1 files changed, 169 insertions, 0 deletions
diff --git a/mobile/android/geckoview_example/src/main/java/org/mozilla/geckoview_example/NestedGeckoView.java b/mobile/android/geckoview_example/src/main/java/org/mozilla/geckoview_example/NestedGeckoView.java
new file mode 100644
index 0000000000..c165acd3c8
--- /dev/null
+++ b/mobile/android/geckoview_example/src/main/java/org/mozilla/geckoview_example/NestedGeckoView.java
@@ -0,0 +1,169 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.geckoview_example;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import androidx.core.view.NestedScrollingChild;
+import androidx.core.view.NestedScrollingChildHelper;
+import androidx.core.view.ViewCompat;
+import org.mozilla.geckoview.GeckoView;
+import org.mozilla.geckoview.PanZoomController;
+
+/**
+ * GeckoView that supports nested scrolls (for using in a CoordinatorLayout).
+ *
+ * <p>This code is a simplified version of the NestedScrollView implementation which can be found in
+ * the support library: [android.support.v4.widget.NestedScrollView]
+ *
+ * <p>Based on: https://github.com/takahirom/webview-in-coordinatorlayout
+ */
+public class NestedGeckoView extends GeckoView implements NestedScrollingChild {
+
+  private int mLastY;
+  private final int[] mScrollOffset = new int[2];
+  private final int[] mScrollConsumed = new int[2];
+  private int mNestedOffsetY;
+  private NestedScrollingChildHelper mChildHelper;
+
+  /**
+   * Integer indicating how user's MotionEvent was handled.
+   *
+   * <p>There must be a 1-1 relation between this values and [EngineView.InputResult]'s.
+   */
+  private int mInputResult = PanZoomController.INPUT_RESULT_UNHANDLED;
+
+  public NestedGeckoView(final Context context) {
+    this(context, null);
+  }
+
+  public NestedGeckoView(final Context context, final AttributeSet attrs) {
+    super(context, attrs);
+    mChildHelper = new NestedScrollingChildHelper(this);
+    setNestedScrollingEnabled(true);
+  }
+
+  @Override
+  public boolean onTouchEvent(MotionEvent ev) {
+    MotionEvent event = MotionEvent.obtain(ev);
+    final int action = event.getActionMasked();
+    int eventY = (int) event.getY();
+
+    switch (action) {
+      case MotionEvent.ACTION_MOVE:
+        final boolean allowScroll =
+            !shouldPinOnScreen() && mInputResult == PanZoomController.INPUT_RESULT_HANDLED;
+        int deltaY = mLastY - eventY;
+
+        if (allowScroll && dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) {
+          deltaY -= mScrollConsumed[1];
+          event.offsetLocation(0f, -mScrollOffset[1]);
+          mNestedOffsetY += mScrollOffset[1];
+        }
+
+        mLastY = eventY - mScrollOffset[1];
+
+        if (allowScroll && dispatchNestedScroll(0, mScrollOffset[1], 0, deltaY, mScrollOffset)) {
+          mLastY -= mScrollOffset[1];
+          event.offsetLocation(0f, mScrollOffset[1]);
+          mNestedOffsetY += mScrollOffset[1];
+        }
+        break;
+
+      case MotionEvent.ACTION_DOWN:
+        // A new gesture started. Reset handled status and ask GV if it can handle this.
+        mInputResult = PanZoomController.INPUT_RESULT_UNHANDLED;
+        updateInputResult(event);
+
+        mNestedOffsetY = 0;
+        mLastY = eventY;
+
+        // The event should be handled either by onTouchEvent,
+        // either by onTouchEventForResult, never by both.
+        // Early return if we sent it to updateInputResult(..) which calls onTouchEventForResult.
+        event.recycle();
+        return true;
+
+        // We don't care about other touch events
+      case MotionEvent.ACTION_UP:
+      case MotionEvent.ACTION_CANCEL:
+        stopNestedScroll();
+        break;
+    }
+
+    // Execute event handler from parent class in all cases
+    final boolean eventHandled = callSuperOnTouchEvent(event);
+
+    // Recycle previously obtained event
+    event.recycle();
+
+    return eventHandled;
+  }
+
+  private boolean callSuperOnTouchEvent(MotionEvent event) {
+    return super.onTouchEvent(event);
+  }
+
+  private void updateInputResult(MotionEvent event) {
+    super.onTouchEventForDetailResult(event)
+        .accept(
+            inputResult -> {
+              mInputResult = inputResult.handledResult();
+              startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
+            });
+  }
+
+  public int getInputResult() {
+    return mInputResult;
+  }
+
+  @Override
+  public void setNestedScrollingEnabled(boolean enabled) {
+    mChildHelper.setNestedScrollingEnabled(enabled);
+  }
+
+  @Override
+  public boolean isNestedScrollingEnabled() {
+    return mChildHelper.isNestedScrollingEnabled();
+  }
+
+  @Override
+  public boolean startNestedScroll(int axes) {
+    return mChildHelper.startNestedScroll(axes);
+  }
+
+  @Override
+  public void stopNestedScroll() {
+    mChildHelper.stopNestedScroll();
+  }
+
+  @Override
+  public boolean hasNestedScrollingParent() {
+    return mChildHelper.hasNestedScrollingParent();
+  }
+
+  @Override
+  public boolean dispatchNestedScroll(
+      int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
+    return mChildHelper.dispatchNestedScroll(
+        dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
+  }
+
+  @Override
+  public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
+    return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
+  }
+
+  @Override
+  public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
+    return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
+  }
+
+  @Override
+  public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
+    return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
+  }
+}