Zoomable is a Compose Multiplatform library that enables the content zoomable by pinch gesture, double-tap, tap-and-drag gesture, or mouse scroll wheel.
| Pinch | Double-tap | Double-tap and drag |
Zoomable provides a simple Modifier extension function Modifier.zoomable.
Here is the simplest sample code. You can make image zoomable by just adding one line code.
Image(
painter = painterResource(id = R.drawable.penguin),
contentDescription = null,
modifier = Modifier.zoomable(rememberZoomState()),
)Zoomable can be used with
- any composable components such as
Image,Text, etc. - asynchronous image composable such as coil's
AsyncImage.
Zoomable also can be used in conjunction with HorizontalPager and VerticalPager.
Zoomable supports Android, iOS, and Desktop.
| Platform | Pinch | Double-tap | Tap-and-drag | Mouse scroll wheel |
|---|---|---|---|---|
| Android | ✅ | ✅ | ✅ | ✅ |
| iOS | ✅ | ✅ | ✅ | *1 |
| Desktop | *2 | ✅ | ✅ | ✅ |
| Wasm | ✅ | ✅ | ✅ | ✅ |
- ✅: Supported
- *1: Mouse wheel scroll may not work on iOS.
- *2: Compose desktop does not support multi-touch gestures.
Zoomable is available on Maven Central.
repositories {
mavenCentral()
}
dependencies {
implementation "net.engawapg.lib:zoomable:$version"
}
The latest version:
You can use Modifier.zoomable to make contents such as an image zoomable.
The zoom state is managed in a ZoomState object that can be created via rememberZoomState.
If contentSize is set, the range of offset will be optimized for the specified size.
val painter = painterResource(id = R.drawable.penguin)
val zoomState = rememberZoomState(contentSize = painter.intrinsicSize)
Image(
painter = painter,
contentDescription = "Zoomable image",
contentScale = ContentScale.Fit,
modifier = Modifier
.fillMaxSize()
.zoomable(zoomState),
)By default, every time double tap is detected, zoomable modifier switches the scale between 1.0f and 2.5f.
To change the scale set for double-tap detection, call toggleScale with desired value in onDoubleTap callback.
val targetScale = 5.0f
zoomable(
zoomState = zoomState,
onDoubleTap = { position -> zoomState.toggleScale(targetScale, position) }
)If you want to implement the logic to determine the scale value yourself, you can use the changeScale function.
In the example below, the scale is switched in three steps.
zoomable(
zoomState = zoomState,
onDoubleTap = { position ->
val targetScale = when {
zoomState.scale < 2f -> 2f
zoomState.scale < 4f -> 4f
else -> 1f
}
zoomState.changeScale(targetScale, position)
}
)To disable double tap action, set empty function to onDoubleTap.
zoomable(
zoomState = zoomState,
onDoubleTap = {}
)By default, one finger zoom action, tap followed by vertical drag, is enabled.
If you want disable it, set false to enableOneFingerZoom.
zoomable(
zoomState = zoomState,
enableOneFingerZoom = false,
)You can choose when to propagate scroll gestures to the parent Pager composable by specifying scrollGesturePropagation.
ContentEdge: Scroll gesture is propagated when the content is scrolled to the edge and attempts to scroll further.NotZoomed: Scroll gesture is propagated when the content is not zoomed.
| ContentEdge | NotZoomed |
By default, zooming works by holding down the Ctrl key and operating the mouse wheel.
This is intended to be used primarily with desktop, but it also works with Android.
You can change the behavior by using the mouseWheelZoom argument of zoomable.
Disableddisables zoom by mouse wheel operation.Enabledenables zoom by mouse wheel operation regardless of whether the modifier key is pressed.EnabledWithCtrlKey,EnabledWithShiftKey,EnabledWithAltKey, andEnabledWithMetaKeyenable zoom by mouse wheel operation while holding down the modifier key.
Modifier.snapBackZoomable allows you to zoom an image with a pinch gesture and automatically return it to its original size when you release your finger.
You can easily achieve Instagram-like behavior.
To zoom a component that itself scrolls, such as a LazyColumn or LazyRow, use zoomableWithScroll.
Warning
zoomableWithScroll is an experimental API and may change in the future.
LazyColumn(
modifier = Modifier.zoomableWithScroll(rememberZoomState())
) {
items(100) { Text("Item $it") }
}It can also be used with Modifier.verticalScroll or Modifier.horizontalScroll.
In that case, put zoomableWithScroll before verticalScroll or horizontalScroll in the Modifier chain.
Column(
modifier = Modifier
.fillMaxSize()
.zoomableWithScroll(rememberZoomState())
.horizontalScroll(rememberScrollState())
) {
repeat(100) { Text("Item $it") }
}You can try sample app that contains following samples.
- Standard Image composable (source)
- Asynchronous image loading using Coil library (source)
- Image on
HorizontalPager(source) - Snap back zoom (source)
LazyColumn(source)- Row with
Modifier.horizontalScroll(source)
Copyright 2022 usuiat
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.