有时候，当我们场景上挂载的资源过多时，我们使用cc.director.loadScene切换场景时会等一段时间才会切换过去，这对游戏的体验是相当不好的。所以我们可以使用cc.director.preloadScene来进行预加载，如：
cc.director.preloadScene("sceneName",
function () {
cc.director.loadScene("sceneName"
);
});
同时搭载一个加载进度条来实现显示加载进度，优化游戏体验：
那么如何获取加载时的进度呢？
在Cocos creator 2.0版本之前，我们可以使用下面这样的方法：
cc.loader.onProgress =
function (completedCount, totalCount, item){
//先开监听
this.loading.progress = completedCount/totalCount;
this.loadLabel.string = Math.floor(completedCount/totalCount * 100) + "%";
}.bind(
this);
cc.director.preloadScene("sceneName",
function () {
cc.log("加载成功"
);
});
loading就是你在脚本中绑定的进度条组件。
Cocos creator升级到2.0版本后，onProgress貌似就无法使用了，所以上述那个方法无法获取到加载进度，但是在cc.director.preloadScene这个函数中新增了一个参数：
所以我们可以通过这个参数来获取加载的进度：
cc.director.preloadScene("sceneName",
this.onProgress.bind(
this),
function(){
cc.log("加载成功"
)；
})
onProgress :function(completedCount, totalCount, item){
this.loading.progress = completedCount/totalCount;
this.loadLabel.string = Math.floor(completedCount/totalCount * 100) + "%";
}
其实无论是预加载场景还是加载资源，本质调用的还是cc.loader.load这个api，看底层代码可以知道：
预加载场景：
preloadScene:
function (sceneName, onProgress, onLoaded) {
if (onLoaded ===
undefined) {
onLoaded =
onProgress;
onProgress =
null;
}
var info =
this._getSceneUuid(sceneName);
if (info) {
this.emit(cc.Director.EVENT_BEFORE_SCENE_LOADING, sceneName);
cc.loader.load({ uuid: info.uuid, type: 'uuid'
},
onProgress,
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);
}
},
加载资源：
proto.loadResDir =
function (url, type, progressCallback, completeCallback) {
var args =
this._parseLoadResArgs(type, progressCallback, completeCallback);
type =
args.type;
progressCallback =
args.onProgress;
completeCallback =
args.onComplete;
var urls =
[];
var uuids =
resources.getUuidArray(url, type, urls);
this._loadResUuids(uuids, progressCallback,
function (errors, assetRes, urlRes) {
// The spriteFrame url in spriteAtlas will be removed after build project
// To show users the exact structure in asset panel, we need to return the spriteFrame assets in spriteAtlas
let assetResLength =
assetRes.length;
for (let i = 0; i < assetResLength; ++
i) {
if (assetRes[i]
instanceof cc.SpriteAtlas) {
let spriteFrames =
assetRes[i].getSpriteFrames();
for (let k
in spriteFrames) {
let sf =
spriteFrames[k];
assetRes.push(sf);
if (urlRes) {
urlRes.push(`${urlRes[i]}/${sf.name}`);
}
}
}
}
completeCallback &&
completeCallback(errors, assetRes, urlRes);
}, urls);
};
proto._loadResUuids =
function (uuids, progressCallback, completeCallback, urls) {
if (uuids.length > 0
) {
var self =
this;
var res = uuids.map(
function (uuid) {
return {
type: 'uuid'
,
uuid: uuid
}
});
this.load(res, progressCallback,
function (errors, items) {
if (completeCallback) {
var assetRes =
[];
var urlRes = urls &&
[];
for (
var i = 0; i < res.length; ++
i) {
var uuid =
res[i].uuid;
var id =
this._getReferenceKey(uuid);
var item =
items.getContent(id);
if (item) {
// should not release these assets, even if they are static referenced in the scene.
self.setAutoReleaseRecursively(uuid,
false);
assetRes.push(item);
if (urlRes) {
urlRes.push(urls[i]);
}
}
}
if (urls) {
completeCallback(errors, assetRes, urlRes);
}
else {
completeCallback(errors, assetRes);
}
}
});
}
else {
if (completeCallback) {
callInNextTick(function () {
if (urls) {
completeCallback(null, [], []);
}
else {
completeCallback(null, []);
}
});
}
}
};
而cc.loader.load的内部实现的参数中就是带有这个回调函数的
所以我们还可以这样写来获取加载场景的进度：
var info = cc.director._getSceneUuid(
this.sceneName);
var self =
this;
if (info) {
cc.loader.load({ uuid: info.uuid, type: 'uuid' }, function(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);
}, function(error, asset){
if (error) {
cc.errorID(1210,
this.sceneName, error.message);
} else {
cc.log("加载完成"
); }
}
});
}
转载于:https://www.cnblogs.com/liylove/p/10475868.html
相关资源：DirectX修复工具V4.0增强版
