上一篇文章讲了如何使用ItemDecoration去实现RecyclerView的万能间距，可是很多时候我们的需求里还会有分割线，有时候既要有合适的间距，也要有分割线，这种需求多出现在列表中，也就是网格布局中，这个时候就需要我们自己去画了，如果你天真的把分割线加到布局里，那效果将会是奇丑无比。。。直接看代码吧：
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.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import com.btime.base_utilities.BTimeUtils;
/**
* Created by kangbaibai on 2018/5/14.
* 网格布局分割线
*/
public class GovAffMatrixItemDecoration extends RecyclerView.ItemDecoration {
private Paint mPaint; //如果需要用画笔手绘
private Drawable mDrawableDivider; //如果需要绘制给定的drawable
private int mPaintDividerLength = 1; //分割线宽度或高度
private DrawType drawType; //用画笔或者特定的drawable绘制
private int spanCount = 1; //网格布局的列数或行数，默认为一
/**
* 注意：列表的方向
* LinearLayoutManager.VERTICAL或LinearLayoutManager.HORIZONTAL
*/
private int mOrientation;
private static final int[] ATTRS = new int[]{android.R.attr.listDivider}; //系统默认的分割线
/**
* 自定义分割线
*
* @param context 上下文
* @param orientation 列表方向
* @param drawableId 分割线图片
*/
public GovAffMatrixItemDecoration(Context context, int orientation, int drawableId) {
if (orientation != LinearLayoutManager.VERTICAL && orientation != LinearLayoutManager.HORIZONTAL) {
throw new IllegalArgumentException("请输入正确的参数！");
}
mOrientation = orientation;
if (drawableId == -100) {
final TypedArray a = context.obtainStyledAttributes(ATTRS); //获取系统的样式
mDrawableDivider = a.getDrawable(0);
a.recycle();
} else {
mDrawableDivider = ContextCompat.getDrawable(context, drawableId);
}
drawType = DrawType.USEDRAWABLE; //表明使用特点的drawable绘制
}
/**
* @param context 上下文
* @param orientation 列表方向
*/
public GovAffMatrixItemDecoration(Context context, int orientation) {
this(context, orientation, -100);
}
/**
* 自定义分割线
*
* @param orientation 列表方向
* @param dividerHeight 分割线高度
* @param dividerColor 分割线颜色
*/
public GovAffMatrixItemDecoration(int orientation, int dividerHeight, int dividerColor) {
if (orientation != LinearLayoutManager.VERTICAL && orientation != LinearLayoutManager.HORIZONTAL) {
throw new IllegalArgumentException("请输入正确的参数！");
}
mOrientation = orientation;
if (dividerHeight != -100) {
//分割线高度
mPaintDividerLength = dividerHeight;
}
//创建特定画笔
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setColor(dividerColor);
mPaint.setStyle(Paint.Style.FILL);
//表明绘制用paint
drawType = DrawType.USEPAINT;
}
/**
* 自定义分割线
*
* @param orientation 列表方向
* @param dividerColor 分割线颜色
*/
public GovAffMatrixItemDecoration(int orientation, int dividerColor) {
this(orientation, -100, dividerColor);
}
/**
* get Item Offsets：获得item的偏移量。
* 通过方法名得知此方法用来控制item的偏移
*
* @param outRect
* @param view
* @param parent
* @param state
*/
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
if (parent.getLayoutManager() instanceof GridLayoutManager) {
GridLayoutManager gridLayoutManager = (GridLayoutManager) parent.getLayoutManager();
spanCount = gridLayoutManager.getSpanCount();
}
/**
* 列表的方向为横向，画分割线就是纵向的，需要确定的是child的右边偏移值
* 留出空间画分割线
*/
if (this.mOrientation == LinearLayoutManager.HORIZONTAL)
switch (drawType) {
case USEPAINT:
outRect.set(0, 0, mPaintDividerLength, 0);
break;
case USEDRAWABLE:
outRect.set(0, 0, mDrawableDivider.getIntrinsicWidth(), 0);
break;
}
/**
* 列表的方向为纵向，画分割线就是横向的，需要确定的是child的下边偏移值
* 留出空间画分割线
*/
else if (this.mOrientation == LinearLayoutManager.VERTICAL)
switch (drawType) {
case USEPAINT:
outRect.set(mPaintDividerLength, 0, 0, mPaintDividerLength);
break;
case USEDRAWABLE:
outRect.set(mDrawableDivider.getIntrinsicHeight(), 0, 0, mDrawableDivider.getIntrinsicHeight());
break;
}
}
/**
* 绘制分割线
*
* @param c
* @param parent
* @param state
*/
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDraw(c, parent, state);
if (mOrientation == LinearLayoutManager.VERTICAL) {
//列表是纵向的，需要绘制横向的分割线
drawHorizontal(c, parent);
drawVertical(c, parent);
} else {
//列表是横向的，需要绘制纵向的分割线
drawVertical(c, parent);
}
}
/**
* 绘制横向 item 分割线。左、上、右都是可计算的，下需要获取给定的高度值
*
* @param canvas
* @param parent
*/
private void drawHorizontal(Canvas canvas, RecyclerView parent) {
//左边：到父容器的left内间距位置值
final int left = parent.getPaddingLeft();
//右边：到父容器的right内间距位置值
final int right = parent.getMeasuredWidth() - parent.getPaddingRight();
final int childSize = parent.getChildCount();
//循环绘制每条分割线
//因为每次绘制会以父布局的宽为长度，所以每行只需绘制一次，在此计算出需要绘制的次数
int drawSize = (childSize / spanCount) + ((childSize % spanCount > 0) ? 1 : 0);
for (int i = 1; i < childSize; i++) {
if (i % spanCount == 0) {
final View child = parent.getChildAt(i - 1);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
//上边：具体的某条分割线的左边以child的(bottom+bottomMargin)位置值
final int top = child.getBottom() + layoutParams.bottomMargin;
//下边：根据类型判断
int bottom;
switch (drawType) {
case USEPAINT://构造方法声明使用画笔绘制
//下边：top加上分割线的高度
bottom = top + mPaintDividerLength;
if (mPaint != null) {
canvas.drawRect(left, top, right, bottom, mPaint);
}
break;
case USEDRAWABLE://构造方法声明使用drawable
if (mDrawableDivider != null) {
//下边：top加上分割线的高度
bottom = top + mDrawableDivider.getIntrinsicHeight();
mDrawableDivider.setBounds(left, top, right, bottom);
mDrawableDivider.draw(canvas);
}
break;
}
}
}
}
/**
* 绘制纵向 item 分割线。上、下、左都是可计算的，右侧需要获取给定的宽度值
*
* @param canvas
* @param parent
*/
private void drawVertical(Canvas canvas, RecyclerView parent) {
//上边：到父容器的top内间距位置值
// final int top = parent.getPaddingTop();
// //下边：到父容器的bottom内间距位置值
// final int bottom = parent.getMeasuredHeight() - parent.getPaddingBottom();
final int childSize = parent.getChildCount();
//循环绘制每条分割线
for (int i = 0; i < childSize - 1; i++) {
if (i % spanCount == 0 || i % spanCount == 1) {
final View child = parent.getChildAt(i);
//获取child的布局参数
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
final int top = child.getTop() + BTimeUtils.DisplayUtil.dip2px(8);
final int bottom = child.getBottom() - BTimeUtils.DisplayUtil.dip2px(8);
//左边：具体的某条分割线的左边以child的(right+rightMargin)位置值
final int left = child.getRight() + layoutParams.rightMargin;
//右边：根据类型判断
int right;
switch (drawType) {
case USEPAINT://构造方法声明使用画笔绘制
//右边：left加上分割线的宽度
right = left + mPaintDividerLength;
if (mPaint != null) {
canvas.drawRect(left, top, right, bottom, mPaint);
}
break;
case USEDRAWABLE://构造方法声明使用drawable
if (mDrawableDivider != null) {
//右边：left加上分割线的宽度
right = left + mDrawableDivider.getIntrinsicWidth();
mDrawableDivider.setBounds(left, top, right, bottom);
mDrawableDivider.draw(canvas);
}
break;
}
}
}
}
public static enum DrawType {
USEPAINT(1),//用自定义颜色的画笔画
USEDRAWABLE(2); //用特定的drawable画
private final int type;
DrawType(int type) {
this.type = type;
}
public int getType() {
return type;
}
}
}