RecyclerView<第二十一篇>：條目動畫之縮放動畫（屬性動畫）

【整體刷新效果】

當第一次顯示RecyclerView的Item或者往下滑動時的動畫效果如下：

217.gif

【刷新指定Item】

218.gif

刷新指定Item代碼：

            urls.set(position, "http://img4.imgtn.bdimg.com/it/u=3209370120,2008812818&fm=26&gp=0.jpg");
            recycleViewAdapter.notifyItemChanged(position);

【刪除效果】

219.gif

刪除刷新代碼：

            urls.remove(position);
            recycleViewAdapter.notifyItemRemoved(position);
            recycleViewAdapter.notifyItemRangeChanged(position, urls.size() - position);

【插入效果】

220.gif

插入刷新代碼：

            urls.add(position, "http://img4.imgtn.bdimg.com/it/u=3209370120,2008812818&fm=26&gp=0.jpg");
            recycleViewAdapter.notifyItemInserted(position);
            recycleViewAdapter.notifyItemRangeChanged(position, urls.size() - position);

【移動效果】

221.gif

移動刷新代碼：

            int fromPosition = position;
            int toPosition = position + 1;
            Collections.swap(urls,fromPosition,toPosition);
            recycleViewAdapter.notifyItemMoved(fromPosition, toPosition);
            recycleViewAdapter.notifyItemRangeChanged(position, toPosition - fromPosition + 1);

縮放動畫實現代碼如下：

AnimationAdapter.java

public abstract class AnimationAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

  private RecyclerView.Adapter<RecyclerView.ViewHolder> mAdapter;
  private int mDuration = 300;
  private Interpolator mInterpolator = new LinearInterpolator();
  private int mLastPosition = -1;

  private boolean isFirstOnly = true;

  public AnimationAdapter(RecyclerView.Adapter<RecyclerView.ViewHolder> adapter) {
    mAdapter = adapter;
  }

  @Override
  public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    return mAdapter.onCreateViewHolder(parent, viewType);
  }

  @Override
  public void registerAdapterDataObserver(RecyclerView.AdapterDataObserver observer) {
    super.registerAdapterDataObserver(observer);
    mAdapter.registerAdapterDataObserver(observer);
  }

  @Override
  public void unregisterAdapterDataObserver(RecyclerView.AdapterDataObserver observer) {
    super.unregisterAdapterDataObserver(observer);
    mAdapter.unregisterAdapterDataObserver(observer);
  }

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

  @Override
  public void onDetachedFromRecyclerView(RecyclerView recyclerView) {
    super.onDetachedFromRecyclerView(recyclerView);
    mAdapter.onDetachedFromRecyclerView(recyclerView);
  }

  @Override
  public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {
    super.onViewAttachedToWindow(holder);
    mAdapter.onViewAttachedToWindow(holder);
  }

  @Override
  public void onViewDetachedFromWindow(RecyclerView.ViewHolder holder) {
    super.onViewDetachedFromWindow(holder);
    mAdapter.onViewDetachedFromWindow(holder);
  }

  @Override
  public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    mAdapter.onBindViewHolder(holder, position);

    int adapterPosition = holder.getAdapterPosition();
    if (!isFirstOnly || adapterPosition > mLastPosition) {
      for (Animator anim : getAnimators(holder.itemView)) {
        anim.setDuration(mDuration).start();
        anim.setInterpolator(mInterpolator);
      }
      mLastPosition = adapterPosition;
    } else {
      holder.itemView.setScaleX(1);
      holder.itemView.setScaleY(1);
    }
  }

  @Override public void onViewRecycled(RecyclerView.ViewHolder holder) {
    mAdapter.onViewRecycled(holder);
    super.onViewRecycled(holder);
  }

  @Override
  public int getItemCount() {
    return mAdapter.getItemCount();
  }

  public void setDuration(int duration) {
    mDuration = duration;
  }

  public void setInterpolator(Interpolator interpolator) {
    mInterpolator = interpolator;
  }

  public void setStartPosition(int start) {
    mLastPosition = start;
  }

  protected abstract Animator[] getAnimators(View view);

  public void setFirstOnly(boolean firstOnly) {
    isFirstOnly = firstOnly;
  }

  @Override
  public int getItemViewType(int position) {
    return mAdapter.getItemViewType(position);
  }

  public RecyclerView.Adapter<RecyclerView.ViewHolder> getWrappedAdapter() {
    return mAdapter;
  }

  @Override
  public long getItemId(int position) {
    return mAdapter.getItemId(position);
  }
}

ScaleInAnimationAdapter.java

public class ScaleInAnimationAdapter extends AnimationAdapter {

  private static final float DEFAULT_SCALE_FROM = .5f;
  private final float mFrom;

  public ScaleInAnimationAdapter(RecyclerView.Adapter adapter) {
    this(adapter, DEFAULT_SCALE_FROM);
  }

  public ScaleInAnimationAdapter(RecyclerView.Adapter adapter, float from) {
    super(adapter);
    mFrom = from;
  }

  @Override protected Animator[] getAnimators(View view) {
    ObjectAnimator scaleX = ObjectAnimator.ofFloat(view, "scaleX", mFrom, 1f);
    ObjectAnimator scaleY = ObjectAnimator.ofFloat(view, "scaleY", mFrom, 1f);
    return new ObjectAnimator[] { scaleX, scaleY };
  }
}

使用縮放Adapter

    ScaleInAnimationAdapter adapter = new ScaleInAnimationAdapter(recycleViewAdapter);
    adapter.setDuration(3000);
    adapter.setFirstOnly(false);
    recyclerview.setAdapter(adapter);

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