java - RecyclerView 滚动时滞后

Question

我不明白滚动浏览我的 RecyclerView 时刹车的原因是什么。滚动由 mRecyclerView.smoothScrollToPosition(position); 调用 当您滚动浏览抽搐列表时(渲染时间范围 > 16 毫秒)

AlphaAdapter.java

public class AlphaAdapter extends RecyclerView.Adapter<AlphaAdapter.ViewHolder> {
    private static final String TAG = "AlphaAdapter";
    private Context mContext;
    private List<PrimaryWeapon> mGunList;
    private boolean isAnimate;

    private final int VIEW_TYPE_NULL        = 0;
    private final int VIEW_TYPE_ITEM        = 1;


    public AlphaAdapter(Context mContext, List<PrimaryWeapon> mGunList) {
        this.mContext = mContext;
        this.mGunList = mGunList;
    }

    public AlphaAdapter(Context mContext, List<PrimaryWeapon> mGunList, boolean a) {
        this.mContext = mContext;
        this.mGunList = mGunList;
        this.isAnimate = a;
    }

    @Override
    public int getItemViewType(int position) {
        try {
            if (mGunList.get(position).getNameWeapon().equals(""))
                return VIEW_TYPE_NULL;
            else return VIEW_TYPE_ITEM;
        } catch (Exception e) {
            e.printStackTrace();
            Log.e("AlphaAdapter", String.valueOf(position));
            return VIEW_TYPE_NULL;
        }
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = null;
        if (viewType == VIEW_TYPE_ITEM)
            view = LayoutInflater.from(mContext).inflate(R.layout.item_game, parent, false);
        else
            view = LayoutInflater.from(mContext).inflate(R.layout.item_null, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onViewDetachedFromWindow(ViewHolder holder) {
        super.onViewDetachedFromWindow(holder);
        holder.itemView.clearAnimation();
    }

    @Override
    public boolean onFailedToRecycleView(ViewHolder holder) {
        return true;
    }

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    @Override
    public void onBindViewHolder(final ViewHolder holder, int position) {
        try {
            long startTime = System.currentTimeMillis();
            if (!getWeapon(position).getNameWeapon().equals("")) {
                if (isAnimate) {
                    if (mLastAnimPosition < position) {
                        mLastAnimPosition = position;
                        Animation a = AnimationUtils.loadAnimation(mContext, R.anim.item_game_anim);
                        holder.itemView.startAnimation(a);
                        a.setAnimationListener(new Animation.AnimationListener() {
                            @Override
                            public void onAnimationStart(Animation animation) {

                            }

                            @Override
                            public void onAnimationEnd(Animation animation) {
                            }

                            @Override
                            public void onAnimationRepeat(Animation animation) {

                            }
                        });
                    }
                }

               Picasso.with(mContext)
                        .load("file:///android_asset/" + getWeapon(position).getImagePath())
                        .placeholder(R.drawable.loading)
                        .error(R.drawable.load_fail)
                        .into(holder.image);
                holder.main.setText(getWeapon(position).getNameWeapon());
                holder.desc.setText(getWeapon(position).getNameSkin());

            }
            Log.i(TAG, String.valueOf(System.currentTimeMillis() - startTime) + "ms onBind (" + String.valueOf(position) + ");");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

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

    private PrimaryWeapon getWeapon(int position) {
        return mGunList.get(position);
    }

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

    class ViewHolder extends RecyclerView.ViewHolder {

        TextView main, desc;
        ImageView image;

        ViewHolder(View itemView) {
            super(itemView);
            main = (TextView) itemView.findViewById(R.id.item_textMain);
            desc = (TextView) itemView.findViewById(R.id.item_textDescription);
            image = (ImageView) itemView.findViewById(R.id.item_image);
        }
    }

}

参与适配器的布局元素包括LinearLayout、ImageView、2个TextView。

一开始我以为是下载图片的问题，尝试将它们加载到AsyncTask中，通过Picasso和不上传位图，但全部去掉它们的标记后，列表仍然会滞后。

dump scroll后的RAM，显示原来ViewHolder有71个内存实例，添加后

@Override
    public boolean onFailedToRecycleView(ViewHolder holder) {
        return true;
    }

这个值减少到 15-16，although the rate for RecyclerView - 5 复制，它应该覆盖它们，但是当你滚动时不会创建新的。

item_null.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="74dp"
    android:layout_height="80dp">

</LinearLayout>

item_game.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_gravity="center"
    android:padding="2dp"
    android:id="@+id/layout"
    android:layout_height="80dp"
    android:fitsSystemWindows="true"
    android:layout_width="74dp">

    <ImageView
        android:id="@+id/item_image"
        android:layout_width="match_parent"
        android:layout_height="56dp"
        />

    <TextView
        android:layout_gravity="top"
        android:layout_width="match_parent"
        android:singleLine="true"
        android:id="@+id/item_textMain"
        android:paddingLeft="4dp"
        android:paddingRight="4dp"
        android:paddingTop="1dp"
        android:gravity="left"
        android:textColor="#FFF"
        android:maxLines="1"
        android:textSize="8sp"
        android:layout_height="10dp" />

        <TextView
            android:layout_gravity="bottom"
            android:layout_width="match_parent"
            android:id="@+id/item_textDescription"
            android:paddingLeft="4dp"
            android:paddingRight="4dp"
            android:gravity="left"
            android:textColor="#FFF"
            android:singleLine="true"
            android:maxLines="1"
            android:maxLength="40"
            android:textSize="6sp"
            android:layout_height="12dp" />

</LinearLayout>

Answer 1

您正在将上下文传递给适配器。首先，这可能会导致内存泄漏，也可能会影响您的性能。无需将上下文传递给适配器，只需简单地从 ViewHolder 获取它即可。您始终可以在 RecyclerView.Adapter 中获取上下文引用，而无需传递它。

To dump the RAM after the scroll is, it shows that there are 71 memory instances originally ViewHolder.

从转储来看，这很可能是这种情况。

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    Context context = parent.getContext();
    ...
}

@Override
public void onBindViewHolder(final ViewHolder holder, int position) {
    Context context = holder.itemView.getContext();
    ...
}