Migrate to AndroidX

app/src/main/java/com/google/android/material/appbar/FlingBehavior.java

@@ -0,0 +1,82 @@
+package com.google.android.material.appbar;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.widget.OverScroller;
+
+import androidx.annotation.Nullable;
+import androidx.coordinatorlayout.widget.CoordinatorLayout;
+
+import java.lang.reflect.Field;
+
+// check this https://stackoverflow.com/questions/56849221/recyclerview-fling-causes-laggy-while-appbarlayout-is-scrolling/57997489#57997489
+public final class FlingBehavior extends AppBarLayout.Behavior {
+
+    public FlingBehavior(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    @Override
+    public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
+        switch (ev.getActionMasked()) {
+            case MotionEvent.ACTION_DOWN:
+                // remove reference to old nested scrolling child
+                resetNestedScrollingChild();
+                // Stop fling when your finger touches the screen
+                stopAppBarLayoutFling();
+                break;
+            default:
+                break;
+        }
+        return super.onInterceptTouchEvent(parent, child, ev);
+    }
+
+    @Nullable
+    private OverScroller getScrollerField() {
+        try {
+            Class<?> headerBehaviorType = this.getClass().getSuperclass().getSuperclass().getSuperclass();
+            if (headerBehaviorType != null) {
+                Field field = headerBehaviorType.getDeclaredField("scroller");
+                field.setAccessible(true);
+                return ((OverScroller) field.get(this));
+            }
+        } catch (NoSuchFieldException | IllegalAccessException e) {
+            // ?
+        }
+        return null;
+    }
+
+    @Nullable
+    private Field getLastNestedScrollingChildRefField() {
+        try {
+            Class<?> headerBehaviorType = this.getClass().getSuperclass().getSuperclass();
+            if (headerBehaviorType != null) {
+                Field field = headerBehaviorType.getDeclaredField("lastNestedScrollingChildRef");
+                field.setAccessible(true);
+                return field;
+            }
+        } catch (NoSuchFieldException e) {
+            // ?
+        }
+        return null;
+    }
+
+    private void resetNestedScrollingChild(){
+        Field field = getLastNestedScrollingChildRefField();
+        if(field != null){
+            try {
+                Object value = field.get(this);
+                if(value != null) field.set(this, null);
+            } catch (IllegalAccessException e) {
+                // ?
+            }
+        }
+    }
+
+    private void stopAppBarLayoutFling() {
+        OverScroller scroller = getScrollerField();
+        if (scroller != null) scroller.forceFinished(true);
+    }
+
+}