添加子视图/约束:试图理解为什么我的子视图没有显示

Question

我想创建一个弹出窗口，让用户知道他们是否尝试输入重复的信息。所以最初我有一个 UILabel，它会弹出并消失。

UILabel *toastView = [[UILabel alloc] init];
toastView.alpha = 0;
toastView.layer.cornerRadius = 4.0f;
toastView.layer.borderColor = [UIColor colorWithRed:200.0/255.0 green:199.0/255.0 blue:204.0/255.0 alpha:1].CGColor;
CGFloat scale = [[UIScreen mainScreen] scale];
if (scale == 2.0)  {
// retina screen;
toastView.layer.borderWidth = 0.5;
} else {
// non-retina screen
toastView.layer.borderWidth = 1.0;
}
toastView.backgroundColor = [UIColor colorWithRed:63.0/255.0 green:63.0/255.0 blue:63.0/255.0 alpha:1];
toastView.textAlignment = NSTextAlignmentCenter;
[toastView setAdjustsFontSizeToFitWidth:YES];
toastView.text = @" E-Mail has already been added  ";
toastView.font = [UIFont fontWithName:@"HelveticaNeue" size:toastView.font.pointSize];
toastView.textColor = [UIColor whiteColor];
[toastView setTranslatesAutoresizingMaskIntoConstraints:NO];
[toastView.layer setMasksToBounds:YES];
[self.superview.superview.superview addSubview:toastView];
[[UIApplication sharedApplication].keyWindow bringSubviewToFront:toastView];
[toastView.bottomAnchor constraintEqualToAnchor:self.superview.superview.superview.centerYAnchor].active = YES;
[toastView.centerXAnchor constraintEqualToAnchor:self.superview.superview.superview.centerXAnchor].active = YES;
[toastView.heightAnchor constraintEqualToConstant:round(self.superview.superview.superview.frame.size.height/12)].active = YES;
[toastView.widthAnchor constraintEqualToConstant:round(self.superview.superview.superview.frame.size.width/1.5)].active = YES;
[UIView animateWithDuration:0.3 animations:^{
toastView.alpha = 0.95;
} completion:^(BOOL finished) {
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 1.0 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
[UIView animateWithDuration:0.3 animations:^{
toastView.alpha = 0;
} completion:nil];
});
}];

这工作正常。然后我想添加一个图像，所以我决定将此弹出窗口的创建移动到一个方法，该方法采用视图和消息并生成一个包含 UILabel 和 UIImageView 的弹出视图。这是代码：

+(void)toastAlert:(UIView*)view message:(NSString*)message {
UIView *toastView = [[UIView alloc] init];
UILabel *toastLabel = [[UILabel alloc] init];
UIImage *infoImage = [UIImage imageNamed:@"info_white"];
UIImageView *imageView = [[UIImageView alloc] initWithImage:infoImage];
toastView.alpha = 0;
toastView.layer.cornerRadius = 4.0f;
toastView.layer.borderColor = [UIColor colorWithRed:200.0/255.0 green:199.0/255.0 blue:204.0/255.0 alpha:1].CGColor;
CGFloat scale = [[UIScreen mainScreen] scale];
if (scale == 2.0)  {
// retina screen;
toastView.layer.borderWidth = 0.5;
} else {
// non-retina screen
toastView.layer.borderWidth = 1.0;
}
[toastLabel setTextAlignment:NSTextAlignmentCenter];
[toastLabel setAdjustsFontSizeToFitWidth:YES];
[toastLabel setText:[NSString stringWithFormat:@"%@", message]];
[toastLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:toastLabel.font.pointSize]];
[toastLabel setTextColor: [UIColor whiteColor]];
toastView.backgroundColor = [UIColor colorWithRed:63.0/255.0 green:63.0/255.0 blue:63.0/255.0 alpha:1];
[toastView setTranslatesAutoresizingMaskIntoConstraints:NO];
[toastView.layer setMasksToBounds:YES];
[view addSubview:toastView];
[[UIApplication sharedApplication].keyWindow bringSubviewToFront:toastView];
[toastView addSubview:toastLabel];
[toastView addSubview:imageView];
[toastView.bottomAnchor constraintEqualToAnchor:view.centerYAnchor].active = YES;
[toastView.centerXAnchor constraintEqualToAnchor:view.centerXAnchor].active = YES;
[toastView.heightAnchor constraintEqualToConstant:round(view.frame.size.height/12)].active = YES;
[toastView.widthAnchor constraintEqualToConstant:round(view.frame.size.width/1.5)].active = YES;
[imageView.centerYAnchor constraintEqualToAnchor:toastView.centerYAnchor].active = YES;
[imageView.leadingAnchor constraintEqualToAnchor:toastView.leadingAnchor constant:padding].active = YES;
[imageView.heightAnchor constraintEqualToConstant:toastView.frame.size.height/2].active = YES;
[imageView.widthAnchor constraintEqualToAnchor:toastView.heightAnchor].active = YES;

[toastLabel.centerYAnchor constraintEqualToAnchor:toastView.centerYAnchor].active = YES;
[toastLabel.centerXAnchor constraintEqualToAnchor:toastView.centerXAnchor constant:imageView.frame.size.width + padding*2].active = YES;
[toastLabel.leadingAnchor constraintEqualToAnchor:imageView.trailingAnchor constant:padding].active = YES;
[toastLabel.heightAnchor constraintEqualToConstant:toastView.frame.size.height/2].active = YES;

[UIView animateWithDuration:0.3 animations:^{
toastView.alpha = 0.95;
} completion:^(BOOL finished) {
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 1.0 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
[UIView animateWithDuration:0.3 animations:^{
toastView.alpha = 0;
} completion:nil];
});
}];
}

然而，无论我做什么，我只能让UIView出现，没有文本或UILabel出现。当我添加 UIImageView 时，它会显示出来，但弄乱了整个 ToastView 的大小调整。

我仍然是初级开发人员，并且确定我错过了一些基本的东西......谁能向我解释我做错了什么？(不仅仅是寻找一个直接的答案，因为解释更有价值(

Answer 1

所以我认为您的自动调整大小蒙版与您的约束相冲突。 从CGRectZero开始。我将尝试解决每个项目，以便您知道出了什么问题。 这是工作代码。

-(void)alteredToastAlert:(UIView*)targetView message:(NSString*)message {
CGFloat padding = 10.0;
// i like to start with real frames buggy things happen with CGRectZero
UIView *toastView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 300, 200)];
//turn all resizing masks off
[toastView setTranslatesAutoresizingMaskIntoConstraints:NO];
UILabel *toastLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 300, 200)];
[toastLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
UIImage *infoImage = [UIImage imageNamed:@"info_white"];
UIImageView *imageView = [[UIImageView alloc] initWithImage:infoImage];
[imageView setTranslatesAutoresizingMaskIntoConstraints:NO];
//has a size but intrinsic
toastView.alpha = 0;
toastView.layer.cornerRadius = 4.0f;
toastView.layer.borderColor = [UIColor colorWithRed:200.0/255.0 green:199.0/255.0 blue:204.0/255.0 alpha:1].CGColor;
CGFloat scale = [[UIScreen mainScreen] scale];
if (scale == 2.0)  {
// retina screen;
toastView.layer.borderWidth = 0.5;
} else {
// non-retina screen
toastView.layer.borderWidth = 1.0;
}
[toastLabel setTextAlignment:NSTextAlignmentCenter];
[toastLabel setText:[NSString stringWithFormat:@"%@", message]];
[toastLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:22]];
[toastLabel setTextColor: [UIColor whiteColor]];
[toastLabel setMinimumScaleFactor:0.01];
toastView.backgroundColor = [UIColor colorWithRed:63.0/255.0 green:63.0/255.0 blue:63.0/255.0 alpha:1];
[toastView setTranslatesAutoresizingMaskIntoConstraints:NO];
[toastView.layer setMasksToBounds:YES];
[targetView addSubview:toastView];
[[UIApplication sharedApplication].keyWindow bringSubviewToFront:toastView];
//adding here but everything has a frame so it is not size 0.  Then apply autolayout
[toastView addSubview:toastLabel];
[toastView addSubview:imageView];
[toastView.bottomAnchor constraintEqualToAnchor:targetView.centerYAnchor].active = YES;
[toastView.centerXAnchor constraintEqualToAnchor:targetView.centerXAnchor].active = YES;
[toastView.heightAnchor constraintEqualToConstant:round(targetView.frame.size.height/12)].active = YES;
[toastView.widthAnchor constraintEqualToConstant:round(targetView.frame.size.width/1.5)].active = YES;
[imageView.centerYAnchor constraintEqualToAnchor:toastView.centerYAnchor].active = YES;
[imageView.leadingAnchor constraintEqualToAnchor:toastView.leadingAnchor constant:padding].active = YES;
[imageView.heightAnchor constraintEqualToConstant:toastView.frame.size.height/2].active = YES;
[imageView.widthAnchor constraintEqualToAnchor:toastView.heightAnchor].active = YES;
imageView.backgroundColor = [UIColor redColor];

[toastLabel.centerYAnchor constraintEqualToAnchor:toastView.centerYAnchor].active = YES;
[toastLabel.leadingAnchor constraintEqualToAnchor:imageView.trailingAnchor constant:padding].active = YES;
// have to have a trailing to keep it inside the view
[toastLabel.trailingAnchor constraintEqualToAnchor:toastView.trailingAnchor constant:padding].active = YES;
[toastLabel.heightAnchor constraintEqualToConstant:toastView.frame.size.height/2].active = YES;
toastView.alpha = 1;
[UIView animateWithDuration:0.3 animations:^{
toastView.alpha = 0.95;
} completion:^(BOOL finished) {
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 1.0 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
[UIView animateWithDuration:0.3 animations:^{
toastView.alpha = 0;
} completion:^(BOOL finished){
//may need to remove from superview
}];
});
}];
}

1(你会注意到我设置了框架开始。 我这样做是因为我注意到从CGRectZero开始做一些疯狂的事情。 我们最终会让视图由自动布局控制，但首先我设置框架。 图像视图将建立其固有框架。

2(接下来，我告诉系统不要从自动调整大小的蒙版中创建约束。 我这样做是为了 toastView 作为标签和图像视图。

3(我告诉标签文本的最小比例因子，我从任意字体大小的值22开始。 您可能会将其提高到 50，它仍然会缩小。 我认为由于CGRectZero，您以前的字体大小为0，但我不确定

4(我让你的约束在标签上可能是一个尾随约束的版本上工作，但我认为就是这样。 你可以看一看。

5(完成所有这些操作后，不要忘记从其超级视图或您正在传递的视图中删除ToastView，因为即使alpha为0，它仍然存在。