万能RecyclerView分割线扩展

该万能分割线参考自博客：RecyclerView的万能分割线_pengkv的博客-CSDN博客_android recyclerview 分割线 在他的基础上添加了距离左右边距的属性。

recyclerview最后一个条目不显示分割线且自定义分割线 - 代码先锋网

该divider可以自己定义宽高、距离左边、右边的距离，颜色等，先来看下效果：

在项目中将RecyclerViewDivider.java考入，然后再引用即可，里面有几个构造函数，可以选择合适自己的，下面举例是参数最多的那个，可以设置颜色，宽高，举例左右边界的距离：

        mRecyclerView.addItemDecoration(new RecycleViewDivider(getApplicationContext(), LinearLayoutManager.VERTICAL, 20, 60, 60, getApplicationContext().getResources().getColor(R.color.colorAccent)));

下面是这个divider的所有代码，注释已经很详细了：

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v4.content.ContextCompat;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;

public class RecycleViewDivider extends RecyclerView.ItemDecoration {

    private Paint mPaint;
    private Drawable mDivider;
    private int mDividerHeight = 2;//分割线高度，默认为1px
    private int mOrientation;//列表的方向：LinearLayoutManager.VERTICAL或LinearLayoutManager.HORIZONTAL
    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
    private int mOffsetLeft = 0;    //分割线偏离左边界
    private int mOffsetRight = 0;   //分割线偏离右边界

    /**
     * 默认分割线：高度为2px，颜色为灰色
     *
     * @param context
     * @param orientation 列表方向
     */
    public RecycleViewDivider(Context context, int orientation) {
        if (orientation != LinearLayoutManager.VERTICAL && orientation != LinearLayoutManager.HORIZONTAL) {
            throw new IllegalArgumentException("请输入正确的参数！");
        }
        mOrientation = orientation;

        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
    }

    /**
     * 自定义分割线
     *
     * @param context
     * @param orientation 列表方向
     * @param drawableId  分割线图片
     */
    public RecycleViewDivider(Context context, int orientation, int drawableId) {
        this(context, orientation);
        mDivider = ContextCompat.getDrawable(context, drawableId);
        mDividerHeight = mDivider.getIntrinsicHeight();
    }

    /**
     * 自定义分割线
     *
     * @param context
     * @param orientation   列表方向
     * @param dividerHeight 分割线高度
     *@param offsetLeft    分割线距离左边距
     * @param offsetRight   分割线距离右边距
     * @param dividerColor  分割线颜色
     */
    public RecycleViewDivider(Context context, int orientation, int dividerHeight, int offsetLeft, int offsetRight, int dividerColor) {
        this(context, orientation);
        mDividerHeight = dividerHeight;
        mOffsetLeft = offsetLeft;
        mOffsetRight = offsetRight;
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(dividerColor);
        mPaint.setStyle(Paint.Style.FILL);
    }


    //获取分割线尺寸
    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        if (mOrientation == LinearLayoutManager.VERTICAL) {
            outRect.set(0, 0, 0, mDividerHeight);
        } else {
            outRect.set(0, 0, mDividerHeight, 0);
        }
    }

    //绘制分割线
    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDraw(c, parent, state);
        if (mOrientation == LinearLayoutManager.VERTICAL) {
            drawVertical(c, parent);
        } else {
            drawHorizontal(c, parent);
        }
    }

    /**
     * 绘制纵向列表时的分隔线  这时分隔线是横着的
     * 每次 left相同，top根据child变化，right相同，bottom也变化
     * @param canvas
     * @param parent
     */
    private void drawVertical(Canvas canvas, RecyclerView parent) {
        final int left = parent.getPaddingLeft();
        final int right = parent.getMeasuredWidth() - parent.getPaddingRight();
        final int childSize = parent.getChildCount();
        for (int i = 0; i < childSize; i++) {
            final View child = parent.getChildAt(i);
            RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int top = child.getBottom() + layoutParams.bottomMargin;
            final int bottom = top + mDividerHeight;
            if (mDivider != null) {
                mDivider.setBounds(left + mOffsetLeft, top, right - mOffsetRight, bottom);
                mDivider.draw(canvas);
            }
            if (mPaint != null) {
                canvas.drawRect(left + mOffsetLeft, top, right - mOffsetRight, bottom, mPaint);
            }
        }
    }

    /**
     * 绘制横向列表时的分隔线  这时分隔线是竖着的
     * l、r 变化； t、b 不变
     * @param canvas
     * @param parent
     */
    private void drawHorizontal(Canvas canvas, RecyclerView parent) {
        final int top = parent.getPaddingTop();
        final int bottom = parent.getMeasuredHeight() - parent.getPaddingBottom();
        final int childSize = parent.getChildCount();
        for (int i = 0; i < childSize; i++) {
            final View child = parent.getChildAt(i);
            RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int left = child.getRight() + layoutParams.rightMargin;
            final int right = left + mDividerHeight;
            if (mDivider != null) {
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(canvas);
            }
            if (mPaint != null) {
                canvas.drawRect(left, top, right, bottom, mPaint);
            }
        }
    }
}

当然也有更简单的方法，使用shape资源文件，不需要写java代码，适用于简单的分割线，效果如下：

但是不好的地方是，无法调整距离左右边距，或者是使用姿势不对？

使用方法：

//添加自定义分割线
        DividerItemDecoration divider = new DividerItemDecoration(this,DividerItemDecoration.VERTICAL);
        divider.setDrawable(ContextCompat.getDrawable(this,R.drawable.divider_mileage));
        mRecyclerView.addItemDecoration(divider);

自定义的分割线的文件，在drawable/divider_mileage.xml：

上面整个项目地址：https://github.com/buder-cp/base_component_learn/tree/master/self_divider