拖动、滑动与快速滑动
跟踪移动和惯性。
拖动、滑动与快速滑动 是 CoddyKit 上的免费 Jetpack Compose Academy 课时。 这是第 2 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Jetpack Compose Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Jetpack Compose Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Following the Finger
Dragging means tracking how far a finger moves and updating the UI to match. Compose makes this smooth with dedicated drag detectors. ✋
Detect Drag Gestures
Inside pointerInput, call detectDragGestures. Its onDrag lambda fires repeatedly with the change and the distance moved since the last event.
detectDragGestures { change, drag -> /* move */ }Accumulate the Offset
Keep a state Offset and add each drag delta to it. Then feed that offset into a Modifier so the element follows your finger.
var offset by remember { mutableStateOf(Offset.Zero) }
offset += dragApply with offset Modifier
Use the offset modifier to move a composable by your tracked pixels. Convert with roundToInt so it positions cleanly on screen.
Modifier.offset { IntOffset(offset.x.roundToInt(), offset.y.roundToInt()) }Consume the Change
Call change.consume() in your drag handler. This tells parents you handled the event so they do not also react to it.
detectDragGestures { change, drag -> change.consume() }Limit to One Axis
Need only sideways motion? Use detectHorizontalDragGestures, or detectVerticalDragGestures for up and down. They report a single Float delta.
detectHorizontalDragGestures { _, dx -> x += dx }Swipe to Dismiss
A swipe is just a drag you judge at the end. If the finger traveled far enough, treat it as a dismiss instead of snapping back.
The High-Level draggable
For simple single-axis dragging, the draggable modifier is easier. Pair it with rememberDraggableState to collect the delta.
Modifier.draggable(state, orientation = Orientation.Horizontal)Fling Needs Velocity
A fling keeps moving after release based on speed. Track velocity with a VelocityTracker as the finger moves to capture that momentum.
val tracker = VelocityTracker()Animate the Decay
Feed the release velocity into an Animatable with a decay spec. It glides to a natural stop, mimicking real physics. 🌀
animatable.animateDecay(velocity, exponentialDecay())Know When It Ends
detectDragGestures also gives you onDragEnd and onDragCancel. Use them to snap back, settle, or kick off your fling animation.
detectDragGestures(onDragEnd = { /* fling here */ }) {...}Quick Check
What does a fling animation need that a plain drag does not?
Recap: Move with Momentum
You tracked drags with detectDragGestures, accumulated an offset, judged swipes, and used velocity for a fling. Touch now feels alive. 🎉
常见问题解答
「拖动、滑动与快速滑动」课时是免费的吗？
是的 — 「拖动、滑动与快速滑动」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Jetpack Compose Academy 课程的其余内容，请升级到 CoddyKit PRO。 Jetpack Compose Academy 课程共包含 4 节课。
「拖动、滑动与快速滑动」这节课中我会学到什么？
跟踪移动和惯性。 你通过在浏览器中直接运行的动手代码来练习 Jetpack Compose Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Jetpack Compose Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Jetpack Compose Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 2 节课，共 4 节。
「拖动、滑动与快速滑动」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Jetpack Compose Academy 课中编写并运行代码吗？
能。每节 Jetpack Compose Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。