android - Error when adding CardView to layout

Question

I wanted to try out the new toys that google gave us and I've run into some trouble.

Here is my build.gradle:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 'android-L'
    buildToolsVersion "20.0.0"

    defaultConfig {
        applicationId "com.tod.android.lpreviewtest"
        minSdkVersion 'L'
        targetSdkVersion 'L'
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            runProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

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

Now my layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MyActivity">
    <android.support.v7.widget.CardView
        xmlns:card_view="http://schemas.android.com/apk/res-auto"
        android:id="@+id/card_view"
        android:layout_gravity="center"
        android:layout_width="200dp"
        android:layout_height="200dp"
        card_view:cardCornerRadius="4dp">

        <TextView
            android:id="@+id/info_text"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </android.support.v7.widget.CardView>
</RelativeLayout>

When I switch to screen preview in android studio, I get a render error:

Rendering Problems The following classes could not be instantiated:
-?android.support.v7.widget.CardView (Open Class, Show Exception)

Exception Details java.lang.ClassFormatError: Illegal field name "CardView.Dark"         
in class android/support/v7/cardview/R$style  at
java.lang.ClassLoader.defineClass1(ClassLoader.java:-2) ??at
java.lang.ClassLoader.defineClass(ClassLoader.java:792) ??at 
java.lang.ClassLoader.defineClass(ClassLoader.java:635) ??at 
java.lang.ClassLoader.loadClass(ClassLoader.java:424) ??at 
java.lang.ClassLoader.loadClass(ClassLoader.java:411) ??at 
java.lang.ClassLoader.loadClass(ClassLoader.java:357) ??at 
android.support.v7.widget.CardView.initialize(CardView.java:69) ??at 
android.support.v7.widget.CardView.<init>(CardView.java:60) ??at 
java.lang.reflect.Constructor.newInstance(Constructor.java:526) ??at 
android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:802) ??at 
android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64) ??at 
android.view.LayoutInflater.rInflate(LayoutInflater.java:778) ??at 
android.view.LayoutInflater.inflate(LayoutInflater.java:500) ??at 
android.view.LayoutInflater.inflate(LayoutInflater.java:381)

I tried ignoring the error and running the app in an avd and while everything compiles fine, no cardview appears in the layout. Please help!

P.s. I'm using the new Android Studio beta 0.8.0

Answer 1

I was able to get it to work on the emulator by changing my build.gradle to this:

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

Make sure you have the support repository installed from the SDK Manager! Hope this helps

EDIT: as someone suggested using 'com.android.support:cardview-v7:23.1' is a better practice but it not required.