RecyclerView的简单使用 可以先回顾一下RecyclerView的使用方式
我们在使用RecyclerView的时候发现，这玩意根本没有分割线，看起来有点丑，查了一下资料，谷歌并没有提供默认的分割线，下面我们就把分割线搞出来，方便以后复制粘贴。
我们可以使用recyclerView的addItemDecoration()来加入分割线，因为谷歌默认没有提供，我们就需要继承RecyclerView.ItemDecoration来自定义分割线。
先贴上已经写好的代码，再进行分析。/**
* 作 者：黑马小杰
* 时 间：2018/3/18
* 邮 箱：[email protected]
*/
public class DividerItemDecoration extends RecyclerView.ItemDecoration {
public static final int HORIZONTAL = LinearLayoutManager.HORIZONTAL;
public static final int VERTICAL = LinearLayoutManager.VERTICAL;
private Drawable mDivider;
private int mOrientation;
private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
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 && orientation != VERTICAL) {
}
mOrientation = orientation;
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
if (mOrientation == VERTICAL) {
drawVertical(c, parent);
} else {
drawHorizontal(c, parent);
}
}
/**
* 竖直排列，画水平分割线
*
* @param c
* @param parent
*/
public void drawVertical(Canvas c, RecyclerView parent) {
/* 当orientation为 Vertical 时，Item的分割线水平线条
分割线的 Top 和 Bottom 则需要计算出有多少个Item
首先由Item的位置获取到child的位置坐标*/
//左边=item左边距
final int left = parent.getPaddingLeft();
//右边的坐标=右边 + 分割线的width
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();
//Top = child的下边坐标 + child外边距距离
final int top = child.getBottom() + params.bottomMargin;
// 然后根据bottom = top +分割线高度
final int bottom = top + mDivider.getIntrinsicHeight();
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
}
}
/**
* 水平排列，画竖直分割线
*
* @param c
* @param parent
*/
public void drawHorizontal(Canvas c, RecyclerView parent) {
/*当orientation为 Horizontal 时，Item的分割线为竖直线
分割线的Top和Bottom就容易确定
分割线的 left 和 right 则需要计算出有多少个Item
根据Item的位置获取到child的位置坐标*/
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();
//所以分割线的left = child的右边的坐标 + child的外边距的距离
final int left = child.getRight() + params.rightMargin;
//然后根据左边 + 分割线的宽度 得到右边的坐标
final int right = left + mDivider.getIntrinsicHeight();
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
}
}
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
/* outRect.set(left, top, right, bottom);
Item的四周间距
垂直时，Item的下方预留出分割线的高度
水平时，Item的右方预留出分割线的宽度*/
if (mOrientation == VERTICAL) {
outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
} else {
outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
}
}
}首先注意的是onDraw方法。根据构造函数来确定分割线的方向。drawHorizontal和drawVertical分别绘制横向item（竖线）和竖直item（横线）.getItemOffsets()设置分割线的尺寸。
调用方式更为简单，通过addItemDecoration方法加入divide的实例就OK了。但是今天踩了个坑，一定要注意。加载分割线一定要在setAdapter之前。谨记！
DividerItemDecoration dividerItemDecoration=new DividerItemDecoration(getInstance().getActivity(), DividerItemDecoration.VERTICAL);
recycler_sensor_list.addItemDecoration( dividerItemDecoration);