如何计算两个时间字符串的间隔？Kotlin代码报错求助

我有两个时分格式的字符串（如19:30、20:30），想要计算它们之间的时长。尝试用DateTimeFormatter实现但失败了，原Kotlin代码如下：

val startTime = LocalDate.parse("19:30", DateTimeFormatter.ofPattern("HH:mm"))
val endTime = LocalDate.parse("20:30", DateTimeFormatter.ofPattern("HH:mm"))
val newDate = Period.between(startTime, endTime) 

考虑过把时间转成毫秒后相减，但不知道具体操作，求解决方案。

错误信息 #

Process: com.example.leetcodedraft, PID: 23723

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.leetcodedraft/com.example.leetcodedraft.MainActivity}: java.time.format.DateTimeParseException: Text '19:30' could not be parsed: Unable to obtain LocalDate from TemporalAccessor: {},ISO resolved to 19:30 of type java.time.format.Parsed
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
    Caused by: java.time.format.DateTimeParseException: Text '19:30' could not be parsed: Unable to obtain LocalDate from TemporalAccessor: {},ISO resolved to 19:30 of type java.time.format.Parsed
        at java.time.format.DateTimeFormatter.createError(DateTimeFormatter.java:1920)
        at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1855)
        at java.time.LocalDate.parse(LocalDate.java:394)
        at com.example.leetcodedraft.Test.startTest(Test.kt:16)
        at com.example.leetcodedraft.MainActivity.onCreate(MainActivity.kt:36)
        at android.app.Activity.performCreate(Activity.java:7136)
        at android.app.Activity.performCreate(Activity.java:7127)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.app.ActivityThread.main(ActivityThread.java:6669) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
    Caused by: java.time.DateTimeException: Unable to obtain LocalDate from TemporalAccessor: {},ISO resolved to 19:30 of type java.time.format.Parsed
        at java.time.LocalDate.from(LocalDate.java:362)
        at java.time.-$$Lambda$Bq8PKq1YWr8nyVk9SSfRYKrOu4A.queryFrom(Unknown Source:0)
        at java.time.format.Parsed.query(Parsed.java:226)
        at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1851)
        at java.time.LocalDate.parse(LocalDate.java:394) 
        at com.example.leetcodedraft.Test.startTest(Test.kt:16) 
        at com.example.leetcodedraft.MainActivity.onCreate(MainActivity.kt:36) 
        at android.app.Activity.performCreate(Activity.java:7136) 
        at android.app.Activity.performCreate(Activity.java:7127) 
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.app.ActivityThread.main(ActivityThread.java:6669) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 

错误根源 #

你用错了时间类：LocalDate是处理年月日的日期类型，而19:30是时分格式的时间，应该用LocalTime类解析。另外Period.between是计算日期间隔的，时间间隔要用到Duration类。

方法一：用LocalTime + Duration直接计算时长 #

用Java/Kotlin原生时间API处理，代码简洁且易维护：

import java.time.LocalTime
import java.time.Duration
import java.time.format.DateTimeFormatter

fun calculateTimeDiff() {
    val formatter = DateTimeFormatter.ofPattern("HH:mm")
    val startTime = LocalTime.parse("19:30", formatter)
    val endTime = LocalTime.parse("20:30", formatter)
    
    // 计算时间间隔
    val duration = Duration.between(startTime, endTime)
    
    // 获取不同单位的时长结果
    val hours = duration.toHours()
    val minutes = duration.toMinutes()
    val seconds = duration.seconds
    
    println("间隔小时数：$hours") // 输出：1
    println("间隔分钟数：$minutes") // 输出：60
    println("间隔秒数：$seconds") // 输出：3600
}

方法二：转成毫秒后相减 #

如果需要基于毫秒计算，可把LocalTime转成当天的毫秒偏移量（从00:00:00开始的毫秒数）再相减：

import java.time.LocalTime
import java.time.format.DateTimeFormatter

fun calculateTimeDiffInMillis() {
    val formatter = DateTimeFormatter.ofPattern("HH:mm")
    val startTime = LocalTime.parse("19:30", formatter)
    val endTime = LocalTime.parse("20:30", formatter)
    
    // 转成当天的毫秒数（从0点开始的偏移）
    val startMillis = startTime.toSecondOfDay() * 1000L
    val endMillis = endTime.toSecondOfDay() * 1000L
    
    val diffMillis = endMillis - startMillis
    println("间隔毫秒数：$diffMillis") // 输出：3600000（即1小时）
    
    // 转成常用单位
    val diffMinutes = diffMillis / (1000 * 60)
    val diffHours = diffMillis / (1000 * 60 * 60)
    println("间隔分钟数：$diffMinutes") // 60
    println("间隔小时数：$diffHours") // 1
}

跨天场景处理 #

如果时间可能跨天（比如23:30到00:30），Duration.between会得到负数，可通过加一天的时长修正：

val duration = Duration.between(startTime, endTime)
val correctedDuration = if (duration.isNegative) duration.plusDays(1) else duration

内容的提问来源于stack exchange，提问作者Jekis Osipov