Android RecyclerView实现下拉列表功能

现在市面上的很多的应用，都带有下拉列表的功能，将所有选项都放在下拉列表中，当用户点击选择的时候，弹出所有的选项，用户选择一项后，下拉列表自动隐藏，很多下拉列表都是用ListView + PopupWindow来实现的，由于Google推出了替代ListView的RecyclerView，所以简单实现一下：

MainActivity.java

package com.jackie.countdowntimer; 
import android.graphics.drawable.BitmapDrawable; 
import android.os.Bundle; 
import android.os.CountDownTimer; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.LinearLayoutManager; 
import android.support.v7.widget.RecyclerView; 
import android.support.v7.widget.Toolbar; 
import android.view.View; 
import android.widget.EditText; 
import android.widget.ImageButton; 
import android.widget.PopupWindow; 
import java.util.ArrayList; 
import java.util.List; 
public class MainActivity extends AppCompatActivity implements View.OnClickListener { 
  private EditText mNumberEditText; 
  private ImageButton mSelectImageButton; 
  private PopupWindow mPopupWindow; 
  private RecyclerView mRecyclerView; 
  private RecyclerViewAdapter mRecyclerViewAdapter; 
  private List<String> mNumberList; 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(toolbar); 
    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
    fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
        Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
            .setAction("Action", null).show(); 
      } 
    }); 
    //初始化数据 
    mNumberList = new ArrayList<>(); 
    for (int i = 0; i < 30; i++) { 
      mNumberList.add("1000000" + i); 
    } 
    mNumberEditText = (EditText) findViewById(R.id.number); 
    mSelectImageButton = (ImageButton) findViewById(R.id.select_number); 
    mSelectImageButton.setOnClickListener(this); 
  } 
  @Override 
  public void onClick(View v) { 
    switch (v.getId()) { 
      case R.id.select_number: 
        showSelectNumberPopupWindow(); 
        break; 
    } 
  } 
   
  private void showSelectNumberPopupWindow() { 
    initRecyclerView(); 
    mPopupWindow = new PopupWindow(mRecyclerView, mNumberEditText.getWidth() - 4, 200); 
    mPopupWindow.setOutsideTouchable(true);   // 设置外部可以被点击 
    mPopupWindow.setBackgroundDrawable(new BitmapDrawable()); 
    mPopupWindow.setFocusable(true);    // 使PopupWindow可以获得焦点 
    // 显示在输入框的左下角 
    mPopupWindow.showAsDropDown(mNumberEditText, 2, -5); 
  } 
   
  private void initRecyclerView(){ 
    mRecyclerView = new RecyclerView(this); 
    //设置布局管理器 
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this)); 
    mRecyclerView.setBackgroundResource(R.drawable.background); 
    //设置Adapter 
    mRecyclerViewAdapter = new RecyclerViewAdapter(this, mNumberList); 
    mRecyclerView.setAdapter(mRecyclerViewAdapter); 
    //设置点击事件 
    mRecyclerViewAdapter.setOnItemClickListener(new RecyclerViewAdapter.OnItemClickListener() { 
      @Override 
      public void onItemClick(View view, int position) { 
        mNumberEditText.setText(mNumberList.get(position)); 
        mNumberEditText.setSelection(mNumberEditText.getText().toString().length()); 
        mPopupWindow.dismiss(); 
      } 
    }); 
    //添加分割线 
    mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL_LIST)); 
  } 
 } 

 RecyclerViewAdapter.java

package com.jackie.countdowntimer; 
import android.content.Context; 
import android.support.v7.widget.RecyclerView; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ImageButton; 
import android.widget.TextView; 
import java.util.List; 
 
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.RecyclerViewHolder> { 
  private OnItemClickListener mOnItemClickListener; 
  private Context mContext; 
  private List<String> mNumberList; 
  public RecyclerViewAdapter(Context context, List<String> numberList) { 
    this.mContext = context; 
    this.mNumberList = numberList; 
  } 
  public interface OnItemClickListener { 
    void onItemClick(View view, int position); 
  } 
  public void setOnItemClickListener(OnItemClickListener onItemClickListener) { 
    this.mOnItemClickListener = onItemClickListener; 
  } 
  @Override 
  public RecyclerViewAdapter.RecyclerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
    RecyclerViewHolder holder = new RecyclerViewHolder(LayoutInflater.from(mContext).inflate(R.layout.number_item, parent, false)); 
    return holder; 
  } 
  @Override 
  public void onBindViewHolder(final RecyclerViewAdapter.RecyclerViewHolder holder, final int position) { 
    holder.numberTextView.setText(mNumberList.get(position)); 
    // 如果设置了回调，则设置点击事件 
    if (mOnItemClickListener != null) { 
      holder.numberTextView.setOnClickListener(new View.OnClickListener() { 
        @Override 
        public void onClick(View v) { 
          mOnItemClickListener.onItemClick(holder.itemView, holder.getLayoutPosition()); 
        } 
      }); 
    } 
    holder.deleteImageButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
        mNumberList.remove(position); 
        //通知刷新 
        notifyItemRemoved(position); 
      } 
    }); 
  } 
  @Override 
  public int getItemCount() { 
    return mNumberList.size(); 
  } 
  public class RecyclerViewHolder extends RecyclerView.ViewHolder { 
    TextView numberTextView; 
    ImageButton deleteImageButton; 
    public RecyclerViewHolder(View itemView) { 
      super(itemView); 
      numberTextView = (TextView) itemView.findViewById(R.id.number_item); 
      deleteImageButton = (ImageButton) itemView.findViewById(R.id.number_item_delete); 
    } 
  } 
} 

 DividerItemDecoration.java

package com.jackie.countdowntimer; 
 
import android.content.Context; 
import android.content.res.TypedArray; 
import android.graphics.Canvas; 
import android.graphics.Rect; 
import android.graphics.drawable.Drawable; 
import android.support.v7.widget.LinearLayoutManager; 
import android.support.v7.widget.RecyclerView; 
import android.view.View; 
 
public class DividerItemDecoration extends RecyclerView.ItemDecoration { 
  private static final int[] ATTRS = new int[]{ 
      android.R.attr.listDivider 
  }; 
  public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL; 
  public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL; 
  private Drawable mDivider; 
  private int mOrientation; 
  public DividerItemDecoration(Context context, int orientation) { 
    final TypedArray a = context.obtainStyledAttributes(ATTRS); 
    mDivider = a.getDrawable(0); 
    a.recycle(); 
    setOrientation(orientation); 
  } 
  public void setOrientation(int orientation) { 
    if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) { 
      throw new IllegalArgumentException("invalid orientation"); 
    } 
    mOrientation = orientation; 
  } 
  @Override 
  public void onDraw(Canvas c, RecyclerView parent) { 
    if (mOrientation == VERTICAL_LIST) { 
      drawVertical(c, parent); 
    } else { 
      drawHorizontal(c, parent); 
    } 
  } 
  public void drawVertical(Canvas c, RecyclerView parent) { 
    final int left = parent.getPaddingLeft(); 
    final int right = parent.getWidth() - parent.getPaddingRight(); 
    final int childCount = parent.getChildCount(); 
    for (int i = 0; i < childCount; i++) { 
      final View child = parent.getChildAt(i); 
      android.support.v7.widget.RecyclerView v = new android.support.v7.widget.RecyclerView(parent.getContext()); 
      final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams(); 
      final int top = child.getBottom() + params.bottomMargin; 
      final int bottom = top + mDivider.getIntrinsicHeight(); 
      mDivider.setBounds(left, top, right, bottom); 
      mDivider.draw(c); 
    } 
  } 
  public void drawHorizontal(Canvas c, RecyclerView parent) { 
    final int top = parent.getPaddingTop(); 
    final int bottom = parent.getHeight() - parent.getPaddingBottom(); 
    final int childCount = parent.getChildCount(); 
    for (int i = 0; i < childCount; i++) { 
      final View child = parent.getChildAt(i); 
      final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams(); 
      final int left = child.getRight() + params.rightMargin; 
      final int right = left + mDivider.getIntrinsicHeight(); 
      mDivider.setBounds(left, top, right, bottom); 
      mDivider.draw(c); 
    } 
  } 
  @Override 
  public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) { 
    if (mOrientation == VERTICAL_LIST) { 
      outRect.set(0, 0, 0, mDivider.getIntrinsicHeight()); 
    } else { 
      outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0); 
    } 
  } 
} 

效果图如下：

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