CODEWITHSUNDEEP
androidmvvm
0leg
0leg

Reputation: 14144

Architecture's ViewModel and observe

In the Google's example ViewModels changes are observed using

model.getUsers().observe(this, users -> {
  // update UI
});

The --> {} pattern is a Java 8 lambda-functions feature. users is undefined in this case. Also Studio shows mismatch error, since Observer<your_type> is expected as the 2nd parameter.

According to the reference:

void observe(LifecycleOwner owner, Observer observer) Adds the given observer to the observers list within the lifespan of the given owner.

So the code supposed to be something like:

class Observer FooObserver() {
  @Override
  public function onChanged(...
}
..
fooObserver = new FooObserver(..
..
model.getUsers().observe(this, fooObserver);

Question:

Is this supposed to be some kind of abstract example or do this shortcut code really suppose to replace Observer usage?

Upvotes: 1

Views: 987

Answers (1)

Andrej Jurkin
Andrej Jurkin

Reputation: 2256

This is just a short form for inner observer implementation.

So this 

model.getUsers().observe(this, users -> {
// update UI
});

Is equal to this

model.getUsers().observe(this, new Observer<User>() {
    @Override
    public void onChanged(User user) {

    }
});

You can integrate lambda expressions and some of the other java8 features into your projects using Retrolambda.

Upvotes: 2

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