版权声明:转载请说明去处,文章仅供学习参考 https://blog.csdn.net/qq_38487155/article/details/81321948
使用前需要导入依赖:
implementation 'com.android.support:recyclerview-v7:26.1.0'
RecyclerView:是ListView、GridView的升级版,很好地解决了耦合的问题,接下来详细讲解下RecyclerView的使用。
首先在layout里设置活动的布局,放置一个RecyclerView:
<?xml version="1.0" encoding="utf-8"?> <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent"> <Button android:id="@+id/removeButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginBottom="9dp" android:layout_weight="1" android:text="删除" app:layout_constraintBottom_toTopOf="@+id/recycleview" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toEndOf="@+id/addButton" app:layout_constraintTop_toTopOf="parent" /> <Button android:id="@+id/addButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginBottom="9dp" android:layout_marginEnd="17dp" android:layout_marginStart="9dp" android:layout_weight="1" android:text="添加" app:layout_constraintBottom_toTopOf="@+id/recycleview" app:layout_constraintEnd_toStartOf="@+id/removeButton" app:layout_constraintHorizontal_chainStyle="packed" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" /> <android.support.v7.widget.RecyclerView android:id="@+id/recycleview" android:layout_width="0dp" android:layout_height="0dp" android:layout_marginBottom="12dp" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toBottomOf="@+id/removeButton" /> </android.support.constraint.ConstraintLayout>
在Activity里获得RecyclerView的实例,同时设置适配器来设置RecyclerView的表现形式:
public class RecycleViewActivity extends Activity {
@BindView(R.id.recycleview)
RecyclerView recycleview;
List<People> DataList;
@BindView(R.id.removeButton)
Button removeButton;
@BindView(R.id.addButton)
Button addButton;
//定义适配器
private MyAdapter adapter;
public void onCreate(Bundle bunle) {
super.onCreate( bunle );
setContentView( R.layout.recycleviewlayout );
ButterKnife.bind( this );
//初始化子项数组数据
DataList = new ArrayList<People>();
initData();
//设置适配器,同时传入数据
adapter = new MyAdapter( this, DataList );
recycleview.setAdapter( adapter );
//创建LinearLayoutManager 对象 这里使用 LinearLayoutManager 是线性布局的意思
LinearLayoutManager layoutmanager = new LinearLayoutManager( this );
//滚动至索引值处的子项,此方法需要使用new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false )构造方法
//第二个参数指定布局垂直或水平,false为是否倒序
//LinearLayoutManager layoutmanager = new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false );
//layoutmanager.scrollToPosition( 19 );
//设置子项布局为横向
//layoutmanager.setOrientation( LinearLayoutManager.HORIZONTAL );
//设置RecyclerView 布局
recycleview.setLayoutManager( layoutmanager );
//使用网格布局,第二个参数为每行拥有的子项数
//GridLayoutManager gridLayoutManager=new GridLayoutManager( this,4,GridLayoutManager.HORIZONTAL,false);
//recycleview.setLayoutManager(gridLayoutManager);
//添加分割线,第一个参数上下文,第二个参数为布局方向
recycleview.addItemDecoration( new DividerItemDecoration( this, DividerItemDecoration.VERTICAL ) );
//使用自定义接口在外部设置点击事件
adapter.setItemClickListener( new MyAdapter.ItemClickListener() {
@Override
public void onItemClick(int position) {
if (position > 2) {
Toast.makeText( RecycleViewActivity.this, "我是大于3的地方", Toast.LENGTH_SHORT ).show();
} else if (position == 2) {
Toast.makeText( RecycleViewActivity.this, "我是=于3的地方", Toast.LENGTH_SHORT ).show();
} else
Toast.makeText( RecycleViewActivity.this, "我是小于3的地方", Toast.LENGTH_SHORT ).show();
}
} );
}
//初始化数据方法,同时传入适配器
private void initData() {
for (int i = 0; i < 6; i++) {
DataList.add( new People( "真理惟一可靠的标准就是永远自相符合。 —— 欧文", R.drawable.ouwen ) );
DataList.add( new People( "土地是以它的肥沃和收获而被估价的;才能也是土地,不过它生产的不是" +
"粮食,而是真理。如果只能滋生瞑想和幻想的话,即使再大的才能也只是砂地或盐池,那上面连小草也长不出来的。"
, R.drawable.bielin ) );
}
}
//添加子项和删除子项
@OnClick({R.id.removeButton, R.id.addButton})
public void onViewClicked(View view) {
switch (view.getId()) {
case R.id.removeButton:
adapter.removeItem( 0 );
break;
case R.id.addButton:
adapter.addItem( 0, new People( "添加的数据", R.drawable.bielin ) );
//还需要滚动至添加位置
recycleview.scrollToPosition( 0 );
break;
}
}
}
这里RecyclerView的很多属性需要适配器的匹配,所以我们要自定义一个适配器(RecyclerView.Adapter),里面包括需要自定义一个子项视图保存类(RecyclerView.ViewHolder)来对子项布局及控件进行加载,DataList是外部传入的子项数据列表,需要与控件进行绑定,以下:
//定义适配器类
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>{
private Context context;
private List<People> DataList;
//编写导入数据的通用构造方法
MyAdapter(Context context, List<People> DataList){
this.context=context;
this.DataList=new ArrayList<>(DataList);
}
/*
以下三个方法和一个类是必须要重写的方法
*/
//ViewHolder(子项视图保存类):将当前Item视图都实例化保存起来,避免反复调用findViewById方法,浪费资源
//此处不能使用Butterknife
class MyViewHolder extends RecyclerView.ViewHolder{
TextView itemText;
ImageView itemImage;
public MyViewHolder(View itemView) {
super( itemView );
itemText=itemView.findViewById( R.id.itemText );
itemImage=itemView.findViewById( R.id.itemImage );
}
}
//创建ViewHolder实例并返回,加载item 的布局
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.itemlayout,parent,false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
//对RecyclerView子项数据进行赋值,将子项数据与ViewHolder里的控件进行绑定(设置)
@Override
public void onBindViewHolder(MyViewHolder holder, final int position) {
holder.itemText.setText( DataList.get( position ).getData() );
holder.itemImage.setImageResource( DataList.get( position ).getImageId() );
//把图片进行按比例缩放
holder.itemImage.setScaleType( ImageView.ScaleType.FIT_CENTER );
//自定义点击事件(直接在Adapter类重写点击事件)
/*holder.itemView.setOnClickListener( new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText( context, ""+position,Toast.LENGTH_SHORT).show();
}
} );*/
//自定义点击事件(定义接口后在外部重写)
if (myItemClickListener != null) {
holder.itemView.setOnClickListener( new View.OnClickListener() {
@Override
public void onClick(View v) {
myItemClickListener.onItemClick(position );
}
} );
}
}
//返回子项(Item)个数
@Override
public int getItemCount() {
return DataList.size();
}
//自定义点击监听事件
private ItemClickListener myItemClickListener;
public interface ItemClickListener{
void onItemClick( int position);//点击监听事件,在外部实现
}
public void setItemClickListener(ItemClickListener myItemClickListener) {
this.myItemClickListener = myItemClickListener;
}
//让外部能添加和删除Item的方法
public void addItem(int position,People people){
DataList.add( position,people );
//增添动作刷新适配器
notifyItemInserted( position );
}
public void removeItem(int position){
DataList.remove( position );
//删除动作刷新适配器
notifyItemRemoved( position );
}
}
这里面onCreateViewHolder方法加载了子项的布局,在这使用图片加文本的子项布局
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout android:layout_width="match_parent"
android:layout_height="134dp"
android:layout_alignParentTop="true"
android:layout_marginTop="92dp"
android:layout_toEndOf="@+id/itemText"
android:layout_toRightOf="@+id/itemText"
xmlns:android="http://schemas.android.com/apk/res/android">
<ImageView
android:id="@+id/itemImage"
android:layout_width="109dp"
android:layout_height="134dp"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true" />
<TextView
android:id="@+id/itemText"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="108dp"
android:layout_marginStart="108dp"
android:layout_weight="1"
android:gravity="center" />
</RelativeLayout>
最后:是数据类,每个数据代表了一张图片(R.drawable.pictureName的数据ID:int型)和文本显示的数据(String型)
//自定义数据类
public class People {
private String Data; //TextView里存放的文本数据
private int ImageId; //ImageView里存放的图片数据(在R.drawable.里的用int形式)
People(String Data, int ImageId){
this.Data=Data;
this.ImageId=ImageId;
}
public String getData() {
return Data;
}
public void setData(String data) {
Data = data;
}
public int getImageId() {
return ImageId;
}
public void setImageId(int imageId) {
ImageId = imageId;
}
public String toString(){
return Data+String.valueOf( ImageId );
}
}