Migrate RecyclerView.ViewHolder from Java to Kotlin

• Kotlin class properties 取代了 Java 构造器和通过构造器初始化的field;
• Kotlin class 继承父类时直接把参数传递给父类，类似 Java 构造器执行super(itemView);
• 构造器执行的初始化代码被移到了 init {} 代码块;
• Kotlin view binding 替代 ButterKnife

Java codes:

- public class ArticleItemViewHolder
-     extends RecyclerView.ViewHolder {
+ class ArticleItemViewHolder(
+         private val mItemView: View,
+         private val mImageLoader: BaseImageLoader
+ ) : RecyclerView.ViewHolder(mItemView) {

-    private View mItemView;
-    private BaseImageLoader mImageLoader;

-    private Consumer<View> mOnItemClickAction;
+    private var mOnItemClickAction: Consumer<View>? = null

-    @BindView(R.id.article_title_view)
-    TextView mTitleView;

-    public ArticleItemViewHolder(View itemView, BaseImageLoader imageLoader) {
-        super(itemView);
-        ButterKnife.bind(this, itemView);
-        itemView.setOnClickListener(...);
-        mItemView = itemView;
-        mImageLoader = imageLoader;
-    }

+    init {
+        itemView.setOnClickListener { // point4: lambda 表达式
+            mOnItemClickAction?.accept(mItemView.articleImageView)
+        }
+    }

-    public void bindArticle(ArticleItem articleItem) {
-        mTitleView.setText(articleItem.getTitle());
-    }
+    fun bindArticle(articleItem: ArticleItem) {
+        mItemView.articleTitleView.text = articleItem.title
+    }

2018-08-27 Weiyi Li