Observer Design Pattern on Android

Question

Observer Design Pattern on Android

Asked 10 years, 9 months ago

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1

Someone would have how to show me an Observer structure within android?

I was trying to build one like the java, but I was unsuccessful.

My test was done as follows:

I created a class Banco and a class ClienteObservable;
At the bank I have the methods of notification, and adicionarObserver (that I pass the ball to clienteObservable);
In the class ClienteObservable I have the method update, who will carry out an action upon being notified.

This is the logic I have about Project Observer Standard, but I don’t know how to structure it in android, someone could develop something very basic to show me?

It follows below the Code:

Na Class Banco inserir a descrição da imagem aqui

In Class clienteObservable inserir a descrição da imagem aqui

2

Could you post the code you implemented in java? Taking advantage you can leave the classes with the default Java with the first letter uppercase.

– Leonardo Otto

2014/03/24 at 18:58
I added the image, and saw that the method notify this without any action with the observer, I figured it might be another strength to use the Observer

– user3456780

2014/03/24 at 20:20
What error is having on android?

– Leonardo Otto

2014/03/24 at 20:32
No error, just not executed anything, I put for every time the observer receives a notification, it displays a Toast, and it does not run, like and I flirted, my method notify Observeer is not running anything(I think), I will test when I get from the service.

– user3456780

2014/03/24 at 20:39
1

You need to explicitly call notifyObservers every time you change your object. the same way I put in my class in the answer below.

– Leonardo Otto

2014/03/24 at 20:41

1 answer

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by Leonardo Otto • **2,328** points · Answer 1 · 2014-03-24T19:28:15+00:00

I believe it’s the same as java.

public class Cliente {
}
public interface ClienteObservable {
    public void update();
}
public class Banco {
    private List<ClienteObservable> observables = new ArrayList<ClienteObservable>();
    public void adicionarObserver(ClienteObservable obs){
       this.observables.add(obs);
    }
}

But there is a conceptual error here. It should actually be like this:

public interface ClienteObserver {
    public void update(Cliente cliente);
}
public class Banco implements ClienteObserver {
    @Override
    public void update(Cliente cliente) {
        //faz algum calculo para o cliente  ..
    }
}
public class Cliente {
    private String nome;
    private List<ClienteObserver> observers = new ArrayList<ClienteObserver>();

    public void adicionarObserver(ClienteObserver obs) {
        this.observers.add(obs);
    }
    public void setNome(String nome) {
        this.nome = nome;
        this.notifyObservers();
    }
    private void notifyObservers() {
        for (ClienteObserver observer : this.observers) {
            observer.update(this);
        }
    }
}

For who you are observing is the Customer object. When it updates its status it should communicate the observers about this modification.