为什么"TextInputEditText cannot be cast to TextInputLayout"可以在 Android Studio 中？

Question

这是我在Android Studio中为Android应用程序构建注册活动的代码。每次运行应用程序时，我都会收到这些类Cast Exception错误。可能是什么问题？

我的RegisterActivity.java代码：

{
private TextInputLayout inputEmail,inputPassword,inputConfirmPassword;
Button btnRegister;
TextView alreadyHaveAccount;
FirebaseAuth mAuth;
ProgressDialog mLoadingBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
inputEmail = findViewById(R.id.inputEmail);
inputPassword = findViewById(R.id.inputPassword);
inputConfirmPassword = findViewById(R.id.inputConfirmPassword);
alreadyHaveAccount = findViewById(R.id.alreadyHaveAccount);
mAuth = FirebaseAuth.getInstance();
mLoadingBar = new ProgressDialog(this);
btnRegister.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
AttemptRegistration();
}
});
alreadyHaveAccount.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(RegisterActivity.this,LoginActivity.class);
startActivity(intent);
}
});
}
private void AttemptRegistration() {
String email = inputEmail.getEditText().getText().toString();
String password = inputPassword.getEditText().getText().toString();
String confirmPassword= inputConfirmPassword.getEditText().getText().toString();
if (email.isEmpty() || !email.contains("@gmail.com"))
{
showError(inputEmail,"Email is not valid");
}
else if(password.isEmpty() || password.length()<5)
{
showError(inputPassword,"Password must be greater than 5 letters ");
}
else if(!confirmPassword.equals (password))
{
showError(inputConfirmPassword,"Password does not match");
}
else
{
mLoadingBar.setTitle("Registration");
mLoadingBar.setMessage("Please Wait, While we Check Your Credentials");
mLoadingBar.setCanceledOnTouchOutside(false);
mLoadingBar.show();
mAuth.createUserWithEmailAndPassword(email,password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull @org.jetbrains.annotations.NotNull Task<AuthResult> task) {
if(task.isSuccessful())
{
mLoadingBar.dismiss();
Toast.makeText(RegisterActivity.this, "Registration Successful", Toast.LENGTH_SHORT).show();
Intent intent = new Intent (RegisterActivity.this,SetupActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK|Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
finish();
}
else
{
mLoadingBar.dismiss();
Toast.makeText(RegisterActivity.this, "Registration Failed", Toast.LENGTH_SHORT).show();
}
}
});
}
}
private void showError(TextInputLayout field, String text) {
field.setError(text);
field.requestFocus();
}
}

xml文件是activity_register.xml，如下所示。

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:background="@mipmap/background"
tools:context=".RegisterActivity">
<TextView
android:id="@+id/logo"
android:layout_width="169dp"
android:layout_height="51dp"
android:fontFamily="serif"
android:text=" REGISTER"
android:textSize="30dp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.207" />
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/inputEmail"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_marginStart="150dp"
android:layout_marginTop="60dp"
android:layout_marginEnd="150dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/logo"
style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox">
<com.google.android.material.textfield.TextInputEditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="textEmailAddress"
android:hint="E-MAIL" />
</com.google.android.material.textfield.TextInputLayout>
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/inputPassword"
style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_marginStart="150dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="150dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/inputEmail">
<com.google.android.material.textfield.TextInputEditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="PASSWORD"
android:inputType="textPassword" />
</com.google.android.material.textfield.TextInputLayout>
<Button
android:id="@+id/btnRegister"
android:layout_width="134dp"
android:layout_height="47dp"
android:layout_marginTop="35dp"
android:text="REGISTER"
android:textAllCaps="false"
app:backgroundTint="#00BCD4"
app:layout_constraintEnd_toEndOf="@+id/inputPassword"
app:layout_constraintStart_toStartOf="@+id/inputPassword"
app:layout_constraintTop_toBottomOf="@+id/textInputLayout" />
<com.google.android.material.textfield.TextInputLayout
android:id="@+id/textInputLayout"
style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_marginStart="150dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="150dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/inputPassword">
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/inputConfirmPassword"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="CONFIRM PASSWORD" />
</com.google.android.material.textfield.TextInputLayout>
<TextView
android:id="@+id/alreadyHaveAccount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:text="ALREADY HAVE AN ACCOUNT?"
android:textSize="12sp"
app:layout_constraintEnd_toEndOf="@+id/textInputLayout"
app:layout_constraintStart_toStartOf="@+id/textInputLayout"
app:layout_constraintTop_toBottomOf="@+id/btnRegister" />
</androidx.constraintlayout.widget.ConstraintLayout>

在运行此注册活动时，我的LogCat中出现以下错误：

Caused by: java.lang.ClassCastException: com.google.android.material.textfield.TextInputEditText cannot be cast to com.google.android.material.textfield.TextInputLayout
at com.example.meetup.RegisterActivity.onCreate(RegisterActivity.java:36)
at android.app.Activity.performCreate(Activity.java:8000)
at android.app.Activity.performCreate(Activity.java:7984)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

这是我的build.gradle文件：

plugins {
id 'com.android.application'
id 'com.google.gms.google-services'
}
android {
compileSdkVersion 30
buildToolsVersion "30.0.3"
defaultConfig {
applicationId "com.example.meetup"
minSdkVersion 19
targetSdkVersion 30
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
dependencies {
implementation 'androidx.appcompat:appcompat:1.3.0'
implementation 'com.google.android.material:material:1.4.0'
implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
implementation 'com.google.firebase:firebase-auth:21.0.1'
implementation 'com.google.firebase:firebase-database:20.0.0'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
implementation 'com.google.android.material:material:1.4.0'
implementation 'org.jetbrains:annotations:16.0.2'
/*
implementation 'com.google.firebase:firebase-auth:21.0.1'
implementation 'com.google.firebase:firebase-core:19.0.0'
implementation 'com.google.firebase:firebase-storage:20.0.0'
implementation 'com.firebaseui:firebase-ui-database:6.2.1'
*/
}

Answer 1

问题就在这里。

在您的布局中，inputConfirmPassword是TextInputEditText

<com.google.android.material.textfield.TextInputLayout
android:id="@+id/textInputLayout"..>
<com.google.android.material.textfield.TextInputEditText
android:id="@+id/inputConfirmPassword"

而在您的代码中，inputConfirmPassword是TextInputLayout:

private TextInputLayout inputEmail,inputPassword,inputConfirmPassword;

@Override
protected void onCreate(Bundle savedInstanceState) {
//..
inputConfirmPassword = findViewById(R.id.inputConfirmPassword);