实现计时器

Android 实现计时器

这周接到个新需求，统计用户在线时长，累积到一定时长后上报，可以通过计时器来实现。本篇文章介绍下安卓端实现计时器的三种方式。

Timer、TimerTask

通过Timer和TimerTask实现计时，代码如下：

class TimeChangeExample : BaseGestureDetectorActivity() {


    private lateinit var binding: LayoutTimeChangeExampleActivityBinding


    private val dateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS")


    private var timerHandler = object : Handler(Looper.myLooper() ?: Looper.getMainLooper()) {

        override fun handleMessage(msg: Message) {

            super.handleMessage(msg)

            if (msg.what == 0) {

                setCountdownTimeText(msg.obj as Long)

            }

        }

    }

    private var timer: Timer? = null

    private var timerTask: TimerTask? = null


    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        binding = DataBindingUtil.setContentView(this, R.layout.layout_time_change_example_activity)

        binding.btnCountdownByTimer.setOnClickListener {

            clearText()

            binding.tvCountdownText.text = "countdown by timer\n"

            startCountdownByTime()

        }

        binding.btnStopTimer.setOnClickListener {

            stopTimer()

        }

    }


    private fun startCountdownByTime() {

        stopTimer()

        timerTask = object : TimerTask() {

            override fun run() {

                timerHandler.sendMessage(timerHandler.obtainMessage(0, System.currentTimeMillis()))

            }

        }

        timer = Timer()

        timer?.schedule(timerTask, 0, 1000)

    }


    private fun stopTimer() {

        timer?.cancel()

        timer = null

        timerTask = null

    }


    private fun setCountdownTimeText(time: Long) {

        binding.tvCountdownText.run {

            post {

                text = text.toString() + "${dateFormat.format(Date(time))}\n"

            }

        }

    }


    private fun clearText() {

        binding.tvCountdownText.text = ""

    }


    override fun onDestroy() {

        super.onDestroy()

        stopTimer()

    }

}

效果如图：

两次计时之间的误差都是毫秒级的。

BroadCastReceiver

通过注册广播，监听系统时间变化实现计时，但是广播回调触发的间隔固定为一分钟，代码如下：

class TimeChangeExample : BaseGestureDetectorActivity() {


    private lateinit var binding: LayoutTimeChangeExampleActivityBinding


    private val dateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS")


    private val timeChangeBroadcastReceiver = object : BroadcastReceiver() {

        override fun onReceive(context: Context?, intent: Intent?) {

            if (intent?.action == Intent.ACTION_TIME_TICK) {

                setCountdownTimeText(System.currentTimeMillis())

            }

        }

    }


    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        binding = DataBindingUtil.setContentView(this, R.layout.layout_time_change_example_activity)

        binding.btnCountdownByBroadcast.setOnClickListener {

            clearText()

            binding.tvCountdownText.text = "countdown by broadcast\n"

            startCountdownByBroadcast()

        }

        binding.btnStopBroadcast.setOnClickListener {

            stopBroadcast()

        }

    }


    private fun startCountdownByBroadcast() {

        registerReceiver(timeChangeBroadcastReceiver, IntentFilter().apply {

            addAction(Intent.ACTION_TIME_TICK)

        })

    }


    private fun stopBroadcast() {

        unregisterReceiver(timeChangeBroadcastReceiver)

    }


    private fun setCountdownTimeText(time: Long) {

        binding.tvCountdownText.run {

            post {

                text = text.toString() + "${dateFormat.format(Date(time))}\n"

            }

        }

    }


    private fun clearText() {

        binding.tvCountdownText.text = ""

    }


    override fun onDestroy() {

        super.onDestroy()

        stopBroadcast()

    }

}

效果如图：

两次计时之间的误差都是毫秒级的。

Handler

通过Handler和Runnable来实现计时，代码如下：

class TimeChangeExample : BaseGestureDetectorActivity() {


    private lateinit var binding: LayoutTimeChangeExampleActivityBinding


    private val dateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS")


    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        binding = DataBindingUtil.setContentView(this, R.layout.layout_time_change_example_activity)

        binding.btnCountdownByHandler.setOnClickListener {

            clearText()

            binding.tvCountdownText.text = "countdown by handler\n"

            startCountdownByHandler()

        }

        binding.btnStopHandler.setOnClickListener {

            stopHandler()

        }

    }


    private val handler = Handler(Looper.myLooper() ?: Looper.getMainLooper())

    private val countdownRunnable = object : Runnable {

        override fun run() {

            setCountdownTimeText(System.currentTimeMillis())

            val currentTime = SystemClock.uptimeMillis()

            val nextTime = currentTime + (1000 - currentTime % 1000)

            handler.postAtTime(this, nextTime)

        }

    }


    private fun startCountdownByHandler() {

        val currentTime = SystemClock.uptimeMillis()

        val nextTime = currentTime + (1000 - currentTime % 1000)

        handler.postAtTime(countdownRunnable, nextTime)

    }


    private fun stopHandler() {

        handler.removeCallbacks(countdownRunnable)

    }


    private fun setCountdownTimeText(time: Long) {

        binding.tvCountdownText.run {

            post {

                text = text.toString() + "${dateFormat.format(Date(time))}\n"

            }

        }

    }


    private fun clearText() {

        binding.tvCountdownText.text = ""

    }


    override fun onDestroy() {

        super.onDestroy()

        stopHandler()

    }

}