Android快速入門之滾動控制元件RecyclerView-有解無憂

之前已經用過了ListView控制元件，雖然可以實作許多放入功能，但是其擴展性還是有一定缺陷的，比如所無法實作橫向布局，為此，Android中提供了一個更強大的滾動控制元件——RecyclerView，它可以實作ListView的功能，同時還在ListView的基礎上進行了優化，

RecyclerView基本使用

想要使用RecyclerView，首先我們應該在app的build.gradle中添加相關依賴：

dependencies {
  、、、
    implementation 'androidx.recyclerview:recyclerview:1.1.0'
  、、、
}

之后就可以直接使用RecyclerView控制元件了：

<!--由于RecyclerView并不是內置在SDK中，所以必須把完整的包路徑寫下來-->
<androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

使用RecyclerView實作ListView相同的效果：

創建主活動CardRecyclerViewActivity，設定布局：

<?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>

撰寫子串列的布局：

<?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>

子串列樣式：
在這里插入圖片描述

創建一個Card類對應我們的串列項，用來封裝資料：

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實作一個配接器，新建CardAdapter類，讓這個類繼承RecyclerView.Adapter，并將泛型置定位CardAdapter.ViewHolder，其中ViewHolder我們定義為內部類，

繼承RecyclerView.Adapter需要實作的三個方法：

onCreateViewHolder(ViewGroup parent, int viewType)：創建ViewHolder實體，在這個方法中可以將串列布局加載進來，之后創建一個ViewHolder實體，并把加載出來的布局傳入到建構式中，最后將ViewHolder實體回傳，
onBindViewHolder(ViewHolder holder, int position)：用于對RecyclerView子項進行賦值，會在每個子項被滾動到螢屏內時執行，我們可以通過position獲取當前串列項對應的實體，然偶進行操作，
getItemCount()：表示RecyclerView中有多少個子項，回傳資料源的長度

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()+"： 奧里給", 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("要拉我上船嗎？");
                    builder.setPositiveButton("確定", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                Toast.makeText(context,card.getName()+"加入了海賊船", 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);
        }
    }
}

配接器準備好就可以撰寫主界面了：

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);
        //設定布局管理器
        recyclerView.setLayoutManager(layoutManager);
        
//        StaggeredGridLayoutManager layoutManager = new
//        StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL);
//        recyclerView.setLayoutManager(layoutManager);

        //添加分割線
        recyclerView.addItemDecoration(new DividerItemDecoration(
                this, DividerItemDecoration.HORIZONTAL));
       
        CardAdapter adapter = new CardAdapter(CardRecyclerViewActivity.this,cardList);
        //設定adapter
        recyclerView.setAdapter(adapter);
    }

    private void initCards() {
        List<Card> list = new ArrayList<Card>();
        list.add(new Card("路飛", R.mipmap.lufei,"【船長】蒙奇·D·路飛（蒙奇·D·路飛 ）","1500000000￥"));
        list.add(new Card("索隆", R.mipmap.suolong,"【劍士】羅羅諾亞·索隆","320000000￥"));
        list.add(new Card("烏索普", R.mipmap.wusuopu,"【狙擊手】烏索普","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,"【廚師】香吉士","330000000￥"));
        list.add(new Card("喬巴", R.mipmap.qiaoba,"【船醫】托尼托尼·喬巴","100￥"));
        list.add(new Card("羅賓", R.mipmap.luobin,"【考古學家】妮可·羅賓 ","130000000￥"));
        list.add(new Card("弗蘭奇", R.mipmap.fulanqi,"【船匠】弗蘭奇","94000000￥"));
        list.add(new Card("布魯克", R.mipmap.buluke,"【音樂家】布魯克","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)));
        }
    }

}

運行結果：
在這里插入圖片描述

實作不同樣式的布局

修改子串列項的布局：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>

修改主活動的代碼：

//LinearLayoutManager layoutManager=new LinearLayoutManager(this);
//recyclerView.setLayoutManager(layoutManager);

//橫向的效果
LinearLayoutManager layoutManager=new LinearLayoutManager(this);
layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerView.setLayoutManager(layoutManager);

//網格布局
GridLayoutManager gridLayoutManager = new GridLayoutManager( this,3);
recyclerView.setLayoutManager(gridLayoutManager);


//流式布局
StaggeredGridLayoutManager layoutManager = new
StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL);
recyclerView.setLayoutManager(layoutManager);

橫向布局：
在這里插入圖片描述
網格布局：

流式布局：
在這里插入圖片描述

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