Add ViewDelegate that does not require ViewHolder (#296)

This PR adds a new & simple `ItemViewDelegate` called `ViewDelegate` that does not require to declare and provide a `RecyclerView.ViewHolder`.

* Add ViewDelegate that does not require ViewHolder

* [sample] Add RichView & RichViewDelegate

* Add a small guide about the data binding

* Remove the square_border for RichView

library/src/main/kotlin/com/drakeet/multitype/ViewDelegate.kt

@@ -0,0 +1,56 @@
+package com.drakeet.multitype
+
+
+import android.content.Context
+import android.view.View
+import android.view.ViewGroup
+import androidx.recyclerview.widget.RecyclerView
+
+/**
+ * This is a simple [ItemViewDelegate] that does not require to declare and provide a [RecyclerView.ViewHolder].
+ * @since v4.2.0
+ * @author Drakeet Xu
+ */
+abstract class ViewDelegate<T, V : View> : ItemViewDelegate<T, ViewDelegate.Holder<V>>() {
+
+  abstract fun onCreateView(context: Context): V
+
+  abstract fun onBindView(view: V, item: T)
+
+  // Override this function if you need a parent ViewGroup
+  open fun onCreateView(context: Context, parent: ViewGroup): V {
+    return onCreateView(context)
+  }
+
+  // Override this function if you need a ViewHolder
+  open fun onBindView(holder: Holder<V>, view: V, item: T) {
+    onBindView(view, item)
+  }
+
+  override fun onCreateViewHolder(context: Context, parent: ViewGroup): Holder<V> {
+    return Holder(onCreateView(context, parent))
+  }
+
+  override fun onBindViewHolder(holder: Holder<V>, item: T) = onBindView(holder, holder.view, item)
+
+  class Holder<V : View>(val view: V) : RecyclerView.ViewHolder(view)
+
+  /**
+   * Warning: this property can only get the correct value in an item root view.
+   * @see RecyclerView.LayoutParams.getViewLayoutPosition
+   */
+  protected val View.layoutPosition get() = recyclerLayoutParams.viewLayoutPosition
+
+  /**
+   * Warning: this property can only get the correct value in an item root view.
+   * @see RecyclerView.LayoutParams.getViewAdapterPosition
+   */
+  protected val View.adapterPosition get() = recyclerLayoutParams.viewAdapterPosition
+
+  /**
+   * RecyclerView will automatically convert any original type of LayoutParam into [RecyclerView.LayoutParams],
+   * so for the item root view, its final LayoutParam must be [RecyclerView.LayoutParams].
+   * @see RecyclerView.LayoutManager.generateLayoutParams
+   */
+  private val View.recyclerLayoutParams get() = layoutParams as RecyclerView.LayoutParams
+}

sample/src/main/kotlin/com/drakeet/multitype/sample/Numbers.kt

@@ -0,0 +1,8 @@
+package com.drakeet.multitype.sample
+
+import android.content.res.Resources
+
+/**
+ * @author Drakeet Xu
+ */
+val Number.dp: Int get() = (toInt() * Resources.getSystem().displayMetrics.density).toInt()

sample/src/main/kotlin/com/drakeet/multitype/sample/normal/NormalActivity.kt

@@ -38,7 +38,8 @@ class NormalActivity : MenuBaseActivity() {
 
     adapter.register(TextItemViewBinder())
     adapter.register(ImageItemViewBinder())
-    adapter.register(RichItemViewBinder())
+    // ✨✨✨
+    adapter.register(RichViewDelegate())
     recyclerView.adapter = adapter
 
     val textItem = TextItem("world")

sample/src/main/kotlin/com/drakeet/multitype/sample/normal/RichView.kt

@@ -0,0 +1,32 @@
+package com.drakeet.multitype.sample.normal
+
+import android.content.Context
+import android.graphics.Color
+import android.view.Gravity
+import android.view.ViewGroup.LayoutParams.WRAP_CONTENT
+import android.widget.LinearLayout
+import androidx.appcompat.widget.AppCompatImageView
+import androidx.appcompat.widget.AppCompatTextView
+import com.drakeet.multitype.sample.R
+import com.drakeet.multitype.sample.dp
+
+/**
+ * @author Drakeet Xu
+ */
+class RichView(context: Context) : LinearLayout(context) {
+
+  val imageView = AppCompatImageView(context).apply {
+    addView(this, LayoutParams(72.dp, 72.dp))
+  }
+
+  val textView = AppCompatTextView(context).apply {
+    setTextColor(Color.BLACK)
+    addView(this, LayoutParams(WRAP_CONTENT, WRAP_CONTENT))
+  }
+
+  init {
+    orientation = VERTICAL
+    gravity = Gravity.CENTER
+    setPadding(16.dp, 16.dp, 16.dp, 16.dp)
+  }
+}

sample/src/main/kotlin/com/drakeet/multitype/sample/normal/RichViewDelegate.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2016-present. Drakeet Xu
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.drakeet.multitype.sample.normal
+
+import android.content.Context
+import android.view.Gravity
+import android.view.ViewGroup
+import android.view.ViewGroup.LayoutParams.MATCH_PARENT
+import android.view.ViewGroup.LayoutParams.WRAP_CONTENT
+import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.RecyclerView.LayoutParams
+import com.drakeet.multitype.ViewDelegate
+import com.drakeet.multitype.sample.dp
+
+/**
+ * @author Drakeet Xu
+ */
+class RichViewDelegate : ViewDelegate<RichItem, RichView>() {
+
+  override fun onCreateView(context: Context): RichView {
+    return RichView(context).apply { layoutParams = LayoutParams(MATCH_PARENT, WRAP_CONTENT) }
+  }
+
+  override fun onBindView(view: RichView, item: RichItem) {
+    view.imageView.setImageResource(item.imageResId)
+    view.textView.text = item.text
+    // Or bind the data in the RichView by calling view.setRichItem(item)
+  }
+}