# NestedScrollingChildHelper

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

*** ** * ** ***


```
public class NestedScrollingChildHelper
```

<br />

*** ** * ** ***

Helper class for implementing nested scrolling child views compatible with Android platform versions earlier than Android 5.0 Lollipop (API 21).

`https://developer.android.com/reference/android/view/View.html` subclasses should instantiate a final instance of this class as a field at construction. For each `View` method that has a matching method signature in this class, delegate the operation to the helper instance in an overridden method implementation. This implements the standard framework policy for nested scrolling.

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 Android 5.0 Lollipop and newer.

## Summary

| ### Public constructors |
|---|
| `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#NestedScrollingChildHelper(android.view.View)(@https://jspecify.dev/docs/api/org/jspecify/annotations/NonNull.html https://developer.android.com/reference/android/view/View.html view)` Construct a new helper for a given view. |

| ### Public methods |
|---|---|
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#dispatchNestedFling(float,float,boolean)(float velocityX, float velocityY, boolean consumed)` Dispatch a nested fling operation to the current nested scrolling parent. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#dispatchNestedPreFling(float,float)(float velocityX, float velocityY)` Dispatch a nested pre-fling operation to the current nested scrolling parent. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#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 pre-scrolling operation to the current nested scrolling parent. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#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 pre-scrolling operation to the current nested scrolling parent. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#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 scrolling operation to the current nested scrolling parent. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#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 scrolling operation to the current nested scrolling parent. |
| `void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#dispatchNestedScroll(int,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, @https://jspecify.dev/docs/api/org/jspecify/annotations/Nullable.html int[] consumed )` Dispatch one step of a nested scrolling operation to the current nested scrolling parent. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#hasNestedScrollingParent()()` Check if this view has a nested scrolling parent view currently receiving events for a nested scroll in progress with the type of touch. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#hasNestedScrollingParent(int)(int type)` Check if this view has a nested scrolling parent view currently receiving events for a nested scroll in progress with the given type. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#isNestedScrollingEnabled()()` Check if nested scrolling is enabled for this view. |
| `void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#onDetachedFromWindow()()` View subclasses should always call this method on their `NestedScrollingChildHelper` when detached from a window. |
| `void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#onStopNestedScroll(android.view.View)(@https://jspecify.dev/docs/api/org/jspecify/annotations/NonNull.html https://developer.android.com/reference/android/view/View.html child)` Called when a nested scrolling child stops its current nested scroll operation. |
| `void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#setNestedScrollingEnabled(boolean)(boolean enabled)` Enable nested scrolling. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#startNestedScroll(int)(int axes)` Start a new nested scroll for this view. |
| `boolean` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#startNestedScroll(int,int)(int axes, int type)` Start a new nested scroll for this view. |
| `void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#stopNestedScroll()()` Stop a nested scroll in progress. |
| `void` | `https://developer.android.com/reference/androidx/core/view/NestedScrollingChildHelper#stopNestedScroll(int)(int type)` Stop a nested scroll in progress. |

## Public constructors

### NestedScrollingChildHelper

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

```
public NestedScrollingChildHelper(@NonNull View view)
```

Construct a new helper for a given view.

## Public methods

### dispatchNestedFling

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

```
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed)
```

Dispatch a nested fling operation to the current nested scrolling parent.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | true if the parent consumed the nested fling |

### dispatchNestedPreFling

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

```
public boolean dispatchNestedPreFling(float velocityX, float velocityY)
```

Dispatch a nested pre-fling operation to the current nested scrolling parent.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | true if the parent consumed the nested fling |

### dispatchNestedPreScroll

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

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

Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | true if the parent consumed any of the nested scroll |

### dispatchNestedPreScroll

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

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

Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | true if the parent consumed any of the nested scroll |

### dispatchNestedScroll

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

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

Dispatch one step of a nested scrolling operation to the current nested scrolling parent.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | `true` if the parent consumed any of the nested scroll distance |

### dispatchNestedScroll

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

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

Dispatch one step of a nested scrolling operation to the current nested scrolling parent.

This is a delegate method. Call it from your `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | `true` if the parent consumed any of the nested scroll distance |

### dispatchNestedScroll

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

```
public void dispatchNestedScroll(
    int dxConsumed,
    int dyConsumed,
    int dxUnconsumed,
    int dyUnconsumed,
    @Nullable int[] offsetInWindow,
    int type,
    @Nullable int[] consumed
)
```

Dispatch one step of a nested scrolling operation to the current nested scrolling parent.

This is a delegate method. Call it from your `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild3` interface method with the same signature to implement the standard policy.

### hasNestedScrollingParent

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

```
public boolean hasNestedScrollingParent()
```

Check if this view has a nested scrolling parent view currently receiving events for a nested scroll in progress with the type of touch.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | true if this view has a nested scrolling parent, false otherwise |

### hasNestedScrollingParent

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

```
public boolean hasNestedScrollingParent(int type)
```

Check if this view has a nested scrolling parent view currently receiving events for a nested scroll in progress with the given type.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | true if this view has a nested scrolling parent, false otherwise |

### isNestedScrollingEnabled

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

```
public boolean isNestedScrollingEnabled()
```

Check if nested scrolling is enabled for this view.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Returns |
|---|---|
| `boolean` | true if nested scrolling is enabled for this view |

### onDetachedFromWindow

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

```
public void onDetachedFromWindow()
```

View subclasses should always call this method on their `NestedScrollingChildHelper` when detached from a window.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

### onStopNestedScroll

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

```
public void onStopNestedScroll(@NonNull View child)
```

Called when a nested scrolling child stops its current nested scroll operation.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Parameters |
|---|---|
| `@https://jspecify.dev/docs/api/org/jspecify/annotations/NonNull.html https://developer.android.com/reference/android/view/View.html child` | Child view stopping its nested scroll. This may not be a direct child view. |

### setNestedScrollingEnabled

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

```
public void setNestedScrollingEnabled(boolean enabled)
```

Enable nested scrolling.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Parameters |
|---|---|
| `boolean enabled` | true to enable nested scrolling dispatch from this view, false otherwise |

### startNestedScroll

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

```
public boolean startNestedScroll(int axes)
```

Start a new nested scroll for this view.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

| Parameters |
|---|---|
| `int axes` | Supported nested scroll axes. See `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild#startNestedScroll(int)`. |

| Returns |
|---|---|
| `boolean` | true if a cooperating parent view was found and nested scrolling started successfully |

### startNestedScroll

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

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

Start a new nested scroll for this view.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2` interface method with the same signature to implement the standard policy.

| Parameters |
|---|---|
| `int axes` | Supported nested scroll axes. See `https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2#startNestedScroll(int,int)`. |
| `int type` | type of the scroll. |

| Returns |
|---|---|
| `boolean` | true if a cooperating parent view was found and nested scrolling started successfully |

### stopNestedScroll

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

```
public void stopNestedScroll()
```

Stop a nested scroll in progress.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild` interface method with the same signature to implement the standard policy.

### stopNestedScroll

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

```
public void stopNestedScroll(int type)
```

Stop a nested scroll in progress.

This is a delegate method. Call it from your `https://developer.android.com/reference/android/view/View.html` subclass method/`https://developer.android.com/reference/androidx/core/view/NestedScrollingChild2` interface method with the same signature to implement the standard policy.