安卓v7支持包下的ListView替代品————RecyclerView

RecyclerView这个控件也出来很久了，相信大家也学习的差不多了，如果还没学习的，或许我可以带领大家体验一把这个艺术般的控件。

项目已经同步至github：https://github.com/nanchen2251/recyclerViewDemo

据官方介绍，该控件是属于之间用的非常多的ListView和GridView的替代品，既然能替代用的如此普遍的它们，这自然有其该有的优势。

1）相对于ListView而言RecyclerView的优势体现在：

①封装了之前ListView的优化，封装了之前ViewHolder的复用，这样在自定义适配器的时候我们面向的不再是View，而是一个ViewHolder.

②提供了插板式的体验，高度解耦，异常灵活，针对每一项的显示抽取出了相应的类来控制每一个item的显示。若想实现网格视图或者瀑布流或者横向的ListView都可以通过制定不一样的LayoutManager来实现高大上的效果，这样就可以针对自己的业务逻辑随意发挥了。

③现在的RecyclerView对增删也有了动画的加入，并且你还可以自定义这些动画。

④对于Adaper适配器，现在刷新也增加了相应的方法，虽然之前的notifyDataSetChanged()同样可以实现这样的效果，但是每次刷新整个界面在数据多的时候必然会大大影响用户体验。所以Adapter增加了更新数据的方法notifyItemInserted和notifyItemRemoved，这样就可以在增删数据的时候只刷新被操作的Item,而且还加入了高大上的动画效果呢。

2）基本用法：

相信描述了这么多，你一定对这个神奇的控件迫不及待想尝试一波了。要用到这个RecyclerView很简单，首先在Gradle中添加支持包：

1	`compile` `'com.android.support:recyclerview-v7:24.0.0'`

下面就先来一个简单的用法，首先来Activity

package com.example.nanchen.recyclerviewdemo;
 
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.Toast;
 
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
 
public class MainActivity extends AppCompatActivity implements MyAdapter.OnRecyclerItemClickListener {
 
    private MyAdapter adapter;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.main_recycler);
        List<String> list = new ArrayList<>();
        for (int i = 0; i < 100; i++) {
//            list.add(String.format(Locale.CHINA, "第%03d条数据%s", i, i % 2 == 0 ? "" : "-----------------------"));
            list.add(String.format(Locale.CHINA, "第%03d条数据", i));
        }
        adapter = new MyAdapter(this, list);
        adapter.setOnRecyclerItemClickListener(this);
        recyclerView.setAdapter(adapter);
 
        DefaultItemAnimator animator = new DefaultItemAnimator();
        animator.setRemoveDuration(1000);
        recyclerView.setItemAnimator(animator);
        //recyclerView.addItemDecoration(new MyDividerItemDecoration(this,MyDividerItemDecoration.VERTICAL_LIST));
 
        //最后一个参数是反转布局一定是false,为true的时候为逆向显示，在聊天记录中可能会有使用
        //这个东西在显示后才会加载，不会像ScollView一样一次性加载导致内存溢出
        LinearLayoutManager layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        recyclerView.setLayoutManager(layoutManager);
 
        //        GridLayoutManager gridLayoutManager = new GridLayoutManager(this, 3);
        //        gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
        //            @Override
        //            public int getSpanSize(int position) {
        //                if (position == 0){
        //                    return 3;
        //                }
        //                return 1;
        //            }
        //        });
        //        recyclerView.setLayoutManager(gridLayoutManager);
 
//        StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL);
//        recyclerView.setLayoutManager(staggeredGridLayoutManager);
    }
 
    @Override
    public void OnRecyclerItemClick(RecyclerView parent, View view, int position, String data) {
        Toast.makeText(this, data, Toast.LENGTH_SHORT).show();
        adapter.remove(position);
    }
}

　　在上面的Activity代码中，可见，我们需要自己指定LayoutManager，代码中用的是LinearLayoutMagener，你可以试试其他的。

再看看Adapter,有一个对大多数人来说很悲催的是，我们的ListView中一定会有的点击事件，而RecyclerView并没有提供这样的方法，这些点击事件都是需要我们自己学的，我这里Adapter就简单的实现了下，点击就会删除该Item。

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package com.example.nanchen.recyclerviewdemo;
 
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 java.util.List;
 
/**
 * 自定义RecyclerView的Adapter
 * Created by 南尘 on 16-7-15.
 */
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> implements View.OnClickListener {
 
    private Context context;
    private List<String> list;
    private OnRecyclerItemClickListener listener;
    private RecyclerView recyclerView;
 
    public void setOnRecyclerItemClickListener(OnRecyclerItemClickListener listener) {
        this.listener = listener;
    }
 
    public MyAdapter(Context context, List<String> list) {
        this.context = context;
        this.list = list;
    }
 
    //在为RecyclerView提供数据的时候调用
    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);
        this.recyclerView = recyclerView;
    }
 
    @Override
    public void onDetachedFromRecyclerView(RecyclerView recyclerView) {
        super.onDetachedFromRecyclerView(recyclerView);
        this.recyclerView = null;
    }
 
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.item,parent,false);
        view.setOnClickListener(this);
        return new ViewHolder(view);
    }
 
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.text.setText(list.get(position));
    }
 
    @Override
    public int getItemCount() {
        return list.size();
    }
 
    @Override
    public void onClick(View v) {
        if (recyclerView != null && listener != null){
            int position = recyclerView.getChildAdapterPosition(v);
            listener.OnRecyclerItemClick(recyclerView,v,position,list.get(position));
        }
    }
 
    /**
     * 删除指定数据
     * @param position 数据位置
     */
    public void remove(int position){
        list.remove(position);
//        notifyDataSetChanged();
        notifyItemRemoved(position);//这样就只会删除这一条数据，而不会一直刷
 
    }
 
    /**
     * 插入数据
     * @param position 插入位置
     * @param data 插入的数据
     */
    public void insert(int position,String data){
        list.add(position,data);
        notifyItemInserted(position);
 
    }
 
    public static class ViewHolder extends RecyclerView.ViewHolder{
 
        private final TextView text;
 
        public ViewHolder(View itemView) {
            super(itemView);
            text = (TextView) itemView.findViewById(R.id.item_text);
        }
    }
 
 
    /**
     * 自定义RecyclerView的点击事件
     */
    interface OnRecyclerItemClickListener{
        void OnRecyclerItemClick(RecyclerView parent,View view,int position,String data);
    }
 
}

　　继承这个Adapter需要指定一个ViewHolder的泛型，当然这个ViewHolder通常是由我们作为一个静态类自己写的。其他这个就像我们之前ListView中的BaseAdapter一样。

自己还可以实现其他的点击事件。

下面看下Xml，第一个是主布局，第二个是每一个项的布局，我这里就简单只实现一个TextView了。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.nanchen.recyclerviewdemo.MainActivity">
 
    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/main_recycler"/>
 
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:orientation="vertical">
 
    <TextView
        android:id="@+id/item_text"
        android:textSize="30sp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

　　这样运行出来你估计就会看到没有分割线，那么分割线怎么弄呢，看下文档，需要我们自己去写，这个网上有很多。

上一个我看到过很多次的。

package com.example.nanchen.recyclerviewdemo;
 
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
 
/**
 * Created by 南尘 on 16-7-15.
 */
public class MyDividerItemDecoration extends RecyclerView.ItemDecoration {
    private static final int[] ATTRS = new int[]{
            android.R.attr. listDivider
    };
 
    public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;
 
    public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;
 
    private Drawable mDivider;
 
    private int mOrientation;
 
    public MyDividerItemDecoration(Context context, int orientation) {
        final TypedArray a = context.obtainStyledAttributes(ATTRS );
        mDivider = a.getDrawable(0);
        a.recycle();
        setOrientation(orientation);
    }
 
    public void setOrientation( int orientation) {
        if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {
            throw new IllegalArgumentException( "invalid orientation");
        }
        mOrientation = orientation;
    }
 
    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if (mOrientation == VERTICAL_LIST) {
            drawVertical(c, parent);
        } else {
            drawHorizontal(c, parent);
        }
    }
 
 
    public void drawVertical(Canvas c, RecyclerView parent) {
        final int left = parent.getPaddingLeft();
        final int right = parent.getWidth() - parent.getPaddingRight();
 
        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int top = child.getBottom() + params.bottomMargin;
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }
 
    public void drawHorizontal(Canvas c, RecyclerView parent) {
        final int top = parent.getPaddingTop();
        final int bottom = parent.getHeight() - parent.getPaddingBottom();
 
        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int left = child.getRight() + params.rightMargin;
            final int right = left + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }
 
    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        if (mOrientation == VERTICAL_LIST) {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        }else{
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        }
    }
}

　　这样使用的是系统的分割线。

这样在Style中可以自己更改。

<resources>
 
    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
         
        <item name="android:listDivider">@drawable/divider_bg</item>
    </style>
 
 
</resources>

　　自定义一个Drawble

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle" >
 
    <gradient
        android:centerColor="#ff00ff00"
        android:endColor="#ff0000ff"
        android:startColor="#ffff0000"
        android:type="linear" />
    <size android:height="4dp"/>
 
</shape>