RecyclerView 在项目中使用的常见问题
目录
- ItemDecoration
- 侧拉菜单
- SnapHelper
- 局部刷新
- 由于复用导致数据的错乱问题
- y 轴上的滑动距离
- 上下左右滑动判断
- 双击置顶
- 添加头布局后，每次刷新内容会跳回头布局：解决办法
ItemDecoration
常见的作用有：分割线、吸顶效果、时光轴等 推荐阅读 https://blog.csdn.net/briblue/article/details/70161917
线性分割线：
以下代码来源于网络，在项目中测试可以通过。
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};
/**
* 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 dividerColor 分割线颜色
*/
public RecycleViewDivider(Context context, int orientation, int dividerHeight, int dividerColor) {
this(context, 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) {
super.getItemOffsets(outRect, view, parent, state);
outRect.set(0, 0, 0, mDividerHeight);
}
//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);
}
}
//绘制横向 item 分割线
private void drawHorizontal(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);
}
}
}
//绘制纵向 item 分割线
private void drawVertical(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);
}
}
}
}
网格分割线：
以下代码来源于网络，在项目中测试可以通过。
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {
private int spanCount;
private int spacing;
private boolean includeEdge;
public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
this.spanCount = spanCount;
this.spacing = spacing;
this.includeEdge = includeEdge;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
int position = parent.getChildAdapterPosition(view); // item position
int column = position % spanCount; // item column
if (includeEdge) {
outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)
if (position < spanCount) { // top edge
outRect.top = spacing;
}
outRect.bottom = spacing; // item bottom
} else {
outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f / spanCount) * spacing)
if (position >= spanCount) {
outRect.top = spacing; // item top
}
}
}
侧拉菜单
实现原理暂时还没去阅读源码，实现的功能就是在
RecyclerView的每个Item添加上侧拉出来的布局，通过侧拉出来的布局实现一些功能。具体可到Github搜索 这个库PinnedSectionItemDecoration,上面有实现的效果。
compile 'com.github.CymChad:BaseRecyclerViewAdapterHelper:2.9.30'
compile 'com.oushangfeng:PinnedSectionItemDecoration:1.2.7'
compile 'com.scwang.smartrefresh:SmartRefreshLayout:1.1.0-alpha-5'
SnapHelper
参考：让你明明白白的使用RecyclerView——SnapHelper详解
SnapHelper是一个抽象类，官方提供了一个LinearSnapHelper的子类，可以让RecyclerView滚动停止时相应的Item停留中间位置。25.1.0版本中官方又提供了一个PagerSnapHelper的子类，可以使RecyclerView像ViewPager一样的效果，一次只能滑一页，而且居中显示。
这两个子类使用方式也很简单，只需要创建对象之后调用attachToRecyclerView()附着到对应的RecyclerView对象上就可以了
new LinearSnapHelper().attachToRecyclerView(mRecyclerView);
//或者
new PagerSnapHelper().attachToRecyclerView(mRecyclerView);
局部刷新
例如点击item中的某个控件，刷新该控件对应的点击数。
// 定义的刷新函数
adapter.refreshPositionItem(view,count,position);
adapter.notifyItemChanged(position,0);
在 adapter 中添加一个方法
public void refreshPositionItem(View view, int count, int position) {
TextView tvCount = view.findViewById(R.id.tv_count);
tvCount.setText(count+"");
}
由于复用导致数据的错乱问题
一定要修改源数据源后再刷新 adapter ，这就不会错乱了
2018-12-18 更新
y 轴上的滑动距离
这里是为了滑动显示
toolbar的标题
/**
* 获取滑动距离
* @return
*/
public int getScollYDistance() {
int position = linearLayoutManager.findFirstVisibleItemPosition();
View firstVisiableChildView = linearLayoutManager.findViewByPosition(position);
int itemHeight = firstVisiableChildView.getHeight();
return (position) * itemHeight - firstVisiableChildView.getTop();
}
上下左右滑动判断
这里是为了滑动显示隐藏发布图标
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// 如果 dx 为正数代表向左滑动，dx 为负数代表向右滑动。
// 如果 dy 为正数代表向上滑动，dy 为负数代表向下滑动。
if (dy > 0 ){
floatingActionButton.setVisibility(View.GONE);
}else {
floatingActionButton.setVisibility(View.VISIBLE);
}
}
});
双击置顶
工具：
public class DoubleClickBackToContentTopListener implements View.OnClickListener {
private final long delayTime = 300;
private long lastClickTime = 0;
private final IDoubleClickListener doubleClickListener;
public interface IDoubleClickListener {
/**
* 双击置顶
*/
void onDoubleClickToTop();
}
@Override
public final void onClick(View v) {
long nowClickTime = System.currentTimeMillis();
if (nowClickTime - lastClickTime > delayTime) {
lastClickTime = nowClickTime;
} else {
onDoubleClick(v);
}
}
public DoubleClickBackToContentTopListener(@NonNull IDoubleClickListener iDoubleClickListener) {
this.doubleClickListener = iDoubleClickListener;
}
public void onDoubleClick(View v) {
doubleClickListener.onDoubleClickToTop();
}
}
使用：
// 双击顶部置顶（直接置顶失效，使用动画滚动置顶）
toolbarHeightLayout.setOnClickListener(new DoubleClickBackToContentTopListener(new DoubleClickBackToContentTopListener.IDoubleClickListener() {
@Override
public void onDoubleClickToTop() {
// rvCirclelist.scrollToPosition(0); // 失效
rvCirclelist.smoothScrollToPosition(0);
}
}));
添加头布局后，每次刷新内容会跳回头布局：解决办法
解决办法有以下几个，推荐第一个
1.recyclerView.setFocusableInTouchMode(false);(亲测成功)
2.recyclerView.setFocusable(false);
3.setHasFixedSize(true);
4.把recyclerview 高度设为match_parent就解决了.....
参考
Android RecyclerView详解