FloatingActionBar has a exception about layout_anchor

Question

problem

When I add property @id/appbar for layout_anchor, layout_anchor give me an exception: Unexpected resource type: 'id' expected: string

I try to fix it by adding a string value, like this

<string name="fab_anchor">\@id/appbar</string>

but it did not work, and throws a exception. What should I do?

there is my xml code

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 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">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appbar"
        android:layout_height="192dp"
        android:layout_width="match_parent">

        <com.google.android.material.appbar.CollapsingToolbarLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:toolbarId="@+id/toolbar"
            app:layout_scrollFlags="scroll|enterAlways|enterAlwaysCollapsed"

            app:contentScrim="?attr/colorPrimary">

            <androidx.appcompat.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_height="?attr/actionBarSize"
                android:layout_width="match_parent" />

        </com.google.android.material.appbar.CollapsingToolbarLayout>
    </com.google.android.material.appbar.AppBarLayout>

    <androidx.core.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"


        app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior">

        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent" >

            <TextView
                android:id="@+id/textView5"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/large_content"
                android:layout_marginTop="@dimen/fab_margin"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

        </androidx.constraintlayout.widget.ConstraintLayout>

    </androidx.core.widget.NestedScrollView>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:src="@drawable/ic_add_black_24dp"
        app:backgroundTint="@color/colorLoginButton"
        app:layout_anchor="@+id/appbar"
        app:layout_anchorGravity="center|bottom" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

and I also add this to my build.gradle(Module:app)

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.yq.signin"
        minSdkVersion 15
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        dataBinding {
            enabled true
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    lintOptions{
        disable "ResourceType"
    }
}

Answer 1

• You can add layout_anchor respect to NestedScrollView.
• Use app:layout_behavior="@string/appbar_scrolling_view_behavior"

Demo

<androidx.core.widget.NestedScrollView
        android:id="@+id/scrollView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"             
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent" >

            <TextView
                android:id="@+id/textView5"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/large_content"
                android:layout_marginTop="@dimen/fab_margin"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

        </androidx.constraintlayout.widget.ConstraintLayout>

    </androidx.core.widget.NestedScrollView>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:src="@drawable/ic_add_black_24dp"
        app:backgroundTint="@color/colorLoginButton"
        app:layout_anchor="@id/scrollView"
        app:layout_anchorGravity="center|bottom" />

Then Clean-Rebuild-Run