Refer to this  ,after to resolved from PaulMeuris's advice ,but it isn't completely about B4i
my code now is belows
	
	
	
	
	
	
	
		
			
			
			
			
			
		
	
	
	
		
	
	
		
	
			
			my code now is belows
			
				B4X:
			
		
		
		' Font Property Setter
Public Sub setFont(newFont As B4XFont)
    mFont = newFont
    #If B4J
        If xLBL.IsInitialized Then
            CSSUtils.SetStyleProperty(xLBL,"-fx-font-weight","bold")
            CSSUtils.SetStyleProperty(xLBL,"-fx-font-size",mTextSize)
            'CSSUtils.SetStyleProperty(xLBL,"-fx-font-family","playpensansthai-extrabold")
            CSSUtils.SetStyleProperty(xLBL,"-fx-font-family",mFont.ToNativeFont.FamilyName)
        End If   
    #Else If B4A
        If xLBL.IsInitialized Then
            xLBL.Font = mFont
        End If
    #Else    'B4i
           ???   'I don't have Mac devices and B4i product
  
    #End If   
End Sub