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TouchTargetHelper.java
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TouchTargetHelper.java
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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
package com.facebook.react.uimanager;
import static com.facebook.react.uimanager.common.UIManagerType.FABRIC;
import android.annotation.SuppressLint;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.Rect;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.Nullable;
import com.facebook.react.bridge.JSApplicationIllegalArgumentException;
import com.facebook.react.bridge.UiThreadUtil;
import com.facebook.react.touch.ReactHitSlopView;
import com.facebook.react.uimanager.common.ViewUtil;
import java.util.ArrayList;
import java.util.EnumSet;
import java.util.List;
import java.util.Objects;
/**
* Class responsible for identifying which react view should handle a given {@link MotionEvent}. It
* uses the event coordinates to traverse the view hierarchy and return a suitable view.
*/
public class TouchTargetHelper {
private static final float[] mEventCoords = new float[2];
private static final PointF mTempPoint = new PointF();
private static final float[] mMatrixTransformCoords = new float[2];
private static final Matrix mInverseMatrix = new Matrix();
/**
* Find touch event target view within the provided container given the coordinates provided via
* {@link MotionEvent}.
*
* @param eventX the X screen coordinate of the touch location
* @param eventY the Y screen coordinate of the touch location
* @param viewGroup the container view to traverse
* @return the react tag ID of the child view that should handle the event
*/
public static int findTargetTagForTouch(float eventX, float eventY, ViewGroup viewGroup) {
return findTargetTagAndCoordinatesForTouch(eventX, eventY, viewGroup, mEventCoords, null);
}
/**
* Find touch event target view within the provided container given the coordinates provided via
* {@link MotionEvent}.
*
* @param eventX the X screen coordinate of the touch location
* @param eventY the Y screen coordinate of the touch location
* @param viewGroup the container view to traverse
* @param nativeViewId the native react view containing this touch target
* @return the react tag ID of the child view that should handle the event
*/
public static int findTargetTagForTouch(
float eventX, float eventY, ViewGroup viewGroup, @Nullable int[] nativeViewId) {
return findTargetTagAndCoordinatesForTouch(
eventX, eventY, viewGroup, mEventCoords, nativeViewId);
}
/**
* Find touch event target view within the provided container given the coordinates provided via
* {@link MotionEvent}.
*
* @param eventX the X screen coordinate of the touch location
* @param eventY the Y screen coordinate of the touch location
* @param viewGroup the container view to traverse
* @param viewCoords an out parameter that will return the X,Y value in the target view
* @param nativeViewTag an out parameter that will return the native view id
* @return the react tag ID of the child view that should handle the event
*/
public static int findTargetTagAndCoordinatesForTouch(
float eventX,
float eventY,
ViewGroup viewGroup,
float[] viewCoords,
@Nullable int[] nativeViewTag) {
UiThreadUtil.assertOnUiThread();
int targetTag = viewGroup.getId();
// Store eventCoords in array so that they are modified to be relative to the targetView found.
viewCoords[0] = eventX;
viewCoords[1] = eventY;
View nativeTargetView = findTouchTargetViewWithPointerEvents(viewCoords, viewGroup, null);
if (nativeTargetView != null) {
View reactTargetView = findClosestReactAncestor(nativeTargetView);
if (reactTargetView != null) {
if (nativeViewTag != null) {
nativeViewTag[0] = reactTargetView.getId();
}
targetTag = getTouchTargetForView(reactTargetView, viewCoords[0], viewCoords[1]);
}
}
return targetTag;
}
/**
* Find touch event target view within the provided container given the coordinates provided via
* {@link MotionEvent}.
*
* @param eventX the X screen coordinate of the touch location
* @param eventY the Y screen coordinate of the touch location
* @param viewGroup the container view to traverse
* @param viewCoords an out parameter that will return the X,Y value in the target view
* @return If a target was found, returns a {@link Lis<ViewTarget>} containing the path through
* the view tree of all react tags and views that are a container for the touch target,
* ordered from target to root (last element)
*/
@SuppressLint("ResourceType")
public static List<ViewTarget> findTargetPathAndCoordinatesForTouch(
float eventX, float eventY, ViewGroup viewGroup, float[] viewCoords) {
UiThreadUtil.assertOnUiThread();
// Store eventCoords in array so that they are modified to be relative to the targetView found.
viewCoords[0] = eventX;
viewCoords[1] = eventY;
List<ViewTarget> pathAccumulator = new ArrayList<>();
View targetView = findTouchTargetViewWithPointerEvents(viewCoords, viewGroup, pathAccumulator);
if (targetView != null) {
View reactTargetView = targetView;
int firstReactAncestor = 0;
// Same logic as findClosestReactAncestor but also track the index
while (reactTargetView != null && reactTargetView.getId() <= 0) {
reactTargetView = (View) reactTargetView.getParent();
firstReactAncestor++;
}
if (firstReactAncestor > 0) {
// Drop non-React views from the path trace
pathAccumulator = pathAccumulator.subList(firstReactAncestor, pathAccumulator.size());
}
int targetTag = getTouchTargetForView(reactTargetView, viewCoords[0], viewCoords[1]);
if (targetTag != reactTargetView.getId()) {
pathAccumulator.add(0, new ViewTarget(targetTag, (View) null));
}
}
return pathAccumulator;
}
@SuppressLint("ResourceType")
private static View findClosestReactAncestor(View view) {
while (view != null && view.getId() <= 0) {
view = (View) view.getParent();
}
return view;
}
/** Types of allowed return values from {@link #findTouchTargetView}. */
private enum TouchTargetReturnType {
/** Allow returning the view passed in through the parameters. */
SELF,
/** Allow returning children of the view passed in through parameters. */
CHILD,
}
/**
* Returns the touch target View that is either viewGroup or one if its descendants. This is a
* recursive DFS since view the entire tree must be parsed until the target is found. If the
* search does not backtrack, it is possible to follow a branch that cannot be a target (because
* of pointerEvents). For example, if both C and E can be the target of an event: A
* (pointerEvents: auto) - B (pointerEvents: box-none) - C (pointerEvents: none) \ D
* (pointerEvents: auto) - E (pointerEvents: auto) If the search goes down the first branch, it
* would return A as the target, which is incorrect. NB: This modifies the eventCoords to always
* be relative to the current viewGroup. When the method returns, it will contain the eventCoords
* relative to the targetView found.
*/
private static View findTouchTargetView(
float[] eventCoords,
View view,
EnumSet<TouchTargetReturnType> allowReturnTouchTargetTypes,
List<ViewTarget> pathAccumulator) {
// We prefer returning a child, so we check for a child that can handle the touch first
if (allowReturnTouchTargetTypes.contains(TouchTargetReturnType.CHILD)
&& view instanceof ViewGroup) {
ViewGroup viewGroup = (ViewGroup) view;
if (!isTouchPointInView(eventCoords[0], eventCoords[1], view)) {
// We don't allow touches on views that are outside the bounds of an `overflow: hidden` and
// `overflow: scroll` View.
if (view instanceof ReactOverflowViewWithInset) {
// If the touch point is outside of the overflowinset for the view, we can safely ignore
// it.
if (ViewUtil.getUIManagerType(view.getId()) == FABRIC
&& !isTouchPointInViewWithOverflowInset(eventCoords[0], eventCoords[1], view)) {
return null;
}
@Nullable String overflow = ((ReactOverflowViewWithInset) view).getOverflow();
if (ViewProps.HIDDEN.equals(overflow) || ViewProps.SCROLL.equals(overflow)) {
return null;
}
}
// We don't allow touches on views that are outside the bounds and has clipChildren set to
// true.
if (viewGroup.getClipChildren()) {
return null;
}
}
int childrenCount = viewGroup.getChildCount();
// Consider z-index when determining the touch target.
ReactZIndexedViewGroup zIndexedViewGroup =
viewGroup instanceof ReactZIndexedViewGroup ? (ReactZIndexedViewGroup) viewGroup : null;
for (int i = childrenCount - 1; i >= 0; i--) {
int childIndex =
zIndexedViewGroup != null ? zIndexedViewGroup.getZIndexMappedChildIndex(i) : i;
View child = viewGroup.getChildAt(childIndex);
PointF childPoint = mTempPoint;
getChildPoint(eventCoords[0], eventCoords[1], viewGroup, child, childPoint);
// The childPoint value will contain the view coordinates relative to the child.
// We need to store the existing X,Y for the viewGroup away as it is possible this child
// will not actually be the target and so we restore them if not
float restoreX = eventCoords[0];
float restoreY = eventCoords[1];
eventCoords[0] = childPoint.x;
eventCoords[1] = childPoint.y;
View targetView = findTouchTargetViewWithPointerEvents(eventCoords, child, pathAccumulator);
if (targetView != null) {
return targetView;
}
eventCoords[0] = restoreX;
eventCoords[1] = restoreY;
}
}
// Check if parent can handle the touch after the children
if (allowReturnTouchTargetTypes.contains(TouchTargetReturnType.SELF)
&& isTouchPointInView(eventCoords[0], eventCoords[1], view)) {
return view;
}
return null;
}
/**
* Checks whether a touch at {@code x} and {@code y} are within the bounds of the View. Both
* {@code x} and {@code y} must be relative to the top-left corner of the view.
*/
private static boolean isTouchPointInView(float x, float y, View view) {
if (view instanceof ReactHitSlopView && ((ReactHitSlopView) view).getHitSlopRect() != null) {
Rect hitSlopRect = ((ReactHitSlopView) view).getHitSlopRect();
if ((x >= -hitSlopRect.left && x < (view.getWidth()) + hitSlopRect.right)
&& (y >= -hitSlopRect.top && y < (view.getHeight()) + hitSlopRect.bottom)) {
return true;
}
return false;
} else {
if ((x >= 0 && x < (view.getWidth())) && (y >= 0 && y < (view.getHeight()))) {
return true;
}
return false;
}
}
private static boolean isTouchPointInViewWithOverflowInset(float x, float y, View view) {
if (!(view instanceof ReactOverflowViewWithInset)) {
return false;
}
final Rect overflowInset = ((ReactOverflowViewWithInset) view).getOverflowInset();
return (x >= overflowInset.left && x < view.getWidth() - overflowInset.right)
&& (y >= overflowInset.top && y < view.getHeight() - overflowInset.bottom);
}
/**
* Returns the coordinates of a touch in the child View. It is transform aware and will invert the
* transform Matrix to find the true local points This code is taken from {@link
* ViewGroup#isTransformedTouchPointInView()}
*/
private static void getChildPoint(
float x, float y, ViewGroup parent, View child, PointF outLocalPoint) {
float localX = x + parent.getScrollX() - child.getLeft();
float localY = y + parent.getScrollY() - child.getTop();
Matrix matrix = child.getMatrix();
if (!matrix.isIdentity()) {
float[] localXY = mMatrixTransformCoords;
localXY[0] = localX;
localXY[1] = localY;
Matrix inverseMatrix = mInverseMatrix;
matrix.invert(inverseMatrix);
inverseMatrix.mapPoints(localXY);
localX = localXY[0];
localY = localXY[1];
}
outLocalPoint.set(localX, localY);
}
/**
* Returns the touch target View of the event given, or null if neither the given View nor any of
* its descendants are the touch target.
*/
private static @Nullable View findTouchTargetViewWithPointerEvents(
float eventCoords[], View view, @Nullable List<ViewTarget> pathAccumulator) {
PointerEvents pointerEvents =
view instanceof ReactPointerEventsView
? ((ReactPointerEventsView) view).getPointerEvents()
: PointerEvents.AUTO;
// Views that are disabled should never be the target of pointer events. However, their children
// can be because some views (SwipeRefreshLayout) use enabled but still have children that can
// be valid targets.
if (!view.isEnabled()) {
if (pointerEvents == PointerEvents.AUTO) {
pointerEvents = PointerEvents.BOX_NONE;
} else if (pointerEvents == PointerEvents.BOX_ONLY) {
pointerEvents = PointerEvents.NONE;
}
}
if (pointerEvents == PointerEvents.NONE) {
// This view and its children can't be the target
return null;
} else if (pointerEvents == PointerEvents.BOX_ONLY) {
// This view may be the target, its children don't matter
View targetView =
findTouchTargetView(
eventCoords, view, EnumSet.of(TouchTargetReturnType.SELF), pathAccumulator);
if (targetView != null && pathAccumulator != null) {
pathAccumulator.add(new ViewTarget(view.getId(), view));
}
return targetView;
} else if (pointerEvents == PointerEvents.BOX_NONE) {
// This view can't be the target, but its children might.
View targetView =
findTouchTargetView(
eventCoords, view, EnumSet.of(TouchTargetReturnType.CHILD), pathAccumulator);
if (targetView != null) {
if (pathAccumulator != null) {
pathAccumulator.add(new ViewTarget(view.getId(), view));
}
return targetView;
}
// PointerEvents.BOX_NONE means that this react element cannot receive pointer events.
// However, there might be virtual children that can receive pointer events, in which case
// we still want to return this View and dispatch a pointer event to the virtual element.
// Note that this currently only applies to Nodes/FlatViewGroup as it's the only class that
// is both a ViewGroup and ReactCompoundView (ReactTextView is a ReactCompoundView but not a
// ViewGroup).
if (view instanceof ReactCompoundView
&& isTouchPointInView(eventCoords[0], eventCoords[1], view)) {
int reactTag = ((ReactCompoundView) view).reactTagForTouch(eventCoords[0], eventCoords[1]);
// make sure we exclude the View itself because of the PointerEvents.BOX_NONE
if (reactTag != view.getId()) {
if (pathAccumulator != null) {
pathAccumulator.add(new ViewTarget(view.getId(), view));
}
return view;
}
}
return null;
} else if (pointerEvents == PointerEvents.AUTO) {
// Either this view or one of its children is the target
if (view instanceof ReactCompoundViewGroup
&& isTouchPointInView(eventCoords[0], eventCoords[1], view)
&& ((ReactCompoundViewGroup) view).interceptsTouchEvent(eventCoords[0], eventCoords[1])) {
if (pathAccumulator != null) {
pathAccumulator.add(new ViewTarget(view.getId(), view));
}
return view;
}
View result =
findTouchTargetView(
eventCoords,
view,
EnumSet.of(TouchTargetReturnType.SELF, TouchTargetReturnType.CHILD),
pathAccumulator);
if (result != null && pathAccumulator != null) {
pathAccumulator.add(new ViewTarget(view.getId(), view));
}
return result;
} else {
throw new JSApplicationIllegalArgumentException(
"Unknown pointer event type: " + pointerEvents.toString());
}
}
private static int getTouchTargetForView(View targetView, float viewX, float viewY) {
if (targetView instanceof ReactCompoundView) {
// Use coordinates relative to the view, which have been already computed by
// {@link #findTouchTargetView()}.
return ((ReactCompoundView) targetView).reactTagForTouch(viewX, viewY);
}
return targetView.getId();
}
public static class ViewTarget {
private final int mViewId;
private final @Nullable View mView;
private ViewTarget(int viewId, @Nullable View view) {
mViewId = viewId;
mView = view;
}
public int getViewId() {
return mViewId;
}
@Nullable
public View getView() {
return mView;
}
@Override
public boolean equals(Object o) {
// If the object is compared with itself then return true
if (o == this) {
return true;
}
// Check if o is an instance of ViewTarget. Note that "null instanceof ViewTarget" also
// returns false.
if (!(o instanceof ViewTarget)) {
return false;
}
ViewTarget other = (ViewTarget) o;
// We only need to compare view id, as we assume the same view id will always map to the same
// view. TargetView is not mutable so this should be safe.
return other.getViewId() == mViewId;
}
@Override
public int hashCode() {
return Objects.hashCode(mViewId);
}
}
}