Android如何利用RecyclerView实现列表倒计时效果实例代码

前言

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

@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

总结

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