android - 从适配器中生成的值而不是对象变量对 RecyclerView 进行排序？

Question

根据 ArrayList 中的值对 ArrayList 进行排序没有问题，但我有一个直接在 Adapter 中计算的 int，我更愿意将它保留在那里，因为它看起来是一个干净的解决方案。

timeLeftinMinutes 是我要为 RecyclerView 排序的值，但我不知道如何将它放入 Activity(具体计算不是那么重要):

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    int dueHour = mTaskList.get(position).getDueHour();
    int dueMinute = mTaskList.get(position).getDueMinute();
    Calendar calendar = Calendar.getInstance();
    int currentHour = calendar.get(Calendar.HOUR_OF_DAY);
    int currentMinute = calendar.get(Calendar.MINUTE);

    //correcting values to over 24 if necessary
    int mBedHourPlus24IfNecessary;
    if (mBedHour < mWakeUpHour || mBedHour == mWakeUpHour && mBedMinute < mWakeUpMinute) mBedHourPlus24IfNecessary = mBedHour + 24;
    else mBedHourPlus24IfNecessary = mBedHour;
    int mDueHourPlus24IfNecessary;
    if (dueHour < mWakeUpHour ) mDueHourPlus24IfNecessary = dueHour + 24;
    else mDueHourPlus24IfNecessary = dueHour;


    int timeLeftInMinutes;
    if (mDueHourPlus24IfNecessary > mBedHourPlus24IfNecessary || mDueHourPlus24IfNecessary == mBedHourPlus24IfNecessary && dueMinute > mBedMinute) {
        holder.mTimeLeft.setText(mContext.getResources().getString(R.string.while_sleeping));
        holder.mCardContainer.setCardBackgroundColor(ContextCompat.getColor(mContext, R.color.task_blue));
        timeLeftInMinutes = 999999999;
    } else {
        timeLeftInMinutes = (mDueHourPlus24IfNecessary * 60 + dueMinute) - (currentHour * 60 + currentMinute);
}

Answer 1

使用 onBindViewHolder 不是一个好主意，因为它只针对将要出现在屏幕上的对象调用，因此您不会知道 timeLeftInMinutes 对于所有项目。

更好的解决方案是在您的适配器中添加一个方法，该方法将遍历您的数组，计算每个项目的时间，将其保存到项目中，通知适配器列表已准备就绪

public void updateAndSort(List<MyObject> list) {
    //Go through all your item and computer their time left.
    for (int i = 0; i < list.size(); i++) {
        //Compute the value you need to compare for each item
        list.get(i).timeLeftInMinute = timeComputed...
    }

    //Then you order your list, for example ascendant
    Collections.sort(list, new Comparator<MyObject>() {
        @Override
        public int compare(MyObject o1, MyObject o2) {
            if (o1.timeLeftInMinute > o2.timeLeftInMinute) {
                return 1;
            } else {
                return -1;
            }
        }
    });

    //replace your mTaskList the sorted list to your adapter
    mTaskList = list;

    //notify the adapter to correctly display the times
    notifyDataSetChanged()

}