为什么我的UIButton没有被添加到我的手机中？

Question

In my cellForRowAtIndexPath: method I have the following code:

        UIButton *signOutButton = [[UIButton alloc] init];

        [signOutButton addTarget:self action:@selector(logoutButtonTapped) forControlEvents:UIControlEventTouchUpInside];
        signOutButton.translatesAutoresizingMaskIntoConstraints = NO;
        signOutButton.titleLabel.textColor = [UIColor colorWithRed:0/255.0 green:180/255.0 blue:35/255.0 alpha:1.0];
        signOutButton.titleLabel.text = @"Sign Out";

        [cell.contentView addSubview:signOutButton];

        [cell.contentView addConstraint:[NSLayoutConstraint constraintWithItem:signOutButton
                                                                     attribute:NSLayoutAttributeLeading
                                                                     relatedBy:NSLayoutRelationEqual
                                                                        toItem:cell.contentView
                                                                     attribute:NSLayoutAttributeLeft
                                                                    multiplier:1.0
                                                                      constant:50.0]];

        [cell.contentView addConstraint:[NSLayoutConstraint constraintWithItem:signOutButton
                                                                     attribute:NSLayoutAttributeTrailing
                                                                     relatedBy:NSLayoutRelationEqual
                                                                        toItem:cell.contentView
                                                                     attribute:NSLayoutAttributeRight
                                                                    multiplier:1.0
                                                                      constant:50.0]];

        [cell.contentView addConstraint:[NSLayoutConstraint constraintWithItem:signOutButton
                                                                     attribute:NSLayoutAttributeBottom
                                                                     relatedBy:NSLayoutRelationEqual
                                                                        toItem:cell.contentView
                                                                     attribute:NSLayoutAttributeBottom
                                                                    multiplier:1.0
                                                                      constant:-6.0]];

But it never shows up when I load the cell. I'm sort of new to Auto Layout, so can anyone figure out what I'm doing wrong?

Oddly enough if I tap the area where the button should be the method executes.

Answer 1

Since the method is executed when you press it, it seems that your button is actually added to the cell. I think that the title is not set. Try replacing signOutButton.titleLabel.text = @"Sign Out" with [signOutButton setTitle:@"Sign Out" forState:UIControlStateNormal]

Answer 2

Your button is getting added, since your label title is not getting set therefore you are not seeing it. You can change the background color to see where is it in the cell as:

[signOutButton setBackgroundColor:[UIColor blueColor]];

And then change title and color as following:

[signOutButton setTitle:@"Sign Out" forState:UIControlStateNormal];
[signOutButton setTitleColor:[UIColor colorWithRed:0/255.0 green:180/255.0 blue:35/255.0 alpha:1.0] forState:UIControlStateNormal];

This how your final code is going to look like:

    UIButton *signOutButton = [[UIButton alloc] init];

[signOutButton addTarget:self action:@selector(logoutButtonTapped) forControlEvents:UIControlEventTouchUpInside];
signOutButton.translatesAutoresizingMaskIntoConstraints = NO;
[signOutButton setTitle:@"Sign Out" forState:UIControlStateNormal];
[signOutButton setTitleColor:[UIColor colorWithRed:0/255.0 green:180/255.0 blue:35/255.0 alpha:1.0] forState:UIControlStateNormal];
[signOutButton setBackgroundColor:[UIColor blueColor]]; //just for testing, you can get rid of this line

[cell.contentView addSubview:signOutButton];

[cell.contentView addConstraint:[NSLayoutConstraint constraintWithItem:signOutButton
                                                             attribute:NSLayoutAttributeLeading
                                                             relatedBy:NSLayoutRelationEqual
                                                                toItem:cell.contentView
                                                             attribute:NSLayoutAttributeLeft
                                                            multiplier:1.0
                                                              constant:50.0]];

[cell.contentView addConstraint:[NSLayoutConstraint constraintWithItem:signOutButton
                                                             attribute:NSLayoutAttributeTrailing
                                                             relatedBy:NSLayoutRelationEqual
                                                                toItem:cell.contentView
                                                             attribute:NSLayoutAttributeRight
                                                            multiplier:1.0
                                                              constant:50.0]];

[cell.contentView addConstraint:[NSLayoutConstraint constraintWithItem:signOutButton
                                                             attribute:NSLayoutAttributeBottom
                                                             relatedBy:NSLayoutRelationEqual
                                                                toItem:cell.contentView
                                                             attribute:NSLayoutAttributeBottom
                                                            multiplier:1.0
                                                              constant:-6.0]];