之前已经用过了ListView控件,虽然可以实现许多放入功能,但是其扩展性还是有一定缺陷的,比如所无法实现横向布局,为此,Android中提供了一个更强大的滚动控件——RecyclerView,它可以实现ListView的功能,同时还在ListView的基础上进行了优化。
RecyclerView基本使用
想要使用RecyclerView,首先我们应该在app的build.gradle中添加相关依赖:
dependencies {
、、、
implementation 'androidx.recyclerview:recyclerview:1.1.0'
、、、
}
之后就可以直接使用RecyclerView控件了:
<!--由于RecyclerView并不是内置在SDK中,所以必须把完整的包路径写下来-->
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
使用RecyclerView实现ListView相同的效果:
创建主活动CardRecyclerViewActivity,设置布局:
<?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="match_parent">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recycler_view_card"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
编写子列表的布局:
<?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="wrap_content"
android:orientation="horizontal">
<ImageView
android:id="@+id/card_image"
android:layout_width="150dp"
android:layout_height="150dp"
android:scaleType="fitCenter"
android:src="@mipmap/ic_launcher" />
<LinearLayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="6"
android:layout_marginTop="3dp"
android:layout_marginLeft="5dp"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dp"
android:text="Name"
android:id="@+id/card_name"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dp"
android:text="Msg"
android:id="@+id/card_msg" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dp"
android:text="Info"
android:id="@+id/card_info"/>
</LinearLayout>
</LinearLayout>
子列表样式:
创建一个Card类对应我们的列表项,用来封装数据:
public class Card {
private String name;
private int imageId;
private String msg;
private String info;
public Card(String name, int imageId,String msg,String info) {
this.name = name;
this.imageId = imageId;
this.msg=msg;
this.info=info;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
public String getMsg() {
return msg;
}
public String getInfo() {
return info;
}
}
使用RecyclerView实现一个适配器,新建CardAdapter类,让这个类继承RecyclerView.Adapter,并将泛型置定位CardAdapter.ViewHolder。其中ViewHolder我们定义为内部类。
继承RecyclerView.Adapter需要实现的三个方法:
- onCreateViewHolder(ViewGroup parent, int viewType):创建ViewHolder实例,在这个方法中可以将列表布局加载进来,之后创建一个ViewHolder实例,并把加载出来的布局传入到构造函数中,最后将ViewHolder实例返回。
- onBindViewHolder(ViewHolder holder, int position):用于对RecyclerView子项进行赋值,会在每个子项被滚动到屏幕内时执行,我们可以通过position获取当前列表项对应的实例,然偶进行操作。
- getItemCount():表示RecyclerView中有多少个子项,返回数据源的长度
public class CardAdapter extends RecyclerView.Adapter<CardAdapter.ViewHolder>{
private Context context;
private List<Card> mCardList;
public CardAdapter(Context context,List<Card> cardList) {
this.context=context;
mCardList = cardList;
}
@Override
public CardAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.card_item, parent, false);
final ViewHolder holder = new ViewHolder(view);
holder.cardView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int position = holder.getAdapterPosition();
Card card = mCardList.get(position);
Toast.makeText(v.getContext(), card.getName()+": 奥里给", Toast.LENGTH_SHORT).show();
}
});
holder.cardImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int position = holder.getAdapterPosition();
final Card card = mCardList.get(position);
AlertDialog.Builder builder=new AlertDialog.Builder(context);
builder.setIcon(card.getImageId());
builder.setTitle(card.getName());
builder.setMessage("要拉我上船吗?");
builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(context,card.getName()+"加入了海贼船", Toast.LENGTH_SHORT).show();
}
});
builder.setNegativeButton("取消", null);
builder.create();
builder.show();
}
});
return holder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Card card = mCardList.get(position);
holder.cardImage.setImageResource(card.getImageId());
holder.cardName.setText(card.getName());
holder.cardMsg.setText(card.getMsg());
holder.cardInfo.setText(card.getInfo());
}
@Override
public int getItemCount() {
return mCardList.size();
}
static class ViewHolder extends RecyclerView.ViewHolder {
View cardView;
ImageView cardImage;
TextView cardName;
TextView cardMsg;
TextView cardInfo;
public ViewHolder(View view) {
super(view);
cardView = view;
cardImage = (ImageView) view.findViewById(R.id.card_image);
cardName = (TextView) view.findViewById(R.id.card_name);
cardMsg=(TextView) view.findViewById(R.id.card_msg);
cardInfo=(TextView) view.findViewById(R.id.card_info);
}
}
}
适配器准备好就可以编写主界面了:
public class CardRecyclerViewActivity extends AppCompatActivity {
private List<Card> cardList = new ArrayList<Card>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_card_recycler_view);
initCards();
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view_card);
LinearLayoutManager layoutManager=new LinearLayoutManager(this);
//设置布局管理器
recyclerView.setLayoutManager(layoutManager);
// StaggeredGridLayoutManager layoutManager = new
// StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL);
// recyclerView.setLayoutManager(layoutManager);
//添加分割线
recyclerView.addItemDecoration(new DividerItemDecoration(
this, DividerItemDecoration.HORIZONTAL));
CardAdapter adapter = new CardAdapter(CardRecyclerViewActivity.this,cardList);
//设置adapter
recyclerView.setAdapter(adapter);
}
private void initCards() {
List<Card> list = new ArrayList<Card>();
list.add(new Card("路飞", R.mipmap.lufei,"【船长】蒙奇·D·路飞(蒙奇·D·路飞 )","1500000000¥"));
list.add(new Card("索隆", R.mipmap.suolong,"【剑士】罗罗诺亚·索隆","320000000¥"));
list.add(new Card("乌索普", R.mipmap.wusuopu,"【狙击手】乌索普","200000000¥"));
list.add(new Card("娜美", R.mipmap.namei,"【航海士】娜美","66000000¥"));
list.add(new Card("山治", R.mipmap.shanzhi,"【厨师】香吉士","330000000¥"));
list.add(new Card("乔巴", R.mipmap.qiaoba,"【船医】托尼托尼·乔巴","100¥"));
list.add(new Card("罗宾", R.mipmap.luobin,"【考古学家】妮可·罗宾 ","130000000¥"));
list.add(new Card("弗兰奇", R.mipmap.fulanqi,"【船匠】弗兰奇","94000000¥"));
list.add(new Card("布鲁克", R.mipmap.buluke,"【音乐家】布鲁克","83000000¥"));
list.add(new Card("香克斯", R.mipmap.xiangkesi,"【四皇】香克斯","4000000000¥"));
for(int i=0;i<60;i++){
cardList.add(list.get((int)(Math.random()*10)));
}
}
}
运行结果:
实现不同样式的布局
修改子列表项的布局:card_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<RelativeLayout
android:layout_width="150dp"
android:layout_height="150dp">
<ImageView
android:id="@+id/card_image"
android:layout_width="150dp"
android:layout_height="150dp"
android:scaleType="fitCenter"
android:src="@mipmap/ic_launcher" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Name"
android:id="@+id/card_name"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="Info"
android:id="@+id/card_info"/>
</RelativeLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="3dp"
android:layout_marginLeft="5dp"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dp"
android:textSize="15dp"
android:text="Msg"
android:id="@+id/card_msg" />
</LinearLayout>
</LinearLayout>
修改主活动的代码:
//LinearLayoutManager layoutManager=new LinearLayoutManager(this);
//recyclerView.setLayoutManager(layoutManager);
//横向的效果
LinearLayoutManager layoutManager=new LinearLayoutManager(this);
layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerView.setLayoutManager(layoutManager);
//网格布局
GridLayoutManager gridLayoutManager = new GridLayoutManager( this,3);
recyclerView.setLayoutManager(gridLayoutManager);
//流式布局
StaggeredGridLayoutManager layoutManager = new
StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL);
recyclerView.setLayoutManager(layoutManager);
横向布局:
网格布局:
流式布局: