No shadow by default on Toolbar?

问题

I'm updating my app with the new Toolbar from the support library v21. My problem is that the toolbar does not cast any shadow if I don't set the "elevation" attribute. Is that the normal behavior or I'm doing something wrong?

My code is:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   android:orientation="vertical">

   <android.support.v7.widget.Toolbar
       xmlns:app="http://schemas.android.com/apk/res-auto"
       android:id="@+id/my_awesome_toolbar"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:background="?attr/colorPrimary"
       android:elevation="4dp"
       android:minHeight="?attr/actionBarSize"
       app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
       app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

   <FrameLayout
       android:id="@+id/FrameLayout1"
       android:layout_width="match_parent"
       android:layout_height="match_parent">
       .
       .
       .

And in my Activity - OnCreate method:

    Toolbar toolbar = (Toolbar) findViewById(R.id.my_awesome_toolbar);
    setSupportActionBar(toolbar);

回答1:

I ended up setting my own drop shadow for the toolbar, thought it might helpful for anyone looking for it:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:app="http://schemas.android.com/apk/res-auto"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_gravity="top"
              android:orientation="vertical">

    <android.support.v7.widget.Toolbar android:id="@+id/toolbar"
                                       android:layout_width="match_parent"
                                       android:layout_height="wrap_content"
                                       android:background="@color/color_alizarin"
                                       android:titleTextAppearance="@color/White"
                                       app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"/>

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

        <!-- **** Place Your Content Here **** -->

        <View android:layout_width="match_parent"
              android:layout_height="5dp"
              android:background="@drawable/toolbar_dropshadow"/>

    </FrameLayout>

</LinearLayout>

@drawable/toolbar_dropshadow:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" 
       android:shape="rectangle">

    <gradient android:startColor="@android:color/transparent"
              android:endColor="#88333333"
              android:angle="90"/>

</shape>

@color/color_alizarin

<color name="color_alizarin">#e74c3c</color>

回答2:

Google released the Design Support library a few weeks ago and there is a nifty solution for this problem in this library.

Add the Design Support library as a dependency in build.gradle :

compile 'com.android.support:design:22.2.0'

Add AppBarLayout supplied by the library as a wrapper around your Toolbar layout to generate a drop shadow.

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
       <android.support.v7.widget.Toolbar
           .../>
    </android.support.design.widget.AppBarLayout>

Here is the result :

There are lots of other tricks with the design support library.

1. http://inthecheesefactory.com/blog/android-design-support-library-codelab/en
2. http://android-developers.blogspot.in/2015/05/android-design-support-library.html

AndroidX

As above but with dependency:

implementation 'com.google.android.material:material:1.0.0'

and com.google.android.material.appbar.AppBarLayout

回答3:

You can't use the elevation attribute before API 21 (Android Lollipop). You can however add the shadow programmatically, for example using a custom view placed below the Toolbar.

@layout/toolbar

<android.support.v7.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/blue"
    android:minHeight="?attr/actionBarSize"
    app:theme="@style/ThemeOverlay.AppCompat.ActionBar" />

<View
    android:id="@+id/toolbar_shadow"
    android:layout_width="match_parent"
    android:layout_height="3dp"
    android:background="@drawable/toolbar_dropshadow" />

@drawable/toolbar_dropshadow

<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
    <gradient
        android:startColor="@android:color/transparent"
        android:endColor="#88333333"
        android:angle="90"/> </shape>

in your activity layout <include layout="@layout/toolbar" />

回答4:

Use /values folders to apply the correct shadow style based on OS version.

For under 5.0 devices, use /values/styles.xml to add windowContentOverlay to the body of your activity:

<style name="MyViewArea">
    <item name="android:foreground">?android:windowContentOverlay</item>
</style>

<style name="MyToolbar">
    <item name="android:background">?attr/colorPrimary</item>
</style>

Then add your own custom shadow by changing your Theme to include:

<item name="android:windowContentOverlay">@drawable/bottom_shadow</item>

You can grab Google's IO app shadow resource here: https://github.com/google/iosched/blob/master/android/src/main/res/drawable-xxhdpi/bottom_shadow.9.png

For 5.0 devices & later, use /values-v21/styles.xml to add elevation to your toolbar using a custom header style:

<style name="MyViewArea">
</style>

<style name="MyToolbar">
    <item name="android:background">?attr/colorPrimary</item>
    <item name="android:elevation">4dp</item>
</style>

Note that in the second case, I had to create an empty MyViewArea style so the windowContentOverlay wouldn't show up too.

[Update: changed resource names and added Google shadow.]

回答5:

This worked for me very well:

<android.support.v7.widget.CardView
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/primary"
    card_view:cardElevation="4dp"
    card_view:cardCornerRadius="0dp">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/primary"
        android:minHeight="?attr/actionBarSize" />

</android.support.v7.widget.CardView>

回答6:

If you are seting the ToolBar as ActionBar then just call:

getSupportActionBar().setElevation(YOUR_ELEVATION);

Note: This must be called after setSupportActionBar(toolbar);

回答7:

My problem is that the toolbar does not cast any shadow if I don't set the "elevation" attribute. Is that the normal behavior or I'm doing something wrong?

That's the normal behavior. Also see the FAQ at the end of this post.

回答8:

Was toying with this for hours, here's what worked for me.

Remove all the elevation attributes from the appBarLayout and Toolbar widgets (including styles.xml if you are applying any styling).

Now inside activity,apply the elvation on your actionBar:

Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setElevation(3.0f);

This should work.

回答9:

i added

<android.support.v7.widget.Toolbar
...
android:translationZ="5dp"/>

in toolbar description and it works for me. Using 5.0+

回答10:

You can also make it work with RelativeLayout. This reduces layout nesting a little bit ;)

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

    <include
        android:id="@+id/toolbar"
        layout="@layout/toolbar" />

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/toolbar" />

    <View
        android:layout_width="match_parent"
        android:layout_height="5dp"
        android:layout_below="@id/toolbar"
        android:background="@drawable/toolbar_shadow" />
</RelativeLayout>

回答11:

actionbar_background.xml

    <item>
        <shape>
            <solid android:color="@color/black" />
            <corners android:radius="2dp" />
            <gradient
                android:startColor="@color/black"
                android:centerColor="@color/black"
                android:endColor="@color/white"
                android:angle="270" />
        </shape>
    </item>

    <item android:bottom="3dp" >
        <shape>

            <solid android:color="#ffffff" />
            <corners android:radius="1dp" />
        </shape>
    </item>
</layer-list>

add to actionbar_style background

<style name="Theme.ActionBar" parent="style/Widget.AppCompat.Light.ActionBar.Solid">
    <item name="background">@drawable/actionbar_background</item>
    <item name="android:elevation">0dp</item>
    <item name="android:windowContentOverlay">@null</item>
    <item name="android:layout_marginBottom">5dp</item>

name="displayOptions">useLogo|showHome|showTitle|showCustom

add to Basetheme

<style name="BaseTheme" parent="Theme.AppCompat.Light">
   <item name="android:homeAsUpIndicator">@drawable/home_back</item>
   <item name="actionBarStyle">@style/Theme.ActionBar</item>
</style>

回答12:

Most solutions work fine here. Would like to show another, similar alternative :

gradle:

implementation 'androidx.appcompat:appcompat:1.0.0-rc02'
implementation 'com.google.android.material:material:1.0.0-rc02'
implementation 'androidx.core:core-ktx:1.0.0-rc02'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'

You layout can have a Toolbar View, and a shadow for it, below, similar to this (need modification of course) :

<LinearLayout
    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:orientation="vertical">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:titleTextAppearance="@style/Base.TextAppearance.Widget.AppCompat.Toolbar.Title"/>

    <include
        layout="@layout/toolbar_action_bar_shadow"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

res/drawable-v21/toolbar_action_bar_shadow.xml

<androidx.appcompat.widget.AppCompatImageView
    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
    android:layout_height="wrap_content" android:src="@drawable/msl__action_bar_shadow"/>

res/drawable/toolbar_action_bar_shadow.xml

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent" android:layout_height="wrap_content"
    android:foreground="?android:windowContentOverlay" tools:ignore="UnusedAttribute"/>

res/drawable/msl__action_bar_shadow.xml

<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
    <item>
        <shape
            android:dither="true"
            android:shape="rectangle" >
            <gradient
                android:angle="270"
                android:endColor="#00000000"
                android:startColor="#33000000" />

            <size android:height="10dp" />
        </shape>
    </item>

</layer-list>

styles.xml

<resources>
    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>
</resources>

MainActivity.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar as Toolbar)
    }
}

Full sample here, as I've noticed the IDE has a bug of saying foreground attribute is too new to be used here.

回答13:

All you need is a android:margin_bottom equal to the android:elevation value. No AppBarLayout, clipToPadding, etc. required.

Example:

<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:layout_marginBottom="4dp"
    android:background="@android:color/white"
    android:elevation="4dp">

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

        <!--Inner layout goes here-->

    </androidx.constraintlayout.widget.ConstraintLayout>
</androidx.appcompat.widget.Toolbar>

回答14:

For 5.0 + : You can use AppBarLayout with Toolbar. AppBarLayout has "elevation" attribure.

 <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:elevation="4dp"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <include layout="@layout/toolbar" />
    </android.support.design.widget.AppBarLayout>

回答15:

I had similar problem with the shadow. The shadow is drawn by direct parent of AppBarLayout in my case. If height of the parent is the same as AppBarLayout's the shadow cannot be drawn. So checking size of the parent layout and maybe layout remake can solve the problem. https://www.reddit.com/r/androiddev/comments/6xddb0/having_a_toolbar_as_a_fragment_the_shadow/

回答16:

The correct answer will be to add
android:backgroundTint="#ff00ff" to the tool bar with android:background="@android:color/white"

If you use other color then white for the background it will remove the shadow. Nice one Google!

来源：https://stackoverflow.com/questions/26575197/no-shadow-by-default-on-toolbar