实时数据观察者对首次更改的数据进行了两倍的评估

Question

我正在尝试将 MVVM 应用于我的项目，并使用 LiveData 。但是，这样做时出现了问题。我有 ：    - LoginActivity ，其中具有 txtEmail 和 btnLogin ；    - LoginViewModel 具有 电子邮件：MutableLiveData 。在活动中设置ViewModel后，请听btnLogin单击以设置 email.value =“ XXXX@YYY.com” 。我两次调试并中断了onChanged事件中的行跳转，但是下次单击时，不是那样的。

BaseActivity

abstract class BaseActivity<T : ViewDataBinding, V : BaseViewModel> : AppCompatActivity() {
    private lateinit var mViewDataBinding: T
    private lateinit var mViewModel: V
    private var mProgressDialog: LoadingProgress? = null

    override fun onCreate(savedInstanceState: Bundle?) {
//        performDependencyInjection()
        super.onCreate(savedInstanceState)
        performDataBinding()
        mProgressDialog = LoadingProgress(this)

    }
    private fun performDataBinding() {
        mViewDataBinding = DataBindingUtil.setContentView(this, getLayoutId())
        this.mViewModel = getViewModel()
        mViewDataBinding.setVariable(getBindingVariable(), mViewModel)
        mViewDataBinding.executePendingBindings()
        mViewDataBinding.lifecycleOwner = this
    }
    /**
     * Override for set binding variable
     *
     * @return variable id
     */
    abstract fun getBindingVariable(): Int

    /**
     * @return layout resource id
     */
    @LayoutRes
    abstract fun getLayoutId(): Int

    /**
     * Override for set view model
     *
     * @return view model instance
     */
    abstract fun getViewModel(): V

    fun onFragmentAttached() {

    }

    fun onFragmentDetached(tag: String) {

    }


    protected fun getViewDataBinding(): T {
        return mViewDataBinding
    }


class LoginViewModel : BaseViewModel() {
    var email=  MutableLiveData<String>()
    var password: MutableLiveData<String>? = null

    fun onLoginClicked(){
        email.value = "huypkhanh@gmail.com"
    }

}

MainActivity

class MainActivity : BaseActivity<ActivityMainBinding, LoginViewModel>() {
    private lateinit var mLoginViewModel: LoginViewModel
    private lateinit var mActivityLoginBinding: ActivityMainBinding

    override fun getBindingVariable(): Int {
        return 1
    }

    override fun getLayoutId(): Int {
        return R.layout.activity_main
    }

    override fun getViewModel(): LoginViewModel {
        mLoginViewModel = ViewModelProviders.of(this).get(LoginViewModel::class.java)
        return mLoginViewModel
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        mActivityLoginBinding = getViewDataBinding()
        mActivityLoginBinding.apply {
            loginViewModel?.email?.observe(this@MainActivity, Observer { email ->
                Log.i("aaa", email + hashCode())
            })
        }
    }
}

XML

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto">
    <data>
        <variable
                name="loginViewModel"
                type="com.nhathoang.loginmvvm.LoginViewModel"/>
    </data>
    <android.support.constraint.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            tools:context=".MainActivity">

        <TextView
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintStart_toEndOf="@+id/btn"
                android:background="@color/colorPrimary"
                android:textSize="16sp"
                android:text="@={loginViewModel.email}"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"/>
        <Button
                android:id="@+id/btn"
                app:layout_constraintTop_toTopOf="parent"
                android:onClick="@{()-> loginViewModel.onLoginClicked()}"
                app:layout_constraintStart_toStartOf="parent"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"/>

    </android.support.constraint.ConstraintLayout>
</layout>