# NestedScrollingChild2

Artifact: [androidx.core:core](https://developer.android.com/jetpack/androidx/releases/core) [View Source](https://cs.android.com/search?q=file:androidx/core/view/NestedScrollingChild2.java+class:androidx.core.view.NestedScrollingChild2) Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/core#1.1.0)

*** ** * ** ***


```
public interface NestedScrollingChild2 extends NestedScrollingChild
```

<br />

Known direct subclasses [NestedScrollingChild3](https://developer.android.com/reference/androidx/core/view/NestedScrollingChild3), [RecyclerView](https://developer.android.com/reference/androidx/recyclerview/widget/RecyclerView), [SwipeRefreshLayout](https://developer.android.com/reference/androidx/swiperefreshlayout/widget/SwipeRefreshLayout)

|---|---|
| `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild3` | This interface should be implemented by `https://developer.android.com/reference/android/view/View.html` subclasses that wish to support dispatching nested scrolling operations to a cooperating parent `https://developer.android.com/reference/android/view/ViewGroup.html`. |
| `https://developer.android.com/reference/androidx/recyclerview/widget/RecyclerView` | A flexible view for providing a limited window into a large data set. |
| `https://developer.android.com/reference/androidx/swiperefreshlayout/widget/SwipeRefreshLayout` | The SwipeRefreshLayout should be used whenever the user can refresh the contents of a view via a vertical swipe gesture. |

Known indirect subclasses [BaseGridView](https://developer.android.com/reference/androidx/leanback/widget/BaseGridView), [HorizontalGridView](https://developer.android.com/reference/androidx/leanback/widget/HorizontalGridView), [NestedScrollView](https://developer.android.com/reference/androidx/core/widget/NestedScrollView), [RecyclerView](https://developer.android.com/reference/androidx/recyclerview/widget/RecyclerView), [SwipeRefreshLayout](https://developer.android.com/reference/androidx/swiperefreshlayout/widget/SwipeRefreshLayout), [VerticalGridView](https://developer.android.com/reference/androidx/leanback/widget/VerticalGridView), [WearableRecyclerView](https://developer.android.com/reference/androidx/wear/widget/WearableRecyclerView)

|---|---|
| `https://developer.android.com/reference/androidx/leanback/widget/BaseGridView` | An abstract base class for vertically and horizontally scrolling lists. |
| `https://developer.android.com/reference/androidx/leanback/widget/HorizontalGridView` | A `https://developer.android.com/reference/android/view/ViewGroup.html` that shows items in a horizontal scrolling list. |
| `https://developer.android.com/reference/androidx/core/widget/NestedScrollView` | NestedScrollView is just like `https://developer.android.com/reference/android/widget/ScrollView.html`, but it supports acting as both a nested scrolling parent and child on both new and old versions of Android. |
| `https://developer.android.com/reference/androidx/recyclerview/widget/RecyclerView` | A flexible view for providing a limited window into a large data set. |
| `https://developer.android.com/reference/androidx/swiperefreshlayout/widget/SwipeRefreshLayout` | The SwipeRefreshLayout should be used whenever the user can refresh the contents of a view via a vertical swipe gesture. |
| `https://developer.android.com/reference/androidx/leanback/widget/VerticalGridView` | A `https://developer.android.com/reference/android/view/ViewGroup.html` that shows items in a vertically scrolling list. |
| `https://developer.android.com/reference/androidx/wear/widget/WearableRecyclerView` | Wearable specific implementation of the `https://developer.android.com/reference/androidx/recyclerview/widget/RecyclerView` enabling `https://developer.android.com/reference/androidx/wear/widget/WearableRecyclerView#setCircularScrollingGestureEnabled(boolean)` circular scrolling} and semi-circular layouts. |

*** ** * ** ***

This interface should be implemented by `https://developer.android.com/reference/android/view/View.html` subclasses that wish to support dispatching nested scrolling operations to a cooperating parent `https://developer.android.com/reference/android/view/ViewGroup.html`.

Classes implementing this interface should create a final instance of a `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper` as a field and delegate any View methods to the `NestedScrollingChildHelper` methods of the same signature.

Views invoking nested scrolling functionality should always do so from the relevant `https://developer.android.com/reference/androidx/core/view/ViewCompat`, `https://developer.android.com/reference/androidx/core/view/ViewGroupCompat` or `https://developer.android.com/reference/androidx/core/view/ViewParentCompat` compatibility shim static methods. This ensures interoperability with nested scrolling views on all versions of Android.

## Summary

| ### Public methods |
|---|---|
| `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedPreScroll(int,int,int[],int[],int)( int dx, int dy, @https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] consumed, @https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] offsetInWindow, int type )` Dispatch one step of a nested scroll in progress before this view consumes any portion of it. |
| `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedScroll(int,int,int,int,int[],int)( int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, @https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] offsetInWindow, int type )` Dispatch one step of a nested scroll in progress. |
| `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#hasNestedScrollingParent(int)(int type)` Returns true if this view has a nested scrolling parent for the given input type. |
| `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#startNestedScroll(int,int)(int axes, int type)` Begin a nestable scroll operation along the given axes, for the given input type. |
| `abstract void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#stopNestedScroll(int)(int type)` Stop a nested scroll in progress for the given input type. |

| ### Inherited methods |
|---|
| From [androidx.core.view.NestedScrollingChild](https://developer.android.com/reference/androidx/core/view/NestedScrollingChild) |---|---| | `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#dispatchNestedFling(float,float,boolean)(float velocityX, float velocityY, boolean consumed)` Dispatch a fling to a nested scrolling parent. | | `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#dispatchNestedPreFling(float,float)(float velocityX, float velocityY)` Dispatch a fling to a nested scrolling parent before it is processed by this view. | | `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#dispatchNestedPreScroll(int,int,int[],int[])( int dx, int dy, @https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] consumed, @https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] offsetInWindow )` Dispatch one step of a nested scroll in progress before this view consumes any portion of it. | | `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#dispatchNestedScroll(int,int,int,int,int[])( int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, @https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] offsetInWindow )` Dispatch one step of a nested scroll in progress. | | `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#hasNestedScrollingParent()()` Returns true if this view has a nested scrolling parent. | | `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#isNestedScrollingEnabled()()` Returns true if nested scrolling is enabled for this view. | | `abstract void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#setNestedScrollingEnabled(boolean)(boolean enabled)` Enable or disable nested scrolling for this view. | | `abstract boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#startNestedScroll(int)(int axes)` Begin a nestable scroll operation along the given axes. | | `abstract void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#stopNestedScroll()()` Stop a nested scroll in progress. | |

## Public methods

### dispatchNestedPreScroll

Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/core#1.1.0)

```
abstract boolean dispatchNestedPreScroll(
    int dx,
    int dy,
    @Nullable int[] consumed,
    @Nullable int[] offsetInWindow,
    int type
)
```

Dispatch one step of a nested scroll in progress before this view consumes any portion of it.

Nested pre-scroll events are to nested scroll events what touch intercept is to touch. `dispatchNestedPreScroll` offers an opportunity for the parent view in a nested scrolling operation to consume some or all of the scroll operation before the child view consumes it.

| Parameters |
|---|---|
| `int dx` | Horizontal scroll distance in pixels |
| `int dy` | Vertical scroll distance in pixels |
| `@https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] consumed` | Output. If not null, consumed\[0\] will contain the consumed component of dx and consumed\[1\] the consumed dy. |
| `@https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] offsetInWindow` | Optional. If not null, on return this will contain the offset in local view coordinates of this view from before this operation to after it completes. View implementations may use this to adjust expected input coordinate tracking. |
| `int type` | the type of input which cause this scroll event |

| Returns |
|---|---|
| `boolean` | true if the parent consumed some or all of the scroll delta |

| See also |
|---|---|
| `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedScroll(int,int,int,int,int[],int)` |   |

### dispatchNestedScroll

Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/core#1.1.0)

```
abstract boolean dispatchNestedScroll(
    int dxConsumed,
    int dyConsumed,
    int dxUnconsumed,
    int dyUnconsumed,
    @Nullable int[] offsetInWindow,
    int type
)
```

Dispatch one step of a nested scroll in progress.

Implementations of views that support nested scrolling should call this to report info about a scroll in progress to the current nested scrolling parent. If a nested scroll is not currently in progress or nested scrolling is not `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#isNestedScrollingEnabled()` for this view this method does nothing.

Compatible View implementations should also call `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedPreScroll(int,int,int[],int[],int)` before consuming a component of the scroll event themselves.

| Parameters |
|---|---|
| `int dxConsumed` | Horizontal distance in pixels consumed by this view during this scroll step |
| `int dyConsumed` | Vertical distance in pixels consumed by this view during this scroll step |
| `int dxUnconsumed` | Horizontal scroll distance in pixels not consumed by this view |
| `int dyUnconsumed` | Horizontal scroll distance in pixels not consumed by this view |
| `@https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] offsetInWindow` | Optional. If not null, on return this will contain the offset in local view coordinates of this view from before this operation to after it completes. View implementations may use this to adjust expected input coordinate tracking. |
| `int type` | the type of input which cause this scroll event |

| Returns |
|---|---|
| `boolean` | true if the event was dispatched, false if it could not be dispatched. |

| See also |
|---|---|
| `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedPreScroll(int,int,int[],int[],int)` |   |

### hasNestedScrollingParent

Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/core#1.1.0)

```
abstract boolean hasNestedScrollingParent(int type)
```

Returns true if this view has a nested scrolling parent for the given input type.

The presence of a nested scrolling parent indicates that this view has initiated a nested scroll and it was accepted by an ancestor view further up the view hierarchy.

| Parameters |
|---|---|
| `int type` | the type of input which cause this scroll event |

| Returns |
|---|---|
| `boolean` | whether this view has a nested scrolling parent |

### startNestedScroll

Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/core#1.1.0)

```
abstract boolean startNestedScroll(int axes, int type)
```

Begin a nestable scroll operation along the given axes, for the given input type.

A view starting a nested scroll promises to abide by the following contract:

The view will call startNestedScroll upon initiating a scroll operation. In the case of a touch scroll type this corresponds to the initial `https://developer.android.com/reference/android/view/MotionEvent.html#ACTION_DOWN`. In the case of touch scrolling the nested scroll will be terminated automatically in the same manner as `https://developer.android.com/reference/android/view/ViewParent.html#requestDisallowInterceptTouchEvent(boolean)`. In the event of programmatic scrolling the caller must explicitly call `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#stopNestedScroll(int)` to indicate the end of the nested scroll.

If `startNestedScroll` returns true, a cooperative parent was found. If it returns false the caller may ignore the rest of this contract until the next scroll. Calling startNestedScroll while a nested scroll is already in progress will return true.

At each incremental step of the scroll the caller should invoke `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedPreScroll(int,int,int[],int[],int)` once it has calculated the requested scrolling delta. If it returns true the nested scrolling parent at least partially consumed the scroll and the caller should adjust the amount it scrolls by.

After applying the remainder of the scroll delta the caller should invoke `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedScroll(int,int,int,int,int[],int)`, passing both the delta consumed and the delta unconsumed. A nested scrolling parent may treat these values differently. See `https://developer.android.com/reference/androidx/core/view/NestedScrollingParent2#onNestedScroll(android.view.View,int,int,int,int,int)`.

| Parameters |
|---|---|
| `int axes` | Flags consisting of a combination of `https://developer.android.com/reference/androidx/core/view/ViewCompat#SCROLL_AXIS_HORIZONTAL()` and/or `https://developer.android.com/reference/androidx/core/view/ViewCompat#SCROLL_AXIS_VERTICAL()`. |
| `int type` | the type of input which cause this scroll event |

| Returns |
|---|---|
| `boolean` | true if a cooperative parent was found and nested scrolling has been enabled for the current gesture. |

| See also |
|---|---|
| `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#stopNestedScroll(int)` |   |
| `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedPreScroll(int,int,int[],int[],int)` |   |
| `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#dispatchNestedScroll(int,int,int,int,int[],int)` |   |

### stopNestedScroll

Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/core#1.1.0)

```
abstract void stopNestedScroll(int type)
```

Stop a nested scroll in progress for the given input type.

Calling this method when a nested scroll is not currently in progress is harmless.

| Parameters |
|---|---|
| `int type` | the type of input which cause this scroll event |

| See also |
|---|---|
| `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#startNestedScroll(int,int)` |   |