Adding a Toolbar to a UIPickerView
In this article, we will explore how to add a toolbar to a UIPickerView in iOS. The toolbar will contain a “done” bar button item that can be clicked to hide and animate the picker offscreen.
Overview of Picker Views and Toolbars
A UIPickerView is a control used to display data in the form of a list, where each item in the list corresponds to a specific value or option. It can be used for tasks such as selecting colors, choosing options from a dropdown menu, or picking dates.
On the other hand, a toolbar is a container that typically contains a set of buttons or controls used to provide navigation or access additional features. In the context of this article, we will add a toolbar above a UIPickerView control.
Creating the Picker View
To create a picker view, we can use the following code snippet:
UIView *pickerGroupView = [[[UIView alloc] initWithFrame: frame] autorelease];
thePicker.frame = pickerGroupView.bounds;
[pickerGroupView addSubview: thePicker];
// Add constraints to ensure proper alignment and sizing of the picker group view
[NSLayoutConstraint activateConstraints:@[
[NSLayoutConstraint constraintWithItem:pickerGroupView attribute:NSLayoutAttributeTop attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0],
[NSLayoutConstraint constraintWithItem:pickerGroupView attribute:NSLayoutAttributeBottom attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0],
[NSLayoutConstraint constraintWithItem:pickerGroupView attribute:NSLayoutAttributeLeft attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0],
[NSLayoutConstraint constraintWithItem:pickerGroupView attribute:NSLayoutAttributeRight attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0]
]];
In this code snippet, we create a new UIView instance with an initial frame that corresponds to the entire screen. We then set the frame of our picker view control (thePicker) to match the bounds of this new view.
We also add the picker view as a subview to our new view and activate constraints to ensure proper alignment and sizing of both views.
Adding the Toolbar
Next, we will create our toolbar:
UIView *toolbar = [[[UIView alloc] initWithFrame: CGRectMake(0, 0, frame.size.width, 44)] autorelease];
theToolbar.frame = toolbar.bounds;
[toolbar addSubview:barButton]; // Add the "done" bar button item to the toolbar
// Add constraints to ensure proper alignment and sizing of the toolbar
[NSLayoutConstraint activateConstraints:@[
[NSLayoutConstraint constraintWithItem:toolbar attribute:NSLayoutAttributeTop attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0],
[NSLayoutConstraint constraintWithItem:toolbar attribute:NSLayoutAttributeBottom attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:-44]
]];
In this code snippet, we create a new UIView instance with an initial frame that corresponds to the desired width of our toolbar (44 points) and a fixed height. We then set the frame of our toolbar view to match its bounds and add it as a subview.
To the toolbar, we will add a “done” bar button item:
UIButton *barButton = [[UIButton alloc] initWithFrame: CGRectMake(0, 0, 44, 44)];
[barButton setTitle:@"Done" forState:UIControlStateNormal];
[barButton addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];
[self.toolbar addSubview:barButton];
In this code snippet, we create a new UIButton instance with an initial frame that corresponds to the desired width and height of our button. We then set its title to “Done”, add an action target, and enable user interaction.
We then add the button to the toolbar view as a subview.
Anchoring the Picker View
To ensure proper alignment of both views when the screen is resized or rotated, we can anchor them together:
// Create anchors for both views
NSLayoutConstraint *anchorPickerGroupView = [NSLayoutConstraint constraintWithItem:pickerGroupView attribute:NSLayoutAttributeCenterX attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0];
NSLayoutConstraint *anchorToolbar = [NSLayoutConstraint constraintWithItem:toolbar attribute:NSLayoutAttributeCenterX attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0];
// Activate anchors
[NSLayoutConstraint activateConstraints:@[
anchorPickerGroupView,
anchorToolbar
]];
In this code snippet, we create anchors for both views that define their center x-coordinate. We then activate these anchors to link the two views together.
Displaying and Animating the Picker View
To display the picker view and animate it offscreen when the “done” bar button item is pressed:
- (void)buttonPressed:(UIButton *)button {
[UIView animateWithDuration:0.2 animations:^{
self.pickerGroupView.frame = CGRectMake(self.pickerGroupView.bounds.size.width, 44, self.pickerGroupView.bounds.size.width, self.pickerGroupView.bounds.size.height);
} completion:^(BOOL finished) {
[self.pickerGroupView removeFromSuperview];
}];
}
In this code snippet, we define an action target for the “done” bar button item. When triggered, this target executes a series of animations that hide and animate the picker view control offscreen.
By anchoring both views together, we ensure proper alignment when displaying and hiding the picker view.
Best Practices
Here are some best practices to keep in mind when implementing toolbars with picker views:
- Anchor Views Together: An anchor helps align two or more objects along a specific axis (e.g., x, y). This ensures that the toolbar and picker view remain properly aligned on screen resizes.
- Set Constraints Properly: Constraints help define the relative positions of objects within your app’s UI layout. Setting constraints for both views allows you to fine-tune their alignment and sizing.
- Use Animations to Enhance User Experience: Animations can greatly enhance user experience by providing smooth transitions between states (e.g., hiding and displaying a picker view).
Last modified on 2023-10-20