如何使用 DiffUtil 更新 RecyclerView 适配器

Question

每次我需要更新 RecycleView 中的警报时，我都会创建一个新的 Adapter 和一个新的 RecycleView。不幸的是，它非常昂贵 "solution"。我在网上看到我可以使用 DiffUti，但我不确定如何实现它。我创建了一个 DiffUtil class:

public class AlarmDiffCallBack extends DiffUtil.Callback{
private final ArrayList<SingleAlarm> oldList;
private final  ArrayList<SingleAlarm> newList;

public AlarmDiffCallBack( ArrayList<SingleAlarm> oldList, ArrayList<SingleAlarm> newList) {
    this.oldList = oldList;
    this.newList = newList;
}

@Override
public int getOldListSize() {
    return oldList.size();
}

@Override
public int getNewListSize() {
    return newList.size();
}

@Override
public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
    return oldList.get(oldItemPosition).getAlarmIndex() == newList.get(newItemPosition).getAlarmIndex();
}

@Override
public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
    return oldList.get(oldItemPosition).getAlarmIndex() == newList.get(newItemPosition).getAlarmIndex();
}

@Nullable
@Override
public Object getChangePayload(int oldItemPosition, int newItemPosition) {
    // Implement method if you're going to use ItemAnimator
    return super.getChangePayload(oldItemPosition, newItemPosition);
}

}

这是我想更新 recycleView 的地方之一（将 "creatAdapter" 替换为 DiffUtil）：

 public void add_alarm(final Context context) {
    //creating a new alarm and set the relevant varible to the addAlarm function
    button_add_alarm.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            //the calndar is without the right day, the day is added in the handler(int the loop)
            Calendar calendarForAlarm = timePickerToCalendar(alarmTimePicker);
            alarmsList = alarmHandler.add_alarm(context, checkBoxes, alarmMessage, alarmsList, alarm_manager, calendarForAlarm, repeatAlarm);
            alarmsList=alarmHandler.sortAlarms(alarmsList);
            creatAdapt();
        }
    });
}

我只是不知道如何使用这个 class 来更新我的适配器。我对 android 和一般编程还很陌生，希望这个报价没问题。谢谢！

Answer 1

所以基本上你需要你的适配器有一个方法来更新你的数据，就像这样：

public void setNewAlarms(List<SingleAlarm> newAlarms){
    // oldAlarms is the list of items currently displayed by the adapter
    AlarmDiffCallBack diffCallBack = new AlarmDiffCallBack(oldAlarms, newAlarms);

    // Second parameter is to detect "movement". If your list is always sorted the same way, you can set it to false to optimize
    DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(diffCallBack, true);

    // This will notify the adapter of what is new data, and will animate/update it for you ("this" being the adapter)
    diffResult.dispatchUpdatesTo(this);
}

然后您只需使用新数据从适配器外部调用 myAdapater.setNewAlarms(alarmsList)。

你也可以看看实现它的following repository

Answer 2

您的 areItemsTheSame 和 areContentsTheSame 方法相同。

getChangePayload 仅在 areItemsTheSame returns 为真且 areContentsTheSame returns 为假时才会触发，所以我认为它永远不会触发

如何使用 DiffUtil 更新 RecyclerView 适配器

How to update RecyclerView adapter using DiffUtil

diff

android

arraylist

android-adapter

android-recyclerview