Question

我需要以编程方式在RecyclerView上设置上边距，但我得到了这个例外：

java.lang.RuntimeException: Unable to resume activity java.lang.ClassCastException: android.view.ViewGroup$LayoutParams cannot be cast to android.support.v7.widget.RecyclerView$LayoutParams

这是我的代码：

RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams)recyclerView.getLayoutParams();
int marginTopDp = (int)getResources().getDimension(R.dimen.margin);
int marginTopPx = (int) (marginTopDp * getResources().getDisplayMetrics().density + 0.5f);
layoutParams.setMargins(0, marginTopPx, 0, 0);
recyclerView.setLayoutParams(layoutParams);

如果我使用ViewGroup.LayoutParams layoutParams = recyclerView.getLayoutParams作为堆栈跟踪建议，我不能再调用setMargin，因为ViewGroup.LayoutParams不存在该方法。

任何帮助都将不胜感激。

Answer 1

试一试。您可以参考this了解更多信息。

ViewGroup.MarginLayoutParams marginLayoutParams = 
      (ViewGroup.MarginLayoutParams) mRecyclerView.getLayoutParams();
marginLayoutParams.setMargins(0, 10, 0, 10);
mRecyclerView.setLayoutParams(marginLayoutParams);

Answer 2

您需要使用MargingLayoutParams的新对象

    final FrameLayout.MarginLayoutParams marginLayoutParams = new      
                      FrameLayout.MarginLayoutParams(rvContacts.getLayoutParams());
    marginLayoutParams.leftMargin = left;
    marginLayoutParams.topMargin = top;
    marginLayoutParams.rightMargin = right;
    marginLayoutParams.bottomMargin = bottom;

    recyclerView.setLayoutParams(marginLayoutParams);
    recyclerView.requestLayout();

Answer 3

对我来说，recyclerview的父母是constraintLayout，

        val margins = (rv.layoutParams as ConstraintLayout.LayoutParams).apply {
        leftMargin = 0
        rightMargin = 0
    }
    rv.layoutParams = margins

否则将发生转换错误，viewGroup.LayoutParams无法转换为COnstarintLayout.LayoutParams

Answer 4

我也面临此类问题，请使用下面的代码来处理recyclerview的保证金问题。

    ViewGroup.MarginLayoutParams marginLayoutParams=
    (ViewGroup.MarginLayoutParams) recyclerView.getLayoutParams();

    // here i try to set only top margin, Get dimension from dimension file.
    int topMargin =  getResources()
    .getDimensionPixelSize(R.dimen.top_margin);

    marginLayoutParams.setMargins(marginLayoutParams.getMarginStart(),
    topMargin, marginLayoutParams.getMarginEnd(), marginLayoutParams.bottomMargin);

    recyclerView.setLayoutParams(marginLayoutParams);

以编程方式在RecyclerView上设置保证金

4 个答案: