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  • 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。
     1 /**
 2 * 设置Adapter
 3 */
 4 mRecyclerView.setAdapter(mListAdapter);
 5 /**
 6 * 设置布局管理器
 7 */
 8 mRecyclerView.setLayoutManager(linearLayoutManager);
 9 /**
10 * 设置item分割线
11 */
12 mRecyclerView.addItemDecoration(itemDecoration);
13 /**
14 * 设置item动画
15 */
16 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:
      1 package com.bbk.lling.recyclerview;
  2 
  3 import android.support.v7.app.ActionBarActivity;
  4 import android.os.Bundle;
  5 import android.support.v7.widget.DefaultItemAnimator;
  6 import android.support.v7.widget.LinearLayoutManager;
  7 import android.support.v7.widget.RecyclerView;
  8 import android.view.Menu;
  9 import android.view.MenuItem;
 10 import android.view.View;
 11 import android.widget.Toast;
 12 
 13 import java.util.ArrayList;
 14 import java.util.List;
 15 
 16 /**
 17  * @Class: ListLayoutActivity
 18  * @Description: RecycleView实现listview的功能
 19  * @author: lling(www.liuling123.com)
 20  * @Date: 2015/10/29
 21  */
 22 public class ListLayoutActivity extends ActionBarActivity {
 23 
 24     private RecyclerView mRecyclerView;
 25     private ListAdapter mListAdapter;
 26     private List<String> mDatas;
 27 
 28     @Override
 29     protected void onCreate(Bundle savedInstanceState) {
 30         super.onCreate(savedInstanceState);
 31         setContentView(R.layout.activity_list_layout);
 32         initData();
 33         mRecyclerView = (RecyclerView) findViewById(R.id.recyclerview);
 34         mListAdapter = new ListAdapter(this, mDatas);
 35         mListAdapter.setOnItemClickListener(new ListAdapter.OnItemClickListener() {
 36             @Override
 37             public void onItemClick(View view, int position) {
 38                 Toast.makeText(ListLayoutActivity.this, "Click" + mDatas.get(position), Toast.LENGTH_SHORT).show();
 39             }
 40 
 41             @Override
 42             public void onItemLongClick(View view, int position) {
 43                 mListAdapter.remove(position); //remove the item
 44                 Toast.makeText(ListLayoutActivity.this, "LongClick" + mDatas.get(position), Toast.LENGTH_SHORT).show();
 45             }
 46         });
 47         mRecyclerView.setAdapter(mListAdapter);
 48         /**
 49          * 设置布局管理器，listview风格则设置为LinearLayoutManager
 50          * gridview风格则设置为GridLayoutManager
 51          * pu瀑布流风格的设置为StaggeredGridLayoutManager
 52          */
 53         mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
 54         // 设置item分
 55         mRecyclerView.addItemDecoration(new ListItemDecoration(this, LinearLayoutManager.VERTICAL));
 56         // 设置item动画
 57         mRecyclerView.setItemAnimator(new DefaultItemAnimator());
 58 
 59     }
 60 
 61     @Override
 62     public boolean onCreateOptionsMenu(Menu menu) {
 63         getMenuInflater().inflate(R.menu.menu_list_layout, menu);
 64         return true;
 65     }
 66 
 67     @Override
 68     public boolean onOptionsItemSelected(MenuItem item) {
 69         switch (item.getItemId()) {
 70             case R.id.add_first:
 71                 mListAdapter.add(0, "add first");
 72                 break;
 73             case R.id.add_last:
 74                 mListAdapter.add(mListAdapter.getItemCount(), "add last");
 75                 break;
 76             case R.id.remove_first:
 77                 String value = mListAdapter.remove(0);
 78                 Toast.makeText(ListLayoutActivity.this, "remove:" + value, Toast.LENGTH_SHORT).show();
 79                 break;
 80             case R.id.remove_last:
 81                 String value1 =  mListAdapter.remove(mListAdapter.getItemCount()-1);
 82                 Toast.makeText(ListLayoutActivity.this, "remove:" + value1, Toast.LENGTH_SHORT).show();
 83                 break;
 84             case R.id.horizontal:
 85                 mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));
 86                 mRecyclerView.addItemDecoration(new ListItemDecoration(this, LinearLayoutManager.HORIZONTAL));
 87                 break;
 88             case R.id.vertical:
 89                 mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
 90                 mRecyclerView.addItemDecoration(new ListItemDecoration(this, LinearLayoutManager.VERTICAL));
 91                 break;
 92         }
 93         return super.onOptionsItemSelected(item);
 94     }
 95 
 96      /* ==========This Part is not necessary========= */
 97 
 98     /**
 99      * Create datas
100      */
101     protected void initData() {
102         mDatas = new ArrayList<String>();
103         for (int i = 0; i < 100; i++) {
104             mDatas.add(String.valueOf(i));
105         }
106     }
107 
108     /* ==========This Part is not necessary========= */
109 }
     
    activity布局：
     1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent" >
 5 
 6     <android.support.v7.widget.RecyclerView
 7         android:id="@+id/recyclerview"
 8         android:layout_width="match_parent"
 9         android:layout_height="match_parent" />
10 
11 </RelativeLayout>
    Adapter：
      1 package com.bbk.lling.recyclerview;
  2 
  3 import android.annotation.SuppressLint;
  4 import android.content.Context;
  5 import android.support.v7.widget.RecyclerView;
  6 import android.util.Log;
  7 import android.view.LayoutInflater;
  8 import android.view.View;
  9 import android.view.ViewGroup;
 10 import android.widget.TextView;
 11 
 12 import java.util.List;
 13 
 14 /**
 15  * @Class: ListAdapter
 16  * @Description: 数据适配器
 17  * @author: lling(www.liuling123.com)
 18  * @Date: 2015/10/29
 19  */
 20 public class ListAdapter extends RecyclerView.Adapter<ListAdapter.ItemViewHolder> {
 21 
 22     private List<String> mDatas;
 23     private LayoutInflater mInflater;
 24     private OnItemClickListener mOnItemClickListener;
 25 
 26     public ListAdapter(Context context, List<String> mDatas) {
 27         this.mDatas = mDatas;
 28         mInflater = LayoutInflater.from(context);
 29     }
 30 
 31     @Override
 32     public int getItemCount() {
 33         return mDatas.size();
 34     }
 35 
 36     @SuppressLint("NewApi")
 37     @Override
 38     public void onBindViewHolder(final ItemViewHolder itemViewHolder, final int i) {
 39         itemViewHolder.mTextView.setText(mDatas.get(i));
 40         if(mOnItemClickListener != null) {
 41             /**
 42              * 这里加了判断，itemViewHolder.itemView.hasOnClickListeners()
 43              * 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
 44              * 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
 45              */
 46             if(!itemViewHolder.itemView.hasOnClickListeners()) {
 47                 Log.e("ListAdapter", "setOnClickListener");
 48                 itemViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
 49                     @Override
 50                     public void onClick(View v) {
 51                         int pos = itemViewHolder.getPosition();
 52                         mOnItemClickListener.onItemClick(v, pos);
 53                     }
 54                 });
 55                 itemViewHolder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
 56                     @Override
 57                     public boolean onLongClick(View v) {
 58                         int pos = itemViewHolder.getPosition();
 59                         mOnItemClickListener.onItemLongClick(v, pos);
 60                         return true;
 61                     }
 62                 });
 63             }
 64         }
 65     }
 66 
 67     @Override
 68     public ItemViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
 69         /**
 70          * 使用RecyclerView，ViewHolder是可以复用的。这根使用ListView的VIewHolder复用是一样的
 71          * ViewHolder创建的个数好像是可见item的个数+3
 72          */
 73         Log.e("ListAdapter", "onCreateViewHolder");
 74         ItemViewHolder holder = new ItemViewHolder(mInflater.inflate(
 75                 R.layout.item_layout, viewGroup, false));
 76         return holder;
 77     }
 78 
 79     /**
 80      * 向指定位置添加元素
 81      * @param position
 82      * @param value
 83      */
 84     public void add(int position, String value) {
 85         if(position > mDatas.size()) {
 86             position = mDatas.size();
 87         }
 88         if(position < 0) {
 89             position = 0;
 90         }
 91         mDatas.add(position, value);
 92         /**
 93          * 使用notifyItemInserted/notifyItemRemoved会有动画效果
 94          * 而使用notifyDataSetChanged()则没有
 95          */
 96         notifyItemInserted(position);
 97     }
 98 
 99     /**
100      * 移除指定位置元素
101      * @param position
102      * @return
103      */
104     public String remove(int position) {
105         if(position > mDatas.size()-1) {
106             return null;
107         }
108         String value = mDatas.remove(position);
109         notifyItemRemoved(position);
110         return value;
111     }
112 
113 
114     public void setOnItemClickListener(OnItemClickListener mOnItemClickListener) {
115         this.mOnItemClickListener = mOnItemClickListener;
116     }
117 
118     /**
119      * 处理item的点击事件和长按事件
120      */
121     interface OnItemClickListener {
122         public void onItemClick(View view, int position);
123         public void onItemLongClick(View view, int position);
124     }
125 
126     class ItemViewHolder extends RecyclerView.ViewHolder {
127 
128         private TextView mTextView;
129 
130         public ItemViewHolder(View itemView) {
131             super(itemView);
132             mTextView = (TextView) itemView.findViewById(R.id.textview);
133         }
134     }
135 
136 }
            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：
     1 <?xml version="1.0" encoding="utf-8"?>
 2 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent">
 5     <TextView
 6         android:id="@+id/textview"
 7         android:layout_width="wrap_content"
 8         android:layout_height="48dp"
 9         android:minWidth="48dp"
10         android:gravity="center"
11         android:layout_centerInParent="true"
12         android:text="XXX"/>
13 </RelativeLayout>
    item分割线：
     1 package com.bbk.lling.recyclerview;
 2 
 3 import android.content.Context;
 4 import android.graphics.Canvas;
 5 import android.graphics.Rect;
 6 import android.graphics.drawable.Drawable;
 7 import android.support.v7.widget.LinearLayoutManager;
 8 import android.support.v7.widget.RecyclerView;
 9 import android.view.View;
10 
11 /**
12  * @Class: ListItemDecoration
13  * @Description: listview的item分割线
14  * @author: lling(www.liuling123.com)
15  * @Date: 2015/10/29
16  */
17 public class ListItemDecoration extends RecyclerView.ItemDecoration {
18 
19     private Drawable mDrawable;
20 
21     private final static int DEFAULT_ORENTATION = LinearLayoutManager.VERTICAL;
22 
23     private int mOrientation;
24 
25     public ListItemDecoration(Context context, int orientation) {
26         if(orientation != LinearLayoutManager.HORIZONTAL && orientation != LinearLayoutManager.VERTICAL) {
27             this.mOrientation = DEFAULT_ORENTATION;
28         } else {
29             this.mOrientation = orientation;
30         }
31         mDrawable = context.getResources().getDrawable(R.drawable.divider);
32     }
33 
34     @Override
35     public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
36         if(mOrientation == LinearLayoutManager.HORIZONTAL) {
37             drawHorizontal(c, parent);
38         } else {
39             drawVertical(c, parent);
40         }
41     }
42 
43     private void drawHorizontal(Canvas c, RecyclerView parent) {
44         int top = parent.getPaddingTop();
45         int bottom = parent.getHeight() - parent.getPaddingBottom();
46 
47         int childCount = parent.getChildCount();
48         for (int i = 0; i < childCount; i++) {
49             View child = parent.getChildAt(i);
50             RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
51                     .getLayoutParams();
52             int left = child.getRight() + params.rightMargin;
53             int right = left + mDrawable.getIntrinsicHeight();
54             mDrawable.setBounds(left, top, right, bottom);
55             mDrawable.draw(c);
56         }
57     }
58 
59     private void drawVertical(Canvas c, RecyclerView parent) {
60         int left = parent.getPaddingLeft();
61         int right = parent.getWidth() - parent.getPaddingRight();
62 
63         int childCount = parent.getChildCount();
64         for (int i = 0; i < childCount; i++) {
65             View child = parent.getChildAt(i);
66             android.support.v7.widget.RecyclerView v = new android.support.v7.widget.RecyclerView(parent.getContext());
67             RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
68                     .getLayoutParams();
69             int top = child.getBottom() + params.bottomMargin;
70             int bottom = top + mDrawable.getIntrinsicHeight();
71             mDrawable.setBounds(left, top, right, bottom);
72             mDrawable.draw(c);
73         }
74     }
75 
76     @Override
77     public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
78         super.getItemOffsets(outRect, view, parent, state);
79     }
80 }
    divider.xml：
    1 <?xml version="1.0" encoding="utf-8"?>
2 <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle" >
3     <size android:height="1dp" android:width="1dp"/>
4     <!--<solid android:color="#e0e0e0"/>-->
5     <solid android:color="#ff0000"/>
6 </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。
     
     
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  • 原文地址：https://www.cnblogs.com/liuling/p/2015-11-04-01.html
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