Android之RecyclerView的使用总结

1.RecycleView的简介

可以简单理解RecyclerView就是ListView，是一个更高级的ListView。

2.RecyclerView的特点

不关心Item显示在正确的位置，以及如何显示。

不关心Item之间如何分割。

不关注Item的添加和删除的效果。

仅仅关注如何回收与复用View。

3.在项目中如何引用

在模块的gradle.build文件中添加如下依赖

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:recyclerview-v7:22.0.0'

}

4.RecyclerView中关键点说明

1.Adapter

这个Adapter比较特殊，是RecyclerView所特有的，它包括以下几个重要的方法：

public abstract VH onCreateViewHolder(ViewGroup parent, int viewType);
public abstract void onBindViewHolder(ViewHolder holder, int position);
public abstract int getItemCount();

onCreateViewHolder：用于创建ViewHolder，或者是根据viewType创建ViewHolder。

onBindViewHolder：通过ViewHolder和数据绑定。

getItemCount：获得Item的数量。

2.ViewHolder

一个抽象类，通过继承此类对View进行封装。

3.LayoutManager

布局管理器，用于管理RecyclerView中数据的显示方式。目前主要有三种布局管理器，分别是：

LinearLayoutManager

GridLayoutManager

StaggeredGridLayoutManager

LinearLayoutManager：线性布局管理器，通过使用这个布局就可以实现ListView的效果。可以实现垂直、水平两种方向的ListView效果，默认的是垂直方向的ListView效果。

GridLayoutManager：网格布局管理器,通过使用这个布局管理器可以实现GridView的效果，同样的，它也用垂直和水平两种显示方式。

StaggeredGridLayoutManager：交错网格布局管理器，可以实现具有瀑布流效果的显示，它也是有垂直和水平两种显示方式的。

5.实例讲解

1.使用LinearLayoutManager实现垂直显示的效果

main_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<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"
tools:context="com.gjg.learn.recycleviewdemo.MainActivity">

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

>

</android.support.v7.widget.RecyclerView>

</RelativeLayout>

MainActivity

public class MainActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private List<String> mDatas;
private RecyclerAdapter recyclerAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initData();
recyclerView= (RecyclerView) this.findViewById(R.id.id_recyclerview);
LinearLayoutManager linearLayoutManager=new LinearLayoutManager(this);

recyclerView.setLayoutManager(linearLayoutManager);

recyclerAdapter=new RecyclerAdapter(mDatas,this);

recyclerView.setAdapter(recyclerAdapter);
//线性布局的分割线
DividerItemDecoration decoration=new DividerItemDecoration(this,DividerItemDecoration.HORIZONTAL_LIST);

recyclerView.addItemDecoration(decoration);
// 设置item动画
recyclerView.setItemAnimator(new DefaultItemAnimator());
initEvent();
}

private void initEvent() {
recyclerAdapter.setOnItemClickLitener(new RecyclerAdapter.OnItemClickLitener() {
@Override
public void onItemClick(View view, int position) {
Toast.makeText(MainActivity.this, "你点击了"+mDatas.get(position),
Toast.LENGTH_SHORT).show();
}

@Override
public void onItemLongClick(View view, int position) {
Toast.makeText(MainActivity.this, "你长按了"+mDatas.get(position),
Toast.LENGTH_SHORT).show();
}
});
}

private void initData() {
mDatas = new ArrayList<String>();
for (int i = 'A'; i < 'z'; i++)
{
mDatas.add("字母：" + (char) i);
}

}
}

RecyclerAdapter

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.MyViewHolder> {
private Context context;
private List<String> mDatas;

public RecyclerAdapter(List<String> mDatas,Context context){
this.mDatas=mDatas;
this.context=context;

}

public interface OnItemClickLitener {
void onItemClick(View view, int position);
void onItemLongClick(View view, int position);
}

private OnItemClickLitener mOnItemClickLitener;

public void setOnItemClickLitener(OnItemClickLitener mOnItemClickLitener) {
this.mOnItemClickLitener = mOnItemClickLitener;
}

@Override
public MyViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {

//需要把viewGroup加进去，否则item永远居左显示
View view = LayoutInflater.from(context).inflate(R.layout.recyclerview_item, viewGroup, false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}

@Override
public void onBindViewHolder(MyViewHolder myViewHolder, int i) {
myViewHolder.tv.setText(mDatas.get(i));
// 如果设置了回调，则设置点击事件
if (mOnItemClickLitener != null)
{
//itemView:ViewHolder的一个item
myViewHolder.itemView.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
int pos = myViewHolder.getLayoutPosition();

mOnItemClickLitener.onItemClick(myViewHolder.itemView, pos);

}
});

myViewHolder.itemView.setOnLongClickListener(new View.OnLongClickListener()
{
@Override
public boolean onLongClick(View v)
{
int pos = myViewHolder.getLayoutPosition();

mOnItemClickLitener.onItemLongClick(myViewHolder.itemView, pos);

return false;
}
});
}
}

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

class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv;

public MyViewHolder(View itemView) {
super(itemView);
tv = (TextView) itemView.findViewById(R.id.id_num);
}
}
}

DividerItemDecoration

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)
{
Log.v("itemdecoration", "onDraw()");
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);
RecyclerView v = new RecyclerView(
parent.getContext());
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, int itemPosition,
RecyclerView parent)
{
if (mOrientation == VERTICAL_LIST)
{
outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
} else
{
outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
}
}
}

分割线的样式：

<style name="MyAppTheme" parent="AppTheme">
<item name="android:listDivider">@drawable/divider_bg</item>
</style>

divider_bg

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">

<gradient android:angle="180"
android:startColor="#95c247"
android:centerColor="#ff099494"
android:endColor="#ea74d3"
android:type="linear"/>
<size android:height="2dp"/>
</shape>

运行效果如下：



注意：在View view = LayoutInflater.from(context).inflate(R.layout.recyclerview_item, viewGroup, false);时，需要把viewGroup加进去，否则item永远居左显示。

因为：

inflater在inflate一个xml时，需要知道parent的类型，才能生成对应的LayoutParams，才可以把xml根节点的attrs（如layout_width）读进去，代码如下：
// android.view.LayoutInflater
public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {
synchronized (mConstructorArgs) {

...

// Temp is the root view that was found in the xml
final View temp = createViewFromTag(root, name, inflaterContext, attrs);

ViewGroup.LayoutParams params = null;

if (root != null) {
if (DEBUG) {
System.out.println("Creating params from root: " +
root);
}
// Create layout params that match root, if supplied
params = root.generateLayoutParams(attrs);
if (!attachToRoot) {
// Set the layout params for temp if we are not
// attaching. (If we are, we use addView, below)
temp.setLayoutParams(params);
}
}

...

}
如果parent传进去为null，生成的View的LayoutParams为null，在RecyclerView.addView时，发现LayoutParams为null，则生成默认的LayoutParams,

// android.view.ViewGroup
protected LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
}

2.使用LinearLayoutManager实现水平显示的效果

只要在MainActivity的onCreateView中添加：

linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);

修改

DividerItemDecoration decoration = new DividerItemDecoration(this, DividerItemDecoration.HORIZONTAL_LIST);

效果如下：

3.使用GridLayoutManager实现垂直显示的效果

将recyclerView.setLayoutManager(linearLayoutManager);

改为recyclerView.setLayoutManager(new GridLayoutManager(this,5));

并且修改分割线的样式：

DividerGridItemDecoration decoration=new DividerGridItemDecoration(this);

即可。

效果如下：

4.使用StaggeredGridLayoutManager实现垂直显示的效果

修改成

recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,

StaggeredGridLayoutManager.VERTICAL));

还有就是，关键是在onBindViewHolder中设置item的高度，高度为随机生成的。

LayoutParams lp = holder.tv.getLayoutParams();

lp.height = mHeights.get(position);

holder.tv.setLayoutParams(lp);

效果如图：