這篇文章將為大家詳細講解有關RecyclerView中怎么實現(xiàn)列表倒計時,文章內容質量較高,因此小編分享給大家做個參考,希望大家閱讀完這篇文章后對相關知識有一定的了解。
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首先看下實現(xiàn)的最終效果
如何顯示列表我相信大家都會,這里我只附上和倒計時功能實現(xiàn)的adapter類。
public class ClockAdapter extends RecyclerView.Adapter<ClockAdapter.ClockViewHolder> { private SparseArray<CountDownTimer> countDownMap = new SparseArray<>(); @Override public ClockViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_rv, parent, false); return new ClockViewHolder(view); } /** * 清空資源 */ public void cancelAllTimers() { if (countDownMap == null) { return; } for (int i = 0,length = countDownMap.size(); i < length; i++) { CountDownTimer cdt = countDownMap.get(countDownMap.keyAt(i)); if (cdt != null) { cdt.cancel(); } } } @Override public void onBindViewHolder(final ClockViewHolder holder, int position) { long betweenDate; if (position == 0) { betweenDate= DateUtil.getLeftTime("2017-8-8 12:10:10"); } else { betweenDate= DateUtil.getLeftTime("2017-8-9 15:10:10"); } if (holder.countDownTimer != null) { holder.countDownTimer.cancel(); } if (betweenDate > 0) { holder.countDownTimer = new CountDownTimer(betweenDate, 1000) { public void onTick(long millisUntilFinished) { millisUntilFinished = millisUntilFinished / 1000; int hours = (int) (millisUntilFinished / (60 * 60)); int leftSeconds = (int) (millisUntilFinished % (60 * 60)); int minutes = leftSeconds / 60; int seconds = leftSeconds % 60; final StringBuffer sBuffer = new StringBuffer(); sBuffer.append(addZeroPrefix(hours)); sBuffer.append(":"); sBuffer.append(addZeroPrefix(minutes)); sBuffer.append(":"); sBuffer.append(addZeroPrefix(seconds)); holder.clock.setText(sBuffer.toString()); } public void onFinish() {// 時間結束后進行相應邏輯處理 } }.start(); countDownMap.put(holder.clock.hashCode(), holder.countDownTimer); } else {// 時間結束 進行相應邏輯處理 } } @Override public int getItemCount() { return 25; } class ClockViewHolder extends RecyclerView.ViewHolder { TextView clock; CountDownTimer countDownTimer; public ClockViewHolder(View itemView) { super(itemView); clock = (TextView) itemView.findViewById(R.id.clock); } }}
其中cancelAllTimer()這個方法解決了內存的問題,通過這行代碼,將item的hashcode作為key設入SparseArray中,這樣在cancelAllTimer方法中可以一個一個取出來進行倒計時取消操作。
countDownMap.put(holder.clock.hashCode(),holder.countDownTimer);
接著通過下面這行代碼新建一個CountDownTimer類
holder.countDownTimer = new CountDownTimer(betweenDate, 1000) { public void onTick(long millisUntilFinished) { millisUntilFinished = millisUntilFinished / 1000; int hours = (int) (millisUntilFinished / (60 * 60)); int leftSeconds = (int) (millisUntilFinished % (60 * 60)); int minutes = leftSeconds / 60; int seconds = leftSeconds % 60; final StringBuffer sBuffer = new StringBuffer(); sBuffer.append(addZeroPrefix(hours)); sBuffer.append(":") sBuffer.append(addZeroPrefix(minutes)); sBuffer.append(":"); sBuffer.append(addZeroPrefix(seconds)); holder.clock.setText(sBuffer.toString());}public void onFinish() {// 時間結束后進行相應邏輯處理}}.start();
分析它的源碼
public CountDownTimer(long millisInFuture, long countDownInterval) { mMillisInFuture = millisInFuture; mCountdownInterval = countDownInterval; }
從中可以很清楚的看出,設置了兩個值,第一個是倒計時結束時間,第二個是刷新時間的間隔時間。 然后通過start方法進行啟動,接著看下start方法中進行的處理
public synchronized final CountDownTimer start() { mCancelled = false; if (mMillisInFuture <= 0) { onFinish(); return this; } mStopTimeInFuture = SystemClock.elapsedRealtime() + mMillisInFuture; mHandler.sendMessage(mHandler.obtainMessage(MSG)); return this; }
源碼中,當?shù)褂嫊r截止時間小于等0時也就是倒計時結束時,調用了onFinish方法,若時間還未結束,則通過handler的異步消息機制,將消息進行發(fā)出,通過一整個流程,最終方法會走到handler的handleMessage方法中,如果有不熟悉這個異步流程的伙伴,可以去看我以前寫的一篇異步消息機制的文章 android異步消息機制,源碼層面徹底解析。好了,接下來就來看看handler的handleMessage方法。
private Handler mHandler = new Handler() { @Override public void handleMessage(Message msg) { synchronized (CountDownTimer.this) { if (mCancelled) { return; } final long millisLeft = mStopTimeInFuture - SystemClock.elapsedRealtime(); if (millisLeft <= 0) { onFinish(); } else if (millisLeft < mCountdownInterval) { // no tick, just delay until done sendMessageDelayed(obtainMessage(MSG), millisLeft); } else {long lastTickStart=SystemClock.elapsedRealtime(); onTick(millisLeft); // take into account user's onTick taking time to execute long delay = lastTickStart + mCountdownInterval - SystemClock.elapsedRealtime();// special case: user's onTick took more than interval to// complete, skip to next interval while (delay < 0) delay += mCountdownInterval; sendMessageDelayed(obtainMessage(MSG), delay); } } } };
關于RecyclerView中怎么實現(xiàn)列表倒計時就分享到這里了,希望以上內容可以對大家有一定的幫助,可以學到更多知識。如果覺得文章不錯,可以把它分享出去讓更多的人看到。
文章標題:RecyclerView中怎么實現(xiàn)列表倒計時
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