进击的RecyclerView之入门

虽然RecyclerView面世有一段时间了，但由于它的学习成本相对较高，很多码友只是粗略的认识了一下而没有细致的品味RecyclerView的真谛。

那么从现在开始我将带你装逼带你飞，一起领略Google工程师们赋予RecyclerView独特的魅力。

首先我们看一下官方文档是怎么介绍RecyclerView的简介：

A flexible view for providing a limited window into a large data set.

Google的工程师写文档还真够精辟的，写的什么鬼？这不等于没写吗？OK，别激动，我们慢慢来。先看看怎么样把RecyclerView跑起来？

接下来简单写一个使用RecyclerView加载网络图片的demo。

布局文件如下：

<?xml version="1.0" encoding="utf-8"?><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="com.zqlite.android.recyclerviewadvance.MainActivity">    <android.support.v7.widget.RecyclerView        android:id="@+id/recyclerView"        android:layout_width="match_parent"        android:layout_height="match_parent">    </android.support.v7.widget.RecyclerView></RelativeLayout>

Activity文件如下：

package com.zqlite.android.recyclerviewadvance;import android.media.Image;import android.os.Handler;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.widget.CardView;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.Gravity;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;import android.widget.LinearLayout;import com.squareup.picasso.Picasso;import java.util.ArrayList;import java.util.List;import java.util.Random;public class MainActivity extends AppCompatActivity {    private RecyclerView recyclerView;    private Handler handler = new Handler();    public static final int ADD_DATA_DURATION = 2000;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initView();    }    private void initView(){        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);        final RecyclerView.LayoutManager layoutManager = new GridLayoutManager(this,3);        recyclerView.setLayoutManager(layoutManager);        recyclerView.setHasFixedSize(true);        RecyclerView.ItemAnimator itemAnimator = new DefaultItemAnimator();        recyclerView.setItemAnimator(itemAnimator);        final MyAdapter adapter = new MyAdapter();        recyclerView.setAdapter(adapter);        handler.postDelayed(new Runnable() {            @Override            public void run() {                adapter.addData();                handler.postDelayed(this, ADD_DATA_DURATION);                layoutManager.scrollToPosition(adapter.getSize());            }        },ADD_DATA_DURATION);    }    private class MyAdapter extends RecyclerView.Adapter{        private final String[] imageUrlArray = {                "http://o6p4e1uhv.bkt.clouddn.com/tu24967_22.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/cce4b48f8c5494ee7008eb9528f5e0fe98257eca.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/tu25422_4.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/ad7fd688d43f879424026deed01b0ef41ad53a2e.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/tu25422_6.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/refsdg.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/ggfnvbn.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/sghgfsh.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/asfasdf.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/fsbgbsfg.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/gsfdtrysrtsfdg.jpg",                "http://o6p4e1uhv.bkt.clouddn.com/sdfgsrters.jpg"};        private List<String> datas = new ArrayList<>();        public MyAdapter(){        }        public void addData(){            Random random = new Random();            datas.add(imageUrlArray[random.nextInt(imageUrlArray.length)]);            notifyItemInserted(datas.size());        }        public int getSize(){            return datas.size();        }        @Override        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {            RecyclerView.LayoutParams reLP = new RecyclerView.LayoutParams(RecyclerView.LayoutParams.MATCH_PARENT,RecyclerView.LayoutParams.WRAP_CONTENT);            reLP.setMargins(20, 20, 20, 20);            CardView cardView = new CardView(parent.getContext());            cardView.setLayoutParams(reLP);            CardView.LayoutParams cLP = new CardView.LayoutParams(parent.getMeasuredWidth()/3,(int)(parent.getMeasuredWidth()/3*1.3));            ImageView imageView = new ImageView(parent.getContext());            imageView.setLayoutParams(cLP);            imageView.setScaleType(ImageView.ScaleType.FIT_XY);            cardView.addView(imageView);            MyHolder holder = new MyHolder(cardView);            return holder;        }        @Override        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {            MyHolder myHolder = (MyHolder)holder;            ImageView imageView = myHolder.imageView;            Picasso.with(imageView.getContext()).load(datas.get(position)).into(imageView);        }        @Override        public int getItemCount() {            return datas.size();        }        private class MyHolder extends RecyclerView.ViewHolder{            public ImageView imageView ;            public MyHolder(View itemView) {                super(itemView);                imageView = (ImageView) ((CardView)itemView).getChildAt(0);            }        }    }}

使用RecyclerView以下几个东西是必备的：
1. RecyclerView.LayoutManager
2. RecyclerView.Adapter
其中LayoutManager负责布局，Adapter负责数据集。
该demo运行结果如下：

后面我们对RecyclerView的研究就给予这个demo，demo完整源码地址：
https://github.com/ZhangQinglian/RecyclerViewAdvance