[UE4][Slate]用C++代码绘制血条(HealthBar)

参考自Epic官方项目StrategyGame

血条效果：

 

StrategyHUD.h

/**  
 * Draws health bar for specific actor. 
 * 
 * @param   ForActor    Actor for which the health bar is for. 
 * @param   HealthPct   Current Health percentage. 
 * @param   BarHeight   Height of the health bar 
 * @param   OffsetY     Y Offset of the health bar. 
 */  
void DrawHealthBar(AActor* ForActor, float HealthPct, int32 BarHeight, int OffsetY = 0) const;

 

StrategyHUD.cpp

void AStrategyHUD::DrawHealthBar(AActor* ForActor, float HealthPercentage, int32 BarHeight, int32 OffsetY) const  
{  
    FBox BB = ForActor->GetComponentsBoundingBox();  
    FVector Center = BB.GetCenter();  
    FVector Extent = BB.GetExtent();  
    FVector2D Center2D = FVector2D(Canvas->Project(FVector(Center.X,Center.Y,Center.Z + Extent.Z)));  
    float ActorExtent = 40;  
    if (Cast<APawn>(ForActor) != NULL)  
    {  
        AStrategyChar* StrategyChar = Cast<AStrategyChar>(ForActor);  
        if( ( StrategyChar != NULL ) && ( StrategyChar->GetCapsuleComponent() != NULL ) )  
        {  
            ActorExtent = StrategyChar->GetCapsuleComponent()->GetScaledCapsuleRadius();  
        }  
    }  
    else if (Cast<AStrategyBuilding>(ForActor) != NULL)  
    {  
        Center2D = FVector2D(Canvas->Project(ForActor->GetActorLocation()));  
        ActorExtent = 60;  
    }  
  
    FVector Pos1 = Canvas->Project(FVector(Center.X,Center.Y - ActorExtent*2, Center.Z + Extent.Z));  
    FVector Pos2 = Canvas->Project(FVector(Center.X,Center.Y + ActorExtent*2, Center.Z + Extent.Z));  
    float HealthBarLength = (Pos2-Pos1).Size2D();  
  
    AStrategyPlayerController* MyPC = GetPlayerController();  
    IStrategyTeamInterface* ActorTeam = Cast<IStrategyTeamInterface>(ForActor);  
    UTexture2D* HealthBarTexture = EnemyTeamHPTexture;  
  
    if (ActorTeam != NULL && MyPC != NULL && ActorTeam->GetTeamNum() == MyPC->GetTeamNum())  
    {  
        HealthBarTexture = PlayerTeamHPTexture;  
    }   
    float X = Center2D.X - HealthBarLength/2;  
    float Y = Center2D.Y + OffsetY;  
    FCanvasTileItem TileItem( FVector2D( X, Y ), HealthBarTexture->Resource, FVector2D( HealthBarLength * HealthPercentage,  BarHeight ), FLinearColor::White );  
    TileItem.BlendMode = SE_BLEND_Translucent;  
    TileItem.UV1 = FVector2D(HealthPercentage, 1.0f);  
  
    Canvas->DrawItem( TileItem );  
    //Fill the rest of health with gray gradient texture  
    X = Center2D.X-HealthBarLength/2 + HealthBarLength * HealthPercentage;  
    Y = Center2D.Y + OffsetY;  
    TileItem.Position = FVector2D( X, Y );  
    TileItem.Texture = BarFillTexture->Resource;  
    TileItem.UV1 = FVector2D(1.0f, 1.0f);  
    TileItem.Size = FVector2D( HealthBarLength * (1.0f - HealthPercentage), BarHeight );  
    TileItem.SetColor(FLinearColor(0.5f, 0.5f, 0.5f, 0.5f));  
    Canvas->DrawItem( TileItem );      
}