android開発 ViewModel オブザーブはMutableでないLiveDataをオブザーブすればよい

2022 Aug. 13.

MainActivity.kt

class MainActivity : AppCompatActivity() {
    val binding:  ActivityMainBinding by lazy {ActivityMainBinding.inflate(layoutInflater)}

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)

        val myViewModel: MyViewModel by viewModels()

        myViewModel._myString.value = "Hello"

        val myStringObserver = Observer<String> { it -> 
            binding.textView01.text = it
        }

        myViewModel.myString.observe(this, myStringObserver)
    }
}

MyViewModel.kt

class MyViewModel: ViewModel() {
    val _myString = MutableLiveData<String>("")
    val myString: LiveData<String> get() = _myString
}