RecyclerView的使用

什么是RecyclerView

RecyclerView是Android 5.0 materials design中的组件之一，相应的还有CardView、Palette等。看名字我们就能看出一点端倪，没错，它主要的特点就是复用。我们知道，Listview中的Adapter中可以实现ViewHolder的复用。RecyclerView提供了一个耦合度更低的方式来复用ViewHolder，并且可以轻松的实现ListView、GridView以及瀑布流的效果。

RecyclerView的用法

首先我们要gradle的依赖库中添加  compile 'com.android.support:recyclerview-v7:21.+'  。如果是eclipse直接导入android-support-v7-recyclerview.jar就可以了。

/**
* 设置Adapter
*/
mRecyclerView.setAdapter(mListAdapter);
/**
* 设置布局管理器
*/
mRecyclerView.setLayoutManager(linearLayoutManager);
/**
* 设置item分割线
*/
mRecyclerView.addItemDecoration(itemDecoration);
/**
* 设置item动画
*/
mRecyclerView.setItemAnimator(new DefaultItemAnimator());

使用RecyclerView，基本上要上面四步。相比ListView只需设置Adapter而言，RecyclerView的使用看起来似乎要复杂一些。但是它的可定制性更高了，你可以自己定制自己的分割线样式或者是item的的动画。

下面我们看下如何使用RecyclerView简单实现ListView的效果。
activity:

package com.bbk.lling.recyclerview;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
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 java.util.ArrayList;
import java.util.List;

/**
 * @Class: ListLayoutActivity
 * @Description: RecycleView实现listview的功能
 * @author: lling(www.liuling123.com)
 * @Date: 2015/10/29
 */
public class ListLayoutActivity extends ActionBarActivity {

    private RecyclerView mRecyclerView;
    private ListAdapter mListAdapter;
    private List<String> mDatas;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list_layout);
        initData();
        mRecyclerView = (RecyclerView) findViewById(R.id.recyclerview);
        mListAdapter = new ListAdapter(this, mDatas);
        mListAdapter.setOnItemClickListener(new ListAdapter.OnItemClickListener() {
            @Override
            public void onItemClick(View view, int position) {
                Toast.makeText(ListLayoutActivity.this, "Click" + mDatas.get(position), Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onItemLongClick(View view, int position) {
                mListAdapter.remove(position); //remove the item
                Toast.makeText(ListLayoutActivity.this, "LongClick" + mDatas.get(position), Toast.LENGTH_SHORT).show();
            }
        });
        mRecyclerView.setAdapter(mListAdapter);
        /**
         * 设置布局管理器，listview风格则设置为LinearLayoutManager
         * gridview风格则设置为GridLayoutManager
         * pu瀑布流风格的设置为StaggeredGridLayoutManager
         */
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        // 设置item分
        mRecyclerView.addItemDecoration(new ListItemDecoration(this, LinearLayoutManager.VERTICAL));
        // 设置item动画
        mRecyclerView.setItemAnimator(new DefaultItemAnimator());

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_list_layout, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.add_first:
                mListAdapter.add(0, "add first");
                break;
            case R.id.add_last:
                mListAdapter.add(mListAdapter.getItemCount(), "add last");
                break;
            case R.id.remove_first:
                String value = mListAdapter.remove(0);
                Toast.makeText(ListLayoutActivity.this, "remove:" + value, Toast.LENGTH_SHORT).show();
                break;
            case R.id.remove_last:
                String value1 =  mListAdapter.remove(mListAdapter.getItemCount()-1);
                Toast.makeText(ListLayoutActivity.this, "remove:" + value1, Toast.LENGTH_SHORT).show();
                break;
            case R.id.horizontal:
                mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));
                mRecyclerView.addItemDecoration(new ListItemDecoration(this, LinearLayoutManager.HORIZONTAL));
                break;
            case R.id.vertical:
                mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
                mRecyclerView.addItemDecoration(new ListItemDecoration(this, LinearLayoutManager.VERTICAL));
                break;
        }
        return super.onOptionsItemSelected(item);
    }

     /* ==========This Part is not necessary========= */

    /**
     * Create datas
     */
    protected void initData() {
        mDatas = new ArrayList<String>();
        for (int i = 0; i < 100; i++) {
            mDatas.add(String.valueOf(i));
        }
    }

    /* ==========This Part is not necessary========= */
}

activity布局：

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

Adapter：

package com.bbk.lling.recyclerview;

import android.annotation.SuppressLint;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.List;

/**
 * @Class: ListAdapter
 * @Description: 数据适配器
 * @author: lling(www.liuling123.com)
 * @Date: 2015/10/29
 */
public class ListAdapter extends RecyclerView.Adapter<ListAdapter.ItemViewHolder> {

    private List<String> mDatas;
    private LayoutInflater mInflater;
    private OnItemClickListener mOnItemClickListener;

    public ListAdapter(Context context, List<String> mDatas) {
        this.mDatas = mDatas;
        mInflater = LayoutInflater.from(context);
    }

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

    @SuppressLint("NewApi")
    @Override
    public void onBindViewHolder(final ItemViewHolder itemViewHolder, final int i) {
        itemViewHolder.mTextView.setText(mDatas.get(i));
        if(mOnItemClickListener != null) {
            /**
             * 这里加了判断，itemViewHolder.itemView.hasOnClickListeners()
             * 目的是减少对象的创建，如果已经为view设置了click监听事件,就不用重复设置了
             * 不然每次调用onBindViewHolder方法，都会创建两个监听事件对象，增加了内存的开销
             */
            if(!itemViewHolder.itemView.hasOnClickListeners()) {
                Log.e("ListAdapter", "setOnClickListener");
                itemViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        int pos = itemViewHolder.getPosition();
                        mOnItemClickListener.onItemClick(v, pos);
                    }
                });
                itemViewHolder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
                    @Override
                    public boolean onLongClick(View v) {
                        int pos = itemViewHolder.getPosition();
                        mOnItemClickListener.onItemLongClick(v, pos);
                        return true;
                    }
                });
            }
        }
    }

    @Override
    public ItemViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
        /**
         * 使用RecyclerView，ViewHolder是可以复用的。这根使用ListView的VIewHolder复用是一样的
         * ViewHolder创建的个数好像是可见item的个数+3
         */
        Log.e("ListAdapter", "onCreateViewHolder");
        ItemViewHolder holder = new ItemViewHolder(mInflater.inflate(
                R.layout.item_layout, viewGroup, false));
        return holder;
    }

    /**
     * 向指定位置添加元素
     * @param position
     * @param value
     */
    public void add(int position, String value) {
        if(position > mDatas.size()) {
            position = mDatas.size();
        }
        if(position < 0) {
            position = 0;
        }
        mDatas.add(position, value);
        /**
         * 使用notifyItemInserted/notifyItemRemoved会有动画效果
         * 而使用notifyDataSetChanged()则没有
         */
        notifyItemInserted(position);
    }

    /**
     * 移除指定位置元素
     * @param position
     * @return
     */
    public String remove(int position) {
        if(position > mDatas.size()-1) {
            return null;
        }
        String value = mDatas.remove(position);
        notifyItemRemoved(position);
        return value;
    }

    public void setOnItemClickListener(OnItemClickListener mOnItemClickListener) {
        this.mOnItemClickListener = mOnItemClickListener;
    }

    /**
     * 处理item的点击事件和长按事件
     */
    interface OnItemClickListener {
        public void onItemClick(View view, int position);
        public void onItemLongClick(View view, int position);
    }

    class ItemViewHolder extends RecyclerView.ViewHolder {

        private TextView mTextView;

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

}

这里值得注意的是，RecyclerView并没有提供setOnItemClickListener方法来设置item的点击事件，所以这里我们自己来实现item的点击事件，这点很坑爹有木有？没有就自己设置呗！上面代码121-124定义了一个点击接口。然后给Adapter设置定义的接口对象，然后在onBindViewHolder中为每个holder设置点击事件就行了。但是有一点得注意，因为只要滑动 RecyclerView，onBindViewHolder就会不停的调用，如果不加判断的话，则会不停的创建新的点击事件对象，浪费内存，所以在设置点击事件之前需要判断一下是否已经设置过了（如上面代码46行），如果设置过了就不需要创建了。

item的布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/textview"
        android:layout_width="wrap_content"
        android:layout_height="48dp"
        android:minWidth="48dp"
        android:gravity="center"
        android:layout_centerInParent="true"
        android:text="XXX"/>
</RelativeLayout>

item分割线：

package com.bbk.lling.recyclerview;

import android.content.Context;
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;

/**
 * @Class: ListItemDecoration
 * @Description: listview的item分割线
 * @author: lling(www.liuling123.com)
 * @Date: 2015/10/29
 */
public class ListItemDecoration extends RecyclerView.ItemDecoration {

    private Drawable mDrawable;

    private final static int DEFAULT_ORENTATION = LinearLayoutManager.VERTICAL;

    private int mOrientation;

    public ListItemDecoration(Context context, int orientation) {
        if(orientation != LinearLayoutManager.HORIZONTAL && orientation != LinearLayoutManager.VERTICAL) {
            this.mOrientation = DEFAULT_ORENTATION;
        } else {
            this.mOrientation = orientation;
        }
        mDrawable = context.getResources().getDrawable(R.drawable.divider);
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if(mOrientation == LinearLayoutManager.HORIZONTAL) {
            drawHorizontal(c, parent);
        } else {
            drawVertical(c, parent);
        }
    }

    private void drawHorizontal(Canvas c, RecyclerView parent) {
        int top = parent.getPaddingTop();
        int bottom = parent.getHeight() - parent.getPaddingBottom();

        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            int left = child.getRight() + params.rightMargin;
            int right = left + mDrawable.getIntrinsicHeight();
            mDrawable.setBounds(left, top, right, bottom);
            mDrawable.draw(c);
        }
    }

    private void drawVertical(Canvas c, RecyclerView parent) {
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();

        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            android.support.v7.widget.RecyclerView v = new android.support.v7.widget.RecyclerView(parent.getContext());
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            int top = child.getBottom() + params.bottomMargin;
            int bottom = top + mDrawable.getIntrinsicHeight();
            mDrawable.setBounds(left, top, right, bottom);
            mDrawable.draw(c);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
    }
}

divider.xml：

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle" >
    <size android:height="1dp" android:width="1dp"/>
    <!--<solid android:color="#e0e0e0"/>-->
    <solid android:color="#ff0000"/>
</shape>

好了，ListView的效果已经实现了，看下效果图

RecyclerView实现GridView以及瀑布流效果的代码这里就不贴出来了，demo源码里面有，需要的可以下载看看。

demo源码下载：https://github.com/liuling07/RecyclerView

posted @ 2017-06-22 23:19 YouseiRaws 阅读(129) 评论(0) 编辑收藏举报

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RecyclerView的使用

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