这个是preloadScene源码:
/**
* !#en
* Preloads the scene to reduces loading time. You can call this method at any time you want.
* After calling this method, you still need to launch the scene by `cc.director.loadScene`.
* It will be totally fine to call `cc.director.loadScene` at any time even if the preloading is not
* yet finished, the scene will be launched after loaded automatically.
* !#zh 预加载场景，你可以在任何时候调用这个方法。
* 调用完后，你仍然需要通过 `cc.director.loadScene` 来启动场景，因为这个方法不会执行场景加载操作。
* 就算预加载还没完成，你也可以直接调用 `cc.director.loadScene`，加载完成后场景就会启动。
*
* @method preloadScene
* @param {String} sceneName - The name of the scene to preload.
* @param {Function} [onLoaded] - callback, will be called after scene loaded.
* @param {Error} onLoaded.error - null or the error object.
*/
preloadScene: function (sceneName, onLoaded) {
var info = this._getSceneUuid(sceneName);
if (info) {
this.emit(cc.Director.EVENT_BEFORE_SCENE_LOADING, sceneName);
cc.loader.load({ uuid: info.uuid, type: 'uuid' }, function (error, asset) {
if (error) {
cc.errorID(1210, sceneName, error.message);
}
if (onLoaded) {
onLoaded(error, asset);
}
});
}
else {
var error = 'Can not preload the scene "' + sceneName + '" because it is not in the build settings.';
onLoaded(new Error(error));
cc.error('preloadScene: ' + error);
}
实测下面这个方式，可以准确获取场景加载进度的.
var info = cc.director._getSceneUuid(this.sceneName);
var self = this;
if (info) {
cc.loader.load({ uuid: info.uuid, type: 'uuid' }, (completedCount, totalCount, item) => {
cc.log("已完成Items:" + completedCount);
cc.log("全部Items:" + totalCount);
cc.log("当前Item:" + item.url);
self._loadingNextStep = parseInt(completedCount / totalCount * 100);
cc.log("加载进度:" + self._loadingNextStep);
}, (error, asset) => {
if (error) {
cc.errorID(1210, this.sceneName, error.message);
} else {
cc.log("加载完成");
}
});
}
