在 Android 中展开 recyclerView 时如何旋转图像

Question

在我的应用程序中，我想要 expand 和 collapse recyclerView!
我可以展开和折叠 recyclerView，为此我使用了这个库：https://github.com/thoughtbot/expandable-recycler-view

我想在点击 recyclerView（展开或折叠）时旋转箭头图像！
我在 viewHolder class 中写了下面的代码，但没有用，也没有旋转箭头图像！
ParentViewHolder 代码：

public class seasonParentViewHolder extends GroupViewHolder {

    private TextView row_epGuideParent_Title, row_epGuideParent_Count, row_epGuideParent_Date;
    private ImageView row_epGuideParent_arrowImg;

    public seasonParentViewHolder(View itemView) {
        super(itemView);
        row_epGuideParent_Title = (TextView) itemView.findViewById(R.id.row_epGuideParent_Title);
        row_epGuideParent_Count = (TextView) itemView.findViewById(R.id.row_epGuideParent_Count);
        row_epGuideParent_Date = (TextView) itemView.findViewById(R.id.row_epGuideParent_Date);
        row_epGuideParent_arrowImg = (ImageView) itemView.findViewById(R.id.row_epGuideParent_arrowImg);
    }

    public void setGenreTitle(ExpandableGroup title) {
        if (title instanceof ExpandableModel) {
            row_epGuideParent_Title.setText(title.getTitle());
            row_epGuideParent_Count.setText(((ExpandableModel) title).getCount());
            row_epGuideParent_Date.setText(((ExpandableModel) title).getDate());
        }
    }

    @Override
    public void expand() {
        animateExpand();
    }

    @Override
    public void collapse() {
        animateCollapse();
    }

    private void animateExpand() {
        RotateAnimation rotate =
                new RotateAnimation(360, 180, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
        rotate.setDuration(300);
        rotate.setFillAfter(true);
        row_epGuideParent_arrowImg.setAnimation(rotate);
    }

    private void animateCollapse() {
        RotateAnimation rotate =
                new RotateAnimation(180, 360, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
        rotate.setDuration(300);
        rotate.setFillAfter(true);
        row_epGuideParent_arrowImg.setAnimation(rotate);
    }
}

在库中调用展开和折叠：

public abstract class GroupViewHolder extends RecyclerView.ViewHolder implements OnClickListener {

  private OnGroupClickListener listener;

  public GroupViewHolder(View itemView) {
    super(itemView);
    itemView.setOnClickListener(this);
  }

  @Override
  public void onClick(View v) {
    if (listener != null) {
      if (listener.onGroupClick(getAdapterPosition())) {
        collapse();
      } else {
        expand();
      }
    }
  }

  public void setOnGroupClickListener(OnGroupClickListener listener) {
    this.listener = listener;
  }

  public void expand() {}

  public void collapse() {}

}

如何解决此问题并在单击 recyclerView（展开或折叠）时旋转箭头图像？？

Answer 1

TL;DR 你必须为你的 ImageView 使用 startAnimation() 而不是 setAnimation().

void setAnimation (Animation animation)

Sets the next animation to play for this view. If you want the animation to play immediately, use startAnimation(android.view.animation.Animation) instead [...]

（引自developer.android.com/reference/android/view/View.html）

Answer 2

@Override
public void expand() {
    arrow_icn.setRotation(180);
}

@Override
public void collapse() {
    arrow_icn.setRotation(0);
}

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