I know CardView is not made for this, but in theory if cardCornerRadius = view_size / 2 it should result in circle.
Am I missing something?
Drawing real, animated shadows is not that difficult and you can try to achieve Lollipop's effect on any Android down to Froyo. Here's how it works:
- Draw your view to an offscreen bitmap using LightingColorFilter(0,0)
- Blur that bitmap using ScriptIntrisincBlur. Set the blur radius to your elevation value.
- Draw that blurred bitmap beneath your floating action button.
For an example implementation see:
- Shadow generator, blurs views: https://github.com/ZieIony/Carbon/blob/master/carbon/src/main/java/carbon/shadow/ShadowGenerator.java
- LinearLayout with shadows support, check drawChild() method: https://github.com/ZieIony/Carbon/blob/master/carbon/src/main/java/carbon/widget/LinearLayout.java#L102
Basically Carbon library tries to mimic Lollipop's effect as good as possible. I'm aware of that importing such library might be an overkill, but if you wish you can copy only the interesting part of code and use it in your app.
It is not suggested, it is against pattern. CardView is used for list. You can make your own Floating Action Button and shadow with ImageView.
activity_layout.xml:
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
....
<ImageButton
android:id="@+id/add_courses_button"
android:layout_width="64dp
android:layout_height="64dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_alignParentBottom="true"
android:layout_marginBottom="16dp"
android:layout_marginRight="16dp"
android:background="@drawable/fab"
android:tint="@color/white"
android:src="@drawable/add_image"/>
...
</LinearLayout>
fab.xml:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true">
<layer-list>
<!-- Shadow -->
<item android:top="1dp" android:right="1dp">
<layer-list>
<item>
<shape android:shape="oval">
<solid android:color="#08000000"/>
<padding
android:bottom="3px"
android:left="3px"
android:right="3px"
android:top="3px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#09000000"/>
<padding
android:bottom="2px"
android:left="2px"
android:right="2px"
android:top="2px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#10000000"/>
<padding
android:bottom="2px"
android:left="2px"
android:right="2px"
android:top="2px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#11000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#12000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#13000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#14000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#15000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#16000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
</layer-list>
</item>
<!-- Blue button pressed -->
<item>
<shape android:shape="oval">
<solid android:color="#0099cc"/>
</shape>
</item>
</layer-list>
</item>
<item android:state_enabled="true">
<layer-list>
<!-- Shadow -->
<item android:top="1dp" android:right="1dp">
<layer-list>
<item>
<shape android:shape="oval">
<solid android:color="#08000000"/>
<padding
android:bottom="3px"
android:left="3px"
android:right="3px"
android:top="3px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#09000000"/>
<padding
android:bottom="2px"
android:left="2px"
android:right="2px"
android:top="2px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#10000000"/>
<padding
android:bottom="2px"
android:left="2px"
android:right="2px"
android:top="2px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#11000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#12000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#13000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#14000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#15000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
<item>
<shape android:shape="oval">
<solid android:color="#16000000"/>
<padding
android:bottom="1px"
android:left="1px"
android:right="1px"
android:top="1px"
/>
</shape>
</item>
</layer-list>
</item>
<!-- Blue button -->
<item>
<shape android:shape="oval">
<solid android:color="#33b5e5"/>
</shape>
</item>
</layer-list>
</item>
</selector>
Result is like this:
Technically seems like possible but practially it doesn't.
If you want to use the button like that, I suggest you to use this library. It works pretty well. https://github.com/navasmdc/MaterialDesignLibrary
来源：https://stackoverflow.com/questions/29005554/is-it-possible-to-use-cardview-to-make-shadow-for-floating-action-button