Objective-C iOS Development for Legacy & Enterprise Apps · Aula

Controles e Eventos Comuns de UI

Trabalhe com controles padrão do UIKit, como botões, rótulos e campos de texto, e aprenda a tratar interações e eventos do usuário.

Aula 2 de 411 etapas

Controles e Eventos Comuns de UI é uma aula grátis de Objective-C iOS Development for Legacy & Enterprise Apps no CoddyKit. Esta é a aula 2 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de Objective-C iOS Development for Legacy & Enterprise Apps, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de Objective-C iOS Development for Legacy & Enterprise Apps inclui 4 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

UI Controls: Your App's Face

User Interface (UI) controls are the interactive elements users see and touch in an app. They are the building blocks of any iOS application's visual experience.

  • Buttons: Tap to perform actions.
  • Labels: Display static text.
  • Text Fields: Input text from the user.

Mastering these controls is crucial for creating intuitive and functional apps, especially when maintaining legacy Objective-C codebases.

Displaying Text with UILabel

A UILabel is used to display static, read-only text in your app. Think of it as a sign or a description.

  • Set its text property to display content.
  • Customize its appearance with properties like textColor, font, and textAlignment.
  • Labels can be single or multi-line.

It's one of the most fundamental UI elements you'll encounter.

UILabel in Action

Let's create a UILabel programmatically and inspect its properties. Remember, in a real app, you'd add this to a view to see it visually!

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // Create a label with a frame (position and size)
        UILabel *myLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 50, 280, 40)];
        myLabel.text = @"Hello CoddyKit!";
        myLabel.textColor = [UIColor darkTextColor];
        myLabel.font = [UIFont boldSystemFontOfSize:20.0];
        myLabel.textAlignment = NSTextAlignmentCenter;

        NSLog(@"Created UILabel:");
        NSLog(@"  Text: %@", myLabel.text);
        NSLog(@"  Font Size: %.1f", myLabel.font.pointSize);
        NSLog(@"  Alignment: %ld", (long)myLabel.textAlignment);
    }
    return 0;
}

Making Apps Interactive with UIButton

The UIButton is arguably the most common interactive control. Users tap buttons to trigger actions.

  • Buttons can display text, an image, or both.
  • They have different states (Normal, Highlighted, Disabled, Selected).
  • You attach actions to buttons to define what happens when they're tapped.

Buttons are key for user interaction in any iOS application.

Responding to Button Presses

To make a UIButton do something, you use the Target-Action pattern. This connects a specific event (like a tap) to a method in an object (the target).

  • addTarget:action:forControlEvents: is the method you call.
  • The target is typically your UIViewController or another handler object.
  • The action is a method selector (e.g., @selector(buttonTapped:)).
  • UIControlEventTouchUpInside is the common event for a tap inside the button's bounds.

Implementing a Tap Action

Here's how you'd set up a button and its action. When you "run" this, imagine the button being tapped and the message appearing in the console!

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface ButtonHandler : NSObject
- (void)buttonTapped:(UIButton *)sender;
@end

@implementation ButtonHandler
- (void)buttonTapped:(UIButton *)sender {
    NSLog(@"Button '%@' was tapped!", [sender titleForState:UIControlStateNormal]);
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        ButtonHandler *handler = [[ButtonHandler alloc] init];

        UIButton *myButton = [UIButton buttonWithType:UIButtonTypeSystem];
        myButton.frame = CGRectMake(10, 100, 200, 50);
        [myButton setTitle:@"Press Me!" forState:UIControlStateNormal];
        
        // Set up the target-action. The handler object will receive the message.
        [myButton addTarget:handler 
                     action:@selector(buttonTapped:)
           forControlEvents:UIControlEventTouchUpInside];

        NSLog(@"Button created. If tapped, console would show action.");
        // In a real app, you'd add myButton to a view hierarchy.
        // For this console example, we simulate the action call.
        // [handler buttonTapped:myButton]; // Uncomment to simulate a tap immediately
    }
    return 0;
}

Accepting Text with UITextField

A UITextField allows users to enter single lines of text. It's perfect for names, passwords, or short messages.

  • It automatically brings up the keyboard when tapped.
  • You can configure its placeholder text, keyboard type (numeric, email, etc.), and security options (for passwords).
  • Use its text property to get the current input.

Handling UITextField Events

UITextField also uses the Target-Action pattern for various events. Common events include:

  • UIControlEventEditingChanged: The text content has changed.
  • UIControlEventEditingDidEndOnExit: The user pressed the "Return" key.
  • UIControlEventEditingDidBegin: The user started editing the text field.

You can also assign a delegate to a text field for more advanced control, like validating input or custom keyboard behavior.

Observing Text Input

This example shows how to set up a text field and react when its content changes. The console will log the text as it's "typed".

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface TextFieldHandler : NSObject
- (void)textFieldDidChange:(UITextField *)sender;
@end

@implementation TextFieldHandler
- (void)textFieldDidChange:(UITextField *)sender {
    NSLog(@"Text field content changed: %@", sender.text);
}
@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        TextFieldHandler *handler = [[TextFieldHandler alloc] init];

        UITextField *myTextField = [[UITextField alloc] initWithFrame:CGRectMake(10, 160, 280, 40)];
        myTextField.placeholder = @"Type here...";
        myTextField.borderStyle = UITextBorderStyleRoundedRect;
        
        // Attach an action for when the text changes
        [myTextField addTarget:handler
                        action:@selector(textFieldDidChange:)
              forControlEvents:UIControlEventEditingChanged];

        NSLog(@"Text field created. Simulating input...");
        // Simulate some input changes
        myTextField.text = @"H";
        [handler textFieldDidChange:myTextField];
        myTextField.text = @"He";
        [handler textFieldDidChange:myTextField];
        myTextField.text = @"Hello";
        [handler textFieldDidChange:myTextField];
    }
    return 0;
}

Identify the UI Control

Which UIKit control is primarily used for displaying static, non-editable text, such as a title or a descriptive message?

Recap: Common Controls & Events

In this lesson, we explored fundamental UIKit controls and how to make them interactive:

  • UILabel: Displays static, read-only text.
  • UIButton: Triggers actions via taps, using the Target-Action pattern.
  • UITextField: Accepts single-line text input, also using Target-Action for changes.

These controls are the foundation for building user interfaces in Objective-C iOS apps. Understanding their properties and event handling is crucial for both new development and maintaining legacy code.

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Perguntas Frequentes

A aula “Controles e Eventos Comuns de UI” é grátis?

Sim — o texto completo de “Controles e Eventos Comuns de UI” é grátis para ler aqui na web. Para praticá-la interativamente (um editor de código integrado e um tutor de IA 24/7) e desbloquear o restante do curso de Objective-C iOS Development for Legacy & Enterprise Apps, atualize para CoddyKit PRO. O curso de Objective-C iOS Development for Legacy & Enterprise Apps inclui 4 aulas no total.

O que vou aprender em “Controles e Eventos Comuns de UI”?

Trabalhe com controles padrão do UIKit, como botões, rótulos e campos de texto, e aprenda a tratar interações e eventos do usuário. Você pratica Objective-C iOS Development for Legacy & Enterprise Apps com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

Preciso ter experiência prévia para começar Objective-C iOS Development for Legacy & Enterprise Apps?

Nenhuma experiência prévia é necessária. Objective-C iOS Development for Legacy & Enterprise Apps no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 2 de 4.

Quanto tempo leva a aula “Controles e Eventos Comuns de UI”?

A maioria das aulas CoddyKit leva cerca de 5–10 minutos. Cada uma é compacta e interativa, então você faz progresso constante e retoma exatamente de onde parou entre web e app.

Posso escrever e executar código nesta aula de Objective-C iOS Development for Legacy & Enterprise Apps?

Sim. Cada aula de Objective-C iOS Development for Legacy & Enterprise Apps inclui um editor de código integrado, então você escreve e executa código real direto no navegador e recebe feedback de IA instantaneamente — nenhuma configuração local necessária.

Todas as aulas deste curso

  1. UIView e UIViewController
  2. Controles e Eventos Comuns de UI
  3. Visões de Tabela e de Coleção
  4. Auto Layout com NSLayoutConstraint
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