: KProperty<*>): T {
+        // onCreateView may be called between onDestroyView and next Main thread cycle.
+        // In this case [binding] refers to the previous fragment view. Check that binding's root view matches current fragment view
+        if (binding != null && binding?.root !== thisRef.view) {
+            binding = null
+        }
+        binding?.let { return it }
+
+        val lifecycle = fragment.viewLifecycleOwner.lifecycle
+        if (!lifecycle.currentState.isAtLeast(Lifecycle.State.INITIALIZED)) {
+            error("Cannot access view bindings. View lifecycle is ${lifecycle.currentState}!")
+        }
+
+        binding = bindMethod.invoke(null, thisRef.requireView()).cast<T>()
+        return binding!!
+    }
+}
+
+/**
+ * Create bindings for a view similar to bindView.
+ *
+ * To use, just call
+ * private val binding: FHomeWorkoutDetailsBinding by viewBinding()
+ * with your binding class and access it as you normally would.
+ */
+inline fun <reified T : ViewBinding> Fragment.viewBinding() = FragmentViewBindingDelegate(T::class.java, this)
diff --git a/ViewViewBindingDelegate.kt b/ViewViewBindingDelegate.kt
@@ -0,0 +1,36 @@
+import android.view.LayoutInflater
+import android.view.ViewGroup
+import androidx.viewbinding.ViewBinding
+import com.tonal.trainer.utils.cast
+import kotlin.properties.ReadOnlyProperty
+import kotlin.reflect.KProperty
+
+class ViewBindingDelegate<T : ViewBinding>(
+    private val bindingClass: Class<T>,
+    val fragment: ViewGroup
+) : ReadOnlyProperty<ViewGroup, T> {
+    private var binding: T? = null
+
+    override fun getValue(thisRef: ViewGroup, property: KProperty<*>): T {
+        binding?.let { return it }
+
+        try {
+            val inflateMethod = bindingClass.getMethod("inflate", LayoutInflater::class.java, ViewGroup::class.java, Boolean::class.javaPrimitiveType)
+            binding = inflateMethod.invoke(null, LayoutInflater.from(thisRef.context), thisRef, true).cast<T>()
+        } catch (e: NoSuchMethodException) {
+            // <merge> tags don't have the boolean parameter.
+            val inflateMethod = bindingClass.getMethod("inflate", LayoutInflater::class.java, ViewGroup::class.java)
+            binding = inflateMethod.invoke(null, LayoutInflater.from(thisRef.context), thisRef).cast<T>()
+        }
+        return binding!!
+    }
+}
+
+/**
+ * Create bindings for a view similar to bindView.
+ *
+ * To use, just call:
+ * private val binding: FHomeWorkoutDetailsBinding by viewBinding()
+ * with your binding class and access it as you normally would.
+ */
+inline fun <reified T : ViewBinding> ViewGroup.viewBinding() = ViewBindingDelegate(T::class.java, this)
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