Enable a button when all EditText complete

Question

I would like to enable a AppCompatButton when all fields in a form are complete.

I am using a ViewModel and would like to use Databinding to enable this.

I have 2 methods that fire when text is changed on the views to update an objects data in the viewmodel.

The issue I am running into is when both fields are complete, I need to enable a button on the layout allowing them to proceed.

An example would be log in, when the username and password fields are fulled in, the log in button becomes enabled.

Answer 1

You can use the same solution like here

But if you want use only AndroidArch and DataBinding you can create your own approach like below:

class MyVM : ViewModel() {
    ...
    val mLoginLiveData = MutableLiveData<String>()
    val mPasswordLiveData = MutableLiveData<String>()
    val mLoginPasswordMediator = MediatorLiveData<Boolean>()
    ...
    init {
      mLoginPasswordMediator.addSource(mLoginLiveData) { validateForm() }
      mLoginPasswordMediator.addSource(mPasswordLiveData) { validateForm() }
      ...
    }

    private fun validateForm() {
        // put your validation logic here, and update the following value
        // as `true` or `false` based on validation result
        // mLoginPasswordMediator.value = ...
    }

    override fun onCleared() {
        // DO NOT forget to remove sources from mediator
        mLoginPasswordMediator.removeSource(mLoginLiveData)
        mLoginPasswordMediator.removeSource(mPasswordLiveData)
    }
}

and in your activity class listen your MediatorLiveData:

class MyActivity : AppCompatActivity() {
    ...
    override fun onCreate(savedInstanceState: Bundle?) {
      //Obtain your ViewModel class here
      //Initialize binding here
      ...
      mBinding.lifecycleOwner = this
      mVM.mLoginPasswordMediator.observe(this, Observer { validationResult ->
          mBinding.yourButton.isEnabled = validationResult
      })
    }
}

And didn't forget to use your LiveDatas' in 'your_activity_layout'.xml:

...
//Add your ViewModel class to layout here
<EditText
  ...
  android:text="@={vm.mLoginLiveData}"
  ... />
...
<EditText
  ...
  android:text="@={vm.mPasswordLiveData}"
  ... />
...