Android RecyclerView实现水平、垂直方向分割线

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android RecyclerView不像过去的ListView那样随意的设置水平方向的分割线，如果要实现RecyclerView的水平/垂直分割线，则需要继承自RecyclerView.ItemDecoration重写getItemOffsets方法，从而增加水平/垂直分割线。

写一个例子。

MainActivity.Java：

package zhangphil.app;

import android.content.Context;
import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

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

    RecyclerView mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);

    // 两列
    int spanCount = 2;

    // StaggeredGridLayoutManager管理RecyclerView的布局。
    StaggeredGridLayoutManager mLayoutManager = new StaggeredGridLayoutManager(spanCount, StaggeredGridLayoutManager.VERTICAL);
    mRecyclerView.setLayoutManager(mLayoutManager);

    //为RecyclerView增加分割线，水平和垂直方向都有。增加分割线值比如为32。
    RecyclerViewItemDecoration decoration = new RecyclerViewItemDecoration(32);
    mRecyclerView.addItemDecoration(decoration);

    RecyclerViewAdapter mAdapter = new RecyclerViewAdapter(this);
    mRecyclerView.setAdapter(mAdapter);
  }

  private class ItemViewHolder extends RecyclerView.ViewHolder {
    private TextView text;

    public ItemViewHolder(View itemView) {
      super(itemView);
      text = (TextView) itemView.findViewById(android.R.id.text1);
      text.setTextColor(Color.WHITE);
    }
  }

  public class RecyclerViewAdapter extends RecyclerView.Adapter<ItemViewHolder> {
    private Context context;

    public RecyclerViewAdapter(Context context) {
      super();
      this.context = context;
    }

    @Override
    public ItemViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
      View view = View.inflate(context, android.R.layout.simple_list_item_1, null);
      view.setBackgroundColor(Color.RED);
      ItemViewHolder holder = new ItemViewHolder(view);
      return holder;
    }

    @Override
    public void onBindViewHolder(ItemViewHolder viewHolder, int pos) {
      viewHolder.text.setText(String.valueOf(pos));
    }

    @Override
    public int getItemCount() {
      return 15;
    }
  }
}

布局文件，很简单，就放一个RecyclerView，注意背景颜色的设置：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="@android:color/holo_orange_light">

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

</RelativeLayout>

最关键的RecyclerViewItemDecoration.java：

package zhangphil.app;

/**
 * Created by Phil on 2016/10/8.
 */

import android.graphics.Rect;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * 为RecyclerView增加间距
 * 预设2列，如果是3列，则左右值不同
 */
public class RecyclerViewItemDecoration extends RecyclerView.ItemDecoration {
  private int space = 0;
  private int pos;

  public RecyclerViewItemDecoration(int space) {
    this.space = space;
  }

  @Override
  public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {

    outRect.top = space;

    //该View在整个RecyclerView中位置。
    pos = parent.getChildAdapterPosition(view);

    //取模

    //两列的左边一列
    if (pos % 2 == 0) {
      outRect.left = space;
      outRect.right = space / 2;
    }

    //两列的右边一列
    if (pos % 2 == 1) {
      outRect.left = space / 2;
      outRect.right = space;
    }
  }
}

代码运行结果：