自从Android 5.0之后,google推出了一个RecyclerView控件,他是support-v7包中的新组件,是一个强大的滑动组件,与经典的ListView相比,同样拥有item回收复用的功能,RecyclerView相当于是ListView的升级版。
RecyclerView封装了ViewHolder的回收复用,也就是说RecyclerView标准化了ViewHolder,编写Adapter面向的是ViewHolder而不是View了,复用的逻辑被封装了,写起来更加简单。
RecyclerView提供一种插拔式的体验,高度的解耦,异常的灵活,针对一个Item的显示RecyclerView专门抽取了相应的类,来控制Item的显示,使其的扩展性特别强。
引入RecyclerVIew
compile 'com.android.support:recyclerview-v7:25.1.0'
创建布局文件
主布局文件
/*activity_main.xml*/
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
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.manu.mrecyclerview.MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/rv"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
Item布局文件
/*item.xml*/
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="5dp">
<TextView
android:id="@+id/tv_recycle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="data"
android:background="#cac3c3"
android:padding="10dp"
android:textSize="20sp"/>
</LinearLayout>
创建Adapter
RecyclerView的Adapter要比ListView的Adapter设置起来稍微复杂一点,这也是RecyclerView高度解耦的体现,虽然代码复杂一点,但扩展性很好,下面介绍一下实现RecyclerView的Adapter的三个方法:
onCreateViewHolder()
该方法主要是为每个Item加载一个View,但是该方法返回的是一个ViewHolder,该方法吧View直接封装的ViewHolder中,然后我们面向的是ViewHolder这个实例,这个ViewHolder也由自己编写,但不用像ListView调用convertView.setTag(vh)和convertView.getTag()了。
onBindViewHolder()
该方法主要用来把数据绑定在View上,直接提供一个ViewHolder而不是convertView。
getItemCount()
该方法返回选项总数。
Adapter代码
/**
* Created by jzman on 2017/5/13 0013.
*/
public class RvAdapter extends RecyclerView.Adapter<RvAdapter.DataViewHolder>{
private Context mContext;
private ArrayList<String> mList;
public RvAdapter() {}
public RvAdapter(Context mContext, ArrayList<String> mList) {
this.mContext = mContext;
this.mList = mList;
}
//用于创建ViewHolder
@Override
public DataViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(mContext).inflate(R.layout.item,null);
//使用代码设置宽高(xml布局设置无效时)
view.setLayoutParams(new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
DataViewHolder holder = new DataViewHolder(view);
return holder;
}
//绑定数据
@Override
public void onBindViewHolder(DataViewHolder holder, int position) {
holder.tv_data.setText(mList.get(position));
}
//数据总数
@Override
public int getItemCount() {
return mList.size();
}
//创建ViewHolder
public static class DataViewHolder extends RecyclerView.ViewHolder{
TextView tv_data;
public DataViewHolder(View itemView) {
super(itemView);
tv_data = (TextView) itemView.findViewById(R.id.tv_recycle);
}
}
使用StaggeredGridLayoutManager管理器时,Adapter参考如下:
/**
* Created by jzman on 2017/5/13 0013.
* RecycleView的Adapter
*/
public class RvAdapter extends RecyclerView.Adapter<RvAdapter.DataViewHolder>{
private Context mContext;
private RecyclerView recyclerView;
private ArrayList<String> mList;
private ArrayList<Integer> mHeight;
public RvAdapter() {}
public RvAdapter(Context mContext, ArrayList<String> mList) {
this.mContext = mContext;
this.mList = mList;
}
/**
* 初始化每个Item的高度(瀑布流效果)
* @return
*/
public ArrayList<Integer> initHeight(){
mHeight = new ArrayList<>();
for (int i=0;i<mList.size();i++){
mHeight.add((int) (Math.random()*300)+200);
}
return mHeight;
}
/**
* 用于创建ViewHolder
* @param parent
* @param viewType
* @return
*/
@Override
public DataViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(mContext).inflate(R.layout.item,null);
//使用代码设置宽高(xml布局设置无效时)
view.setLayoutParams(new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
DataViewHolder holder = new DataViewHolder(view);
return holder;
}
/**
* 绑定数据
* @param holder
* @param position
*/
@Override
public void onBindViewHolder(DataViewHolder holder, int position) {
//设置每个Item的高度
ViewGroup.LayoutParams h = holder.tv_data.getLayoutParams();
h.height = mHeight.get(position);
holder.tv_data.setText(mList.get(position));
}
/**
* 选项总数
* @return
*/
@Override
public int getItemCount() {
return mList.size();
}
/**
* 创建ViewHolder
*/
public static class DataViewHolder extends RecyclerView.ViewHolder{
TextView tv_data;
public DataViewHolder(View itemView) {
super(itemView);
tv_data = (TextView) itemView.findViewById(R.id.tv_recycle);
}
}
/**
* 将RecycleView附加到Adapter上
*/
@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
this.recyclerView= recyclerView;
//初始化每个Item的高度
initHeight();
}
/**
* 将RecycleView从Adapter解除
*/
@Override
public void onDetachedFromRecyclerView(RecyclerView recyclerView) {
super.onDetachedFromRecyclerView(recyclerView);
this.recyclerView = null;
}
}
MainActivity
/**
* Created by jzman on 2017/5/13 0013.
*/
public class MainActivity extends AppCompatActivity {
private RecyclerView rv;
RvAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
rv = (RecyclerView) findViewById(R.id.rv);
//设置布局管理器
rv.setLayoutManager(new LinearLayoutManager(this));//线性
// rv.setLayoutManager(new GridLayoutManager(this,4));//线性
// rv.setLayoutManager(new StaggeredGridLayoutManager(4,StaggeredGridLayoutManager.VERTICAL));//线性
adapter = new RvAdapter(this,initData());
rv.setAdapter(adapter);
}
public static ArrayList<String> initData(){
ArrayList<String> arrayList = new ArrayList<>();
for (int i=0;i<50;i++){
arrayList.add("第"+i+"条数据");
}
return arrayList;
}
}
显示效果
LinearLayoutManager | GridLayoutManager | StaggeredGridLayoutManager |
---|---|---|
image | image | image |
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