发球练得怎么样，一目了然See how your serve is really going
为业余球友设计：不需要雷达，不需要别人帮你记。Built for club players: no radar gun, no one to keep notes for you.
每一球，一个速度A speed for every ball
App 用击球声和球落地的时间，再结合校正过的球场尺寸，算出每一球的大致速度，并统计平均和最快。The app uses the sound of contact and the time the ball lands, together with your calibrated court, to estimate each ball's speed — plus your average and fastest.
这是估算值，适合和自己的过去比较，不等同雷达读数。看不到落点的球会标注「估」，不计入平均和最快。These are estimates — good for comparing with your own past sessions, not a radar reading. Balls whose landing isn't seen are marked as estimates and left out of average and fastest.
落在哪里，一眼看清See exactly where it lands
自动识别球场线，在发球区图上标出每一球：进区、出界、下网分开显示。进区率按水平从红到绿着色，哪里不稳，一看就知道。The app finds the court lines automatically and plots every ball on the service box — in, out or net, each in its own color. In-rate is shaded from red to green so weak spots stand out.
一区二区分开算，趋势看得见Deuce and ad tracked apart, progress in a line
一区、二区分别统计进区率和最快球速，也记下每次训练的发球数。记录页按时间排列，数据页画出变化趋势，练了多少、进步多少，都有数字。In-rate and top speed are counted separately for each service box, along with serves per session. The Records tab lists every session and the Stats tab draws your trend over time.
手腕上的遥控器A remote on your wrist
用 Apple Watch 开始和结束训练、查看校正是否对齐，并用手腕动作辅助数发球次数。放下手腕，也会继续记录。Start and stop a session from Apple Watch, check that calibration is lined up, and let wrist motion help count serves. It keeps recording when you drop your arm.
手表是可选的，没有手表也能完整使用。The watch is optional — everything works without one.
四步开练Four steps to start
一个三脚架、一部 iPhone，不用走来走去换机位。One tripod, one iPhone, no moving the camera around.
摆位Set up
三脚架放在接发球一侧，升到最高。手机横屏，画面里要同时看到球网和两个发球区。Put the tripod on the receiving side, as high as it goes. Phone in landscape, with the net and both service boxes in frame.
校正Calibrate
App 先自动识别球场线，你确认四个点，需要时拖动微调。The app detects the court lines first. You confirm four points and nudge them if needed.
录制Record
点开始，10 秒倒计时，走回发球线。一次最长 20 分钟，可以连续录多组。Tap start, take the 10-second countdown to walk to the baseline. Up to 20 minutes a session, with as many sets as you like.
看结果Review
录完自动在手机上分析，不用传到电脑。每一球的落点、速度和进出情况都可以点开看。Analysis runs on the phone as soon as you stop — nothing to upload. Tap any ball to see its landing, speed and result.
你的录像，只留在你的手机里Your footage stays on your phone
不联网No network
App 不上传任何数据，也没有服务器。The app uploads nothing and there is no server.
不注册No account
不需要账号、手机号或邮箱，打开就能用。No sign-up, phone number or email. Open it and go.
无追踪No tracking
没有广告，也没有第三方统计。阅读隐私政策No ads, no third-party analytics. Read the privacy policy
关于这个项目About the project
独立开发者Independent developer
网球发球训练由我一个人开发。起因很简单：想用手机，把自己练发球时的速度和进区率记下来。Tennis Serve Trainer is built by one person. The idea was simple: use a phone to keep track of my own serve speed and in-rate while practicing.
它面向业余球友，所以我更看重上手容易、结果好懂，而不是实验室级的精度。后面会继续改进识别和界面，也会陆续做更多小工具。It is made for club players, so I care more about being easy to set up and easy to read than about lab-grade precision. Recognition and design will keep improving, and more small tools may follow.
有想法或遇到问题，欢迎写信：davewell3010@gmail.comIdeas or problems? Write to me: davewell3010@gmail.com
常见问题FAQ
需要什么设备？What do I need?
一部 iPhone（iOS 17 或更高）和一个三脚架。Apple Watch 可选。An iPhone running iOS 17 or later and a tripod. Apple Watch is optional.
球速准吗？How accurate is the speed?
球速是根据录像和击球声估算的，适合对比自己不同时间的发球、看进步。它不是雷达，不建议拿去和雷达数字逐个比较。Speeds are estimated from video and impact sound. They suit comparing your own serves over time. They are not radar readings, so don't expect them to match a radar gun ball for ball.
需要联网吗？Does it need internet?
不需要。录制和分析都在手机上完成。No. Recording and analysis both happen on the phone.
录像会占很多空间吗？Will videos fill my storage?
高帧率录像比较大，20 分钟可能有几个 GB。可以在设置里关闭「保留录像」，分析完只保留每一球的小片段。High-frame-rate video is large — 20 minutes can reach several GB. Turn off “Keep full video” in settings to keep only a short clip per ball after analysis.
有安卓版吗？Is there an Android version?
目前只有 iPhone 版。安卓版在计划中，暂时没有确切时间。iPhone only for now. Android is planned, with no date yet.