Reset cached bindings

src/androidTest/kotlin/butterknife/ViewTest.kt

@@ -144,6 +144,19 @@ public class ViewTest : AndroidTestCase() {
     assertEquals(2, example.name.size)
   }
 
+  public fun testReset() {
+    class Example(context: Context) : FrameLayout(context) {
+      val name : View? by bindOptionalView(1)
+    }
+
+    val example = Example(getContext())
+    example.addView(viewWithId(1))
+    assertNotNull(example.name)
+    example.removeAllViews()
+    ButterKnife.reset(example)
+    assertNull(example.name)
+  }
+
   private fun viewWithId(id: Int) : View {
     val view = View(getContext())
     view.setId(id)

src/main/kotlin/butterknife/ButterKnife.kt

@@ -8,6 +8,8 @@ import android.support.v7.widget.RecyclerView.ViewHolder
 import android.view.View
 import android.view.ViewGroup
 import kotlin.properties.ReadOnlyProperty
+import java.util.WeakHashMap
+import java.util.Collections
 
 public fun <T : View> ViewGroup.bindView(id: Int): ReadOnlyProperty<Any, T> = ViewBinding(id)
 public fun <T : View> Activity.bindView(id: Int): ReadOnlyProperty<Any, T> = ViewBinding(id)
@@ -37,6 +39,12 @@ public fun <T : View> Fragment.bindOptionalViews(vararg ids: Int): ReadOnlyPrope
 public fun <T : View> SupportFragment.bindOptionalViews(vararg ids: Int): ReadOnlyProperty<Any, List<T>> = OptionalViewListBinding(ids)
 public fun <T : View> ViewHolder.bindOptionalViews(vararg ids: Int): ReadOnlyProperty<Any, List<T>> = OptionalViewListBinding(ids)
 
+object ButterKnife {
+  fun reset(target: Any) {
+    LazyRegistry.reset(target)
+  }
+}
+
 private fun findView<T : View>(thisRef: Any, id: Int): T? {
   [suppress("UNCHECKED_CAST")]
   return when (thisRef) {
@@ -50,39 +58,38 @@ private fun findView<T : View>(thisRef: Any, id: Int): T? {
   } as T?
 }
 
-private class ViewBinding<T : View>(val id: Int) : ReadOnlyProperty<Any, T> {
-  private val lazy = Lazy<T>()
-
-  override fun get(thisRef: Any, desc: PropertyMetadata): T = lazy.get {
-    findView<T>(thisRef, id)
-        ?: throw IllegalStateException("View ID $id for '${desc.name}' not found.")
-  }
+private class ViewBinding<T : View>(val id: Int) : LazyReadOnlyProperty<T>() {
+  override fun create(thisRef: Any, desc: PropertyMetadata): T =
+      findView<T>(thisRef, id)
+          ?: throw IllegalStateException("View ID $id for '${desc.name}' not found.")
 }
 
-private class OptionalViewBinding<T : View>(val id: Int) : ReadOnlyProperty<Any, T?> {
-  private val lazy = Lazy<T?>()
-
-  override fun get(thisRef: Any, desc: PropertyMetadata): T? = lazy.get {
-    findView<T>(thisRef, id)
-  }
+private class OptionalViewBinding<T : View>(val id: Int) : LazyReadOnlyProperty<T?>() {
+  override fun create(thisRef: Any, desc: PropertyMetadata): T? =
+      findView(thisRef, id)
 }
 
-private class ViewListBinding<T : View>(val ids: IntArray) : ReadOnlyProperty<Any, List<T>> {
-  private var lazy = Lazy<List<T>>()
+private class ViewListBinding<T : View>(val ids: IntArray) : LazyReadOnlyProperty<List<T>>() {
+  override fun create(thisRef: Any, desc: PropertyMetadata): List<T> =
+      ids.map { id -> findView<T>(thisRef, id)
+          ?: throw IllegalStateException("View ID $id for '${desc.name}' not found.")
+      }
+}
 
-  override fun get(thisRef: Any, desc: PropertyMetadata): List<T> = lazy.get {
-    ids.map { id -> findView<T>(thisRef, id)
-        ?: throw IllegalStateException("View ID $id for '${desc.name}' not found.")
-    }
-  }
+private class OptionalViewListBinding<T : View>(val ids: IntArray) : LazyReadOnlyProperty<List<T>>() {
+  override fun create(thisRef: Any, desc: PropertyMetadata): List<T> =
+      ids.map { id -> findView<T>(thisRef, id) }.filterNotNull()
 }
 
-private class OptionalViewListBinding<T : View>(val ids: IntArray) : ReadOnlyProperty<Any, List<T>> {
-  private var lazy = Lazy<List<T>>()
+private abstract class LazyReadOnlyProperty<T : Any?> : ReadOnlyProperty<Any, T> {
+  private val lazy: Lazy<T> = Lazy()
 
-  override fun get(thisRef: Any, desc: PropertyMetadata): List<T> = lazy.get {
-    ids.map { id -> findView<T>(thisRef, id) }.filterNotNull()
+  override fun get(thisRef: Any, desc: PropertyMetadata): T = lazy.get {
+    LazyRegistry.register(thisRef, lazy)
+    create(thisRef, desc)
   }
+
+  protected abstract fun create(thisRef: Any, desc: PropertyMetadata): T
 }
 
 private class Lazy<T> {
@@ -96,4 +103,20 @@ private class Lazy<T> {
     [suppress("UNCHECKED_CAST")]
     return value as T
   }
+
+  fun reset() {
+    value = EMPTY
+  }
+}
+
+private object LazyRegistry {
+  private val lazyMap = WeakHashMap<Any, MutableCollection<Lazy<*>>>()
+
+  fun register(target: Any, lazy: Lazy<*>) {
+    lazyMap.getOrPut(target, { Collections.newSetFromMap(WeakHashMap()) }).add(lazy)
+  }
+
+  fun reset(target: Any) {
+    lazyMap.get(target)?.forEach { it.reset() }
+  }
 }