Question

我每次需要更新RecycleView中的警报时都会创建一个新的Adapter和一个新的RecycleView。不幸的是，它只是一个非常昂贵的解决方案＆＃34;。我在网上看到我可以使用DiffUti，但我不知道如何实现它。我创建了一个DiffUtil类：

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);
}

}

这是我想要更新recycleView的地方之一（用＃Diff;替换＆＃34; creatAdapter＆＃34;）：

 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();
        }
    });
}

我只是想弄清楚如何使用这个类来更新我的适配器。我对Android和编程一般都很新，希望这个引用还可以。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，如：

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);
}

然后你必须使用新数据从适配器外部调用myAdapater.setNewAlarms(alarmsList)。

您还可以查看实现它的following repository

Answer 2

您的 isItemsTheSame 和 areContentsTheSame 方法是相同的。

如果areItemsTheSame返回true并且areContentsTheSame返回false，则仅触发getChangePayload，因此我认为它永远不会触发

如何使用DiffUtil更新RecyclerView适配器

2 个答案: