macos label没了，用NSTextField

    NSTextField *label = [[NSTextField alloc] initWithFrame:self.win.contentView.frame];
    label.backgroundColor = [NSColor clearColor];
    label.selectable = FALSE;
    label.bordered = FALSE;
    label.editable = FALSE;
    label.alignment = NSTextAlignmentCenter;
    label.font = [NSFont systemFontOfSize:15];
    label.stringValue = @"label";
    [self.win.contentView addSubview:label];