设置UITextField inputAccessoryView的alpha无效

Question

inputAccessoryView显示成功，但它是完全黑色的。

    _textField = [[UITextField alloc] initWithFrame: CGRectZero]; // update frame later
    _textField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;

    UIView *inputAccessoryView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 180)];
    inputAccessoryView.backgroundColor = [UIColor blackColor];
    inputAccessoryView.alpha = 0.2;

    _textField.inputAccessoryView = inputAccessoryView;

我完全不明白这一点...有人能解释一下为什么会这样吗？

Answer 1

在前一行上使用此UIColor方法，而不是设置alpha:-

[UIColor  colorWithHue:saturation:brightness:alpha:];