RecyclerView详解

public class RecyclerView extends ViewGroup implements ScrollingView, NestedScrollingChild {

由上面的继承结构，我们容易看出，RecyclerView实际上也是一个ViewGroup继承了ScrollingView和NestedScrolling，方便实现横向与纵向滑动。

RecyclerView是support-v7包中的新组件，是一个强大的滑动组件，与经典的ListView相比，同样拥有item回收复用的功能，但是直接把viewholder的实现封装起来，用户只要实现自己的viewholder就可以了，该组件会自动帮你回收复用每一个item。

RecyclerView的优点：

1.它不关心item是否显示的位置与方式    ---> layoutManager   我们可以仅仅使用layoutManager一句话就可以切换RecyclerView的样式

2.它不关心item如何分割         --->ItemDecoration   我们可以根据自己项目的需要自定义自己的分割线

3.它不关心item增加与删除动画的效果 --->ItemAnimator
 我们可以根据自己的需要定义item的增加与删除动画

4.仅仅关心如何服用view --->ViewHolder        google强制我们使用viewHolder，我们需要自己定义自己的ViewHolder哦。

RecyclerView的缺点：

1.内部没有实现对单个Item点击事件的监听，需要自己定义item的单击和长按事件。

2.对item增加后的position测量不准确，需要在adapter中使用holer.getLayoutPosition()方法获取。

由上我们不难看出，RecyclerView的优点远远大于它的缺点啊，再说它的缺点也不算缺点啊，都有很好的解决办法，那么我们还有什么理由不是哟不过它呢？

SO，我们开始吧。

首先，我们需要引入官方提供的向下兼容的V7包，具体引入方法，这里不再赘述。

下一步在xml文件中引入 RecyclerView。

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

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
         />

</RelativeLayout>

MainActivity

package com.flyou.henucenter.recycterview;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;

import com.flyou.henucenter.recycterview.adpater.RecyclerViewAdapter;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private RecyclerViewAdapter recyclerViewAdapter;
    private List<String> datas;
    private RecyclerView recyclerview;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initdate();
        initView();
    }

    private void initdate() {
        datas = new ArrayList<>();
        for (int i = 'A'; i < 'z'; i++) {

            datas.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) {
            //Gridview
            case R.id.action_Gridview:
                GridLayoutManager gridLayoutManager = new GridLayoutManager(this, 4, GridLayoutManager.VERTICAL, false);
                recyclerview.setLayoutManager(gridLayoutManager);
                break;
            case R.id.action_Listview:
                LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);

                recyclerview.setLayoutManager(linearLayoutManager);
                break;

            case R.id.action_hor_GridView:
                GridLayoutManager hor_gridLayoutManager = new GridLayoutManager(this, 4, GridLayoutManager.HORIZONTAL, false);
                recyclerview.setLayoutManager(hor_gridLayoutManager);
                break;
            case R.id.action_pubu:
                break;

            case R.id.action_add:
                recyclerViewAdapter.add(1);
                break;
            case R.id.action_delete:

                recyclerViewAdapter.delete(1);
                break;
        }

        return super.onOptionsItemSelected(item);
    }

    private void initView() {
        recyclerview = (RecyclerView) findViewById(R.id.recyclerview);
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        recyclerview.setLayoutManager(layoutManager);
//        recyclerview.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL_LIST));

        recyclerview.setItemAnimator(new DefaultItemAnimator());
        recyclerViewAdapter = new RecyclerViewAdapter(datas, this);
        recyclerview.setAdapter(recyclerViewAdapter);
        recyclerViewAdapter.setOnItemClickListener(new RecyclerViewAdapter.OnItemClickListener() {
            @Override
            public void onItemClick(View view, int Position) {
                Toast.makeText(MainActivity.this, "itemClick" + Position, Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onItemLongClick(View view, int Position) {

                Toast.makeText(MainActivity.this, "ItemLongClick" + Position, Toast.LENGTH_SHORT).show();
            }
        });

    }
}

Adapter文件

package com.flyou.henucenter.recycterview.adpater;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import com.flyou.henucenter.recycterview.R;
import java.util.List;

/**
 * 项目名称:My Application
 *
 * 包名:com.flyou.henucenter.myapplication.adpater
 * 作者: flyou
 * 创建时间:15/8/19 11:42
 * 描述:
 */
public class RecyclerViewAdapter extends RecyclerView.Adapter<MyViewHolder> {
    private List<String> mDatas;
    private Context mContex;
    private LayoutInflater mInFlater;
//设置item的回调
    public interface OnItemClickListener {
        void onItemClick(View view, int Position);

        void onItemLongClick(View view, int Position);
    }

    private OnItemClickListener onItemClickListener;

    public void setOnItemClickListener(OnItemClickListener listener) {

        this.onItemClickListener = listener;
    }

    public RecyclerViewAdapter(List<String> datas, Context Contex) {
        this.mContex = Contex;
        this.mDatas = datas;
        mInFlater = LayoutInflater.from(mContex);
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInFlater.inflate(R.layout.item_view, parent, false);
        MyViewHolder viewHolder = new MyViewHolder(view);
        return viewHolder;
    }

    public void add(int pos) {
        mDatas.add(pos, "I am new item ");
        notifyItemInserted(pos);

    }

    public void delete(int pos) {

        mDatas.remove(pos);
        notifyItemRemoved(pos);
    }

    @Override
    public void onBindViewHolder(final MyViewHolder holder, final int position) {
        holder.textView.setText(mDatas.get(position));
        if (onItemClickListener != null) {
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    int layoutPosition = holder.getLayoutPosition();
                    onItemClickListener.onItemClick(holder.itemView,layoutPosition);
                }
            });
            holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    int layoutPosition = holder.getLayoutPosition();//增加或删除item使用这个方法获得其position
                    onItemClickListener.onItemLongClick(holder.itemView,layoutPosition);
                    return false;
                }
            });
        }
    }

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

class MyViewHolder extends RecyclerView.ViewHolder {
    TextView textView;

    public MyViewHolder(View itemView) {

        super(itemView);
        textView = (TextView) itemView.findViewById(R.id.textInfo);
    }

}

单个Item

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:background="@drawable/item_selector"
    android:layout_margin="3dp"
    android:layout_width="match_parent"
    android:layout_height="70dp"
    >

<TextView
    android:id="@+id/textInfo"
    android:gravity="center"
    android:layout_width="72dp"
    android:layout_height="match_parent" />

</RelativeLayout>

menu文件

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".MainActivity">

    <item
        android:id="@+id/action_Listview"
        android:orderInCategory="100"
        android:title="listview"
        app:showAsAction="never" />
    <item
        android:id="@+id/action_Gridview"
        android:orderInCategory="100"
        android:title="gridView"
        app:showAsAction="never" />
    <item
        android:id="@+id/action_hor_GridView"
        android:orderInCategory="100"
        android:title="hor_GridView"
        app:showAsAction="never" />
    <item
        android:id="@+id/action_pubu"
        android:orderInCategory="100"
        android:title="pubuliu"
        app:showAsAction="never" />
    <item
        android:id="@+id/action_add"
        android:orderInCategory="100"
        android:icon="@drawable/ic_menu_add"
        android:title="add"
        app:showAsAction="always" />
    <item
        android:id="@+id/action_delete"
        android:orderInCategory="100"
        android:icon="@drawable/ic_menu_delete"
        android:title="delete"
        app:showAsAction="always" />
</menu>

//设置回调接口，方便在调用出进行处理。

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

        void onItemLongClick(View view, int Position);
    }

    private OnItemClickListener onItemClickListener;

    public void setOnItemClickListener(OnItemClickListener listener) {

        this.onItemClickListener = listener;
    }

没有录制gif大家凑合着看效果。

当然，item的增加和删除是有动画的，大家也可以在github上所有相关的动画库进行使用

https://github.com/gabrielemariotti/RecyclerViewItemAnimators

上面给出其中一个比较出色的RecylerView库。

大家也可以根据自己的需要自行定制，ok就先介绍到这里。

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