Xamarin.iOS – Handle UIButton Taps with C#

In this lesson

  • Use Debugger break points
  • Implement Lambda expressions to handle TouchUpInside event for button taps

Transcript

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00:00

How do we handle button clicks? We’re going to say testButton. There is no click property or event. Instead, you have TouchUpInside. To basically create an event handler, we hit += and this generates a lambda expression for us. I’m going to say Debug.WriteLine(“Pressed”) like this, now when I run this, when I hit button, we’ll see in our application how to put down pressed.

00:49

What’s all this stuff here? If I put a breakpoint in here, when I hit Goodbye, the app stops running and we go back to Xamarin Studio where I can start inspecting things and seeing what’s going on. If I double click on this and then right click on it, I can say Expression Evaluator. Basically, it will tell me what Sender is. As we can see, it’s a UIButton. Whenever it gets clicked it sends a reference to yourself in case you have to do some logic on it. You can see what our current title is, what the title color is, etc.

01:25

Another way you can see what’s going on is called Locals, the Locals tab here. If I increase this, you’ll see we have the event arguments that are being passed and there’s nothing to be passed with it. In this particular case, that’s not so useful.

01:43

That said, let’s actually have it do something with our UI. I’m going to say TestLabel.Text = Goodbye. Now, when we run this, it will change our UILabel. We can add some logic to this. If TestLabel.Text does not = Goodbye you do this, else you say Hello. As I toggle it, it will change.