Android：Intellij Buttom 导航模板创建未使用的空间，隐藏其下的节点

Question

I created an Android project in Intellij with the buttom nav template. I can not use a certain space on the top (see screenshot) which corelates in size with the buttom nav bar, even though the constrains seem to be right. As well it hides/converes elements which are placed under it, actually there is a TextView and a spinner.

<?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:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingTop="?attr/actionBarSize">

    <com.google.android.material.bottomnavigation.BottomNavigationView
            android:id="@+id/nav_view"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="0dp"
            android:layout_marginEnd="0dp"
            android:background="?android:attr/windowBackground"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:menu="@menu/bottom_nav_menu"/>

    <fragment
            android:id="@+id/nav_host_fragment_activity_main"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:defaultNavHost="true"
            app:navGraph="@navigation/mobile_navigation"
            android:scrollbars="vertical" app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintBottom_toTopOf="@+id/nav_view" android:layout_marginBottom="40dp"
            android:paddingBottom="40dp"/>

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

You have to remove the fragment height from wrap_content to 0dp ie match_constraint ( match_parent )

match_constraint or 0dp : The view expands as much as possible to meet the constraints on each side (after accounting for the view's margins).

Chain : A chain is a group of views that are linked to each other with bi-directional position constraints. The views within a chain can be distributed either vertically or horizontally. For your case we need a Vertical Chain. See video

And last I remove the android:paddingTop="?attr/actionBarSize" from you ConstraintLayout

Try the below code:

<?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:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">


<fragment
    android:id="@+id/nav_host_fragment_activity_main"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:scrollbars="vertical"
    app:defaultNavHost="true"
    android:name="androidx.navigation.fragment.NavHostFragment"
    app:layout_constraintBottom_toTopOf="@+id/nav_view"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.5"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:navGraph="@navigation/mobile_navigation" />
<com.google.android.material.bottomnavigation.BottomNavigationView
    android:id="@+id/nav_view"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:background="?android:attr/windowBackground"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/nav_host_fragment_activity_main"
    app:menu="@menu/bottom_nav_menu"/>

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 2

Remove

android:paddingTop="?attr/actionBarSize"

from your root ConstraintLayout.