EDIT2： 使用
fragTransaction.add(fragment, tag);
代替
fragTransaction.add(id, fragment);
OR
出于某种奇怪的原因，删除MainActivity中的所有Fragments代码会使应用程序再次运行。
当按下按钮时，通过.getText().toString()获取文本将返回null / empty。
尝试手动.setText("something")，当调用.getText().toString()时有效，
修改文本后，调用.getText().toString()仍会返回“内容”。
MainActivity.java
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_main);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragTransaction = fragmentManager.beginTransaction();
Fragment loginFrag = new LoginFragment();
fragTransaction.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);
fragTransaction.add(R.id.mainFrag, loginFrag);
fragTransaction.commit();
}
LoginFragment.java
public class LoginFragment extends Fragment{
EditText fieldID;
EditText fieldPassword;
Button logButton;
private FirebaseAuth mAuth;
View view;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.login_menu, container, false);
}
@Override
public void onViewCreated(View v, Bundle savedInstanceState) {
super.onViewCreated(v, savedInstanceState);
mAuth = FirebaseAuth.getInstance();
view = v;
fieldID = v.findViewById(R.id.fieldID);
fieldPassword = v.findViewById(R.id.fieldPassword);
logButton = v.findViewById(R.id.button_login);
logButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
signIn(fieldID.getText().toString(), fieldPassword.getText().toString());
}
});
}
private void signIn(String email, String password) {
System.out.println("Email: " + email);
System.out.println("Pass: " + password);
if(!email.isEmpty() && !password.isEmpty()) {
mAuth.signInWithEmailAndPassword(email, password)
.addOnCompleteListener(getActivity(), new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
// Sign in success, update UI with the signed-in user's information
Log.d("Auth", "signInWithEmail:success");
FirebaseUser user = mAuth.getCurrentUser();
//updateUI(user);
view.findViewById(R.id.logoMain).setVisibility(View.GONE);
} else {
// If sign in fails, display a message to the user.
Log.w("Auth", "signInWithEmail:failure", task.getException());
//updateUI(null);
}
}
});
}
}
}
主要活动
<?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"
tools:context=".presenter.Activity.MainActivity">
<fragment
android:id="@+id/mainFrag"
android:name="com.raze.mfa.presenter.Fragment.LoginFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
片段布局
<?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="#FFFFFF"
android:orientation="vertical">
<ImageView
android:id="@+id/imageView2"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginTop="110dp"
android:adjustViewBounds="true"
android:scaleType="fitXY"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/logoMain"
app:layout_constraintVertical_bias="1.0"
app:srcCompat="@drawable/bak"
tools:srcCompat="@drawable/bak" />
<ImageView
android:id="@+id/iconlock"
android:layout_width="43dp"
android:layout_height="43dp"
android:layout_marginStart="8dp"
android:layout_marginTop="28dp"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toStartOf="@+id/fieldPassword"
app:layout_constraintHorizontal_bias="0.523"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/iconuser"
app:srcCompat="@mipmap/lockicon" />
<ImageView
android:id="@+id/iconuser"
android:layout_width="43dp"
android:layout_height="43dp"
android:layout_marginStart="8dp"
android:layout_marginTop="320dp"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toStartOf="@+id/fieldID"
app:layout_constraintHorizontal_bias="0.522"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@mipmap/usericon" />
<Button
android:id="@+id/button_login"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
android:text="@string/loginText"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/fieldPassword"
app:layout_constraintVertical_bias="0.188" />
<EditText
android:id="@+id/fieldPassword"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="24dp"
android:layout_marginEnd="72dp"
android:autofillHints=""
android:ems="10"
android:hint="@string/password"
android:inputType="textPassword"
android:singleLine="true"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toBottomOf="@+id/fieldID" />
<EditText
android:id="@+id/fieldID"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="320dp"
android:layout_marginEnd="72dp"
android:autofillHints=""
android:ems="10"
android:hint="@string/email"
android:inputType="textEmailAddress"
android:singleLine="true"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageView
android:id="@+id/logoMain"
android:layout_width="128dp"
android:layout_height="128dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="108dp"
android:adjustViewBounds="true"
android:scaleType="fitCenter"
app:layout_constraintBottom_toTopOf="@+id/fieldID"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.498"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0"
app:srcCompat="@drawable/logoimg" />
<Button
android:id="@+id/button_register"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
android:text="@string/register"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button_login"
app:layout_constraintVertical_bias="0.0" />
</androidx.constraintlayout.widget.ConstraintLayout>
不相关： 我已经使用Google进行了几乎所有内容的搜索，但是似乎我不了解使用Fragments，Activites，上下文，View等的基础知识。
答案 0 :(得分：2)
好的，我知道，您已经在MainActivity布局中使用了{% for username in usernames %}
Username: {{ username }}
{% endfor %}
标签，然后在其中添加了<fragment/>片段。
该事务适用于FragmentTransaction个为空且有片段的容器。通过FrameLayout标签静态添加片段时，片段已经加载到屏幕中。
当您将新片段添加到片段标签时，可能发生了奇怪的事情，也许它复制了片段，并且正在读取实际片段后面的片段，而没有从用户那里得到输入。
请阅读此处以正确使用FragmentTransaction：https://developer.android.com/training/basics/fragments/fragment-ui
根据上述文档，了解他们如何使用<fragment/>作为容器。
XML：
FrameLayoutJava：
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />