默认的浅灰色的分割线在某些时候并不能满足我们的要求，这时就需要自定义分割线了。
我们可以通过两种方式来实现：调用 DividerItemDecoration.setDrawable 方法或者继承实现 RecyclerView.ItemDecoration 类来实现。
一、调用 DividerItemDecoration.setDrawable 方法
实现分割线只需要调用 setDrawable(@NonNull Drawable drawable)方法，然后传入一个Drawable函数对象就可以了。
现在可以用shape来编写一个分割线样式：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"> <gradient
android:centerColor="#ff00ff00" //绿色
android:endColor="#ff0000ff" //蓝色
android:startColor="#ffff0000" //红色
android:type="linear" />
<size android:height="3dp" /> </shape>
添加分割线的代码改为如下：
//添加自定义分割线
DividerItemDecoration divider = new DividerItemDecoration(this,DividerItemDecoration.VERTICAL);
divider.setDrawable(ContextCompat.getDrawable(this,R.drawable.custom_divider));
recyclerView.addItemDecoration(divider);
运行起来之后，就可以看到一条多彩的分割线了：
二、继承实现 RecyclerView.ItemDecoration 类
这块就不多赘述了，直接贴代码：
public class RecyclerViewDivider extends RecyclerView.ItemDecoration{
private Paint mPaint;
//分割线
private Drawable mDivider;
//分割线高度，默认是2px
private int mDividerHeight = 2;
//列表的方向：LinearLayoutManager.VERTICAL或LinearLayoutManager.HORIZONTAL
private int mOrientation;
private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
/**
*
* 默认分割线：高度为2px，颜色为灰色
* 获取属性值，
*
* @param context
* @param orientation 列表方向
*/
public RecyclerViewDivider(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 array = context.obtainStyledAttributes(ATTRS);
mDivider = array.getDrawable(0);
array.recycle();
mDividerHeight = mDivider.getIntrinsicHeight();
}
/**
* 自定义分割线
*
* @param context
* @param orientation 列表方向
* @param drawableId 分割线图片
*/
public RecyclerViewDivider(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;
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 dividerColor 分割线颜色
*/
public RecyclerViewDivider(Context context, 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;
mDividerHeight = dividerHeight;
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) {
if (mOrientation == LinearLayoutManager.VERTICAL) {
outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
} else {
outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
}
outRect.set(0, 0, 0, mDividerHeight);
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDraw(c, parent, state);
if(mOrientation==LinearLayoutManager.VERTICAL){
drawVerticalLine(c,parent);
}else{
drawHorizontalLine(c,parent);
}
}
//为横方向item, 画分割线
private void drawHorizontalLine(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);
}
}
}
//为竖方向item, 画分割线
private void drawVerticalLine(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, top, right, bottom);
mDivider.draw(canvas);
}
if (mPaint != null) {
canvas.drawRect(left, top, right, bottom, mPaint);
}
}
}
}