使用LiveData和DataBinding进行双向绑定

1 引入依赖包

dependencies {    // ...    implementation "androidx.fragment:fragment:1.0.0"    implementation "androidx.lifecycle:lifecycle-viewmodel:2.0.0"    implementation "androidx.lifecycle:lifecycle-extensions:2.0.0"}

2 开启数据绑定

android {    dataBinding {        enabled = true    }}

3 建立模型

class AuthenticationInformation(val username: String = "", val encryptedPassword: String = "")

4 建立视图模型

class AuthenticationViewModel() : ViewModel() {    var authenticationInformation = MutableLiveData
    
     ()    var username = "Alan"    set(value) {        field = value        authenticationInformation.postValue(AuthenticationInformation(username, encryptPassword(password)))    }    var password = ""    set(value) {        field = value        authenticationInformation.postValue(AuthenticationInformation(username, encryptPassword(password)))    }    private fun encryptPassword(originalPassword: String): String {        // ...        return "******"    }}
    

5 更新布局

6 在Activity中建立绑定关系

class MainActivity : AppCompatActivity() {    override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)        var binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)        binding.authenticationViewModel = ViewModelProviders.of(this).get(AuthenticationViewModel::class.java)        binding.lifecycleOwner = this        binding.getAuthenticationViewModel()?.authenticationInformation?.observe(this, object: Observer
    
     {            override fun onChanged(authenticationInformation: AuthenticationInformation) {                Log.d("TEST", authenticationInformation.username)            }        })    }}
    

7 在Fragment中建立绑定关系

override fun onCreateView(        inflater: LayoutInflater, container: ViewGroup?,        savedInstanceState: Bundle?): View? {    var binding = ActivityMainBinding.inflate(inflater, container, false)    binding.authenticationViewModel = ViewModelProviders.of(activity)            .get(AuthenticationViewModel::class.java)    binding.lifecycleOwner = activity    binding.getAuthenticationViewModel()?            .authenticationInformation?            .observe(this, object: Observer
    
      {                override fun onChanged(authenticationInformation: AuthenticationInformation) {                    Log.d("TEST", authenticationInformation.username)                }            })    return binding.root}