改变UIStackView中uilabel的背景渐变颜色

Question

我是iOS开发的新手，我正在与UIStackView合作。
当我使用StoryBoard创建两个UILabels作为UIStackView的子对象时，下面的代码使每个UILabel的渐变背景色工作得很好。

UILabel *label;
for (int ii = 1; ii < 3; ii++) {
    label = [self.view viewWithTag:ii];
    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = label.bounds;
    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor yellowColor]CGColor], (id)[[UIColor grayColor]CGColor], nil];
    [label.layer insertSublayer:gradient atIndex:0];
    UILabel *newLabel = [[UILabel alloc] initWithFrame:label.bounds];
    newLabel.backgroundColor = [UIColor clearColor];
    newLabel.text = label.text;
    [label addSubview:newLabel];
}

但是当我使用下面的代码以编程方式创建两个UILabels时，我上面为每个UILabel制作渐变背景的代码不起作用，背景颜色保持白色。
有人能帮我一下吗?

UILabel *myLabel;
myLabel = [[UILabel alloc] init];
[myLabel setText:@"text1"];
[myLabel setTag:1];
[stackView addArrangedSubview:myLabel];
myLabel = [[UILabel alloc] init];
[myLabel setText:@"text2"];
[myLabel setTag:2];
[stackView addArrangedSubview:myLabel];

Answer 1

问题似乎与标签边界有关。下面的代码添加了一个UIStackView和几个带渐变的uilabel。

const int STACK_WIDTH = 200;
const int NUM_LABELS = 3;
const int LABEL_WIDTH = STACK_WIDTH / NUM_LABELS;
UIStackView* stack = [[UIStackView alloc] initWithFrame:CGRectMake(0, 0, STACK_WIDTH, 100)];
stack.axis = UILayoutConstraintAxisHorizontal;
stack.distribution = UIStackViewDistributionFillProportionally;
stack.alignment = UIStackViewAlignmentLeading;
stack.spacing = LABEL_WIDTH;
stack.backgroundColor = [UIColor greenColor];
[self.view addSubview:stack];
for(int i = 0; i < NUM_LABELS; i++){
    UIView* myLabelView = [[UIView alloc] initWithFrame:CGRectMake(i * LABEL_WIDTH, 0, LABEL_WIDTH, stack.frame.size.height)];
    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = myLabelView.bounds;
    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor yellowColor]CGColor], (id)[[UIColor grayColor]CGColor], nil];
    gradient.startPoint = CGPointMake(0, 0);
    gradient.endPoint = CGPointMake(1, 0);
    [myLabelView.layer addSublayer:gradient];
    UILabel* myLabel = [[UILabel alloc] initWithFrame:myLabelView.bounds];
    myLabel.text = [NSString stringWithFormat:@"label: %d", i];
    [myLabelView addSubview:myLabel];
    [stack addArrangedSubview:myLabelView];
}