[Android] Initialize the Handler fields eagerly

[m-bert]

Description

Tap, LongPress, Fling, Pan and Hover gesture handlers kept their Handler as a nullable field created on first use, guarded by null checks and !! at every call site (with a TODO: lazy init left in Tap since the Kotlin conversion).

Handler object was never cleared anyway (except LongPress, where it used to serve as a flag, and Hover).

Also adds a comment explaining the 4 ms delay in HoverGestureHandler.

Test plan

• :react-native-gesture-handler:compileDebugKotlin builds clean in basic-example
• yarn format:android passes

Tested on the following code:

import React, { useCallback, useState } from 'react';
import { StyleSheet, Text, View } from 'react-native';
import {
  Directions,
  GestureDetector,
  useFlingGesture,
  useHoverGesture,
  useLongPressGesture,
  usePanGesture,
  useTapGesture,
} from 'react-native-gesture-handler';
import { scheduleOnRN } from 'react-native-worklets';

type Counters = { begin: number; act: number; end: number; fail: number };
type Results = Record<string, Counters>;

const EMPTY: Counters = { begin: 0, act: 0, end: 0, fail: 0 };

export default function EmptyExample() {
  const [results, setResults] = useState<Results>({});

  const report = useCallback((key: string, kind: keyof Counters) => {
    setResults((prev) => {
      const current = prev[key] ?? EMPTY;
      return { ...prev, [key]: { ...current, [kind]: current[kind] + 1 } };
    });
  }, []);

  const tap = useTapGesture({
    onBegin: () => scheduleOnRN(report, 'tap', 'begin'),
    onActivate: () => scheduleOnRN(report, 'tap', 'act'),
    onFinalize: (e) =>
      scheduleOnRN(report, 'tap', e.canceled ? 'fail' : 'end'),
  });

  const doubleTap = useTapGesture({
    numberOfTaps: 2,
    onBegin: () => scheduleOnRN(report, 'doubleTap', 'begin'),
    onActivate: () => scheduleOnRN(report, 'doubleTap', 'act'),
    onFinalize: (e) =>
      scheduleOnRN(report, 'doubleTap', e.canceled ? 'fail' : 'end'),
  });

  const longPress = useLongPressGesture({
    minDurationMs: 400,
    onBegin: () => scheduleOnRN(report, 'longPress', 'begin'),
    onActivate: () => scheduleOnRN(report, 'longPress', 'act'),
    onFinalize: (e) =>
      scheduleOnRN(report, 'longPress', e.canceled ? 'fail' : 'end'),
  });

  const fling = useFlingGesture({
    direction: Directions.RIGHT,
    onBegin: () => scheduleOnRN(report, 'fling', 'begin'),
    onActivate: () => scheduleOnRN(report, 'fling', 'act'),
    onFinalize: (e) =>
      scheduleOnRN(report, 'fling', e.canceled ? 'fail' : 'end'),
  });

  const pan = usePanGesture({
    activateAfterLongPress: 400,
    onBegin: () => scheduleOnRN(report, 'pan', 'begin'),
    onActivate: () => scheduleOnRN(report, 'pan', 'act'),
    onFinalize: (e) =>
      scheduleOnRN(report, 'pan', e.canceled ? 'fail' : 'end'),
  });

  const hover = useHoverGesture({
    onBegin: () => scheduleOnRN(report, 'hover', 'begin'),
    onActivate: () => scheduleOnRN(report, 'hover', 'act'),
    onFinalize: (e) =>
      scheduleOnRN(report, 'hover', e.canceled ? 'fail' : 'end'),
  });

  const rows: { key: string; label: string; gesture: any }[] = [
    { key: 'tap', label: 'Tap', gesture: tap },
    { key: 'doubleTap', label: 'DoubleTap', gesture: doubleTap },
    { key: 'longPress', label: 'LongPress 400ms', gesture: longPress },
    { key: 'fling', label: 'Fling right', gesture: fling },
    { key: 'pan', label: 'Pan holdActivate 400ms', gesture: pan },
    { key: 'hover', label: 'Hover', gesture: hover },
  ];

  return (
    <View style={styles.container}>
      {rows.map(({ key, label, gesture }) => {
        const c = results[key] ?? EMPTY;
        return (
          <GestureDetector key={key} gesture={gesture}>
            <View style={styles.box}>
              <Text style={styles.label}>{label}</Text>
              <Text style={styles.status}>
                {`${key} b:${c.begin} a:${c.act} e:${c.end} f:${c.fail}`}
              </Text>
            </View>
          </GestureDetector>
        );
      })}
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    padding: 12,
    gap: 10,
  },
  box: {
    height: 88,
    borderRadius: 12,
    backgroundColor: '#dbe4ff',
    justifyContent: 'center',
    alignItems: 'center',
  },
  label: {
    fontSize: 18,
    fontWeight: '600',
  },
  status: {
    fontSize: 15,
    fontVariant: ['tabular-nums'],
  },
});

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: ac780245-7caa-4edd-b848-1e21e644d3d8

📥 Commits

Reviewing files that changed from the base of the PR and between 592d951 and 65dcbc2.

📒 Files selected for processing (5)

• packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/FlingGestureHandler.kt
• packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/HoverGestureHandler.kt
• packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/LongPressGestureHandler.kt
• packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/PanGestureHandler.kt
• packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/TapGestureHandler.kt

Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review.

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Improved the reliability of fling, hover, long-press, pan, and tap gesture timing and callback handling on Android.
  • Ensured gesture delays and cancellations are processed consistently on the main thread.
• Refactor
  • Simplified internal gesture scheduling and cleanup, with no changes to the public API.

Walkthrough

The Android gesture handlers now create main-looper Handler instances eagerly. Callback scheduling and cleanup no longer use nullable checks, lazy initialization, or force-unwrapping.

Changes

Gesture handler callback lifecycle

Layer / File(s)	Summary
Eager Handler initialization packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/*GestureHandler.kt	Fling, hover, long-press, pan, and tap handlers now store non-null handlers initialized on the main looper.
Callback scheduling and cleanup packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/*GestureHandler.kt	Gesture start, completion, cancellation, reset, and hover transitions directly schedule or remove callbacks through the initialized handlers.

Merge Risk: ⚪ Minimal · up to 65dcb

The change eagerly initializes gesture-handler fields without any supplied evidence of a concrete correctness or production-impact risk; no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: eager initialization of Handler fields on Android.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[Copilot]

Pull request overview

Initializes Android gesture-handler Handler instances eagerly and removes nullable access patterns, while documenting Hover’s delayed exit behavior.

Changes:

• Eagerly initializes handlers for Tap, Pan, LongPress, Fling, and Hover.
• Removes null checks and non-null assertions.
• Documents the 4 ms Hover delay.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/TapGestureHandler.kt	Updated as part of this pull request.
packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/PanGestureHandler.kt	Updated as part of this pull request.
packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/LongPressGestureHandler.kt	Updated as part of this pull request.
packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/HoverGestureHandler.kt	Updated as part of this pull request.
packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/FlingGestureHandler.kt	Updated as part of this pull request.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.