如何设置单击侦听器并传递edittext字段值以使用数据绑定查看模型
问题描述：
嗨我想在我的android应用程序中使用数据绑定和mvvm体系结构。我想在布局中添加使用数据绑定的点击监听器，并将用户名和密码edittext的值发送到视图模型，并执行web服务并调用LoginActivity的适当方法，如startHomeActivity()。如何设置单击侦听器并传递edittext字段值以使用数据绑定查看模型
有没有人知道如何做到这一点或我采取错误的做法？我有下面的我的活动，布局和视图模型的代码片段
LoginActivity.kt
class LoginActivity : BaseActivity(), LoginNavigator {
@Inject
lateinit var loginViewModel: LoginActivityViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val activityLoginBinding = DataBindingUtil.setContentView<ActivityLoginBinding>(this, R.layout.activity_login)
}
override fun startHomeActivity() {
TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}
override fun startRegistrationActivity() {
TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}
override fun startForgotPasswordActivity() {
TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}
override fun handleError(throwable: Throwable) {
TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}
}
LoginActivityViewModel.kt
class LoginActivityViewModel {
fun login(email: String, password: String) {
}
/**
* Validate email and password. It checks email and password is empty or not
* and validate email address is correct or not
* @param email email address for login
* @param password password for login
* @return true if email and password pass all conditions else false
*/
fun isEmailAndPasswordValid(email: String, password: String): Boolean {
if (email.isEmpty()) return false
if (!Patterns.EMAIL_ADDRESS.matcher(email).matches()) return false
if (password.isEmpty()) return false
return true
}
}
activity_login.xml
<layout>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true"
tools:context="com.app.android.login.LoginActivity"
tools:ignore="missingPrefix">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="@dimen/default_view_margin_bottom_8dp">
<android.support.design.widget.TextInputLayout
android:id="@+id/til_login_email"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="@dimen/default_view_margin_right_8dp"
android:layout_marginStart="@dimen/default_view_margin_left_8dp"
android:textColorHint="@color/colorSecondaryText"
app:hintTextAppearance="@style/AppTheme.InputLayoutStyle"
app:layout_constraintBottom_toTopOf="@+id/til_login_password"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_chainStyle="packed">
<android.support.design.widget.TextInputEditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/login_email"
android:imeOptions="actionNext"
android:singleLine="true"
android:textColor="@color/colorPrimaryText" />
</android.support.design.widget.TextInputLayout>
<android.support.design.widget.TextInputLayout
android:id="@+id/til_login_password"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="@dimen/default_view_margin_right_8dp"
android:layout_marginStart="@dimen/default_view_margin_left_8dp"
android:textColorHint="@color/colorSecondaryText"
app:hintTextAppearance="@style/AppTheme.InputLayoutStyle"
app:layout_constraintBottom_toTopOf="@+id/btn_login_login"
app:layout_constraintTop_toBottomOf="@+id/til_login_email"
app:layout_constraintVertical_chainStyle="packed">
<android.support.design.widget.TextInputEditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/login_password"
android:imeOptions="actionDone"
android:singleLine="true"
android:textColor="@color/colorPrimaryText" />
</android.support.design.widget.TextInputLayout>
<Button
android:id="@+id/btn_login_login"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="@dimen/default_view_margin_right_8dp"
android:layout_marginStart="@dimen/default_view_margin_left_8dp"
android:layout_marginTop="48dp"
android:text="@string/login_btn_text"
android:textColor="@color/colorWhite"
app:layout_constraintBottom_toTopOf="@+id/textview_login_forgot_password"
app:layout_constraintTop_toBottomOf="@+id/til_login_password"
app:layout_constraintVertical_chainStyle="packed" />
<TextView
android:id="@+id/textview_login_forgot_password"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="@dimen/default_view_margin_right_8dp"
android:layout_marginStart="@dimen/default_view_margin_left_8dp"
android:layout_marginTop="36dp"
android:gravity="center"
android:text="@string/login_forgot_password"
app:layout_constraintBottom_toTopOf="@+id/btn_login_register"
app:layout_constraintTop_toBottomOf="@+id/btn_login_login"
app:layout_constraintVertical_chainStyle="packed" />
<Button
android:id="@+id/btn_login_register"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="@dimen/default_view_margin_right_8dp"
android:layout_marginStart="@dimen/default_view_margin_left_8dp"
android:text="@string/login_sign_up"
android:textColor="@color/colorWhite"
app:layout_constraintBottom_toBottomOf="parent" />
</android.support.constraint.ConstraintLayout>
</ScrollView>
</layout>
答
首先所有重命名您的ViewModel。它由View分隔，这意味着名称应该像LoginViewModel一样。对于这种尝试（这是在Android中使用mvvm模式的最佳选择），您需要AAC/LiveData。
其次，您应该执行双向数据绑定并将ViewModel分配给您的布局。
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable name="viewModel" type="...YourVm" />
</data>
<android.support.design.widget.TextInputEditText ...
android:text="@={viewModel.yourField}" />
<Button ... onClick="@{viewModel.onClick}" />
</layout>
这需要在您的ViewModel ObservableField<String>。
现在您想验证在活动中传递点击事件是否发生了点击。对于这种情况，您可以在ViewModel中创建Listener并将数据传递给Observable。
class LoginViewModel {
val yourField = ObservableField<String>()
val uiEventLiveData = SingleLiveData<Int>()
fun onClick(view:View) {
uiObservable.data = 1 // or any other event
}
}
之后，您可以使用您的Activity或Fragment来观察使用LiveData的UIEvents（它是生命周期感知！）。
现在你可以用它绑定到视图模型的任何片段/活动观察像UI事件：
class YourActivity {
private val yourvm by lazy { ViewModelProviders.of(this, viewModelFactory).get(Yourvm::class.java) }
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
// ....
binding.viewModel = yourVm
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
yourVm.uiEventLiveData.observe(this, Observer {
when(it) {
1-> { doSomeLoginStuff(yourVm.yourField, ...) } //click happened, do something
else -> .... // unknown ui event
}
})
}
您需要的类SingleLiveData这是一个MutableLiveData而抵消你的数据onec其发射。
class SingleLiveData<T> : MutableLiveData<T>() {
private val mPending = AtomicBoolean(false)
@MainThread
override fun observe(owner: LifecycleOwner, observer: Observer<T>) {
if (hasActiveObservers()) {
Log.w(TAG, "Multiple observers registered but only one will be notified of changes.")
}
// Observe the internal MutableLiveData
super.observe(owner, Observer { t ->
if (mPending.compareAndSet(true, false)) {
observer.onChanged(t)
}
})
}
@MainThread
override fun setValue(t: T?) {
mPending.set(true)
super.setValue(t)
}
/**
* Used for cases where T is Void, to make calls cleaner.
*/
@MainThread
fun call() {
value = null
}
companion object {
private val TAG = "SingleLiveData"
}
}
有几个尝试使用WeakReferences来避免上下文泄漏，但我强烈建议不要这样做。原因是你想用你的视图分割逻辑。即使他们是懒惰或弱的参考，也会打破体系结构。
非常感谢你+1 :) –