如何在 RecyclerView 上正确突出显示所选项目? [英] How to properly highlight selected item on RecyclerView?

问题描述

我正在尝试使用 RecyclerView 作为水平 ListView.我想弄清楚如何突出显示所选项目.当我单击其中一个项目时，它被选中并正确突出显示，但是当我单击另一个项目时，第二个项目与旧项目一起突出显示.

I am trying to use a RecyclerView as a horizontal ListView. I am trying to figure out how to highlight the selected item. When I click on one of the items, it gets selected and it is highlighted properly but when I click on another one, the second one gets highlighted with the older one.

这是我的 onClick 函数:

Here is my onClick function:

@Override
public void onClick(View view) {

    if(selectedListItem!=null){
        Log.d(TAG, "selectedListItem " + getPosition() + " " + item);
        selectedListItem.setBackgroundColor(Color.RED);
    }
    Log.d(TAG, "onClick " + getPosition() + " " + item);
    viewHolderListener.onIndexChanged(getPosition());
    selectedPosition = getPosition();
    view.setBackgroundColor(Color.CYAN); 
    selectedListItem = view;
}

这是onBindViewHolder:

@Override
public void onBindViewHolder(ViewHolder viewHolder, int position) {   
    viewHolder.setItem(fruitsData[position]);
    if(selectedPosition == position)
        viewHolder.itemView.setBackgroundColor(Color.CYAN);    
    else
        viewHolder.itemView.setBackgroundColor(Color.RED);

}

推荐答案

我编写了一个基本的适配器类来使用 RecyclerView 自动处理项目选择.只需从中派生出您的适配器并使用 state_selected 的可绘制状态列表，就像使用列表视图一样.

I wrote a base adapter class to automatically handle item selection with a RecyclerView. Just derive your adapter from it and use drawable state lists with state_selected, like you would do with a list view.

我有一个关于它的博客帖子，但是这是代码:

I have a Blog Post Here about it, but here is the code:

public abstract class TrackSelectionAdapter<VH extends TrackSelectionAdapter.ViewHolder> extends RecyclerView.Adapter<VH> {
    // Start with first item selected
    private int focusedItem = 0;

    @Override
    public void onAttachedToRecyclerView(final RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);

        // Handle key up and key down and attempt to move selection
        recyclerView.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {
                RecyclerView.LayoutManager lm = recyclerView.getLayoutManager();

                // Return false if scrolled to the bounds and allow focus to move off the list
                if (event.getAction() == KeyEvent.ACTION_DOWN) {
                    if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN) {
                        return tryMoveSelection(lm, 1);
                    } else if (keyCode == KeyEvent.KEYCODE_DPAD_UP) {
                        return tryMoveSelection(lm, -1);
                    }
                }

                return false;
            }
        });
    }

    private boolean tryMoveSelection(RecyclerView.LayoutManager lm, int direction) {
        int tryFocusItem = focusedItem + direction;

        // If still within valid bounds, move the selection, notify to redraw, and scroll
        if (tryFocusItem >= 0 && tryFocusItem < getItemCount()) {
            notifyItemChanged(focusedItem);
            focusedItem = tryFocusItem;
            notifyItemChanged(focusedItem);
            lm.scrollToPosition(focusedItem);
            return true;
        }

        return false;
    }

    @Override
    public void onBindViewHolder(VH viewHolder, int i) {
        // Set selected state; use a state list drawable to style the view
        viewHolder.itemView.setSelected(focusedItem == i);
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        public ViewHolder(View itemView) {
            super(itemView);

            // Handle item click and set the selection
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    // Redraw the old selection and the new
                    notifyItemChanged(focusedItem);
                    focusedItem = getLayoutPosition();
                    notifyItemChanged(focusedItem);
                }
            });
        }
    }
} 

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