Material Design之RecyclerView的使用（一）

• setLayoutManager设置RecyclerView的布局管理器。默认给我们提供了三种： LinearLayoutManager、GridLayoutManager、StaggeredGridLayoutManager。

  当然也能够继承LayoutManager来自己定义。

• setItemAnimator  设置item的加入、删除动画效果。默认给我们提供了一种默认动画效果：DefaultItemAnimator。同理也能够我们自己自己定义想要的动画效果。
• addItemDecoration  加入item之间的分隔线，默认没有提供类给我们使用。假设须要使用到切割线则须要我们自己定义。

• setAdapter设置RecyclerView的适配器。这个须要我们自己继承RecyclerView.Adapter来实现。
• RecyclerView中默认没有提供onItemClick和onItemLongClick点击事件方法。须要我们自己在适配器中写接口来实现。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?attr/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        />

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/toolbar"
        android:scrollbars="none" />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:background="@drawable/recyclerview_item"
    android:layout_margin="10dp"
    android:orientation="vertical"
    android:layout_height="72dp">
    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:padding="20dp"
        android:layout_height="72dp"
        android:textAppearance="?
android:attr/textAppearanceLarge" />
</LinearLayout>

public class MainActivity extends AppCompatActivity {
    private Toolbar mToolbar;
    private RecyclerView mRecyclerView;
    private List<String> lists;
    private MyAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mToolbar = (Toolbar)this.findViewById(R.id.toolbar);
        setSupportActionBar(mToolbar);
        initData();
        mRecyclerView = (RecyclerView) this.findViewById(R.id.recyclerView);
//        mRecyclerView.setHasFixedSize(true);//假设能够确定每一个item的高度是固定的。设置这个选项能够提高性能

        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));//设置RecyclerView的布局管理
//      mRecyclerView.addItemDecoration();//设置RecyclerView中item的切割线，用的少。一般都用在item中设置margin分隔两个item
        mRecyclerView.setItemAnimator(new DefaultItemAnimator());//设置item的加入删除动画，採用默认的动画效果
        adapter = new MyAdapter(this,lists);
        mRecyclerView.setAdapter(adapter);//设置Adapter
        adapter.setOnItemClickListener(new MyAdapter.OnItemClickListener() {//加入监听器
            @Override
            public void onItemClick(View view, int postion) {
                Toast.makeText(MainActivity.this,"点击的是："+postion,Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onItemLongClick(View view, int postion) {
                Toast.makeText(MainActivity.this, "长按的是：" + postion, Toast.LENGTH_SHORT).show();
            }
        });
    }
    private void initData(){
        lists = new ArrayList<String>();
        for (int i = ‘A‘; i < ‘z‘; i++)
        {
            lists.add(""+(char)i);
        }
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        switch (id){
            case R.id.action_add:
                lists.add(1, "add");
//                adapter.notifyDataSetChanged();//用这个则能够更新数据。可是没有动画效果
                adapter.notifyItemInserted(1);//注意：RecyclerView中加入用notifyItemInserted()。才有动画效果
                break;
            case R.id.action_delete:
                lists.remove(1);
                adapter.notifyItemRemoved(1);//RecyclerView中删除用notifyItemRemoved()；才有动画效果
                break;
            case R.id.action_linear:
                mRecyclerView.setLayoutManager(new LinearLayoutManager(this));//设置RecyclerView的GridLayoutManager布局管理,默认垂直，另一个设置水平排列的构造方法
                break;
            case R.id.action_grid:
                mRecyclerView.setLayoutManager(new GridLayoutManager(this,3));//设置RecyclerView的GridLayoutManager布局管理，默觉得垂直
                break;
            case R.id.action_grid_horizontal:
                mRecyclerView.setLayoutManager(new GridLayoutManager(this,3,GridLayoutManager.HORIZONTAL,false));//设置RecyclerView的GridLayoutManager的水平布局管理，參数分别为context，列数或行数，排列方式，是否反转布局的内容
                break;
            case R.id.action_staggeredgrid:
                mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL));//设置RecyclerView的StaggeredGridLayoutManager的布局管理，它是GridLayout升级版，能够显示交错式网格布局。參数分别为列数或行数，排列方式
                break;
        }
        return super.onOptionsItemSelected(item);
    }
}

/**
 * 继承RecyclerView的Adapter，它会强制开发人员使用ViewHolder模式,所以继承适配器的时候传入的泛型是一个继承自ViewHolder的实现类
 * 只是RecyclerView中没有提供给我们Click和onLongClick监听器，须要我们自己实现
 */
public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> {

    private Context context;
    private List<String> lists;
    private OnItemClickListener mOnItemClickListener;

    public interface OnItemClickListener {
        void onItemClick(View view, int postion);

        void onItemLongClick(View view, int postion);
    }

    public void setOnItemClickListener(OnItemClickListener listener) {//对外提供的一个监听方法
        this.mOnItemClickListener = listener;
    }

    public MyAdapter(Context context, List<String> lists) {
        this.context = context;
        this.lists = lists;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {//创建一个ViewHolder
        View itemView = LayoutInflater.from(context).inflate(R.layout.item, viewGroup, false);//填充这个item布局
        MyViewHolder viewHolder = new MyViewHolder(itemView);//创建ViewHolder
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(final MyViewHolder myViewHolder, int pos) {//绑定ViewHolder
        myViewHolder.mTextView.setText(lists.get(pos));//为ViewHolder里的控件设置值
        if (mOnItemClickListener != null) {//假设设置了监听那么它就不为空，然后回调对应的方法
            myViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    int postion = myViewHolder.getLayoutPosition();//得到当前点击item的位置postion
                    mOnItemClickListener.onItemClick(myViewHolder.itemView, postion);
                }
            });
            myViewHolder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    int postion = myViewHolder.getLayoutPosition();
                    mOnItemClickListener.onItemLongClick(myViewHolder.itemView, postion);
                    return true;
                }
            });
        }

    }

    @Override
    public int getItemCount() {
        return lists.size();
    }
}

class MyViewHolder extends RecyclerView.ViewHolder {
    TextView mTextView;

    public MyViewHolder(View itemView) {
        super(itemView);
        mTextView = (TextView) itemView.findViewById(R.id.textView);
    }
}