Android 中RecyclerView使用详解（一）
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概述
针对RecyclerView，谷歌有一段介绍的话：
RecyclerView is a more advanced and flexible version of ListView. This widget is a Container for large sets of views that can be recycled and scrolled very efficiently. Use the RecyclerView widget when you have lists with elements that change dynamically.
大概就是说RecyclerView是一个更加高效灵活的ListView。当你有一系列的元素需要动态加载的时候，可以使用RecyclerView这个控件。
RecyclerView提供了高度自由化定制的功能，比如：
通过LayoutManager（布局管理器），控制item的显示方式；
通过ItemDecoration，控制item间的背景；
通过ItemAnimator，控制动态增删item的动画；
虽然RecyclerView提供了非常自由化的定制操作，但是它自身并不支持item的点击事件，也不像ListView一样能够简单的添加头和尾布局。想要实现这样的功能，同样需要自身去实现。
从上面我们可以看出使用RecyclerView的基本步骤：
recyclerView = (RecyclerView) findViewById(R.id.recyclerView); recyclerView.setLayoutManager(); //设置布局管理器 recyclerView.setAdapter(); //设置Adapter，同ListView recyclerView.addItemDecoration(); //设置Item的间隔背景 recyclerView.setItemAnimator(); //设置Item增删时的动画下面我将通过代码来逐步介绍RecyclerView的具体使用。
代码示例
1.布局文件content_main.xml
<?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"> <android.support.v7.widget.RecyclerView android:id="@+id/recyclerView" android:layout_width="match_parent" android:layout_height="match_parent" /></RelativeLayout>2.Activity中的代码
package mo.yumf.com.mddemo;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.widget.GridLayoutManager;import android.support.v7.widget.LinearLayoutManager;import android.support.v7.widget.RecyclerView;import android.view.View;import android.view.ViewGroup;import android.widget.TextView;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity { private RecyclerView recyclerView; private List<String> mDatas; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.content_main); initData(); recyclerView = (RecyclerView) findViewById(R.id.recyclerView); recyclerView.setLayoutManager(new LinearLayoutManager(this)); //设置布局管理器 recyclerView.setAdapter(new MyAdapter(this,mDatas)); //设置Adapter } private void initData() { mDatas = new ArrayList<>(); for(int i = 0;i < 20;i ++){ mDatas.add("Test"+i); } }}3.自定义Adapter
package mo.yumf.com.mddemo;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;public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>{ private Context context; private List<String> mDatas; public MyAdapter(Context context,List<String> mDatas) { this.context = context; this.mDatas = mDatas; } @Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { MyViewHolder holder = new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item_recyclerview,parent,false)); return holder; } @Override public void onBindViewHolder(MyViewHolder holder, int position) { holder.textView.setText(mDatas.get(position)); } @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.item_text); } }}4.item的布局文件item_recyclerview.xml
<?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="100dp" android:background="#D1EEEE" android:orientation="vertical"> <TextView android:id="@+id/item_text" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_gravity="center_horizontal" android:gravity="center" android:text="Large Text" android:textAppearance="?android:attr/textAppearanceLarge" /></LinearLayout>上述代码执行后效果图：
可以看到上面的Item之间没有分割线，给人感觉十分不友好，现在我们给它加上一个分割线背景。
添加分割线背景
文章开头的部分，我们提到过设置分割线是通过方法addItemDecoration(ItemDecoration decor)。但是通过查看代码能够知道ItemDecoration 类是一个抽象类：
public static abstract class ItemDecoration { /** * 该方法会在item view 的绘制之前调用 */ public void onDraw(Canvas c, RecyclerView parent, State state) { onDraw(c, parent); } @Deprecated public void onDraw(Canvas c, RecyclerView parent) { } /** * 该方法会在item view 的绘制之后调用 */ public void onDrawOver(Canvas c, RecyclerView parent, State state) { onDrawOver(c, parent); } @Deprecated public void onDrawOver(Canvas c, RecyclerView parent) { } @Deprecated public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) { outRect.set(0, 0, 0, 0); } /** *为每个item设置偏移量 */ public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) { getItemOffsets(outRect, ((LayoutParams) view.getLayoutParams()).getViewLayoutPosition(),parent); }}我们在继承该类来设置分割线时，需要用到的方法只有两个：
1.绘制分割线 public void onDraw(Canvas c, RecyclerView parent, State state)；
2.设置偏移量 public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state)；
接下来我们看看具体是如何实现绘制分割线：
package mo.yumf.com.mddemo;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.support.v7.widget.RecyclerView.State;import android.view.View;public class DividerItemDecoration 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 DividerItemDecoration(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, 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, State state) { if (mOrientation == VERTICAL_LIST) { outRect.set(0, 0, 0, mDivider.getIntrinsicHeight()); } else { outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0); } }}接着需要在原来的代码中添加：
recyclerView.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL_LIST));修改之后，继续运行：
可以看到在执行addItemDecoration()之后，可以看到一条分割线。那么如果想要继续修改这天分割线的高度，背景色，需要怎么办呢？其实从上面的DividerItemDecoration类中，可以看到这条分割线的绘制是从android.R.attr.listDivider中读取的，所以我们在设置好这个类之后，可以再修改这个属性值来达到修改分割线的目的。如下：
系统主题设置：
<resources> <!-- Base application theme. --> <style name="AppTheme" parent="Theme.AppCompat.Light"> <!-- Customize your theme here. --> <item name="colorPrimary">@color/colorPrimary</item> <item name="colorPrimaryDark">@color/colorPrimaryDark</item> <item name="colorAccent">@color/colorAccent</item> <!--修改RecyclerView item背景色--> <item name="android:listDivider">@drawable/divider_bg</item> </style></resources>drawable/divider_bg.xml
<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle"> <solid android:color="@android:color/white"></solid> <size android:height="6dp"></size></shape>运行代码，效果图：
好了，以上只是实现了类似ListView的布局效果，那么还有没有其他形式的布局效果呢，这就需要通过LayoutManager来实现了。
布局管理器（LayoutManager）
系统中LayoutManager是一个抽象类，他目前给我们提供了三个子类可以直接使用，如：
LinearLayoutManager：线性布局管理器，提供类似ListView的功能，如上；
GridLayoutManager：网格布局管理器；
StaggeredGridLayoutManager：瀑布流式布局管理器。
上面我们已经试过了LinearLayoutManager效果，现在我们可以继续使用GridLayoutManager效果，修改代码：
// recyclerView.setLayoutManager(new LinearLayoutManager(this)); recyclerView.setLayoutManager(new GridLayoutManager(this,3)); //每一行的列数还需要重新绘制分割线，之前的DividerItemDecoration类已经不能使用了，我们需要重新绘制分割线：
package mo.yumf.com.mddemo;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.GridLayoutManager;import android.support.v7.widget.LinearLayoutManager;import android.support.v7.widget.RecyclerView;import android.support.v7.widget.RecyclerView.State;import android.support.v7.widget.StaggeredGridLayoutManager;import android.view.View;public class DividerGridItemDecoration extends RecyclerView.ItemDecoration{ private static final int[] ATTRS = new int[]{ android.R.attr.listDivider }; private Drawable mDivider; public DividerGridItemDecoration(Context context) { final TypedArray a = context.obtainStyledAttributes(ATTRS); mDivider = a.getDrawable(0); a.recycle(); } @Override public void onDraw(Canvas c, RecyclerView parent, State state) { drawHorizontal(c, parent); drawVertical(c, parent); } public void drawVertical(Canvas c, RecyclerView parent) { int childCount = parent.getChildCount(); for(int i = 0 ; i < childCount ; i ++){ View child = parent.getChildAt(i); RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams(); int top = child.getTop() - params.topMargin; int bottom = child.getBottom() + params.bottomMargin; int left = child.getRight() + params.leftMargin; int right = left + mDivider.getIntrinsicWidth(); mDivider.setBounds(left,top,right,bottom); mDivider.draw(c); } } public void drawHorizontal(Canvas c, RecyclerView parent) { int childCount = parent.getChildCount(); for(int i = 0 ; i < childCount ; i ++){ View child = parent.getChildAt(i); RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams(); int top = child.getBottom() + params.bottomMargin; int bottom = top + mDivider.getIntrinsicHeight(); int left = child.getLeft() - params.leftMargin; int right = child.getRight() + params.rightMargin + mDivider.getIntrinsicWidth(); mDivider.setBounds(left,top,right,bottom); mDivider.draw(c); } } @Override public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) { int itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewLayoutPosition(); int spanCount = getSpanCount(parent); int childCount = parent.getAdapter().getItemCount(); if (isLastRaw(parent, itemPosition, spanCount, childCount)){ // 如果是最后一行，则不需要绘制底部 outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0); } else if (isLastColum(parent, itemPosition, spanCount, childCount)){ // 如果是最后一列，则不需要绘制右边 outRect.set(0, 0, 0, mDivider.getIntrinsicHeight()); } else{ outRect.set(0, 0, mDivider.getIntrinsicWidth(),mDivider.getIntrinsicHeight()); } } private boolean isLastColum(RecyclerView parent, int pos, int spanCount, int childCount) { RecyclerView.LayoutManager layoutManager = parent.getLayoutManager(); if (layoutManager instanceof GridLayoutManager){ if ((pos + 1) % spanCount == 0){ // 如果是最后一列，则不需要绘制右边 return true; } } else if (layoutManager instanceof StaggeredGridLayoutManager){ int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation(); if (orientation == StaggeredGridLayoutManager.VERTICAL){ // // 如果是最后一列，则不需要绘制右边 } else{ childCount = childCount - childCount % spanCount; if (pos >= childCount){ // 如果是最后一列，则不需要绘制右边 return true; } } } return false; } private boolean isLastRaw(RecyclerView parent, int pos, int spanCount, int childCount) { RecyclerView.LayoutManager layoutManager = parent.getLayoutManager(); if (layoutManager instanceof GridLayoutManager) { childCount = childCount - childCount % spanCount; if (pos >= childCount)// 如果是最后一行，则不需要绘制底部 return true; } else if (layoutManager instanceof StaggeredGridLayoutManager){ int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation(); // StaggeredGridLayoutManager 且纵向滚动 if (orientation == StaggeredGridLayoutManager.VERTICAL){ childCount = childCount - childCount % spanCount; // 如果是最后一行，则不需要绘制底部 if (pos >= childCount) return true; } else{ // StaggeredGridLayoutManager 且横向滚动,如果是最后一行，则不需要绘制底部 if ((pos + 1) % spanCount == 0){ return true; } } } return false; } private int getSpanCount(RecyclerView parent) { // 列数 int spanCount = -1; RecyclerView.LayoutManager layoutManager = parent.getLayoutManager(); if (layoutManager instanceof GridLayoutManager){ spanCount = ((GridLayoutManager) layoutManager).getSpanCount(); }else if (layoutManager instanceof StaggeredGridLayoutManager){ spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount(); } return spanCount; }}这个DividerGridItemDecoration类，非本人所写，借鉴自hongyang大神^-^!!。
然后，在修改一下divider_bg.xml中的宽度：
<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle"> <solid android:color="@android:color/white"></solid> <size android:height="6dp" android:width="6dp"></size></shape>执行后，效果图：
下面我们将继续使用StaggeredGridLayoutManager布局管理器，来实现瀑布流的效果。
1.设置布局管理器为StaggeredGridLayoutManager
recyclerView.setLayoutManager(new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL));
注：
在第二个参数为VERTICAL：前面的数字表示多少列；
在第二个参数为HORIZONTAL：前面的数字表示多少行；
2.设置item的分割线背景色，可以使用上面DividerGridItemDecoration类；
recyclerView.addItemDecoration(new DividerGridItemDecoration(this));
3.在Adapter中的onBindViewHolder方法里，为Item设置随机的高度。
......private List<Integer> mHeights;......mHeights = new ArrayList<Integer>();for (int i = 0; i < mDatas.size(); i++){ mHeights.add( (int) (100 + Math.random() * 300));}..... @Override public void onBindViewHolder(MyViewHolder holder, int position) { ViewGroup.LayoutParams lp = holder.textView.getLayoutParams(); lp.height = mHeights.get(position); holder.textView.setLayoutParams(lp); holder.textView.setText(mDatas.get(position)); }.....完成上述修改后，运行代码：
添加点击功能
前面我们说过recyclerView自身并不提供点击的接口回调，这需要我们自己实现。为了能够到达与传统的ListView相同的点击效果，我们可以在自定义的Adapter中，定义一个接口，通过该接口的方法可以将View以接口回调的方式传递出来。代码如下：
package mo.yumf.com.mddemo;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.ArrayList;import java.util.List;public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>{ private Context context; private List<String> mDatas; private List<Integer> mHeights; /** 定义接口*/ interface OnItemClickListener{ void onItemClick(View v,int position); } private OnItemClickListener onItemClickListener; /** 对外提供方法，接收示例对象*/ public void setOnItemClickListener(OnItemClickListener onItemClickListener){ this.onItemClickListener = onItemClickListener; } public MyAdapter(Context context,List<String> mDatas) { this.context = context; this.mDatas = mDatas; mHeights = new ArrayList<Integer>(); for (int i = 0; i < mDatas.size(); i++){ mHeights.add( (int) (100 + Math.random() * 300)); } } @Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { MyViewHolder holder = new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item_recyclerview,parent,false)); return holder; } @Override public void onBindViewHolder(MyViewHolder holder, final int position) { ViewGroup.LayoutParams lp = holder.textView.getLayoutParams(); lp.height = mHeights.get(position); holder.textView.setLayoutParams(lp); holder.textView.setText(mDatas.get(position)); if(onItemClickListener != null){ holder.textView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { onItemClickListener.onItemClick(v,position); //使用接口回调的方法将参数传递出来 } }); } } @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.item_text); } }}-------------------------------Activity中调用方法：MyAdapter adapter = new MyAdapter(this,mDatas);adapter.setOnItemClickListener(new MyAdapter.OnItemClickListener() { @Override public void onItemClick(View v,int position) { Toast.makeText(getApplicationContext(),position +"=="+((TextView)v).getText(),Toast.LENGTH_SHORT).show(); }});完成上述修改后，运行代码：
以上便是RecyclerView的基本使用，接下来将继续介绍RecyclerView的其他知识点。
参考博客：
http://blog.csdn.net/sanjay_f/article/details/48830311
http://blog.csdn.net/lmj623565791/article/details/45059587
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