How to align Floating Action Button to end|bottom

Question

I have one FloatingActionButton. I want it to be end|bottom like

What I want

this.

Currently, My design is like this

What I have

I want it to be at the exact end|bottom of the screen. How to do that? Which layout is best to use?

This is my whole xml code

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:padding="30dp">


    <ImageView
        android:id="@+id/post_request_back_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:src="@drawable/general_back_icon" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:fontFamily="@font/muli_black"
        android:text="@string/_post_request_header_name"
        android:textAllCaps="true"
        android:textColor="@color/colorAccent"
        android:textSize="30sp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:text="@string/how_requests_work"
        android:textColor="@color/colorAccent"
        android:textSize="10sp" />

    <ListView
        android:id="@+id/postlist"
        android:layout_width="match_parent"
        android:layout_height="420dp"
        android:layout_marginStart="0dp"
        android:layout_marginTop="10dp"
        android:layout_marginEnd="0dp"
        app:layout_constraintBottom_toTopOf="@+id/postadd"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0" />


    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/postadd"
        android:layout_marginTop="20dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="16dp"
        android:src="@drawable/postrequest_add_btn" />


</LinearLayout> 

Answer 1

You can wrap your FAB button into a RelativeLayout and keep other views in your LinearLayout

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="30dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <ImageView
            android:id="@+id/post_request_back_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="5dp"
            android:src="@drawable/general_back_icon" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:fontFamily="@font/muli_black"
            android:text="@string/_post_request_header_name"
            android:textAllCaps="true"
            android:textColor="@color/colorAccent"
            android:textSize="30sp" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:text="@string/how_requests_work"
            android:textColor="@color/colorAccent"
            android:textSize="10sp" />

        <ListView
            android:id="@+id/postlist"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp" />

    </LinearLayout>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/postadd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentBottom="true"
        android:layout_margin="16dp"
        android:layout_marginTop="20dp"
        android:src="@drawable/postrequest_add_btn" />


</RelativeLayout>

Note: I removed the Constraints you added to the ListView as they are related to ConstraintLayout, also made its height as wrap_content

And here is with the ConstraintLayout

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="30dp">

    <ImageView
        android:id="@+id/post_request_back_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:src="@drawable/general_back_icon"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tv_post_request_header_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:fontFamily="@font/muli_black"
        android:text="@string/_post_request_header_name"
        android:textAllCaps="true"
        android:textColor="@color/colorAccent"
        android:textSize="30sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/post_request_back_button" />

    <TextView
        android:id="@+id/id_how_requests_work"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:text="@string/how_requests_work"
        android:textColor="@color/colorAccent"
        android:textSize="10sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tv_post_request_header_name" />

    <ListView
        android:id="@+id/postlist"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_how_requests_work" />


    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/postadd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_margin="16dp"
        android:layout_marginTop="20dp"
        android:src="@drawable/postrequest_add_btn" />

</androidx.constraintlayout.widget.ConstraintLayout>