How to perform two-way data binding with a ToggleButton?

Question

I have an ObservableBoolean field in my activity class, which is bound to the \"checked\" attribute of my ToggleButton like so:

and         


        

Answer 1

Here are ways to set OnCheckedChangeListener in data binding:

(1) Set by method expression

In layout

In Activity

class HomeActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = DataBindingUtil.setContentView(this, R.layout.activity_calendar)
        binding.activity = this
        binding.model = Model()
    }

    fun onGenderChanged(buttonView: CompoundButton, isChecked: Boolean) {
        println("buttonView = [$buttonView], isChecked = [$isChecked]")
    }
}

(2) Set by lambda expression and method call

In Activity

class HomeActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = DataBindingUtil.setContentView(this, R.layout.activity_calendar)
        binding.activity = this
        binding.model = Model()
    }

    fun saveGender(isChecked: Boolean) {
        println("isChecked = [$isChecked]")
    }
}

(3) Pass OnCheckedChangeListener anonymous class to layout

In Activity

class HomeActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = DataBindingUtil.setContentView(this, R.layout.activity_calendar)
        binding.model = Model()
        binding.setOnGenderChange { buttonView, isChecked ->
            println("buttonView = [$buttonView], isChecked = [$isChecked]")
        }
    }
}

(4) Pass OnCheckedChangeListener by reference

Activity

class HomeActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = DataBindingUtil.setContentView(this, R.layout.activity_calendar)
        binding.model = Model()
        binding.onGenderChange2 = onGenderChange
    }

    private val onGenderChange: CompoundButton.OnCheckedChangeListener = CompoundButton.OnCheckedChangeListener { buttonView, isChecked ->
        println("buttonView = [$buttonView], isChecked = [$isChecked]")
    }
}

This will never work

Because you can't set two callback on one component. One callback is already set by two way binding, so your callback will not work.

binding.toggleButton.setOnCheckedChangeListener { buttonView, isChecked ->
    println("buttonView = [$buttonView], isChecked = [$isChecked]")
}

Check CompoundButtonBindingAdapter class to see how Switch Binding works.