Android AppCompat 21 Elevation

问题

Is there any way to add elevation to a View in pre-lollipop devices without wrapping them in a CardView?

回答1:

ViewCompat.setElevation(View, int) currently creates no shims.

The only way to simulate elevation right now is to apply a shadow pre-v21. Define your style/layout/drawable in values and override it in values-v21. For buttons I use style overrides. For layouts, I usually go for reference override (use @null to get rid of a drawable).

Hopefully in the future an update to the support library will add shims.

This reddit thread keeps track of said update.

Edit

The new support design library actually does create shims for the floating action button.

回答2:

This is an example how to add a shadow below the Toolbar on pre-lollipop devices:

The layout should be this:

<RelativeLayout
    android:id="@+id/toolbar_container"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true" >

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

    <View
        android:id="@+id/toolbar_shadow"
        android:layout_width="match_parent"
        android:layout_height="@dimen/toolbar_shadow"
        android:layout_below="@id/toolbar"
        android:background="@drawable/toolbar_dropshadow" />
</RelativeLayout>

And the shadow is:

<?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="#88444444"
        android:startColor="@android:color/transparent" />

</shape>

回答3:

I achieve same effect using,

  android:background="@android:drawable/dialog_holo_light_frame"

My tested output:

reference - https://stackoverflow.com/a/25683148/3879847

Update : If you want change color of this drawable try @Irfan answer

https://stackoverflow.com/a/40815944/3879847

回答4:

You can now use the schema xmlns:app="http://schemas.android.com/apk/res-auto" and app:elevation

<?xml version="1.0" encoding="utf-8"?>
<layout 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">
...

<LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|end"
            app:elevation="5dp">

来源：https://stackoverflow.com/questions/26728570/android-appcompat-21-elevation