When a bottom sheet is closed in Jetpack Compose, the app often automatically focuses on the previously focused element. This can be disruptive to the user experience, especially if the previously focused element is no longer relevant or visible. We want to prevent this automatic refocusing and instead control the focus ourselves.
### Key Points to Consider
1. Bottom sheets in Jetpack Compose handle focus management differently from regular composables.
2. The `bottomSheetState` object provides information about the current state of the bottom sheet.
3. We need to intercept the focus change events to control the focus behavior.
4. Proper timing is crucial when modifying focus states.
5. Accessibility considerations should be kept in mind when changing focus behavior.
### Step-by-Step Thought Process
1. Identify the current focus state before closing the bottom sheet.
2. Create a custom composable that wraps the bottom sheet content.
3. Implement a function to handle focus changes when the bottom sheet is closed.
4. Use `DisposableEffect` to manage the lifecycle of our custom composable.
5. Modify the focus state programmatically when the bottom sheet is closed.
6. Ensure proper cleanup of focus-related operations.
### Implementation Steps
#### 1. Create a Custom Composable Wrapper
First, let's create a custom composable wrapper that handles focus management:
```kotlin
@Composable
fun FocusAwareBottomSheet(
modifier: Modifier = Modifier,
content: @Composable () -> Unit,
onDismissRequest: () -> Unit
) {
val focusManager = LocalFocusManager.current
DisposableEffect(Unit) {
onDispose {
// Cleanup focus-related operations here
}
LaunchedEffect(Unit) {
// Handle focus changes when the bottom sheet is dismissed
onDismissRequest = {
focusManager.clearFocus()
onDismissRequest()
}
}
}
ModalBottomSheetLayout(
modifier = modifier,
onDismissRequest = onDismissRequest
) {
content()
}
}
```
#### 2. Use the Custom Composable
Now, let's use our custom composable in a sample UI:
```kotlin
@Composable
fun SampleScreen() {
var showBottomSheet by remember { mutableStateOf(false) }
Column(modifier = Modifier.fillMaxSize()) {
Text("Main Screen")
Button(onClick = { showBottomSheet = true }) {
Text("Show Bottom Sheet")
}
if (showBottomSheet) {
FocusAwareBottomSheet(
onDismissRequest = {
showBottomSheet = false
},
content = {
Text("Bottom Sheet Content")
TextField(value = "", onValueChange = {})
}
)
}
}
}
```
#### 3. Handling Focus Changes
To handle focus changes when the bottom sheet is closed, we'll modify our `SampleScreen`:
```kotlin
@Composable
fun SampleScreen() {
var showBottomSheet by remember { mutableStateOf(false) }
var lastFocusedElement: Any? by remember { mutableStateOf(null) }
Column(modifier = Modifier.fillMaxSize()) {
Text("Main Screen")
Button(onClick = { showBottomSheet = true }) {
Text("Show Bottom Sheet")
}
if (showBottomSheet) {
FocusAwareBottomSheet(
onDismissRequest = {
showBottomSheet = false
lastFocusedElement = null
},
content = {
Text("Bottom Sheet Content")
TextField(value = "", onValueChange = {
lastFocusedElement = it
})
}
)
} else {
// Handle focus changes when the bottom sheet is closed
if (lastFocusedElement != null && lastFocusedElement is TextField) {
(lastFocusedElement as TextField).requestFocus()
}
}
}
}
```
#### 4. Implementing Keyboard Manager
For a more robust solution, especially when dealing with keyboard interactions, we can implement a custom keyboard manager:
```kotlin
class KeyboardManager(context: Context) {
private val activity = context as Activity
private var keyboardDismissListener: KeyboardDismissListener? = null
private abstract class KeyboardDismissListener(
private val rootView: View,
private val onKeyboardDismiss: () -> Unit
) : ViewTreeObserver.OnGlobalLayoutListener {
private var isKeyboardClosed: Boolean = false
override fun onGlobalLayout() {
val r = Rect()
rootView.getWindowVisibleDisplayFrame(r)
val screenHeight = rootView.rootView.height
val keypadHeight = screenHeight - r.bottom
if (keypadHeight > screenHeight * 0.15) {
isKeyboardClosed = false
} else if (!isKeyboardClosed) {
isKeyboardClosed = true
onKeyboardDismiss.invoke()
}
}
}
fun attachKeyboardDismissListener(onKeyboardDismiss: () -> Unit) {
val rootView = activity.findViewById<View>(android.R.id.content)
keyboardDismissListener = object : KeyboardDismissListener(rootView, onKeyboardDismiss) {}
keyboardDismissListener?.let {
rootView.viewTreeObserver.addOnGlobalLayoutListener(it)
}
}
fun release() {
val rootView = activity.findViewById<View>(android.R.id.content)
keyboardDismissListener?.let {
rootView.viewTreeObserver.removeOnGlobalLayoutListener(it)
}
keyboardDismissListener = null
}
}
@Composable
fun AppKeyboardFocusManager() {
val context = LocalContext.current
val focusManager = LocalFocusManager.current
DisposableEffect(key1 = context) {
val keyboardManager = KeyboardManager(context)
keyboardManager.attachKeyboardDismissListener {
focusManager.clearFocus()
}
onDispose {
keyboardManager.release()
}
}
}
```
Apply this `AppKeyboardFocusManager` at the root level of your app:
```kotlin
setContent {
AppKeyboardFocusManager()
YourAppMaterialTheme {
// Rest of your app content
}
}
```
### Best Practices Followed
1. **Separation of Concerns**: The focus handling logic is encapsulated within a custom composable.
2. **Lifecycle Management**: Using `DisposableEffect` ensures proper cleanup of focus-related operations.
3. **Flexibility**: The solution adapts to different types of focusable elements.
4. **Accessibility**: Maintaining focus control improves accessibility for screen reader users.
5. **Performance**: Efficient focus management prevents unnecessary redraws.
### Troubleshooting Tips
1. **Debugging Focus Issues**: Use `LocalFocusManager.current.focus()` to manually set focus for debugging.
2. **Check for Conflicting Logic**: Ensure no other parts of your app are interfering with focus management.
3. **Test with Different Devices**: Verify the behavior across various Android devices and emulators.
4. **Consider Keyboard Layout**: Be aware of different keyboard layouts that might affect focus behavior.
5. **Handle Edge Cases**: Account for situations where the bottom sheet might be closed unexpectedly.
### Summary
Avoiding auto-focus after closing a bottom sheet in Jetpack Compose requires careful management of focus states and events. By creating a custom composable wrapper and implementing a keyboard manager, we can gain fine-grained control over focus behavior. This approach ensures a smoother user experience by preventing unexpected focus shifts when interacting with bottom sheets.
Remember that focus management is crucial for maintaining good UX and adhering to accessibility guidelines. Always test your implementations thoroughly, considering various scenarios and edge cases, to ensure a consistent and predictable user interaction.