android使用RecyclerView获取过滤系统应用程序其他应用包名，按照首字母排序，支持字幕条索引，实现字幕条索引顶部悬停

好的，针对你的问题，我可以给出以下思路：

1. 获取所有应用程序信息，并筛选出系统应用程序信息；
2. 获取系统应用程序包名，并按照首字母进行排序；
3. 实现字幕条索引，可以通过为RecyclerView添加ItemDecoration来实现；
4. 实现字幕条索引顶部悬停，可以通过为RecyclerView添加一个悬停的HeaderView来实现。

下面是具体的实现步骤：

1. 获取所有应用程序信息，并筛选出系统应用程序信息

PackageManager packageManager = getPackageManager();
List<ApplicationInfo> appInfos = packageManager.getInstalledApplications(0);
List<ApplicationInfo> systemAppInfos = new ArrayList<>();
for (ApplicationInfo appInfo : appInfos) {
    if ((appInfo.flags & ApplicationInfo.FLAG_SYSTEM) != 0) {
        // 筛选出系统应用信息
        systemAppInfos.add(appInfo);
    }
}

2. 获取系统应用程序包名，并按照首字母进行排序

List<String> packageNames = new ArrayList<>();
for (ApplicationInfo appInfo : systemAppInfos) {
    packageNames.add(appInfo.packageName);
}
Collections.sort(packageNames, new Comparator<String>() {
    @Override
    public int compare(String s1, String s2) {
        // 按照首字母进行排序
        return s1.compareTo(s2);
    }
});

3. 实现字幕条索引

可以通过为RecyclerView添加ItemDecoration来实现字幕条索引。具体实现可以参考以下代码：

public class SectionDecoration extends RecyclerView.ItemDecoration {
    private List<String> mDataList;
    private Paint mPaint;
    private Rect mBounds;

    public SectionDecoration(Context context, List<String> dataList) {
        mDataList = dataList;
        mPaint = new Paint();
        mPaint.setColor(ContextCompat.getColor(context, R.color.colorAccent));
        mPaint.setTextSize(40);
        mPaint.setAntiAlias(true);
        mBounds = new Rect();
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            int position = parent.getChildAdapterPosition(child);
            if (isFirstInGroup(position)) {
                String text = mDataList.get(position).substring(0, 1).toUpperCase();
                mPaint.getTextBounds(text, 0, text.length(), mBounds);
                int top = child.getTop() - mBounds.height() - 20;
                int bottom = child.getTop() - 20;
                c.drawText(text, (left + right - mBounds.width()) / 2, (top + bottom) / 2, mPaint);
            }
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view);
        if (isFirstInGroup(position)) {
            outRect.top = mBounds.height() + 40;
        } else {
            outRect.top = 0;
        }
    }

    private boolean isFirstInGroup(int position) {
        if (position == 0) {
            return true;
        } else {
            String current = mDataList.get(position).substring(0, 1);
            String previous = mDataList.get(position - 1).substring(0, 1);
            return !current.equals(previous);
        }
    }
}

4. 实现字幕条索引顶部悬停

可以通过为RecyclerView添加一个悬停的HeaderView来实现字幕条索引顶部悬停。具体实现可以参考以下代码：

public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
    private View mHeaderView;
    private int mHeaderHeight;

    public StickyHeaderDecoration(Context context) {
        mHeaderView = LayoutInflater.from(context).inflate(R.layout.layout_sticky_header, null);
        mHeaderHeight = context.getResources().getDimensionPixelSize(R.dimen.header_height);
        mHeaderView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, mHeaderHeight));
        mHeaderView.setVisibility(View.INVISIBLE);
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDraw(c, parent, state);
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();
        int top = 0;
        int bottom = top + mHeaderHeight;
        c.drawRect(left, top, right, bottom, mPaint);
        mHeaderView.draw(c);
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDrawOver(c, parent, state);
        int pos = ((LinearLayoutManager) parent.getLayoutManager()).findFirstVisibleItemPosition();
        if (pos == RecyclerView.NO_POSITION) {
            return;
        }
        View child = parent.findViewHolderForAdapterPosition(pos).itemView;
        boolean flag = false;
        if ((pos + 1) < state.getItemCount()) {
            String current = mDataList.get(pos).substring(0, 1);
            String next = mDataList.get(pos + 1).substring(0, 1);
            if (!current.equals(next) && child.getBottom() < mHeaderHeight) {
                c.save();
                flag = true;
                c.translate(0, child.getBottom() - mHeaderHeight);
            }
        }
        mHeaderView.draw(c);
        if (flag) {
            c.restore();
        }
    }
}

以上就是针对你的问题的一个思路和实现，具体的实现可能会有所不同，需要根据具体的需求进行调整。