Android 用 ListView 實現(xiàn)倒計時列表功能

在很多時候我們會用到一個場景，在 list 的 item 上顯示不同的倒計時，如下圖所示。

listView效果

需要注意的地方也沒多少：

1.ViewHolder 的重復(fù)使用與倒計時顯示沖突。
2.退出應(yīng)用時釋放所有 CountDownTimer 資源。

關(guān)于使用 Android 用 RecyclerView 實現(xiàn)倒計時列表功能。

Step00.核心代碼 MyAdapter.java

public static class MyAdapter extends BaseAdapter {
    private List<TimerItem> mDatas;
    private Context mContext;

    //用于退出 Activity,避免 Countdown，造成資源浪費。
    private SparseArray<CountDownTimer> countDownCounters;

    public MyAdapter(Context mContext, List<TimerItem> mDatas) {
        this.mContext = mContext;
        this.mDatas = mDatas;
        this.countDownCounters = new SparseArray<>();
    }

    /**
     * 清空當(dāng)前 CountTimeDown 資源
     */
    public void cancelAllTimers() {
        if (countDownCounters == null) {
            return;
        }
        Log.e("TAG",  "size :  " + countDownCounters.size());
        for (int i = 0, length = countDownCounters.size(); i < length; i++) {
            CountDownTimer cdt = countDownCounters.get(countDownCounters.keyAt(i));
            if (cdt != null) {
                cdt.cancel();
            }
        }
    }

    @Override
    public int getCount() {
        if (mDatas != null && !mDatas.isEmpty()) {
            return mDatas.size();
        }
        return 0;
    }

    @Override
    public Object getItem(int position) {
        if (mDatas != null && !mDatas.isEmpty()) {
            return mDatas.get(position);
        }
        return null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ViewHolder viewHolder;
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.list_item_common, parent, false);
            viewHolder = new ViewHolder();
            viewHolder.statusTv = (TextView) convertView.findViewById(R.id.tv_status);
            viewHolder.timeTv = (TextView) convertView.findViewById(R.id.tv_time);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        final TimerItem data = mDatas.get(position);
        viewHolder.statusTv.setText(data.name);

        CountDownTimer countDownTimer = countDownCounters.get(viewHolder.timeTv.hashCode());
        if (countDownTimer != null) {
            //將復(fù)用的倒計時清除
            countDownTimer.cancel();
        }
        long timer = data.expirationTime;
        timer = timer - System.currentTimeMillis();
        //expirationTime 與系統(tǒng)時間做比較，timer 小于零，則此時倒計時已經(jīng)結(jié)束。
        if (timer > 0) {
            countDownTimer = new CountDownTimer(timer, 1000) {
                public void onTick(long millisUntilFinished) {
                    viewHolder.timeTv.setText(TimeTools.getCountTimeByLong(millisUntilFinished));
                    Log.e("TAG", data.name + " :  " + millisUntilFinished);
                }
                public void onFinish() {
                    viewHolder.timeTv.setText("00:00:00");
                    viewHolder.statusTv.setText(data.name + ":結(jié)束");
                }
            }.start();
            //將此 countDownTimer 放入list.
            countDownCounters.put(viewHolder.timeTv.hashCode(), countDownTimer);
        } else {
            viewHolder.timeTv.setText("00:00:00");
            viewHolder.statusTv.setText(data.name + ":結(jié)束");
        }
        return convertView;
    }

    public class ViewHolder {
        public TextView statusTv;
        public TextView timeTv;
    }
}

主要通過 SparseArray<CountDownTimer> 類保存每個 Item 上的 CountDownTimer 類。
當(dāng)需要復(fù)用時，通用 TextView 的 hashCode 取出對應(yīng)的 CountDownTimer。重新啟動并顯示。
當(dāng)退出此頁面時，調(diào)用 cancelAllTimers() 方法，遍歷 countDownCounters 關(guān)閉所有的 CountDownTimer 類。避免造成內(nèi)存泄漏。

Step01.數(shù)據(jù)填充

mAdapter = new MyAdapter(mContext,TimerItemUtil.getTimerItemList());
mListView.setAdapter(mAdapter);

Step02.Entity 類

public class TimerItem {
    //其他屬性
    public String name;
    //倒計時長，單位毫秒
    public long expirationTime;
    public TimerItem(String name, long expirationTime) {
        this.name = name;
        this.expirationTime = expirationTime;
    }
}

Step03.獲取倒計時集合（自定義時間）。

public static List<TimerItem> getTimerItemList() {
    List<TimerItem> lstTimerItems = new ArrayList<>();
    lstTimerItems.add(new TimerItem("A", System.currentTimeMillis() + 11 * 1000));
    lstTimerItems.add(new TimerItem("B", System.currentTimeMillis() + 22 * 1000));
    lstTimerItems.add(new TimerItem("C", System.currentTimeMillis() + 26 * 1000));
    lstTimerItems.add(new TimerItem("D", System.currentTimeMillis() + 33 * 1000));
    lstTimerItems.add(new TimerItem("E", System.currentTimeMillis() + 24 * 1000));
    lstTimerItems.add(new TimerItem("F", System.currentTimeMillis() + 98 * 1000));
    lstTimerItems.add(new TimerItem("G", System.currentTimeMillis() + 14 * 1000));
    lstTimerItems.add(new TimerItem("H", System.currentTimeMillis() + 36 * 1000));
    lstTimerItems.add(new TimerItem("I", System.currentTimeMillis() + 58 * 1000));
    lstTimerItems.add(new TimerItem("J", System.currentTimeMillis() + 47 * 1000));
    lstTimerItems.add(new TimerItem("K", System.currentTimeMillis() + 66 * 1000));
    lstTimerItems.add(new TimerItem("L", System.currentTimeMillis() + 55 * 1000));
    lstTimerItems.add(new TimerItem("M", System.currentTimeMillis() + 62 * 1000));
    lstTimerItems.add(new TimerItem("N", System.currentTimeMillis() + 45 * 1000));
    lstTimerItems.add(new TimerItem("O", System.currentTimeMillis() + 14 * 1000));

    return lstTimerItems;
}

Step04.list_item_common.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="64dp"
    android:orientation="horizontal"
    android:padding="10dp">

    <TextView
        android:id="@+id/tv_status"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        tools:text="status"
        android:layout_gravity="center"
        android:gravity="center"
        />

    <TextView
        android:id="@+id/tv_time"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:textSize="15sp"
        android:layout_gravity="center_vertical"
        tools:text="00:01:54"/>
</LinearLayout>

Step05.當(dāng)退出 Activity 時釋放資源.

@Override
protected void onDestroy() {
    super.onDestroy();
    if (mAdapter != null) {
        mAdapter.cancelAllTimers();
    }
}

Step06.源代碼 Github