问题
版本：Cocos creator 3.8.3
打包安卓后，真机运行场景地图，发现缩放相机时，画面会闪烁随后卡住，移动相机也会偶尔掉帧卡顿。logcat会有日志：
明显是有gc压力了。检查相机控制的代码，发现平移和缩放的实现都对临时对象做了缓存复用，理论上不存在频繁创建对象的操作
排查
为了排查是否是业务代码的影响，弄了一个单场景，挂上相机控制，发现还是会有上述日志。最后将平移和缩放的逻辑都去掉，只留下touchmove的回调事件，发现还是一样，那就应该是引擎层的问题了。
解决
1.临时解决：限制帧率
根据游戏类型，原生一般跑30帧就行，限制game.frameRate=30，立马就不卡了
2.优化引擎代码：
引擎对触摸的处理在touch-input.ts中，注意这里分了web，minigame，和native。核心方法在_createCallback，这个方法会频繁创建新的对象：Touch数组，EventTouch对象和Vec2对象：
private _createCallback (eventType: InputEventType) {
return (changedTouches: TouchList, windowId: number): void => {
// 创建了Touch数组
const handleTouches: Touch[] = [];
const length = changedTouches.length;
const windowSize = this._windowManager.getWindow(windowId).getViewSize() as Size;
for (let i = 0; i < length; ++i) {
const changedTouch = changedTouches[i];
const touchID = changedTouch.identifier;
if (touchID === null) {
continue;
}
// 创建了Vec2对象
const location = this._getLocation(changedTouch, windowSize);
// 可能会创建Touch对象，但是有map做了缓存
const touch = touchManager.getOrCreateTouch(touchID, location.x, location.y);
if (!touch) {
continue;
}
if (eventType === InputEventType.TOUCH_END || eventType === InputEventType.TOUCH_CANCEL) {
touchManager.releaseTouch(touchID);
}
handleTouches.push(touch);
}
if (handleTouches.length > 0) {
// 创建了EventTouch对象
const eventTouch = new EventTouch(
handleTouches,
false,
eventType,
// // getAllTouches创建了Touch数组
macro.ENABLE_MULTI_TOUCH ? touchManager.getAllTouches() : handleTouches,
);
eventTouch.windowId = windowId;
this._eventTarget.emit(eventType, eventTouch);
}
};
}
优化后代码：
// 缓存EventTouch
private _eventTouchPool: EventTouch[] = [];
// 缓存Location
private _tmpLocation: Vec2 = new Vec2();
private _createCallback (eventType: InputEventType) {
return (changedTouches: TouchList, windowId: number): void => {
const length = changedTouches.length;
const windowSize = this._windowManager.getWindow(windowId).getViewSize() as Size;
if (length <= 0) return;
let eventTouch: EventTouch;
if(this._eventTouchPool.length > 0) {
eventTouch = this._eventTouchPool.shift()!;
eventTouch.type = eventType;
eventTouch.bubbles = false;
}
else {
eventTouch = new EventTouch([], false, eventType, []);
}
const handleTouches = eventTouch.getTouches();
handleTouches.length = 0;
let allTouches = eventTouch.getAllTouches();
allTouches.length = 0;
for (let i = 0; i < length; ++i) {
const changedTouch = changedTouches[i];
const touchID = changedTouch.identifier;
if (touchID === null) {
continue;
}
const location = this._getLocation(changedTouch, windowSize, this._tmpLocation);
const touch = touchManager.getOrCreateTouch(touchID, location.x, location.y);
if (!touch) {
continue;
}
if (eventType === InputEventType.TOUCH_END || eventType === InputEventType.TOUCH_CANCEL) {
touchManager.releaseTouch(touchID);
}
handleTouches.push(touch);
}
allTouches = macro.ENABLE_MULTI_TOUCH ? touchManager.getAllTouches(allTouches) : handleTouches;
eventTouch.windowId = windowId;
// console.error('eventTouch: ',eventType);
this._eventTarget.emit(eventType, eventTouch);
this._eventTouchPool.push(eventTouch);
};
}
private _getLocation (touch: globalThis.Touch, windowSize: Size, out?: Vec2): Vec2 {
const dpr = screenAdapter.devicePixelRatio;
const x = touch.clientX * dpr;
const y = windowSize.height - touch.clientY * dpr;
const ret = out || new Vec2();
ret.set(x, y);
return ret;
}
// touch-manager.ts
public getAllTouches (out?: Touch[]): Touch[] {
const touches: Touch[] = out || [];
this._touchMap.forEach((touch) => {
if (touch) {
touches.push(touch);
}
});
return touches;
}
优化后注意：由于回传出去的eventTouch变成了池化对象，上层使用时必须保证同步消费完，如果要缓存，需要进行深拷贝