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1.NestedScrollingChild
public interface NestedScrollingChild {
@Override
public void setNestedScrollingEnabled(boolean enabled) {
}
@Override
public boolean isNestedScrollingEnabled() {
return false;
}
@Override
public boolean startNestedScroll(int axes) {
return false;
}
@Override
public void stopNestedScroll() {
}
@Override
public boolean hasNestedScrollingParent() {
return false;
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
return false;
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
return false;
}
@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return false;
}
@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return false;
}
}
2.NestedScrollingParent
public interface NestedScrollingParent {
public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
return false;
}
@Override
public void onNestedScrollAccepted(View child, View target, int nestedScrollAxes) {
}
@Override
public void onStopNestedScroll(View target) {
}
@Override
public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
}
@Override
public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
}
@Override
public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
return false;
}
@Override
public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
return false;
}
@Override
public int getNestedScrollAxes() {
return 0;
}
}
3.NestedScrollingChildHelper
public class NestedScrollingChildHelper {
private final View mView;
private ViewParent mNestedScrollingParent;
private boolean mIsNestedScrollingEnabled;
private int[] mTempNestedScrollConsumed;
/**
* Construct a new helper for a given view.
*/
public NestedScrollingChildHelper(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 android.support.v4.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 android.support.v4.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.
*
* <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
* method/{@link android.support.v4.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 mNestedScrollingParent != 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 android.support.v4.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*
* @param axes Supported nested scroll axes.
* See {@link android.support.v4.view.NestedScrollingChild#startNestedScroll(int)}.
* @return true if a cooperating parent view was found and nested scrolling started successfully
*/
public boolean startNestedScroll(int axes) {
if (hasNestedScrollingParent()) {
// Already in progress
return true;
}
if (isNestedScrollingEnabled()) {
ViewParent p = mView.getParent();
View child = mView;
while (p != null) {
if (ViewParentCompat.onStartNestedScroll(p, child, mView, axes)) {
mNestedScrollingParent = p;
ViewParentCompat.onNestedScrollAccepted(p, child, mView, axes);
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 android.support.v4.view.NestedScrollingChild} interface method with the same
* signature to implement the standard policy.</p>
*/
public void stopNestedScroll() {
if (mNestedScrollingParent != null) {
ViewParentCompat.onStopNestedScroll(mNestedScrollingParent, mView);
mNestedScrollingParent = 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 android.support.v4.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 dispatchNestedScroll(int dxConsumed, int dyConsumed,
int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
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];
}
ViewParentCompat.onNestedScroll(mNestedScrollingParent, mView, dxConsumed,
dyConsumed, dxUnconsumed, dyUnconsumed);
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 android.support.v4.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, int[] consumed, int[] offsetInWindow) {
if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
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) {
if (mTempNestedScrollConsumed == null) {
mTempNestedScrollConsumed = new int[2];
}
consumed = mTempNestedScrollConsumed;
}
consumed[0] = 0;
consumed[1] = 0;
ViewParentCompat.onNestedPreScroll(mNestedScrollingParent, mView, dx, dy, consumed);
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 android.support.v4.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() && mNestedScrollingParent != null) {
return ViewParentCompat.onNestedFling(mNestedScrollingParent, 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 android.support.v4.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() && mNestedScrollingParent != null) {
return ViewParentCompat.onNestedPreFling(mNestedScrollingParent, 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 android.support.v4.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 android.support.v4.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(View child) {
ViewCompat.stopNestedScroll(mView);
}
}
4.NestedScrollingParentHelper
public class NestedScrollingParentHelper {
private final ViewGroup mViewGroup;
private int mNestedScrollAxes;
/**
* Construct a new helper for a given ViewGroup
*/
public NestedScrollingParentHelper(ViewGroup viewGroup) {
mViewGroup = viewGroup;
}
/**
* Called when a nested scrolling operation initiated by a descendant view is accepted
* by this ViewGroup.
*
* <p>This is a delegate method. Call it from your {@link android.view.ViewGroup ViewGroup}
* subclass method/{@link android.support.v4.view.NestedScrollingParent} interface method with
* the same signature to implement the standard policy.</p>
*/
public void onNestedScrollAccepted(View child, View target, int axes) {
mNestedScrollAxes = axes;
}
/**
* Return the current axes of nested scrolling for this ViewGroup.
*
* <p>This is a delegate method. Call it from your {@link android.view.ViewGroup ViewGroup}
* subclass method/{@link android.support.v4.view.NestedScrollingParent} interface method with
* the same signature to implement the standard policy.</p>
*/
public int getNestedScrollAxes() {
return mNestedScrollAxes;
}
/**
* React to a nested scroll operation ending.
*
* <p>This is a delegate method. Call it from your {@link android.view.ViewGroup ViewGroup}
* subclass method/{@link android.support.v4.view.NestedScrollingParent} interface method with
* the same signature to implement the standard policy.</p>
*
* @param target View that initiated the nested scroll
*/
public void onStopNestedScroll(View target) {
mNestedScrollAxes = 0;
}
}
