android - How to add a gradient to a ImageView nested in a CollapsingToolbar

Question

I'am working on an Android app with material design. I have a detail view with a CollapsingToolbarLayout and a ImageView (works fine so far). Unfortunately the title is not readable if there is a bright image. So far I tried to add a gradient (Add gradient to imageview) but this solution didn't work for me because of the CollapsingToolbarLayout. Here you can see my code:

<android.support.design.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"
android:fitsSystemWindows="true">

<android.support.design.widget.AppBarLayout
    android:layout_height="256dp"
    android:layout_width="match_parent"
    android:fitsSystemWindows="true"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">


    <android.support.design.widget.CollapsingToolbarLayout
        android:id="@+id/collapsing_toolbar"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_scrollFlags="scroll|exitUntilCollapsed"
        app:contentScrim="@color/primary"
        android:fitsSystemWindows="true"
        app:expandedTitleMarginEnd="50dp"
        app:expandedTitleMarginStart="50dp"
        >


        <!--<View
            android:background="@drawable/actionbar_gradient_dark"
        />-->
            <ImageView
                android:id="@+id/backimg"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:fitsSystemWindows="true"
                app:layout_collapseMode="parallax"
                android:scaleType="centerCrop"
                app:layout_scrollFlags="scroll|enterAlways"
                />

        <android.support.v7.widget.Toolbar
            android:id="@+id/detailToolbar"
            android:layout_height="?attr/actionBarSize"
            android:layout_width="match_parent"
            app:layout_collapseMode="pin"
            app:layout_collapseParallaxMultiplier="0.7"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>

    </android.support.design.widget.CollapsingToolbarLayout>

Does anyone know a solution for this issue?

Answer 1

Wrap your ImageView in a FrameLayout and add a View with a background:

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/backimg"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        app:layout_collapseMode="parallax"
        android:scaleType="centerCrop"
        android:src="@drawable/image"
        app:layout_scrollFlags="scroll|enterAlways" />
    <View
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/actionbar_gradient_dark" />
</FrameLayout>

Make sure your gradient is something like this:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >
    <gradient
        android:angle="90"
        android:endColor="@android:color/transparent"
        android:startColor="@android:color/black" />
    <corners android:radius="0dp" />
</shape>