Android利用RecyclerView实现列表倒计时效果

最近面试时，面试官问了一个列表倒计时效果如何实现，然后脑袋突然懵的了O(∩_∩)O，现在记录一下。

运行效果图

实现思路

实现方法主要有两个：

1.为每个开始倒计时的item启动一个定时器，再做更新item处理；

2.只启动一个定时器，然后遍历数据，再做再做更新item处理。

经过思考，包括性能、实现等方面，决定使用第2种方式实现。

实现过程

• 数据实体

/**
  * 总共的倒计时的时间(结束时间-开始时间),单位：毫秒
  * 例: 2019-02-23 11:00:30 与 2019-02-23 11:00:00 之间的相差的毫秒数
  */
 private long totalTime;
 /**
  * 倒计时是否在暂停状态
  */
 private boolean isPause = true;

• 倒计时
  
  Timer

mTimer.schedule(mTask, 0, 1000);

TimerTask

 class MyTask extends TimerTask {
        @Override
        public void run() {
            if (mList.isEmpty()) {
                return;
            }
            int size = mList.size();
            CountDownTimerBean bean;
            long totalTime;
            for (int i = 0; i < size; i++) {
                bean = mList.get(i);
                if (!bean.isPause()) {//不处于暂停状态
                    totalTime = bean.getTotalTime() - 1000;
                    if (totalTime <= 0) {
                        bean.setPause(true);
                        bean.setTotalTime(0);
                    }
                    bean.setTotalTime(totalTime);
                    Message message = mHandler.obtainMessage(1);
                    message.arg1 = i;
                    mHandler.sendMessage(message);
                }
            }
        }
    }

• 线程交互更新item

 mHandler = new Handler(Looper.getMainLooper()) {
            @Override
            public void handleMessage(Message msg) {
                switch (msg.what) {
                    case 1:
                        notifyItemChanged(msg.arg1, "update-time");
                        break;
                }
            }
        };

• 性能优化方面
  
  1.调用notifyItemChanged()方法后，不要更新整个item(比如说item包含图片，不需要变的)，所以要重写onBindViewHolder( Holder , int , List )方法：

@Override
    public void onBindViewHolder(@NonNull Holder holder, int position, @NonNull List<Object> payloads) {
        if (payloads.isEmpty()) {
            onBindViewHolder(holder, position);
            return;
        }
        //更新某个控件,比如说只需要更新时间信息，其他不用动
        CountDownTimerBean bean = mList.get(position);
        long day = bean.getTotalTime() / (1000 * 60 * 60 * 24);
        long hour = (bean.getTotalTime() / (1000 * 60 * 60) - day * 24);
        long min = ((bean.getTotalTime() / (60 * 1000)) - day * 24 * 60 - hour * 60);
        long s = (bean.getTotalTime() / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);
        holder.tvTime.setText("剩余时间: " + day + "天" + hour + "小时" + min + "分" + s + "秒");
        holder.btnAction.setText(bean.isPause() ? "开始" : "暂停");
        holder.btnAction.setEnabled(bean.getTotalTime() != 0);
    }

2.销毁资源操作：

   /**
     * 销毁资源
     */
    public void destroy() {
        mHandler.removeMessages(1);
        if (mTimer != null) {
            mTimer.cancel();
            mTimer.purge();
            mTimer = null;
        }
    }

• RecyclerView.Adapter部分源码

public class CountDownTimerAdapter extends RecyclerView.Adapter<CountDownTimerAdapter.Holder> {
    private static final String TAG = "CountDownTimerAdapter->";
    private List<CountDownTimerBean> mList;//数据
    private Handler mHandler;//线程调度，用来更新列表

    private Timer mTimer;
    private MyTask mTask;

    public CountDownTimerAdapter() {
        mList = new ArrayList<>();
        mHandler = new Handler(Looper.getMainLooper()) {
            @Override
            public void handleMessage(Message msg) {
                switch (msg.what) {
                    case 1:
                        notifyItemChanged(msg.arg1, "update-time");
                        break;
                }
            }
        };
        mTask = new MyTask();
    }

    public void bindAdapterToRecyclerView(@NonNull RecyclerView view) {
        view.setAdapter(this);
    }

    /**
     * 设置新的数据源
     *
     * @param list 数据
     */
    public void setNewData(@NonNull List<CountDownTimerBean> list) {
        destroy();
        mList.clear();
        mList.addAll(list);
        notifyDataSetChanged();
        if (mTimer == null) {
            mTimer = new Timer();
        }
        mTimer.schedule(mTask, 0, 1000);
    }

    /**
     * 销毁资源
     */
    public void destroy() {
        mHandler.removeMessages(1);
        if (mTimer != null) {
            mTimer.cancel();
            mTimer.purge();
            mTimer = null;
        }
    }

    @NonNull
    @Override
    public Holder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item_count_down_timer, viewGroup, false);
        return new Holder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull Holder holder, int position, @NonNull List<Object> payloads) {
        if (payloads.isEmpty()) {
            onBindViewHolder(holder, position);
            return;
        }
        //更新某个控件,比如说只需要更新时间信息，其他不用动
        CountDownTimerBean bean = mList.get(position);
        long day = bean.getTotalTime() / (1000 * 60 * 60 * 24);
        long hour = (bean.getTotalTime() / (1000 * 60 * 60) - day * 24);
        long min = ((bean.getTotalTime() / (60 * 1000)) - day * 24 * 60 - hour * 60);
        long s = (bean.getTotalTime() / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);
        holder.tvTime.setText("剩余时间: " + day + "天" + hour + "小时" + min + "分" + s + "秒");
        holder.btnAction.setText(bean.isPause() ? "开始" : "暂停");
        holder.btnAction.setEnabled(bean.getTotalTime() != 0);
    }

    @Override
    public void onBindViewHolder(@NonNull final Holder holder, int position) {
        holder.ivIcon.setImageResource(R.mipmap.ic_launcher_round);
        final CountDownTimerBean bean = mList.get(position);
        long day = bean.getTotalTime() / (1000 * 60 * 60 * 24);
        long hour = (bean.getTotalTime() / (1000 * 60 * 60) - day * 24);
        long min = ((bean.getTotalTime() / (60 * 1000)) - day * 24 * 60 - hour * 60);
        long s = (bean.getTotalTime() / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);
        holder.tvTime.setText("剩余时间: " + day + "天" + hour + "小时" + min + "分" + s + "秒");
        holder.btnAction.setText(bean.isPause() ? "开始" : "暂停");
        holder.btnAction.setEnabled(bean.getTotalTime() != 0);
        holder.btnAction.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (bean.isPause()) {
                    bean.setPause(false);
                    holder.btnAction.setText("暂停");
                } else {
                    bean.setPause(true);
                    holder.btnAction.setText("开始");
                }
            }
        });
    }

    @Override
    public int getItemCount() {
        return mList.size();
    }

    class Holder extends RecyclerView.ViewHolder {
        private ImageView ivIcon;
        private TextView tvTime;
        private Button btnAction;

        Holder(@NonNull View itemView) {
            super(itemView);
            ivIcon = itemView.findViewById(R.id.iv_icon);
            tvTime = itemView.findViewById(R.id.tv_time);
            btnAction = itemView.findViewById(R.id.btn_action);
        }
    }

    class MyTask extends TimerTask {
        @Override
        public void run() {
            if (mList.isEmpty()) {
                return;
            }
            int size = mList.size();
            CountDownTimerBean bean;
            long totalTime;
            for (int i = 0; i < size; i++) {
                bean = mList.get(i);
                if (!bean.isPause()) {//不处于暂停状态
                    totalTime = bean.getTotalTime() - 1000;
                    if (totalTime <= 0) {
                        bean.setPause(true);
                        bean.setTotalTime(0);
                    }
                    bean.setTotalTime(totalTime);
                    Message message = mHandler.obtainMessage(1);
                    message.arg1 = i;
                    mHandler.sendMessage(message);
                }
            }
        }
    }
}

项目地址

源码

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如有问题，欢迎及时沟通。