UE4 C++ Tips

本篇写的是关于ue4的c++方面的小技巧：

1.在构造函数里

//构建组件
rootcomponent = createdefaultsubobject<uscenecomponent>(text("rootcomponent"));
camera = createdefaultsubobject<ucameracomponent>(text("camera"));
//把组件放到其它组件下
vrcamera->setupattachment(vrorigin);
//下面这条不能用于构造函数中，否则编辑器崩溃或报错
//vrcamera->attachtocomponent(vrorigin, fattachmenttransformrules::snaptotargetincludingscale);

2.加载资源

具体细节教程（非本人制作）：

//同步加载，一般用于少量物体加载
//从内存中读取文件，但由于还没从硬盘中读取，所以内存中没有（耗时相对较短），因此读取失败
uhapticfeedbackeffect_base* shakeeffect = findobject<uhapticfeedbackeffect_base>(null,text("hapticfeedbackeffect_curve'/game/virtualrealitybp/blueprints/motioncontrollerhaptics.motioncontrollerhaptics'"));

//从硬盘中读取文件，放到内存中(耗时相对较长)
uhapticfeedbackeffect_base* shakeeffect = loadobject<uhapticfeedbackeffect_base>(null,text("hapticfeedbackeffect_curve'/game/virtualrealitybp/blueprints/motioncontrollerhaptics.motioncontrollerhaptics'"));

.h:
fstreamablemanager* wealthloader;
tsharedptr<fstreamablehandle> wealthhandle;

.cpp:
//异步加载，一般用于大量物体加载
void awelathactor::streamablemanageroperate()
{
    //创建加载管理器
    wealthloader = new fstreamablemanager();
    //执行异步加载，添加资源链接数组和加载完成回调函数，其中texturepath为加载内容的地址
    wealthhandle = wealthloader->requestasyncload(texturepath, fstreamabledelegate::createuobject(this,
        &awelathactor::streamablemanagerloadcomplete));
}

void awelathactor::streamablemanagerloadcomplete()
{
    //加载完成后动态修改图片
    tarray<uobject* >outobjects;
    wealthhandle->getloadedassets(outobjects);
    for (int32 i = 0; i < outobjects.num(); ++i)
    {
        utexture2d* worktexture = cast<utexture2d>(outobjects[i]);
        if (worktexture)
        {
            texturegroup.add(worktexture);
        }
    }
}

3.通过uobjectlibrary获取批量内容的地址

.h:
class uobjectlibrary* objectlibrary;

.cpp:
void awelathactor::objectlibraryoperate()
{
    if (!objectlibrary)
    {
        objectlibrary = uobjectlibrary::createlibrary(uobject::staticclass(), false, false);
        //添加到根那，防止被ue4的垃圾回收机制干掉
        objectlibrary->addtoroot();
    }

    //搜索所有texture的路径
    objectlibrary->loadassetdatafrompath(text("/game/resource/ui/texture/menutex"));

    tarray<fassetdata> texturedata;
    objectlibrary->getassetdatalist(texturedata);

    for (int32 i=0; i<texturedata.num(); ++i)
    {
        texturepath.addunique(texturedata[i].tosoftobjectpath());
    }
}

4.计时器

.h:
ftimerhandle countdowntimerhandle;

.cpp:
//事件委托
ftimerdelegate updatetexturedele = ftimerdelegate::createuobject(this, &awelathactor::updatetexture);
//每0.5秒执行一次事件委托
getworld()->gettimermanager().settimer(countdowntimerhandle, updatetexturedele, 0.5f, true);
//停止运行定时器
getworldtimermanager().cleartimer(countdowntimerhandle);