objektif-c - iOS Bagaimana untuk menetapkan teks menjadi legap apabila menetapkan ketelusan latar belakang label UI

Question

UILabel *leftLabel = [[UILabel alloc]initWithFrame:CGRectMake(0 20, UIViewHeight - 20, UIViewWidth, 20)];

leftLabel.textColor = [UIColor whiteColor];

// leftLabel.backgroundColor = [UIColor lightGrayColor];

leftLabel.backgroundColor = [[UIColor blackColor]colorWithAlphaComponent:0.7f];