Capture a daily log entry

Record a measurement in three taps, one-handed, without leaving the screen the person was already on.

The task

Somebody has to record the same thing every day: a blood pressure reading, a blood glucose value, a weight, a dose taken, how they slept. They will do it while holding a cup, on a bus, half-asleep, for months. The design constraint is not elegance; it is that the entry must cost so little that it still happens in week twelve.

Friction here is not a usability nuisance, it is a data-quality problem. An entry flow that takes eight taps produces a log with gaps in it, and a log with gaps is a trend you cannot draw and a summary you cannot show a clinician. Every extra decision you put in the way removes data from the rest of the product.

The target is three taps from the screen the person was on: open, enter, save.

What you need

The components this entry flow composes are all shipped: the code exists and installs, the API may change in any release, and none of it has been through an accessibility or a clinical review. Every part below installs, the stepped and segmented entry in the last row included. Composing them into the flow is still yours to do.

Part	Component	Status	What it does here
The capture surface	LogSheet	Shipped	Low-friction bottom sheet, sized to the entry.
The number entry	ReadingInput	Shipped	Numeric input with a unit switch and a plausibility warning.
The sheet mechanics	Sheet	Shipped	Detents, drag, keyboard-safe insets, focus return.
Label and error	Field	Shipped	The label/control/hint/error composition every input sits inside.
Save and undo	Button	Shipped	The primary action, within thumb reach.
The confirmation	Value · RelativeTime	Shipped	Shows what was saved, where it will live.
First run	EmptyState	Shipped	Before there is anything logged.
Stepped entry	NumberField · SegmentedControl	Shipped	A stepped or segmented entry, when a free number is not the fit.

Tokens, by family:

Family	Where it applies	Reference
Space scale	Target size, separation, thumb-reach zone	Density and touch
Material rung	The sheet's rung above the page, and its opaque fallback	Choosing a layer
Motion	Sheet presentation and dismissal, and their reduced-motion forms	Reduced motion
`--opsin-category-*`	The category of the thing being logged, as identity only	Category identity

Build it

Put the entry point where the person already is

The log action belongs on the surface that shows the metric, such as the tile or the detail screen. It does not belong behind a plus button in a navigation bar three levels away. The best entry point is the thing the person is already looking at when they remember they need to log.

Whatever you choose, it is one target, at least 44pt, and it is in the lower third of the screen where a thumb reaches without a grip change.

Present a sheet, not a screen

A full-screen form says this is a task. A sheet says this is a moment. The sheet keeps the context visible behind it, which both reassures the person that they have not lost their place and makes dismissal obviously safe.

Size the sheet to its content with a detent, not to an arbitrary half-screen. The primary control sits above the keyboard, and the sheet respects the keyboard-safe inset so the save button is never underneath the keyboard. Sheet owns that mechanic.

Default everything you legitimately can

Every default you supply removes a decision:

Time: now. Editable, because a person logs a reading twenty minutes late.
Unit: whatever they used last. Never make somebody re-pick their own unit system daily.
Category and metric: implied by the entry point they used.

Do not default the measurement itself. Pre-filling yesterday's value is tempting because it is fast, and it is exactly how a log fills with numbers nobody measured. A blank field is honest.

Make the number easy to type and hard to get wrong

ReadingInput is the specialist here, and it has three jobs beyond being a text box:

The right keyboard, first time. A decimal measurement needs a decimal pad, not a spelling keyboard with a numbers layer.
The unit beside the field, switchable, with the value converting when it is switched. Because switching it changes the number without anybody typing, the product announces the conversion. See Unit systems.
A plausibility warning, not a block. A body temperature of 96 is implausible in °C and ordinary in °F; a systolic of 400 is almost certainly a typo. Say so, softly, and let it be saved anyway. A hard maximum means the one person whose real reading is out of your range cannot record it, and their reading is the one that mattered.

Confirm in place, without a dialog

On save, the sheet dismisses and the value appears where it will live from now on, briefly distinguished so the eye finds it. That is the confirmation. A modal saying "Saved!" costs a tap to dismiss and tells the person less than seeing the number in position.

Offer undo instead of asking "are you sure?"

Confirmation dialogs tax every correct action to prevent a rare incorrect one. Save immediately and offer undo for a short window. Undo restores the previous state exactly, including the case where the entry replaced an earlier value for the same slot.

Deletion of a saved reading is a different matter and may confirm. A deleted measurement cannot be re-measured.

Handle the second entry of the day

The most-missed case. If a value already exists for this slot, decide in advance whether the new entry replaces it, sits beside it, or is refused, and say which before the person types. Several readings a day is normal for glucose and unusual for weight, so this is per metric, not global.

The copy

Labels are questions, in the reader's words, with the unit in the label and repeated beside the field.

Sheet title is the thing being logged: "Blood pressure".
Field label is "Systolic (top number)". The parenthetical is not clutter; it is the difference between a correct entry and a transposed one.
Primary action is the verb for what happens: "Save reading", not "OK", "Done" or "Submit".
Plausibility warning describes and asks, never accuses: "That is much higher than your usual readings. Check the number, or save it anyway."
Confirmation uses no words at all, if the value is visible in place.

A field labelled "Systolic (top number)" showing "120 mmHg", with the unit beside the field and a decimal keypad already open.

Don’t

"SYS" with no unit, a spelling keyboard, and a validation message reading "Invalid input". None of those tell the person what to type or what went wrong.

Error text says what to do, not what happened: Error and empty messages. "Enter a number between 30 and 300" is help; "Invalid value" is a shrug.

Get it right

Safety

No measurement is ever pre-filled from a previous entry.
A plausibility warning never silently discards or corrects a value. The person's number is their number.
The time recorded is the time of measurement, and the person can change it. Include the time zone; a reading logged while travelling must not move a day.
The unit is stored with the value, or the value is converted to a canonical unit on the way in and the original preserved. A stored number with an implicit unit is a future incident.
Logging on behalf of somebody else must be visibly distinct, or attributed readings will end up on the wrong person's chart. The person logging might be a carer or a parent.

Accessibility

Every target clears 44pt with real separation, and the primary control is reachable one-handed. See Target size and motor accessibility.
Focus moves into the sheet on open, is trapped while it is modal, and returns to the control that opened it on dismissal. Keyboard and focus specifies that contract.
The sheet is dismissible from the keyboard with Escape, not only by dragging.
The save is announced politely; the undo affordance is reachable by keyboard for as long as it is available. An undo that only a mouse can reach is not an undo.
Switching the unit converts the number on screen without anybody typing, so the product routes ReadingInputChange.effectText through the same polite announcer it uses for the save, on every change where effectText is not null. ReadingInput hands you the exact sentence and deliberately mounts no live region of its own, so if the product stays silent a reader hears only the new unit and saves a number they were never told about. Screen readers has the announcement rules.
Validation is announced when it appears and is associated with its field, so it is heard rather than only seen. Screen readers covers the announcement.
Typed input survives rotation, backgrounding and a keyboard dismissal. Losing a half-typed reading is the fastest way to end a logging habit.
At 200% text the sheet scrolls; the primary control stays reachable and never moves under the keyboard.

Variations

Several fields in one reading. Blood pressure is systolic, diastolic and often pulse: one reading, one save, one timestamp. Do not split it into three entries. A systolic without its diastolic is not usable.

A value on a scale rather than a number. Pain, mood, fatigue. ScaleInput now ships for this. Prefer its labelled set of options over a free slider, because a slider invites false precision on a scale that has none.

A dose or a medication taken. DoseTracker now ships. Adherence data is more sensitive than most measurements and needs an explicit consent conversation. See Ask for consent before collecting.

Backfilling several days at once. A different task with a different shape, and a real one after a holiday. It is a list of dates, not a repeated sheet.

Automatic capture from a device. Then there is no entry flow, and a different problem: the reading arrives with provenance, and the display has to be able to say which device produced it and how accurate that device is.

Daily logging covers the same task at flow scale: reminders, streaks, and what to do about a missed day.
LogSheet and ReadingInput are the two component specifications this recipe assembles.
Daily log screen is the whole surface this entry flow lives on.

Capture a daily log entry

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