自学鸿蒙应用开发（39）- 使用多线程功能实现定时器

<?xml version="1.0" encoding="utf-8"?>
<DirectionalLayout
    xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:height="match_parent"
    ohos:width="match_parent"
    ohos:orientation="vertical">
    <TimePicker
        ohos:id="$+id:time_picker"
        ohos:height="match_content"
        ohos:width="match_parent"
        ohos:normal_text_size="25fp"
        ohos:selected_text_size="80fp"/>
</DirectionalLayout>

public class MainAbilitySlice extends AbilitySlice {
    static final HiLogLabel LABEL_LOG = new HiLogLabel(HiLog.LOG_APP, 0x00201, "MainAbilitySlice");
    long lastSecond = 0;
    TimePicker timePicker = null;
    @Override
    public void onStart(Intent intent) {
        super.onStart(intent);
        super.setUIContent(ResourceTable.Layout_ability_main);
        timePicker = (TimePicker)findComponentById(ResourceTable.Id_time_picker);
        onTimer();
    }
    void onTimer(){
        final long delayTime = 50L;
        TaskDispatcher uiTaskDispatcher = getUITaskDispatcher();
        Revocable revocable = uiTaskDispatcher.delayDispatch(new Runnable() {
            @Override
            public void run() {
                Calendar rightNow = Calendar.getInstance();
                long currentSecond = rightNow.get(Calendar.SECOND);
                if(lastSecond != currentSecond) {
                    timePicker.setHour(rightNow.get(Calendar.HOUR_OF_DAY));
                    timePicker.setMinute(rightNow.get(Calendar.MINUTE));
                    timePicker.setSecond(rightNow.get(Calendar.SECOND));
                    lastSecond = currentSecond;
                }
                onTimer();
            }
        }, delayTime);
    }
}