Understanding the Issue with Programmatically Added Buttons in Table View Controllers

As developers, we often encounter scenarios where we need to add buttons or other UI elements programmatically to our views. In this case, we’re dealing with a UITableViewController and a button that’s being added to it using UIButton buttonWithType:. However, the button seems to be getting stuck in the cell that occupies its frame space, causing it to appear as if it’s “stuck” or not behaving as expected.

The Problem at Hand

Let’s dive into the provided code snippet and understand what’s going on:

-(void)createFlipButton {
    UIButton *button = [UIButton buttonWithType:UIButtonTypeInfoDark];
    button.frame = CGRectMake(282, 372, 18, 19);
    [button addTarget:self action:@selector(flipView) forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:button];
    [self.view bringSubviewToFront:button];
}

Here, we’re creating a UIButton instance and adding it to the view hierarchy. We also bring it to the front using [self.view bringSubviewToFront:]. However, when we run this code, the button appears to be stuck in the cell that occupies its frame space.

The Solution: Creating a Floating View

The answer lies in understanding how the table view and its scroll content interact with other views. To create a floating view that doesn’t move when the table scrolls, we need to adjust the position of our added view accordingly.

One way to achieve this is by implementing the scrollViewDidScroll: delegate method, which gets called whenever the user scrolls the scroll content. We can then update the frame of our button based on the current scroll offset and the bounds of the table view.

Implementing the scrollViewDidScroll: Method

Let’s implement the scrollViewDidScroll: method to adjust the position of our button:

-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CGPoint buttonOrigin = CGPointMake(200, 50);
    self.button.frame = CGRectMake(buttonOrigin.x, buttonOrigin.y + scrollView.contentInset.top, self.button.frame.size.width, self.button.frame.size.height);
}

Here, we’re getting the current scroll offset and bounds of the table view. We then calculate the new frame for our button based on these values.

Storing a Reference to the Button

To access the button in the scrollViewDidScroll: method, we need to store a reference to it. We can do this by declaring an instance variable (_button) and initializing it when we create the button:

- (void)createFlipButton {
    _button = [UIButton buttonWithType:UIButtonTypeInfoDark];
    _button.frame = CGRectMake(282, 372, 18, 19);
    [_button addTarget:self action:@selector(flipView) forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:_button];
    [self.view bringSubviewToFront:_button];
}

By doing this, we ensure that we can access the button in the scrollViewDidScroll: method.

Additional Considerations

When working with table views and scroll content, it’s essential to consider the following:

• The contentInset property of the table view affects the scroll offset. We need to take this into account when calculating the new frame for our button.
• When scrolling the table view, other views in the scroll content may also move. We should be aware of these interactions and adjust our code accordingly.

Conclusion

By implementing the scrollViewDidScroll: method and adjusting the position of our added view based on the current scroll offset and bounds, we can create a floating view that doesn’t move when the table scrolls. This approach allows us to add buttons or other UI elements programmatically without being tied to a specific cell or frame space.

If you have access to the WWDC 2011 videos, Session 125 covers this topic in detail. It provides additional insights and techniques for working with table views and scroll content.

Example Use Cases

Here’s an example of how we can use this technique to add multiple buttons to a table view:

- (void)createMultipleFlipButtons {
    UIButton *button1 = [UIButton buttonWithType:UIButtonTypeInfoDark];
    button1.frame = CGRectMake(282, 372, 18, 19);
    [_button1 addTarget:self action:@selector(flipView1) forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:_button1];
    [self.view bringSubviewToFront:_button1];

    UIButton *button2 = [UIButton buttonWithType:UIButtonTypeInfoDark];
    button2.frame = CGRectMake(282, 400, 18, 19);
    [_button2 addTarget:self action:@selector(flipView2) forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:_button2];
    [self.view bringSubviewToFront:_button2];

    UIButton *button3 = [UIButton buttonWithType:UIButtonTypeInfoDark];
    button3.frame = CGRectMake(282, 428, 18, 19);
    [_button3 addTarget:self action:@selector(flipView3) forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:_button3];
    [self.view bringSubviewToFront:_button3];
}

In this example, we create three separate buttons and add them to the view hierarchy. We then use the createMultipleFlipButtons method to adjust their positions based on the current scroll offset and bounds.

By using this technique, we can easily add multiple floating views without being tied to a specific cell or frame space.

Last modified on 2024-05-06