在RecyclerView中实现列表项展开和收起的动画效果,可以通过设置ItemAnimator来实现。
首先,在RecyclerView的Adapter中,根据列表项的展开状态,在onBindViewHolder方法中设置相应的布局参数,比如设置View的高度为0或者设置View的可见性为GONE。
然后,在RecyclerView的ItemAnimator中,根据列表项的展开状态,设置相应的动画效果,比如通过ValueAnimator设置View的高度或者透明度变化,实现展开和收起的动画效果。
具体实现步骤如下:
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
if (isExpanded) {
holder.itemView.setVisibility(View.VISIBLE);
holder.itemView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
} else {
holder.itemView.setVisibility(View.GONE);
holder.itemView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 0));
}
}
public class MyItemAnimator extends DefaultItemAnimator {
@Override
public boolean animateChange(@NonNull RecyclerView.ViewHolder oldHolder, @NonNull RecyclerView.ViewHolder newHolder, @NonNull ItemHolderInfo preInfo, @NonNull ItemHolderInfo postInfo) {
if (preInfo instanceof MyItemHolderInfo && postInfo instanceof MyItemHolderInfo) {
MyItemHolderInfo pre = (MyItemHolderInfo) preInfo;
MyItemHolderInfo post = (MyItemHolderInfo) postInfo;
if (pre.isExpanded() != post.isExpanded()) {
ValueAnimator animator = ValueAnimator.ofInt(pre.getHeight(), post.getHeight());
animator.addUpdateListener(valueAnimator -> {
int height = (int) valueAnimator.getAnimatedValue();
post.itemView.getLayoutParams().height = height;
post.itemView.requestLayout();
});
animator.setDuration(500);
animator.start();
return true;
}
}
return super.animateChange(oldHolder, newHolder, preInfo, postInfo);
}
static class MyItemHolderInfo extends ItemHolderInfo {
private int height;
private boolean expanded;
public MyItemHolderInfo(int height, boolean expanded) {
this.height = height;
this.expanded = expanded;
}
public int getHeight() {
return height;
}
public boolean isExpanded() {
return expanded;
}
}
}
通过以上步骤,可以实现RecyclerView列表项展开和收起的动画效果。当展开和收起时,列表项的高度会发生变化,并且会有动画效果。
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