Migrate VelocityHelper.java- to Kotlin (#45715)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/45715

# Changelog:
[Internal] -

As in the title.

Reviewed By: tdn120

Differential Revision: D60283416

fbshipit-source-id: 62241bc3a7bcb0a4eb95b660a01233c269296621

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/scroll/VelocityHelper.java

@@ -1,64 +0,0 @@
-/*
- * 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.views.scroll;
-
-import android.view.MotionEvent;
-import android.view.VelocityTracker;
-import androidx.annotation.Nullable;
-import com.facebook.infer.annotation.Nullsafe;
-
-/**
- * This Class helps to calculate the velocity for all ScrollView. The x and y velocity will later on
- * send to ReactScrollViewHelper for further use.
- */
-@Nullsafe(Nullsafe.Mode.LOCAL)
-class VelocityHelper {
-
-  private @Nullable VelocityTracker mVelocityTracker;
-  private float mXVelocity;
-  private float mYVelocity;
-
-  /**
-   * Call from a ScrollView in onTouchEvent. Calculating the velocity for END_DRAG movement and send
-   * them back to react ScrollResponder.js
-   */
-  public void calculateVelocity(MotionEvent ev) {
-    int action = ev.getAction() & MotionEvent.ACTION_MASK;
-    if (mVelocityTracker == null) {
-      mVelocityTracker = VelocityTracker.obtain();
-    }
-    mVelocityTracker.addMovement(ev);
-
-    switch (action) {
-      case MotionEvent.ACTION_UP:
-      case MotionEvent.ACTION_CANCEL:
-        {
-          // Calculate velocity on END_DRAG
-          mVelocityTracker.computeCurrentVelocity(1); // points/millisecond
-          mXVelocity = mVelocityTracker.getXVelocity();
-          mYVelocity = mVelocityTracker.getYVelocity();
-
-          if (mVelocityTracker != null) {
-            mVelocityTracker.recycle();
-            mVelocityTracker = null;
-          }
-          break;
-        }
-    }
-  }
-
-  /* Needs to call ACTION_UP/CANCEL to update the mXVelocity */
-  public float getXVelocity() {
-    return mXVelocity;
-  }
-
-  /* Needs to call ACTION_UP/CANCEL to update the mYVelocity */
-  public float getYVelocity() {
-    return mYVelocity;
-  }
-}

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/scroll/VelocityHelper.kt

@@ -0,0 +1,51 @@
+/*
+ * 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.views.scroll
+
+import android.view.MotionEvent
+import android.view.VelocityTracker
+
+/**
+ * This Class helps to calculate the velocity for all ScrollView. The x and y velocity will later on
+ * send to ReactScrollViewHelper for further use.
+ */
+internal class VelocityHelper {
+  private var velocityTracker: VelocityTracker? = null
+
+  /* Needs to call ACTION_UP/CANCEL to update the xVelocity/yVelocity */
+  public var xVelocity = 0f
+    private set
+
+  public var yVelocity = 0f
+    private set
+
+  /**
+   * Call from a ScrollView in onTouchEvent. Calculating the velocity for END_DRAG movement and send
+   * them back to react ScrollResponder.js
+   */
+  public fun calculateVelocity(ev: MotionEvent): Unit {
+    if (velocityTracker == null) {
+      velocityTracker = VelocityTracker.obtain()
+    }
+
+    velocityTracker?.let { tracker ->
+      tracker.addMovement(ev)
+      when (ev.action and MotionEvent.ACTION_MASK) {
+        MotionEvent.ACTION_UP,
+        MotionEvent.ACTION_CANCEL -> {
+          // Calculate velocity on END_DRAG
+          tracker.computeCurrentVelocity(1) // points/millisecond
+          xVelocity = tracker.xVelocity
+          yVelocity = tracker.yVelocity
+          tracker.recycle()
+          velocityTracker = null
+        }
+      }
+    }
+  }
+}