Android 中RecyclerView使用详解（一）
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
<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 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 mDatas;
public MyAdapter(Context context,List 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
<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>
<style name="AppTheme" parent="Theme.AppCompat.Light">
-- Customize your theme here. -->
<item name="colorPrimary">@color/colorPrimary
- "colorPrimaryDark"
>@color/colorPrimaryDark
- "colorAccent">@color/colorAccent
- "android:listDivider">@drawable/divider_bg
style>
resources>drawable/divider_bg.xml
<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：
<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 mHeights;
......
mHeights = new ArrayList();
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 mDatas;
private List 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 mDatas) {
this.context = context;
this.mDatas = mDatas;
mHeights = new ArrayList();
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