前言
最近面試時，面試官問了一個列表倒計時效果如何實現，然后腦袋突然懵的了O(∩_∩)O，現在記錄一下。
運行效果圖
實現思路
實現方法主要有兩個：
1.為每個開始倒計時的item啟動一個定時器，再做更新item處理；
2.只啟動一個定時器，然后遍歷數據，再做再做更新item處理。
經過思考，包括性能、實現等方面，決定使用第2種方式實現。
實現過程
數據實體
/** * 總共的倒計時的時間(結束時間-開始時間),單位：毫秒 * 例: 2019-02-23 11:00:30 與 2019-02-23 11:00:00 之間的相差的毫秒數 */ private long totalTime; /** * 倒計時是否在暫停狀態 */ private boolean isPause = true;
倒計時
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()) {//不處于暫停狀態 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); } } } }線程交互更新item
mHandler = new Handler(Looper.getMainLooper()) { @Override public void handleMessage(Message msg) { switch (msg.what) { case 1: notifyItemChanged(msg.arg1, "update-time"); break; } } };性能優化方面
1.調用notifyItemChanged()方法后，不要更新整個item(比如說item包含圖片，不需要變的)，所以要重寫onBindViewHolder( Holder , int , List
@Override public void onBindViewHolder(@NonNull Holder holder, int position, @NonNull List<Object> payloads) { if (payloads.isEmpty()) { onBindViewHolder(holder, position); return; } //更新某個控件,比如說只需要更新時間信息，其他不用動 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("剩余時間: " + day + "天" + hour + "小時" + min + "分" + s + "秒"); holder.btnAction.setText(bean.isPause() ? "開始" : "暫停"); holder.btnAction.setEnabled(bean.getTotalTime() != 0); }2.銷毀資源操作：
/** * 銷毀資源 */ public void destroy() { mHandler.removeMessages(1); if (mTimer != null) { mTimer.cancel(); mTimer.purge(); mTimer = null; } }RecyclerView.Adapter部分源碼
public class CountDownTimerAdapter extends RecyclerView.Adapter<CountDownTimerAdapter.Holder> { private static final String TAG = "CountDownTimerAdapter->"; private List<CountDownTimerBean> mList;//數據 private Handler mHandler;//線程調度，用來更新列表 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); } /** * 設置新的數據源 * * @param list 數據 */ 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); } /** * 銷毀資源 */ 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; } //更新某個控件,比如說只需要更新時間信息，其他不用動 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("剩余時間: " + day + "天" + hour + "小時" + min + "分" + s + "秒"); holder.btnAction.setText(bean.isPause() ? "開始" : "暫停"); 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("剩余時間: " + day + "天" + hour + "小時" + min + "分" + s + "秒"); holder.btnAction.setText(bean.isPause() ? "開始" : "暫停"); 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("暫停"); } else { bean.setPause(true); holder.btnAction.setText("開始"); } } }); } @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()) {//不處于暫停狀態 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); } } } }}項目地址
總結
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