RecyclerView

更加强大的滚动控件 RecyclerView #P123

基本用法

• 需要在build.gradle添加依赖库 recyclerview
• activity_main.xml文件添加RecyclerView
• 图片,Furit类,fruit_item.xml

• 新建FruitAdapter类,作为适配器,继承自RecyclerView.Adapter ,并且泛型指定为FruitAdapter.ViewHolder ViewHolder是内部类
  xml
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />


  新建FruitAdapter

  1. 定义内部类ViewHoler ,继承自RecyclerView.ViewHolder
  2. ViewHoler的构造函数传入一个View参数,这个参数通常就是RecyclerView子项的最外层布局,通过findViewById() 方法来获取布局中的Imageiew和TextView的实例
  3. FruitAdapter 中也有构造函数,这个方法用于把要展示的数据源传进来,并赋值给一个全部变量mFruitList

  4. FruitAdapter继承自RecyclerView.Adapter,所以要重写onCreatViewHolder(),onBingViewHolder(),getItemCount()

     1. onCreatViewHolder()用来创建ViewHolder实例,将fruit_item布局加载进来,然后创建一个ViewHoler实例,并把加载出来的布局传入构造函数中,最后将ViewHoler的实例返回
     2. onBingViewHolder()用于对RecyclerView子项的数据进行赋值,会在每个子项被滚动到屏幕内的时候执行,通过position 参数得到当前项的Fruit实例,然后将数据设置到ViewHolder的ImageView和TextView当中即可
     3. getItemCount() 告诉RecyclerView有多少子项 ,返回 mFruitList.size()
        

        public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {private List<Fruit> mFruitList;/** * Created by Mason on 2017/11/16. */static class ViewHolder extends RecyclerView.ViewHolder {    ImageView fruitImage;    TextView fruitName;    public ViewHolder(View view) {        super(view);        fruitImage = (ImageView) view.findViewById(R.id.fruit_image);        fruitName = (TextView) view.findViewById(R.id.fruit_name);    }  }   public FruitAdapter(List<Fruit> fruitList) {    mFruitList = fruitList;}@Overridepublic ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item, parent, false);    ViewHolder holder = new ViewHolder(view);    return holder;}@Overridepublic void onBindViewHolder(ViewHolder holder, int position) {    Fruit fruit = mFruitList.get(position);    holder.fruitImage.setImageResource(fruit.getImageId());    holder.fruitName.setText(fruit.getName());}@Overridepublic int getItemCount() {    return mFruitList.size();}}

改变为横向RecyclerView

• fruit_item.xml 的LinearLayout布局改为orientation:"vertical" 垂直布局 ,默认horizontal水平布局
• 修改TextView和ImageView的layout_gravity 修改成水平居中center_horizontal

• MainActivity.java文件 调用LinearLayoutManager的setOrientation()方法设置布局排列方向 添加layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL)

  • xml
    “`xml
    

RecyclerView 点击事件

• 需要自己给子项具体的View注册点击事件
• 虽然比ListView繁琐,但是ListView给单独按钮注册事件更加繁琐
  
  1. 修改ViewHolder,添加fruitView变量来保存子项最外层布局的实例
  2. 然后在onCreatViewHolder()方法中注册点击事件就行了.
  3. 这里项目分别为最外层布局和Image注册了点击事件.

• RecyclerView强大在于,可以轻松实现子项中任意控件或布局的点击事件

  1. 我们先获取用户点击的position
  2. 通过position拿到相应的Fruit实例
  3. 再使用Toast弹出两种不同的内容
     

     public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {   private List<Fruit> mFruitList;   /**    * Created by Mason on 2017/11/16.    */   static class ViewHolder extends RecyclerView.ViewHolder {       View fruitView;  // 添加       ImageView fruitImage;       TextView fruitName;       public ViewHolder(View view) {           super(view);           fruitView = view;  //添加           fruitImage = (ImageView) view.findViewById(R.id.fruit_image);           fruitName = (TextView) view.findViewById(R.id.fruit_name);       }   }   public FruitAdapter(List<Fruit> fruitList) {       mFruitList = fruitList;   }   @Override   public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {       View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item, parent, false);       final ViewHolder holder = new ViewHolder(view);  // 添加       holder.fruitView.setOnClickListener(new View.OnClickListener() {           @Override           public void onClick(View v) {               int position = holder.getAdapterPosition();               Fruit fruit = mFruitList.get(position);               Toast.makeText(v.getContext(), "you click view   " + fruit.getName(), Toast.LENGTH_SHORT).show();           }       });       holder.fruitImage.setOnClickListener(new View.OnClickListener() {           @Override           public void onClick(View v) {               int position = holder.getAdapterPosition();               Fruit fruit = mFruitList.get(position);               Toast.makeText(v.getContext(), "you click image   " + fruit.getName(), Toast.LENGTH_SHORT).show();           }       });       return holder;   }   ...}

  这是我学习Android的笔记,参考书<<第一行代码-第二版>>,感谢郭霖大神
  如有不足之处,可以一起讨论
  附上郭霖的blog http://blog.csdn.net/guolin_blog