参考链接：https://github.com/abcghy/CountDownView

商城中的秒杀倒计时样式，自定义view。
相关gradle依赖

//可选择性的将相关代码给自己写一个时间工具类
implementation 'com.blankj:utilcode:1.3.6'
implementation 'io.reactivex.rxjava2:rxjava:2.1.14'
implementation 'io.reactivex.rxjava2:rxandroid:2.0.2'

1、相关代码

public class CountDownView extends View {

    private Context mContext;

    private Paint mPaint;

    private int mTextSize;

    private int mBgColor = Color.WHITE;//定义背景颜色
    private int mTextColor = Color.BLACK;//定义字体颜色

    private int size = 40;

    private long hour;
    private long min;
    private long sec;

    private long mTargetTime;//从什么时候开始倒计时，传入毫秒值。

    public CountDownView(Context context) {
        this(context, null);
    }

    public CountDownView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CountDownView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mContext = context;

        TypedArray a = mContext.obtainStyledAttributes(attrs, R.styleable.CountDownView);

//        defalutSize = a.getDimensionPixelSize(R.styleable.MyView_default_size, 100);
        mTextSize = a.getDimensionPixelSize(R.styleable.CountDownView_textSize, dp2px(12));

        a.recycle();

        initPaint();
    }


    private void initPaint() {
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setColor(mTextColor);
        mPaint.setTextSize(mTextSize);
        mPaint.setStrokeWidth(dp2px(2));
        mPaint.setTextAlign(Paint.Align.CENTER);
    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.translate(getMeasuredWidth() / 2, getMeasuredHeight() / 2);

//        mPaint.setColor(Color.BLACK);
//        canvas.drawLine(dp2px(-100), 0, dp2px(100), 0, mPaint);

        drawRect(canvas, -size);
        drawRect(canvas, 0);
        drawRect(canvas, size);

        mPaint.setColor(mTextColor);

        String strHour = hour < 10 ? "0" + hour : hour + "";
        canvas.drawText(strHour, dp2px(-size), dp2px(4), mPaint);

        String strMinute = min < 10 ? "0" + min : min + "";
        canvas.drawText(strMinute, 0, dp2px(4), mPaint);
//        drawCenter(canvas, mPaint, strMinute);

        String strSec = sec < 10 ? "0" + sec : sec + "";
        canvas.drawText(strSec, dp2px(size), dp2px(4), mPaint);

        mPaint.setColor(mBgColor);
        canvas.drawText(":", dp2px(-18), dp2px(4), mPaint);
        canvas.drawText(":", dp2px(18), dp2px(4), mPaint);
    }

//    Rect r = new Rect();
//
//    private void drawCenter(Canvas canvas, Paint paint, String text) {
//        canvas.getClipBounds(r);
//        int cHeight = r.height();
//        int cWidth = r.width();
//        paint.setTextAlign(Paint.Align.LEFT);
//        paint.getTextBounds(text, 0, text.length(), r);
//        float x = cWidth / 2f - r.width() / 2f - r.left;
//        float y = cHeight / 2f + r.height() / 2f - r.bottom;
//        canvas.drawText(text, x, y, paint);
//    }

    private void drawRect(Canvas canvas, float x) {
        mPaint.setColor(mBgColor);
        RectF rect = new RectF(dp2px(x - 15), dp2px(-15f), dp2px(x + 15), dp2px(15f));
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            canvas.drawRoundRect(rect, dp2px(4), dp2px(4), mPaint);
        } else {
            canvas.drawRect(rect, mPaint);
        }
    }

/**
  *调用此方法开始进行倒计时
  */
    public void start() {
        Observable.interval(1, TimeUnit.SECONDS)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
//                .subscribe(new Consumer<Long>() {
//                    @Override
//                    public void accept(Long aLong) throws Exception {
//                        calculateTargetTime();
//                        invalidate();
//                    }
//                });
                .subscribe(new Observer<Long>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

                    @Override
                    public void onNext(Long aLong) {
                        calculateTargetTime();
                        invalidate();
                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onComplete() {

                    }
                });
    }


    public void setColor(int bgColor, int textColor) {
        mBgColor = bgColor;
        mTextColor = textColor;
        invalidate();
    }

    public void setCountDownTime(long targetTime) {
        this.mTargetTime = targetTime;
        calculateTargetTime();
    }

    private void calculateTargetTime() {
        if (mTargetTime != 0) {
            long countDownTime = mTargetTime-System.currentTimeMillis();
            if (countDownTime >= 0) {
                hour = ConvertUtils.millis2TimeSpan(countDownTime, ConstUtils.TimeUnit.HOUR);
                min = ConvertUtils.millis2TimeSpan(countDownTime, ConstUtils.TimeUnit.MIN) % 60;
                sec = ConvertUtils.millis2TimeSpan(countDownTime, ConstUtils.TimeUnit.SEC) % 60;
            }
        }
    }


    /**
     * dp转px
     *
     * @param dpValue dp值
     * @return px值
     */
    public int dp2px(float dpValue) {
        final float scale = mContext.getResources().getDisplayMetrics().density;
        return (int) (dpValue * scale + 0.5f);
    }
}

Style文件

  <declare-styleable name="CountDownView">
        <attr name="textSize" format="dimension" />
        <attr name="defaultTime" format="integer" />
    </declare-styleable>

应用

 private void initCountDownView(BusinessEntity entity) {

        CountDownView mCountDownView = findViewById(R.id.count_down_view);
        TextView mTitleText = findViewById(R.id.miaosha_text1);
        //展示秒杀,根据服务端返回的时间戳格式进行format后转为Date再获取毫秒值
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
        long startTime = dateFormat.parse(entity.getRedStartTime()).getTime();
        long endTime = dateFormat.parse(entity.getRedEndTime()).getTime();
        long duringTime = 0;

        int timeFlag = redPointUtil.checkValidDataFlag(entity.getRedStartTime(), entity.getRedEndTime());
        if (timeFlag == -1) {//未开始
            mTitleText .setText(entity.getTitle());
            mTitleText .setTextColor(ColorUtil.rgb(entity.getMiaoShaStartTextColor()));
            duringTime = startTime;

        } else if (timeFlag == 0) {//已开始
            mTitleText .setText(entity.getMenuLittleName());
            mTitleText .setTextColor(ColorUtil.rgb(entity.getMiaoShaEndTextColor()));
            duringTime = endTime;
        }
        mCountDownView.setCountDownTime(duringTime);
        mCountDownView.setColor(Color.BLACK, Color.WHITE);
        mCountDownView.start();
    }

根据服务端返回字段动态设置字体颜色----

public class ColorUtil {
//格式对应为rgbStriing=rgba(0,0,255,1)，也就是json返回的value值的解析。
    public  static int rgb(String rgbStriing){
        int   rgbColor = Color.rgb(0,0,0);
        try {
            String colorString =   rgbStriing.replace("rgba(","").replace(")","");
            String[]  rgbs =  colorString.split(",");
            rgbColor = Color.rgb(Integer.parseInt(rgbs[0]),Integer.parseInt(rgbs[1]),Integer.parseInt(rgbs[2]));
            return rgbColor;
        }catch (Exception e){
            e.printStackTrace();
        }
        return rgbColor;
    }
}

检测返回的开始时间和结束时间对比当前时间

可参考时间工具文章:https://www.jianshu.com/p/19f248d5f4c3

    /**
     * 检查任务是否在有效期内
     * 时间比较格式:20180613163000年月日时分秒
     */
    public int checkValidDataFlag(String startTime, String endTime) {
        int flag = 0;
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmmss");//年-月-日
        try {
            Date currentDate = new Date();
            Date startDate = dateFormat.parse(startTime.trim());//开始时间

            Date endDate = dateFormat.parse(endTime.trim());//结束时间
            if (currentDate.before(startDate)) {
                flag = -1;//未开始
            } else if (currentDate.after(startDate) && currentDate.before(endDate)) {
                flag = 0;//进行中倒计时
            }else if(currentDate.after(endDate)){
                flag=1;//结束
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return flag;
    }

xml布局文件

    <com.cqx.view.CountDownView
                    android:id="@+id/count_down_view"
                    android:layout_width="150dp"
                    android:layout_height="match_parent"
                    android:layout_alignParentRight="true"
                    android:layout_marginTop="15dp"
                    app:textSize="15sp" />

背景

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">

    <corners android:radius="2dp"/>

    <solid android:color="#000000"/>

</shape>