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效果

背景

业务场景需要显示带有毫秒级别的倒计时，于是自己封装一个通用的倒计时组件

源码分析

1. 核心倒计时逻辑，主要是每隔100毫秒计算一次从开始倒计时到现在的剩余时间，并通过process接口返回出去
2. Handler每次设置100毫秒的延迟
3. 将返回出来的时间解析出来

private fun formatTimeToView(remainTime: Long) {val lengthSec = remainTime / 1000val hours = lengthSec / 3600val rem = lengthSec % 3600val minutes = rem / 60val seconds = rem % 60val milliseconds = remainTime % 1000tvMill.text = String.format("%03d", milliseconds)tvHour.text = String.format("%02d", hours)tvMin.text = String.format("%02d", minutes)tvSecond.text = String.format("%02d", seconds)
}

完整源码

class MillCountdownView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null
) : LinearLayout(context, attrs) {private val root = LayoutInflater.from(context).inflate(R.layout.view_count_down, this, true)private val countDownTask: CountDownRunnableprivate val tvHour: TextViewprivate val tvMin: TextViewprivate val tvSecond: TextViewprivate val tvMill: TextViewinit {background = context.getDrawable(R.drawable.count_down_item_bg)orientation = HORIZONTALgravity = Gravity.CENTER_VERTICALtvHour = root.findViewById(R.id.tvHour)tvMin = root.findViewById(R.id.tvMin)tvSecond = root.findViewById(R.id.tvSecond)tvMill = root.findViewById(R.id.tvMill)countDownTask = CountDownRunnable(1).apply {listener = object : TaskListener {override fun finish() {tvHour.text = "00"tvMin.text = "00"tvSecond.text = "00"tvMill.text = "000"Toast.makeText(context, "倒计时结束", Toast.LENGTH_SHORT).show()}override fun process(remainTime: Long) {if (remainTime < 1) {tvHour.text = "00"tvMin.text = "00"tvSecond.text = "00"tvMill.text = "000"return}formatTimeToView(remainTime)}}}}private fun formatTimeToView(remainTime: Long) {val lengthSec = remainTime / 1000val hours = lengthSec / 3600val rem = lengthSec % 3600val minutes = rem / 60val seconds = rem % 60val milliseconds = remainTime % 1000tvMill.text = String.format("%03d", milliseconds)tvHour.text = String.format("%02d", hours)tvMin.text = String.format("%02d", minutes)tvSecond.text = String.format("%02d", seconds)}/*** 预先展示倒计时文本* @param remainTime 倒计时时间，单位毫秒*/fun preShowRemainSecs(remainTime: Long) {countDownTask.totalCountDownTime = remainTimeformatTimeToView(remainTime)}/*** 开始倒计时* @param remainTime 倒计时时间，单位毫秒*/fun startCountdown(remainTime: Long) {countDownTask.destroy()countDownTask.totalCountDownTime = remainTimecountDownTask.start()}fun destroyCountdown() {countDownTask.destroy()}
}

class CountDownRunnable(@IntRange(from = 1)var totalCountDownTime: Long) : Runnable {private val mHandler = Handler(Looper.getMainLooper())var listener: TaskListener? = nullprivate var startCountDownTime = 0L //开始时当前系统时间private var isTaskExecuting = falseoverride fun run() {if (!isTaskExecuting) {return}val dur = SystemClock.elapsedRealtime() - startCountDownTimeval remainTime = totalCountDownTime - durval mill = remainTime % 1000if (remainTime <= 0) {listener?.finish()isTaskExecuting = falsereturn} else {listener?.process(remainTime)}mHandler.postDelayed(this, 100)}fun start() {startCountDownTime = SystemClock.elapsedRealtime()mHandler.post(this)isTaskExecuting = true}fun resume() {val remainTime = totalCountDownTime - ((SystemClock.elapsedRealtime() - startCountDownTime) / 1000).toInt()if (remainTime <= 0) {listener?.finish()return}mHandler.removeCallbacks(this)isTaskExecuting = truemHandler.post(this)}fun pause() {isTaskExecuting = falsemHandler.removeCallbacks(this)}fun destroy() {isTaskExecuting = falsemHandler.removeCallbacks(this)}
}interface TaskListener {fun finish()fun process(remainTime: Long)
}

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="wrap_content"android:layout_height="wrap_content"android:gravity="center_vertical"android:orientation="horizontal"tools:parentTag="LinearLayout"><androidx.appcompat.widget.AppCompatTextViewandroid:id="@+id/tvHour"android:layout_width="wrap_content"android:layout_height="wrap_content"android:minWidth="30dp"android:gravity="center"android:textColor="#000"android:textSize="25sp"android:textStyle="bold"android:layout_marginStart="10dp"android:layout_marginVertical="5dp"tools:text="1" /><androidx.appcompat.widget.AppCompatTextViewandroid:id="@+id/divider1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginHorizontal="4dp"android:gravity="center"android:text=":"android:textColor="#000"android:textSize="25sp"android:textStyle="bold" /><androidx.appcompat.widget.AppCompatTextViewandroid:id="@+id/tvMin"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginStart="5dp"android:gravity="center"android:textColor="#000"android:minWidth="30dp"android:textSize="25sp"android:textStyle="bold"tools:text="8" /><androidx.appcompat.widget.AppCompatTextViewandroid:id="@+id/divider2"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginHorizontal="4dp"android:gravity="center"android:text=":"android:textColor="#000"android:textSize="25sp"android:textStyle="bold" /><androidx.appcompat.widget.AppCompatTextViewandroid:id="@+id/tvSecond"android:layout_width="wrap_content"android:layout_height="wrap_content"android:gravity="center"android:textColor="#000"android:textSize="25sp"android:textStyle="bold"android:minWidth="30dp"tools:text="3" /><androidx.appcompat.widget.AppCompatTextViewandroid:id="@+id/divider3"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginHorizontal="4dp"android:gravity="center"android:text=":"android:textColor="#000"android:textSize="25sp"android:textStyle="bold" /><androidx.appcompat.widget.AppCompatTextViewandroid:id="@+id/tvMill"android:layout_width="wrap_content"android:minWidth="49dp"android:layout_height="wrap_content"android:layout_marginStart="5dp"android:gravity="center"android:textColor="#a00"android:textSize="25sp"android:textStyle="bold"tools:text="000"android:layout_marginEnd="10dp"/></merge>