在新片段中显示上一个片段的按钮

Question

我尝试从当前片段中打开一个新片段。但是当我这样做时，我遇到了一个问题，上一个片段中的按钮没有返回到新片段

我做了this，但对我来说却不是那么有益

片段容器XML

<fragment
    android:id="@+id/fragment_container_navbar"
    class="com.example.poplify.baby_guru_sample.Bottom_Tabs.Paytab_frag"
    android:layout_width="match_parent"
    android:layout_height="@dimen/_385sdp"
    android:layout_marginEnd="@dimen/_2sdp"
    android:layout_marginStart="@dimen/_2sdp"
    android:layout_marginTop="8dp"
    app:layout_constraintBottom_toTopOf="@+id/bottomNavigationView"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="@+id/toolbar1"
    app:layout_constraintVertical_bias="0.97" />

将第一个片段替换为第二个

  final Fragment fragment = new Reff_code_frag();
    fragmentManager = getActivity().getSupportFragmentManager();
    reff_code.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            fragmentManager.beginTransaction().replace(R.id.fragment_container_navbar,fragment).addToBackStack("Paytab_frag").commit();

        }
    });

底部导航栏代码

private BottomNavigationView.OnNavigationItemSelectedListener navlistener = new BottomNavigationView.OnNavigationItemSelectedListener() {
    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
        Fragment selectFrag=null;

        switch (menuItem.getItemId())
        {
            case R.id.tab1:
                selectFrag = new Paytab_frag();
                break;

            case R.id.tab2 :
                selectFrag = new Add_child_tab_frag();
                    break;

            case R.id.tab3:
                Toast.makeText(getApplicationContext(),"tab3",Toast.LENGTH_LONG).show();
                     break;

             case R.id.tab4:
                 Toast.makeText(getApplicationContext(),"tab4",Toast.LENGTH_LONG).show();
                    break;
        }
        fragmentManager.beginTransaction().replace(R.id.fragment_container_navbar,selectFrag).commit();
        return true;
    }
};

第一个片段的xml

<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:background="@color/dark_grey"
tools:context=".Bottom_Tabs.Paytab_frag">
<TextView
    android:id="@+id/textView"
    android:layout_width="@dimen/_214sdp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="@dimen/_8sdp"
    android:layout_marginStart="@dimen/_8sdp"
    android:layout_marginTop="128dp"
    android:gravity="center_horizontal"
    android:lineSpacingExtra="@dimen/_4sdp"
    android:text="@string/Paytxt1"
    android:textSize="@dimen/_14sdp"
    app:layout_constraintEnd_toStartOf="@+id/guideline6"
    app:layout_constraintHorizontal_bias="0.531"
    app:layout_constraintStart_toStartOf="@+id/guideline5"
    app:layout_constraintTop_toTopOf="@+id/guideline4" />
<EditText
    android:id="@+id/amt_txt"
    android:layout_width="@dimen/_150sdp"
    android:layout_height="@dimen/_40sdp"
    android:layout_marginEnd="@dimen/_8sdp"
    android:layout_marginStart="@dimen/_8sdp"
    android:layout_marginTop="20dp"
    android:background="@drawable/button_with_border"
    android:ems="10"
    android:gravity="center_horizontal"

    android:hint="Enter Amount"
    android:inputType="textPersonName"
    android:paddingTop="@dimen/_10sdp"
    app:layout_constraintEnd_toStartOf="@+id/guideline6"
    app:layout_constraintHorizontal_bias="0.516"
    app:layout_constraintStart_toStartOf="@+id/guideline5"
    app:layout_constraintTop_toBottomOf="@+id/textView" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="@dimen/_214sdp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="@dimen/_8sdp"
    android:layout_marginStart="@dimen/_8sdp"
    android:layout_marginTop="21dp"
    android:gravity="center_horizontal"
    android:text="@string/paytxt2"
    android:textSize="@dimen/_14sdp"
    app:layout_constraintEnd_toStartOf="@+id/guideline6"
    app:layout_constraintHorizontal_bias="0.531"
    app:layout_constraintStart_toStartOf="@+id/guideline5"
    app:layout_constraintTop_toBottomOf="@+id/amt_txt" />

<TextView
    android:id="@+id/ref_code_txt"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="@dimen/_8sdp"
    android:layout_marginStart="@dimen/_8sdp"
    android:layout_marginTop="25dp"
    android:text="@string/refe_link"
    app:layout_constraintEnd_toStartOf="@+id/guideline6"
    app:layout_constraintHorizontal_bias="0.51"
    app:layout_constraintStart_toStartOf="@+id/guideline5"
    app:layout_constraintTop_toBottomOf="@+id/textView2" />

<Button
    android:id="@+id/pay_btn"
    android:layout_width="@dimen/_215sdp"
    android:layout_height="@dimen/_40sdp"
    android:layout_marginBottom="@dimen/_8sdp"
    android:layout_marginEnd="@dimen/_8sdp"
    android:layout_marginStart="@dimen/_8sdp"
    android:layout_marginTop="22dp"
    android:background="@drawable/button_backgrond"
    android:text="@string/pay"
    android:textAllCaps="false"
    android:textSize="@dimen/_18sdp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toStartOf="@+id/guideline6"
    app:layout_constraintHorizontal_bias="0.545"
    app:layout_constraintStart_toStartOf="@+id/guideline5"
    app:layout_constraintTop_toBottomOf="@+id/ref_code_txt"
    app:layout_constraintVertical_bias="0.04000002" />

第二个片段

<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:background="@drawable/frag_background"

tools:context=".Bottom_Tabs.Reff_code_frag">



<TextView
    android:id="@+id/textView4"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="76dp"

    android:text="@string/enter_ref"
    app:layout_constraintEnd_toStartOf="@+id/guideline16"
    app:layout_constraintHorizontal_bias="0.47"
    app:layout_constraintStart_toStartOf="@+id/guideline15"
    app:layout_constraintTop_toTopOf="@+id/guideline3" />

<EditText
    android:id="@+id/ref_code_txt"
    android:layout_width="@dimen/_150sdp"
    android:layout_height="@dimen/_40sdp"
    android:background="@drawable/button_with_border"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="36dp"
    android:paddingTop="@dimen/_10sdp"
    android:gravity="center_horizontal"
    android:ems="10"
    android:inputType="textPersonName"
    android:hint="@string/ref_txt_hint"
    app:layout_constraintEnd_toStartOf="@+id/guideline16"
    app:layout_constraintStart_toStartOf="@+id/guideline15"
    app:layout_constraintTop_toBottomOf="@+id/textView4" />

<TextView
    android:id="@+id/textView5"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="16dp"
    android:layout_marginTop="36dp"
    android:text="@string/ref_code"
    app:layout_constraintEnd_toStartOf="@+id/guideline16"
    app:layout_constraintHorizontal_bias="0.48"
    app:layout_constraintStart_toStartOf="@+id/guideline15"
    app:layout_constraintTop_toBottomOf="@+id/ref_code_txt" />

<Button
    android:id="@+id/apply_btn"
    android:layout_width="@dimen/_215sdp"
    android:layout_height="@dimen/_40sdp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="68dp"
    android:background="@drawable/button_backgrond"
    android:text="@string/apply"
    android:textAllCaps="false"
    app:layout_constraintEnd_toStartOf="@+id/guideline16"
    app:layout_constraintHorizontal_bias="0.486"
    app:layout_constraintStart_toStartOf="@+id/guideline15"
    app:layout_constraintTop_toBottomOf="@+id/textView5" />

<Button
    android:id="@+id/cancel_btn"
    android:layout_width="@dimen/_215sdp"
    android:layout_height="@dimen/_40sdp"
    android:layout_marginBottom="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"

    android:text="@string/cancel"
    android:textAllCaps="false"
    android:background="@drawable/button_with_border"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toStartOf="@+id/guideline16"
    app:layout_constraintHorizontal_bias="0.486"
    app:layout_constraintStart_toStartOf="@+id/guideline15"
    app:layout_constraintTop_toBottomOf="@+id/apply_btn"
    app:layout_constraintVertical_bias="0.164" />