在RecyclerViewAdapter中实现计时器

Question

我在RecyclerView中实现倒数计时器时遇到问题。 输入到RecyclerView的数据来自Dialog，用户可以在其中键入项目名称，设置SeekBar时间（以秒为单位）并选择带有自定义小部件的日期。 信息保存在Realm数据库中。

问题是重新启动应用程序或添加新项目后，所有项目中的所有计时器都会重新启动并从头开始计数。 如何实现即使在应用程序不处于活动状态或添加新项目时也要计数的计时器。 预先感谢您的帮助。

public class AdapterDrops extends RecyclerView.Adapter<RecyclerView.ViewHolder> implements SwipeListener {

public static final int COUNT_FOOTER = 1;
public static final int COUNT_NO_ITEMS = 1;
public static final int ITEM = 0;
public static final int NO_ITEM = 1;
public static final int FOOTER = 2;
private final ResetListener mResetListener;
private MarkListener mMarkListener;
//inflater object which converts xml file to view object
private LayoutInflater mInflater;
public RealmResults<Drop> mResults;
private AddListener mAddListener;
private int mFilterOption;
private Realm mRealm;
private Context mContext;
Handler handler;
public long duration;


public AdapterDrops(Context context, Realm realm, RealmResults<Drop> results, AddListener listener, MarkListener markListener, ResetListener resetListener) {
    mContext = context;
    mInflater = LayoutInflater.from(context);
    update(results);
    mRealm = realm;
    mAddListener = listener;
    mMarkListener = markListener;
    mResetListener = resetListener;

}

public void update(RealmResults<Drop> results) {
    mResults = results;
    mFilterOption = AppBucketDrops.load(mContext);
    //notification do Apdapter that database was changed
    notifyDataSetChanged();

}

@Override
public long getItemId(int position) {
    if (position < mResults.size()) {
        return mResults.get(position).getAdded();
    }
    return RecyclerView.NO_ID;
}

@Override
public int getItemViewType(int position) {
    if (!mResults.isEmpty()) {
        if (position < mResults.size()) {
            return ITEM;
        } else {
            return FOOTER;
        }
    } else {
        if (mFilterOption == Filter.COMPLETE ||
                mFilterOption == Filter.INCOMPLETE) {
            if (position == 0) {
                return NO_ITEM;
            } else {
                return FOOTER;
            }
        } else {
            return ITEM;
        }
    }
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    if (viewType == FOOTER) {
        View view = mInflater.inflate(R.layout.footer, parent, false);
        //footerHolder class which we created below
        return new FooterHolder(view);
    } else if (viewType == NO_ITEM) {
        View view = mInflater.inflate(R.layout.no_item, parent, false);
        return new NoItemsHolder(view);
    } else {
        //layourInflater converts xml file to java View object
        View view = mInflater.inflate(R.layout.row_drop, parent, false);
        return new DropHolder(view, mMarkListener);
    }
}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    if (holder instanceof DropHolder) {
        DropHolder dropHolder = (DropHolder) holder;
        //returning an item from the paricular position
        Drop drop = mResults.get(position);
        //seting MtextView to proper drop.getWhat text
        dropHolder.setWhat(drop.getWhat());
        dropHolder.setWhen(drop.getWhen());
        dropHolder.setTimer(drop.getTimer());
        dropHolder.setBackground(drop.isCompleted());
    }

}

@Override
public int getItemCount() {
    if (!mResults.isEmpty()) {
        return mResults.size() + COUNT_FOOTER;
    } else {
        if (mFilterOption == Filter.LEAST_TIME_LEFT
                || mFilterOption == Filter.MOST_TIME_LEFT
                || mFilterOption == Filter.NONE) {
            return 0;
        } else {
            return COUNT_NO_ITEMS + COUNT_FOOTER;
        }
    }

}


@Override
public void onSwipe(int position) {
    //delete item with transaction from database
    if (position < mResults.size()) {
        mRealm.beginTransaction();
        mResults.get(position).deleteFromRealm();
        mRealm.commitTransaction();
        notifyItemRemoved(position);
    }
    resetFilterIfEmpty();
}

private void resetFilterIfEmpty() {
    if (mResults.isEmpty() && (mFilterOption == Filter.COMPLETE || mFilterOption == Filter.INCOMPLETE)) {
        mResetListener.onReset();
    }
}

public void markComplete(int position) {
    //checking that item is not a footer
    if (position < mResults.size()) {
        mRealm.beginTransaction();
        mResults.get(position).setCompleted(true);
        mRealm.commitTransaction();
        notifyItemChanged(position);
    }
}

public static class DropHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    TextView mTextWhat;
    TextView mTextWhen;
    MarkListener mMarkListener;
    Context mContext;
    View mItemView;
    TextView mTimer;
    //timer
    Handler handler;
    public long timeRemaining;
    public Drop drop;

    public DropHolder(View itemView, MarkListener listener) {
        super(itemView);
        mItemView = itemView;
        mContext = itemView.getContext();
        itemView.setOnClickListener(this);
        mTextWhat = (TextView) itemView.findViewById(R.id.tv_what);
        mTextWhen = (TextView) itemView.findViewById(R.id.tv_when);
        mTimer = (TextView) itemView.findViewById(R.id.tv_timer);
        mMarkListener = listener;

    }

    public void setWhat(String what) {
        mTextWhat.setText(what);
    }

    public Drop getDrop(Drop drop) {
        return drop;
    }

    public void setTimer(long timer) {

        handler = new Handler();
        timeRemaining = timer * 1000;
        final Runnable runnable = new Runnable() {
            @Override
            public void run() {
                timeRemaining = timeRemaining - 1000;

                if (timeRemaining > 0) {
                    handler.postDelayed(this, 1000);
                    timeRemaining = timeRemaining / 1000;
                    mTimer.setText(Long.toString(timeRemaining));
                    timeRemaining = timeRemaining * 1000;
                }
                if (timeRemaining == 0) {
                    mTimer.setText("Czas na lek !");
                }
            }
        };
        //kickstart
        handler.postDelayed(runnable, 1000);
    }

    @Override
    public void onClick(View v) {
        mMarkListener.onMark(getAdapterPosition());
    }

    public void setBackground(boolean completed) {
        Drawable drawable;
        if (completed) {
            drawable = ContextCompat.getDrawable(mContext, R.color.colorLightBlueAfterClick);
        } else {
            drawable = ContextCompat.getDrawable(mContext, R.drawable.bg_row_drop);
        }
        /*if(Build.VERSION.SDK_INT > 15){
            mItemView.setBackground(drawable);
        } else{
            mItemView.setBackgroundDrawable(drawable);
        }*/
        Util.setBackground(mItemView, drawable);

    }

    public void setWhen(long when) {
        mTextWhen.setText(DateUtils.getRelativeTimeSpanString(when, System.currentTimeMillis(), DateUtils.DAY_IN_MILLIS, 0));

    }
}

public static class NoItemsHolder extends RecyclerView.ViewHolder {

    public NoItemsHolder(View itemView) {
        super(itemView);
    }
}

public class FooterHolder extends RecyclerView.ViewHolder implements View.OnClickListener { 
    Button mBtnAdd;

    public FooterHolder(View itemView) {
        super(itemView);
        mBtnAdd = (Button) itemView.findViewById(R.id.btn_footer);
        mBtnAdd.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        //were using from this place AddListener
        mAddListener.add();
    }
}

}

Answer 1

不用保存倒计时时间，而是保存结束日期时间（现在的日期时间+倒数），并在此基础上进行逻辑运算。 这样，当应用程序重置或视图重置时，通过将现在的日期时间与结束日期时间进行比较，倒数计时逻辑将从上次停止的地方继续。

此外，您发布的代码正在为每个视图每秒发布一个Runnable ，即使对于用户不可见的视图也是如此。 这会导致应用程序性能下降。 而是创建一个计时器，该计时器可能由托管RecyclerView.Adapter的Activity进行控制，它将调用RecyclerView.Adapter.notifyDataSetChanged() ，后者将依次调用RecyclerView.Adapter.onBindViewHolder()来更新UI。 因此，适配器将更新所有可见的UI元素，这意味着倒数UI（当然也只有可见的UI）也将每秒更新一次。 即使在滚动时，也会调用RecyclerView.Adapter.onBindViewHolder()来处理。 当数据集很大时，这将大大提高应用程序的性能。