“android:elevation=” doesn't work on devices pre-Lollipop with compile API21

问题

I'm trying to use "android: elevation =" in my application but once I run it does not appear in the device with android 4.1.2

gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "com.example.alvaro.proyectocaronte"
        minSdkVersion 14
        targetSdkVersion 21
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:21.0.3'
}

layout.xml

<RelativeLayout
                android:layout_width="1100dp"
                android:layout_height="fill_parent"
                android:background="@drawable/rounded_corner"
                android:layout_alignParentTop="true"
                android:layout_alignParentRight="true"
                android:layout_alignParentEnd="true"
                android:layout_marginRight="93dp"
                android:layout_marginEnd="93dp"
                android:elevation="3dp"/>

maybe I'm not compiling correctly Lollipop for pre-lollipop devices, Any suggestions?

If you need to see other parts of the code, I'll edit the question

Thanks

回答1:

Elevation requires the device to run Lollipop. See this answer on how to simulate elevation https://stackoverflow.com/a/26747592/680249

回答2:

UPDATED ::

1. Best Practice to do that is

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

   and add library for cardview

   dependencies {
      ...
      compile 'com.android.support:cardview-v7:21.0.+'
    }
   

2. On Pre-Lollipop you can use this drawable

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

   it will give you the look of elevation

3. you can create your own like this

   <?xml version="1.0" encoding="utf-8"?>
   <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
   
   <item>
   <shape android:shape="rectangle">
       <solid android:color="#BDBDBD"/>
       <corners android:radius="5dp"/>
   </shape>
   </item>
   
   <item
   android:left="0dp"
   android:right="0dp"
   android:top="0dp"
   android:bottom="2dp">
   <shape android:shape="rectangle">
       <solid android:color="#ffffff"/>
       <corners android:radius="5dp"/>
   </shape>
   </item>
   </layer-list>
   

reference

回答3:

You can also use a CardView from the support library to implement surfaces.
To do so add a dependency to your build.gradle:

compile 'com.android.support:cardview-v7:23.1.1'

And then simply use it in your layouts:

  <android.support.v7.widget.CardView
      android:layout_width="match_parent"
      android:layout_height="150dp"
      android:layout_margin="16dp"
      android:background="#fff"
      >
  </android.support.v7.widget.CardView>

Here you have a quite more options to customise it comparing to using @android:drawable/dialog_holo_light_frame as a background

EDIT:
Also notice, that this approach allows you to simply implement
Material Design on Pre-Lolipop devices.
You can change the elevation,
round the corners etc.
To do so you have to:

 app:cardElevation="8dp"
 app:cardCornerRadius="8dp"
 app:contentPadding="5dp">

And not forget to add xmlns:app="http://schemas.android.com/apk/res-auto" to the root layout.

Also you can easily change the elevation in your code:

CardView card = (CardView) findViewById(R.id.yourPreetyCoolCardView);
card.setCardElevation(getResources()
    .getDimension(R.dimen.card_picked_up_elevation));

Use 8dp for picked up and 2dp for resting (usual) state and you will be awesome.

回答4:

As described here, you can mimic the elevation on pre-lollipop with:

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

来源：https://stackoverflow.com/questions/27693843/androidelevation-doesnt-work-on-devices-pre-lollipop-with-compile-api21