Question

我正在尝试在Android中使用数据绑定。但最终得到StackOverflow错误。

loginViewModel.kt

class loginViewModel(): BaseObservable() {

    @Bindable
    var errorEmail:String?=null
        get() {
            if (userEmailAddress.isNullOrBlank())
                return "Please Enter the Email Address"
            else if (!isValidEmail(userEmailAddress))
                return "Enter Valid Email Id."
            else
                return null
        }

    var userEmailAddress:String= String()
        set(userEmailAddress){
            field=userEmailAddress
            notifyPropertyChanged(R.id.email_address)
            /*to check Email for validation on every character inserted by user*/
            notifyPropertyChanged(BR.errorEmail)

        }
        get() {
        return userEmailAddress
    }



}

错误日志：

07-04 13:54:15.435 6865-6865/com.example.itstym.reminder D/AndroidRuntime: Shutting down VM
07-04 13:54:15.513 6865-6865/com.example.itstym.reminder E/AndroidRuntime: FATAL EXCEPTION: main
                                                                           Process: com.example.itstym.reminder, PID: 6865
                                                                           java.lang.StackOverflowError: stack size 8MB
                                                                               at com.example.itstym.reminder.loginViewModel.getUserEmailAddress(loginViewModel.kt:49)
                                                                               at com.example.itstym.reminder.loginViewModel.getUserEmailAddress(loginViewModel.kt:49)

我知道有任何递归调用时会发生StackOverflow错误，但我无法弄清楚如何解决这个错误？

<?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"
        xmlns:tools="http://schemas.android.com/tools">

    <data class="ActivityMainBinding">
        <variable
            name="login"
            type="com.example.itstym.reminder.loginViewModel" />
    </data>

<android.support.constraint.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.itstym.reminder.MainActivity">


    <EditText
        app:error="@{login.errorEmail}"
        android:text="@{login.userEmailAddress}"
        android:hint="Email Address"
        android:id="@+id/email_address"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:ems="10"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginTop="24dp"/>


</layout>

Answer 1

你递归地调用了getter。你应该写

get() = field

而不是

get() {
    return userEmailAddress
}

field标识符用于属性的访问者以提供对backing field的访问权限，而引用userEmailAddress最终调用getUserEmailAddress()方法会导致无限循环和StackOverflowError。

Answer 2

你也应该在你的getter中使用field，否则会递归调用自己：

var userEmailAddress: String = String()
    set(userEmailAddress){
        field = userEmailAddress
        ...
    }
    get() {
        return field // <-- here
    }

getter方法抛出StackOverflowError

2 个答案: