Recyclerview

RecyclerView可以说是ListView的增强版，它解决了ListView很多的不足。
目前 Android 官方更推荐使用RecyclerView。

由于RecyclerView是新增控件，位于support库，因此需要引入。
implementation 'com.android.support:recyclerview-v7:27.1.1'

主界面布局
<android.support.constraint.ConstraintLayout
    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=".ui.activity.MainActivity">

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

</android.support.constraint.ConstraintLayout>


RecyclerView 的 Item 要显示的布局，和上面List View的布局一致
Model也一致

Adapter配置

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> {

    private ArrayList<UserModel> mList;

    public void setData(ArrayList<UserModel> list) {
        this.mList = list;
        notifyDataSetChanged();
    }

    public void insertData(UserModel user, int position) {
        mList.add(position, user);
        notifyItemInserted(position);
    }

    public void removeData(int position) {
        mList.remove(position);
        notifyItemRemoved(position);
    }


    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
                .inflate(
                        R.layout.item_lv_cell,
                        parent,
                        false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, final int position) {
        final UserModel userModel = mList.get(position);
        holder.ivHead.setImageResource(R.drawable.ic_launcher_background);
        holder.tvName.setText(userModel.getName());
        holder.tvAge.setText(userModel.getAge() + "");

        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mIOnItemClickListener != null)
                    mIOnItemClickListener.onItemClick(v, userModel, position);
            }
        });
    }

    @Override
    public int getItemCount() {
        return mList != null ? mList.size() : 0;
    }

    class ViewHolder extends RecyclerView.ViewHolder {

        private ImageView ivHead;
        private TextView tvName, tvAge;

        public ViewHolder(View itemView) {
            super(itemView);

            ivHead = itemView.findViewById(R.id.iv_head);
            tvName = itemView.findViewById(R.id.tv_name);
            tvAge = itemView.findViewById(R.id.tv_age);
        }
    }

    //RecyclerView不提供点击事件需要自定义
    public interface IOnItemClickListener<T> {
        void onItemClick(View v, T t, int position);
    }

    private IOnItemClickListener mIOnItemClickListener;

    public void setOnItemClickListener(IOnItemClickListener listener) {
        this.mIOnItemClickListener = listener;
    }
}

public class MainActivity extends AppCompatActivity {

    private RecyclerView mRvDemo;
    private ArrayList<UserModel> mList;
    private RecyclerAdapter mRvAdp;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initView();
        loadData();
        initEvent();
    }

    private void initEvent() {
        mRvAdp.setOnItemClickListener(
                new RecyclerAdapter.IOnItemClickListener<UserModel>() {
                    
            @Override
            public void onItemClick(View v, UserModel userModel, int position) {
                Toast.makeText(v.getContext(),
                        userModel.getName(),
                        Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void loadData() {
        mList = new ArrayList<>();
        mRvAdp = new RecyclerAdapter();
        for (int i = 1; i <= 20; i++) {
            mList.add(new UserModel("Name" + i, i));
        }
        mRvAdp.setData(mList);
        mRvDemo.setAdapter(mRvAdp);
    }

    private void initView() {
        mRvDemo = findViewById(R.id.rv_demo);
        mRvDemo.setLayoutManager(new LinearLayoutManager(
                this,
                LinearLayoutManager.VERTICAL,
                false));
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.insert:
                if (mRvAdp != null)
                    mRvAdp.insertData(
                            new UserModel("Insert", 18),
                            mList.size());
                break;

            case R.id.delete:
                if (mRvAdp != null)
                    mRvAdp.removeData(mList.size() - 1);
                break;
        }
        return super.onOptionsItemSelected(item);
    }
}

Recycler多布局实现

• 首先准备两个布局，其中两个布局内控件的ID相同，只是摆放位置不同。

• 重写RecyclerView.Adapter的getItemViewType方法，getItemViewType的返回值对应onCreateViewHolder(int viewType)

  private static final int ITEM_LEFT = 0;
  private static final int ITEM_RIGHT = 1;

   @Override
    public int getItemViewType(int position) {
        if (position % 2 == 0) {
            return ITEM_LEFT;
        }
        return ITEM_RIGHT;
    }

   @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        mContext = parent.getContext();
        LayoutInflater mInflater = LayoutInflater.from(mContext);
        View view;
        if (viewType == ITEM_LEFT) {
            view = mInflater.inflate(R.layout.item_home_cardview, parent, false);
        } else {
            view = mInflater.inflate(R.layout.item_home_cardview2, parent, false);
        }
        return new ViewHolder(view);
    }

Adapter封装

分析通用实现，可以发现
1.  集合的数据类型与布局，不能写死
    集合的数据类型可以通过泛型处理，具体的布局样式，可以通过构造方法传入。

2.  ViewHolder是通用的
    提取ViewHolder，用于findView和设置整体点击事件

3.  onBindViewHolder()处理的Item，需要暴露出去
    onBindViewHolder() 需要暴露出去，可以用抽象方法暴露出去。

1.  封装Adapter
    构建成抽象类，将onBindViewHolder()暴漏出去
    构建泛型来传递数据

public abstract class BaseAdapter<T, H extends BaseViewHolder>
        extends RecyclerView.Adapter<BaseViewHolder> {

    protected List<T> mDatas;
    private int mLayoutResId;
    //设置事件回调
    private OnItemClickListener mOnItemClickListener;

    //填充数据，布局
    public BaseAdapter(List<T> mDatas, int layoutResId) {
        this.mDatas = mDatas;
        this.mLayoutResId = layoutResId;
    }

    @Override
    public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
                .inflate(mLayoutResId, parent, false);

        return new BaseViewHolder(view, mOnItemClickListener);
    }

    //暴露出去用来绑定数据
    public abstract void convert(H holder, T t, int position);

    @Override
    public void onBindViewHolder(BaseViewHolder holder, int position) {
        T t = mDatas.get(position);
        convert((H) holder, t, position);
    }

    @Override
    public int getItemCount() {
        return mDatas != null ? mDatas.size() : 0;
    }

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

    public void setOnItemClickListener(OnItemClickListener listener) {
        this.mOnItemClickListener = listener;
    }


    public void clear() {
        if (mDatas == null || mDatas.size() <= 0)
            return;

        for (Iterator it = mDatas.iterator(); it.hasNext(); ) {
            T t = (T) it.next();
            int position = mDatas.indexOf(t);
            it.remove();
            notifyItemRemoved(position);
        }
    }

    /**
     * 从列表中删除某项
     */
    public void removeItem(T t) {
        int position = mDatas.indexOf(t);
        mDatas.remove(position);
        notifyItemRemoved(position);
    }

    public void addData(int position, List<T> list) {
        if (list != null && list.size() > 0) {
            for (T t : list) {
                mDatas.add(position, t);
                notifyItemInserted(position);
            }
        }
    }

    public void addData(List<T> datas) {
        addData(0, datas);
    }
}

2.  构建加载数据的ViewHolder，绑定点击事件
public class BaseViewHolder extends RecyclerView.ViewHolder 
        implements View.OnClickListener {

    private SparseArray<View> views;

    //Adapter提供的点击事件
    private BaseAdapter.OnItemClickListener mOnItemClickListener;

    public BaseViewHolder(View itemView, 
                          BaseAdapter.OnItemClickListener onItemClickListener) {
        
        super(itemView);
        this.views = new SparseArray<>();

        //注册点击事件
        itemView.setOnClickListener(this);
        this.mOnItemClickListener = onItemClickListener;
    }

    @Override
    public void onClick(View view) {
        if (mOnItemClickListener != null)
            mOnItemClickListener.onItemClick(view, getLayoutPosition());
    }

    /**
     * 注册View控件
     */
    protected <T extends View> T registerView(int viewId) {
        View view = views.get(viewId);
        if (view == null) {
            //itemView 继承ViewHolder的父类成员
            view = itemView.findViewById(viewId);
            views.put(viewId, view);
        }
        return (T) view;
    }

    /**
     * 获取View
     *
     * @param viewId
     * @return
     */
    public View getView(int viewId) {
        return registerView(viewId);
    }

    /**
     * 避免findView时强转
     */
    public TextView getTextView(int viewId) {
        return registerView(viewId);
    }

    public CheckBox getCheckBox(int viewId) {
        return registerView(viewId);
    }

    public Button getButton(int viewId) {
        return registerView(viewId);
    }

    public ImageView getImageView(int viewId) {
        return registerView(viewId);
    }
}

3.  封装一层，少写一个泛型
public abstract class SimpleAdapter<T> extends BaseAdapter<T, BaseViewHolder> {

    public SimpleAdapter(List<T> mDatas, int layoutResId) {
        super(mDatas, layoutResId);
    }
}

4.  调用

private void initData() {
    mUserModules = new ArrayList<>();
    UserModule userModule;
    for (int i = 1; i < 20; i++) {
        userModule = new UserModule();
        userModule.setUserHeadIcon(R.mipmap.ic_launcher);
        userModule.setUserName("UserName" + i);
        userModule.setUserInfo("UserInfo" + i);
        mUserModules.add(userModule);
    }

    SimpleAdapter simpleAdapter = new SimpleAdapter<UserModule>(
            mUserModules,
            R.layout.item_user_info) {

        @Override
        public void convert(BaseViewHolder holder,
                            UserModule userModule,
                            int position) {

            if (position == 1)
                holder.getTextView(R.id.tv_user_info).setText("Test");
        }
    };

    simpleAdapter.setOnItemClickListener(new BaseAdapter.OnItemClickListener() {
        @Override
        public void onItemClick(View view, int position) {
            Log.i(TAG, "onItemClick: " + position);
        }
    });

    mRecyclerView.addItemDecoration(new MyDivider(MainActivity.this,
            LinearLayoutManager.VERTICAL));
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    mRecyclerView.setAdapter(simpleAdapter);
}