Fragment resizing after left application

Question

I have a problem when I click to EditText. First time nothing happened, but if I load a new fragment and left the app, then it happened.

Flow:

• Activity Start.
• Fragment loaded.
• Click into EditText (id=myedittext) (Image: First Time) (it works good, the layout is match_parent)
• Another fragment added
• Home button (Important step!)
• Go back to app(onRestart)
• Push back button (getSupportFragmentManager().popBackStack();)
• Click into EditText (id=myedittext)(Image: Second Time) (Err: The layout is adjustPan. Its resized when keyboard shows. WHY?)

Add fragment:

FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.add(frameId, fragment);
transaction.addToBackStack(null);
transaction.commit();

Pop fragment:

getSupportFragmentManager().popBackStack();

Activity:

 <activity
            android:name=".MyActivity"
            android:configChanges="keyboardHidden|orientation"
            android:screenOrientation="portrait" />

MyActivity layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MyActivity">

    <FrameLayout
        android:fitsSystemWindows="true"
        android:id="@+id/contentFrame"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

Fragment xml details:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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:gravity="center"
    android:orientation="vertical">


    <com.rengwuxian.materialedittext.MaterialEditText
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />


    <LinearLayout
        android:id="@+id/body"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:orientation="vertical"
        app:layout_constraintBottom_toTopOf="@+id/next_button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/title">

        <com.rengwuxian.materialedittext.MaterialEditText
            android:id="@+id/myedittext"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </LinearLayout>


    <Button
        android:id="@+id/next_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/next_button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />


</android.support.constraint.ConstraintLayout>

Anyone know how can I fix the screen when second time it's loaded?