今天我有一个很奇怪的问题:我有一个RecyclerView,水平显示一些缩略图,我用smoothScrollToPosition
导航到我需要的项目,但我注意到一个问题:它会不滚动到最后一个项目。经过进一步的调试,我发现我的回收站的儿童数量比显示的少!我看到五个项目,每次显示三个项目。但儿童数(得到recyclerView.getChildCount
)返回4而不是5,我不能得到getChildAt(4)
最后一个孩子。更怪,adapter.getItemCount()
回报5,和recyclerView.getAdapter().getItemCount()
回报5 ...RecyclerView儿童数量少于儿童人数
在检查,recyclerView.getLayoutManager().getItemCount()
回报5,和'recyclerView..getLayoutManager()。getChildCount()返回4 ...
我需要两件东西:首先,我需要我的recyclerView滚动到最后一个项目,第二:我需要能够获取所有孩子,因为我在用户与项目进行交互时对其进行了一些修改。
一些代码:
// Scrolling and editing the item inside the recyclerView
// It doesn't scroll to position 4, even having a item there...
mLayoutManager.smoothScrollToPosition(recyclerView, null, position);
// the code bellow returns null if position = 4, even if the recyclerView adapter has a item at index 4, and it is visible...
ImageView iv = (ImageView) recyclerView.getChildAt(position);
if (iv != null) {
iv.setPadding(10, 10, 10, 10);
iv.setBackgroundColor(getResources().getColor(R.color.colorPrimaryDark));
ImageView ivo = (ImageView) recyclerView.getChildAt(position - 1);
if (position - 1 == 0) {
ivo.setPadding(10, 10, 10, 10);
} else {
ivo.setPadding(0, 10, 10, 10);
}
ivo.setBackgroundColor(getResources().getColor(R.color.transparent));
}
smoothScrollToPosition实现:
public class SnappingLinearLayoutManager extends LinearLayoutManager {
private static final float MILLISECONDS_PER_INCH = 150f;
public SnappingLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
}
@Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
int position) {
RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext()){
@Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return new PointF(0, 1);
}
//This returns the milliseconds it takes to scroll one pixel.
@Override
protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
return MILLISECONDS_PER_INCH/displayMetrics.densityDpi;
}
};
smoothScroller.setTargetPosition(position);
startSmoothScroll(smoothScroller);
}
private class TopSnappedSmoothScroller extends LinearSmoothScroller {
public TopSnappedSmoothScroller(Context context) {
super(context);
}
@Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return SnappingLinearLayoutManager.this
.computeScrollVectorForPosition(targetPosition);
}
@Override
protected int getVerticalSnapPreference() {
return SNAP_TO_ANY;
}
}
}
RecycleView不包含适配器中的所有项目。它只能显示视图的视图+在回收站视图列表的开始和结尾处有一些额外的视图,因此它可以使其更快。也许这是问题所在。 – Rafal