android - 更改 recyclerview 中第一个可见项目的边距

Question

如何使用卡片更改水平回收 View 上第一个完整可见项目的边距(底部 20 dp)？我只能获取第一个完整可见项目的索引，但无法获取对 View 的任何引用。

 mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
       @Override
       public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
           super.onScrolled(recyclerView, dx, dy);

           firstVisibleItem = lm.findFirstCompletelyVisibleItemPosition();
        View view=  mRecyclerView.getChildAt(firstVisibleItem);

        RelativeLayout.LayoutParams lp= new RelativeLayout.LayoutParams(300, 150);
        lp.setMargins(0, 0, 0, 20);
        view.setLayoutParams(lp);

       }
    });

Answer 1

假设 view 包含对要更改边距的 View 的引用，您可以使用以下命令将底部边距设置为 20 像素:

LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,
    LinearLayout.LayoutParams.WRAP_CONTENT);
lp.setMargins(0, 0, 0, 20);
view.setLayoutParams(lp);

请注意，这会将底部边距更改为 20 像素，而不是 20dp。您需要将 20dp 值转换为像素。 Converting pixels to dp将是了解如何完成转换的好地方。

您可能还需要更改 LinearLayout.LayoutParams 构造函数的高度和宽度参数以满足您的需要。

如果问题是获取对 View 的引用，发布一些代码会有所帮助。

编辑/更新 该代码有帮助。我认为您没有设置对所需 View 的访问权限。这是另一种方法:

 mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
   @Override
   public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
       super.onScrolled(recyclerView, dx, dy);

       // Find the adapter position of the first fully visible item
       // May return RecyclerView.NO_POSITION that is not handled here.
       firstVisibleItem = lm.findFirstCompletelyVisibleItemPosition();

       // Find the corresponding view holder for this position.
       // MyViewHolder should already be defined (just don't know the name).
       MyViewHolder vh = (MyViewHolder) mRecyclerView
           .findViewHolderForAdapterPosition(firstVisibleItem);

       // Get the layout parameters from the top-level item of this view.
       // This could also be another view captured within the view holder.
       RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) vh.itemView.getLayoutParams();

       // Make our changes and set them.
       lp.setMargins(0, 0, 0, 50);
       vh.itemView.setLayoutParams(lp);
   }
});