如何保存recyclerview滚动位置，与recyclerview.state或无 [英] how to save recyclerview scroll position , with recyclerview.state or no

问题描述

任何人，我对Android的RecyclerView.State问题 我有一个RecyclerView，我该如何使用它RecyclerView.State绑定？ 目的是我想保存recyclerview滚动位置，有什么想法？

anyone, I have a question on Android RecyclerView.State I have a RecyclerView, How can I use it bind with RecyclerView.State ? the purpose is i want to save the recyclerview scroll position, have any idea?

推荐答案

你怎么打算上次保存保存的位置与 RecyclerView.State ？

How do you plan to save last saved position with RecyclerView.State?

您可以随时依靠醇'好保存状态。扩展 RecyclerView 和覆盖的onSaveInstanceState（）和 onRestoreInstanceState（）：

You can always rely on ol' good save state. Extend RecyclerView and override onSaveInstanceState() and onRestoreInstanceState():

@Override
    protected Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();
        LayoutManager layoutManager = getLayoutManager();
        if(layoutManager != null && layoutManager instanceof LinearLayoutManager){
            mScrollPosition = ((LinearLayoutManager) layoutManager).findFirstVisibleItemPosition();
        }
        SavedState newState = new SavedState(superState);
        newState.mScrollPosition = mScrollPosition;
        return newState;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {
        super.onRestoreInstanceState(state);
        if(state != null && state instanceof SavedState){
            mScrollPosition = ((SavedState) state).mScrollPosition;
            LayoutManager layoutManager = getLayoutManager();
            if(layoutManager != null){
              int count = layoutManager.getChildCount();
              if(mScrollPosition != RecyclerView.NO_POSITION && mScrollPosition < count){
                  layoutManager.scrollToPosition(mScrollPosition);
              }
            }
        }
    }

    static class SavedState extends android.view.View.BaseSavedState {
        public int mScrollPosition;
        SavedState(Parcel in) {
            super(in);
            mScrollPosition = in.readInt();
        }
        SavedState(Parcelable superState) {
            super(superState);
        }

        @Override
        public void writeToParcel(Parcel dest, int flags) {
            super.writeToParcel(dest, flags);
            dest.writeInt(mScrollPosition);
        }
        public static final Parcelable.Creator<SavedState> CREATOR
                = new Parcelable.Creator<SavedState>() {
            @Override
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }

            @Override
            public SavedState[] newArray(int size) {
                return new SavedState[size];
            }
        };
    }

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