java.lang.Object
↳androidx.core.view.NestedScrollingChildHelper
Gradle dependencies
compile group: 'androidx.core', name: 'core', version: '1.9.0-alpha04'
- groupId: androidx.core
- artifactId: core
- version: 1.9.0-alpha04
Artifact androidx.core:core:1.9.0-alpha04 it located at Google repository (https://maven.google.com/)
Androidx artifact mapping:
androidx.core:core com.android.support:support-compat
Androidx class mapping:
androidx.core.view.NestedScrollingChildHelper android.support.v4.view.NestedScrollingChildHelper
Overview
Helper class for implementing nested scrolling child views compatible with Android platform
versions earlier than Android 5.0 Lollipop (API 21).
View
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
ViewCompat, ViewGroupCompat or
ViewParentCompat compatibility
shim static methods. This ensures interoperability with nested scrolling views on Android
5.0 Lollipop and newer.
Summary
Methods |
---|
public boolean | dispatchNestedFling(float velocityX, float velocityY, boolean consumed)
Dispatch a nested fling operation to the current nested scrolling parent. |
public boolean | dispatchNestedPreFling(float velocityX, float velocityY)
Dispatch a nested pre-fling operation to the current nested scrolling parent. |
public boolean | dispatchNestedPreScroll(int dx, int dy, int[] consumed[], int[] offsetInWindow[])
Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent. |
public boolean | dispatchNestedPreScroll(int dx, int dy, int[] consumed[], int[] offsetInWindow[], int type)
Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent. |
public boolean | dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow[])
Dispatch one step of a nested scrolling operation to the current nested scrolling parent. |
public boolean | dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow[], int type)
Dispatch one step of a nested scrolling operation to the current nested scrolling parent. |
public void | dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow[], int type, int[] consumed[])
Dispatch one step of a nested scrolling operation to the current nested scrolling parent. |
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. |
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. |
public boolean | isNestedScrollingEnabled()
Check if nested scrolling is enabled for this view. |
public void | onDetachedFromWindow()
View subclasses should always call this method on their
NestedScrollingChildHelper when detached from a window. |
public void | onStopNestedScroll(View child)
Called when a nested scrolling child stops its current nested scroll operation. |
public void | setNestedScrollingEnabled(boolean enabled)
Enable nested scrolling. |
public boolean | startNestedScroll(int axes)
Start a new nested scroll for this view. |
public boolean | startNestedScroll(int axes, int type)
Start a new nested scroll for this view. |
public void | stopNestedScroll()
Stop a nested scroll in progress. |
public void | stopNestedScroll(int type)
Stop a nested scroll in progress. |
from java.lang.Object | clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructors
public
NestedScrollingChildHelper(View view)
Construct a new helper for a given view.
Methods
public void
setNestedScrollingEnabled(boolean enabled)
Enable nested scrolling.
This is a delegate method. Call it from your View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Parameters:
enabled: true to enable nested scrolling dispatch from this view, false otherwise
public boolean
isNestedScrollingEnabled()
Check if nested scrolling is enabled for this view.
This is a delegate method. Call it from your View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Returns:
true if nested scrolling is enabled for this view
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 View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Returns:
true if this view has a nested scrolling parent, false otherwise
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 View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Returns:
true if this view has a nested scrolling parent, false otherwise
public boolean
startNestedScroll(int axes)
Start a new nested scroll for this view.
This is a delegate method. Call it from your View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Parameters:
axes: Supported nested scroll axes.
See NestedScrollingChild.startNestedScroll(int).
Returns:
true if a cooperating parent view was found and nested scrolling started successfully
public boolean
startNestedScroll(int axes, int type)
Start a new nested scroll for this view.
This is a delegate method. Call it from your View
subclass
method/NestedScrollingChild2 interface method with the same
signature to implement the standard policy.
Parameters:
axes: Supported nested scroll axes.
See NestedScrollingChild2.startNestedScroll(int, int).
Returns:
true if a cooperating parent view was found and nested scrolling started successfully
public void
stopNestedScroll()
Stop a nested scroll in progress.
This is a delegate method. Call it from your View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
public void
stopNestedScroll(int type)
Stop a nested scroll in progress.
This is a delegate method. Call it from your View
subclass
method/NestedScrollingChild2 interface method with the same
signature to implement the standard policy.
public boolean
dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, 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 View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Returns:
true
if the parent consumed any of the nested scroll distance
public boolean
dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, 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 NestedScrollingChild2 interface
method with the same signature to implement the standard policy.
Returns:
true
if the parent consumed any of the nested scroll distance
public void
dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow[], int type, 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 NestedScrollingChild3 interface
method with the same signature to implement the standard policy.
public boolean
dispatchNestedPreScroll(int dx, int dy, int[] consumed[], 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 View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Returns:
true if the parent consumed any of the nested scroll
public boolean
dispatchNestedPreScroll(int dx, int dy, int[] consumed[], 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 View
subclass
method/NestedScrollingChild2 interface method with the same
signature to implement the standard policy.
Returns:
true if the parent consumed any of the nested scroll
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 View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Returns:
true if the parent consumed the nested fling
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 View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Returns:
true if the parent consumed the nested fling
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 View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
public void
onStopNestedScroll(View child)
Called when a nested scrolling child stops its current nested scroll operation.
This is a delegate method. Call it from your View
subclass
method/NestedScrollingChild interface method with the same
signature to implement the standard policy.
Parameters:
child: Child view stopping its nested scroll. This may not be a direct child view.
Source
/*
* Copyright 2018 The Android Open Source Project
*
* 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.
*/
package androidx.core.view;
import static androidx.core.view.ViewCompat.TYPE_NON_TOUCH;
import static androidx.core.view.ViewCompat.TYPE_TOUCH;
import android.view.View;
import android.view.ViewParent;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.core.view.ViewCompat.NestedScrollType;
import androidx.core.view.ViewCompat.ScrollAxis;
/**
* Helper class for implementing nested scrolling child views compatible with Android platform
* versions earlier than Android 5.0 Lollipop (API 21).
*
* <p>{@link android.view.View View} subclasses should instantiate a final instance of this
* class as a field at construction. For each <code>View</code> 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.</p>
*
* <p>Views invoking nested scrolling functionality should always do so from the relevant
* {@link androidx.core.view.ViewCompat}, {@link androidx.core.view.ViewGroupCompat} or
* {@link androidx.core.view.ViewParentCompat} compatibility
* shim static methods. This ensures interoperability with nested scrolling views on Android
* 5.0 Lollipop and newer.</p>
*/
public class NestedScrollingChildHelper {
private ViewParent mNestedScrollingParentTouch;
private ViewParent mNestedScrollingParentNonTouch;
private final View mView;
private boolean mIsNestedScrollingEnabled;
private int[] mTempNestedScrollConsumed;
/**
* Construct a new helper for a given view.
*/
public NestedScrollingChildHelper(@NonNull View view) {
mView = view;
}
/**
* Enable nested scrolling.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @param enabled true to enable nested scrolling dispatch from this view, false otherwise
*/
public void setNestedScrollingEnabled(boolean enabled) {
if (mIsNestedScrollingEnabled) {
ViewCompat.stopNestedScroll(mView);
}
mIsNestedScrollingEnabled = enabled;
}
/**
* Check if nested scrolling is enabled for this view.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @return true if nested scrolling is enabled for this view
*/
public boolean isNestedScrollingEnabled() {
return mIsNestedScrollingEnabled;
}
/**
* Check if this view has a nested scrolling parent view currently receiving events for
* a nested scroll in progress with the type of touch.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @return true if this view has a nested scrolling parent, false otherwise
*/
public boolean hasNestedScrollingParent() {
return hasNestedScrollingParent(TYPE_TOUCH);
}
/**
* Check if this view has a nested scrolling parent view currently receiving events for
* a nested scroll in progress with the given type.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @return true if this view has a nested scrolling parent, false otherwise
*/
public boolean hasNestedScrollingParent(@NestedScrollType int type) {
return getNestedScrollingParentForType(type) != null;
}
/**
* Start a new nested scroll for this view.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @param axes Supported nested scroll axes.
* See {@link androidx.core.view.NestedScrollingChild#startNestedScroll(int)}.
* @return true if a cooperating parent view was found and nested scrolling started successfully
*/
public boolean startNestedScroll(@ScrollAxis int axes) {
return startNestedScroll(axes, TYPE_TOUCH);
}
/**
* Start a new nested scroll for this view.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild2} interface method with the same
* signature to implement the standard policy.</p>
*
* @param axes Supported nested scroll axes.
* See {@link androidx.core.view.NestedScrollingChild2#startNestedScroll(int,
* int)}.
* @return true if a cooperating parent view was found and nested scrolling started successfully
*/
public boolean startNestedScroll(@ScrollAxis int axes, @NestedScrollType int type) {
if (hasNestedScrollingParent(type)) {
// Already in progress
return true;
}
if (isNestedScrollingEnabled()) {
ViewParent p = mView.getParent();
View child = mView;
while (p != null) {
if (ViewParentCompat.onStartNestedScroll(p, child, mView, axes, type)) {
setNestedScrollingParentForType(type, p);
ViewParentCompat.onNestedScrollAccepted(p, child, mView, axes, type);
return true;
}
if (p instanceof View) {
child = (View) p;
}
p = p.getParent();
}
}
return false;
}
/**
* Stop a nested scroll in progress.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*/
public void stopNestedScroll() {
stopNestedScroll(TYPE_TOUCH);
}
/**
* Stop a nested scroll in progress.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild2} interface method with the same
* signature to implement the standard policy.</p>
*/
public void stopNestedScroll(@NestedScrollType int type) {
ViewParent parent = getNestedScrollingParentForType(type);
if (parent != null) {
ViewParentCompat.onStopNestedScroll(parent, mView, type);
setNestedScrollingParentForType(type, null);
}
}
/**
* Dispatch one step of a nested scrolling operation to the current nested scrolling parent.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @return <code>true</code> if the parent consumed any of the nested scroll distance
*/
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed,
int dxUnconsumed, int dyUnconsumed, @Nullable int[] offsetInWindow) {
return dispatchNestedScrollInternal(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, TYPE_TOUCH, null);
}
/**
* Dispatch one step of a nested scrolling operation to the current nested scrolling parent.
*
* <p>This is a delegate method. Call it from your {@link NestedScrollingChild2} interface
* method with the same signature to implement the standard policy.
*
* @return <code>true</code> if the parent consumed any of the nested scroll distance
*/
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
int dyUnconsumed, @Nullable int[] offsetInWindow, @NestedScrollType int type) {
return dispatchNestedScrollInternal(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, type, null);
}
/**
* Dispatch one step of a nested scrolling operation to the current nested scrolling parent.
*
* <p>This is a delegate method. Call it from your {@link NestedScrollingChild3} interface
* method with the same signature to implement the standard policy.
*/
public void dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
int dyUnconsumed, @Nullable int[] offsetInWindow, @NestedScrollType int type,
@Nullable int[] consumed) {
dispatchNestedScrollInternal(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, type, consumed);
}
private boolean dispatchNestedScrollInternal(int dxConsumed, int dyConsumed,
int dxUnconsumed, int dyUnconsumed, @Nullable int[] offsetInWindow,
@NestedScrollType int type, @Nullable int[] consumed) {
if (isNestedScrollingEnabled()) {
final ViewParent parent = getNestedScrollingParentForType(type);
if (parent == null) {
return false;
}
if (dxConsumed != 0 || dyConsumed != 0 || dxUnconsumed != 0 || dyUnconsumed != 0) {
int startX = 0;
int startY = 0;
if (offsetInWindow != null) {
mView.getLocationInWindow(offsetInWindow);
startX = offsetInWindow[0];
startY = offsetInWindow[1];
}
if (consumed == null) {
consumed = getTempNestedScrollConsumed();
consumed[0] = 0;
consumed[1] = 0;
}
ViewParentCompat.onNestedScroll(parent, mView,
dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type, consumed);
if (offsetInWindow != null) {
mView.getLocationInWindow(offsetInWindow);
offsetInWindow[0] -= startX;
offsetInWindow[1] -= startY;
}
return true;
} else if (offsetInWindow != null) {
// No motion, no dispatch. Keep offsetInWindow up to date.
offsetInWindow[0] = 0;
offsetInWindow[1] = 0;
}
}
return false;
}
/**
* Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @return true if the parent consumed any of the nested scroll
*/
public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed,
@Nullable int[] offsetInWindow) {
return dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, TYPE_TOUCH);
}
/**
* Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild2} interface method with the same
* signature to implement the standard policy.</p>
*
* @return true if the parent consumed any of the nested scroll
*/
public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed,
@Nullable int[] offsetInWindow, @NestedScrollType int type) {
if (isNestedScrollingEnabled()) {
final ViewParent parent = getNestedScrollingParentForType(type);
if (parent == null) {
return false;
}
if (dx != 0 || dy != 0) {
int startX = 0;
int startY = 0;
if (offsetInWindow != null) {
mView.getLocationInWindow(offsetInWindow);
startX = offsetInWindow[0];
startY = offsetInWindow[1];
}
if (consumed == null) {
consumed = getTempNestedScrollConsumed();
}
consumed[0] = 0;
consumed[1] = 0;
ViewParentCompat.onNestedPreScroll(parent, mView, dx, dy, consumed, type);
if (offsetInWindow != null) {
mView.getLocationInWindow(offsetInWindow);
offsetInWindow[0] -= startX;
offsetInWindow[1] -= startY;
}
return consumed[0] != 0 || consumed[1] != 0;
} else if (offsetInWindow != null) {
offsetInWindow[0] = 0;
offsetInWindow[1] = 0;
}
}
return false;
}
/**
* Dispatch a nested fling operation to the current nested scrolling parent.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @return true if the parent consumed the nested fling
*/
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
if (isNestedScrollingEnabled()) {
ViewParent parent = getNestedScrollingParentForType(TYPE_TOUCH);
if (parent != null) {
return ViewParentCompat.onNestedFling(parent, mView, velocityX,
velocityY, consumed);
}
}
return false;
}
/**
* Dispatch a nested pre-fling operation to the current nested scrolling parent.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @return true if the parent consumed the nested fling
*/
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
if (isNestedScrollingEnabled()) {
ViewParent parent = getNestedScrollingParentForType(TYPE_TOUCH);
if (parent != null) {
return ViewParentCompat.onNestedPreFling(parent, mView, velocityX,
velocityY);
}
}
return false;
}
/**
* View subclasses should always call this method on their
* <code>NestedScrollingChildHelper</code> when detached from a window.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*/
public void onDetachedFromWindow() {
ViewCompat.stopNestedScroll(mView);
}
/**
* Called when a nested scrolling child stops its current nested scroll operation.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link androidx.core.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @param child Child view stopping its nested scroll. This may not be a direct child view.
*/
public void onStopNestedScroll(@NonNull View child) {
ViewCompat.stopNestedScroll(mView);
}
private ViewParent getNestedScrollingParentForType(@NestedScrollType int type) {
switch (type) {
case TYPE_TOUCH:
return mNestedScrollingParentTouch;
case TYPE_NON_TOUCH:
return mNestedScrollingParentNonTouch;
}
return null;
}
private void setNestedScrollingParentForType(@NestedScrollType int type, ViewParent p) {
switch (type) {
case TYPE_TOUCH:
mNestedScrollingParentTouch = p;
break;
case TYPE_NON_TOUCH:
mNestedScrollingParentNonTouch = p;
break;
}
}
private int[] getTempNestedScrollConsumed() {
if (mTempNestedScrollConsumed == null) {
mTempNestedScrollConsumed = new int[2];
}
return mTempNestedScrollConsumed;
}
}