2019独角兽企业重金招聘Python工程师标准>>> 
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
}