<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".ChronomterActivity">

    <Chronometer

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:textColor="#000FFF"

        android:id="@+id/chronmeter"/>

</RelativeLayout>

package com.badao.relativelayouttest;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import android.os.SystemClock;

import android.widget.Chronometer;

public class ChronomterActivity extends AppCompatActivity {

    Chronometer chronometer ;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_chronomter);

        //获取计时器

        chronometer = (Chronometer) findViewById(R.id.chronmeter);

        //设置起始时间为当前时间

        chronometer.setBase(SystemClock.elapsedRealtime());

        //设置显示格式

        chronometer.setFormat("%s");

        //启动计时器

        chronometer.start();

        //设置计时器该改变监听事件

        chronometer.setOnChronometerTickListener(new Chronometer.OnChronometerTickListener() {

            @Override

            public void onChronometerTick(Chronometer chronometer) {

                //如果当前时间 - 计时器的起始时间 >= 15秒

                if(SystemClock.elapsedRealtime() - chronometer.getBase() >=)

                {

                    //停止计时器

                    chronometer.stop();

                }

            }

        });

    }

}