XML : Android - Unable to instantiate cardview

The following is the stack trace I got when I used CardView support library

  java.lang.NoClassDefFoundError: android/support/v7/cardview/R$color      at android.support.v7.widget.CardView.initialize(CardView.java:227)      at android.support.v7.widget.CardView.<init>(CardView.java:113)      at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)      at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)      at java.lang.reflect.Constructor.newInstance(Constructor.java:423)      at org.jetbrains.android.uipreview.ViewLoader.createNewInstance(ViewLoader.java:465)      at org.jetbrains.android.uipreview.ViewLoader.loadClass(ViewLoader.java:172)      at org.jetbrains.android.uipreview.ViewLoader.loadView(ViewLoader.java:105)      at com.android.tools.idea.rendering.LayoutlibCallbackImpl.loadView(LayoutlibCallbackImpl.java:178)      at android.view.BridgeInflater.loadCustomView(BridgeInflater.java:247)      at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:171)      at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)      at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:858)      at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:70)      at android.view.LayoutInflater.rInflate(LayoutInflater.java:834)      at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)      at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:861)      at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:70)      at android.view.LayoutInflater.rInflate(LayoutInflater.java:834)      at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)      at android.view.LayoutInflater.inflate(LayoutInflater.java:518)      at android.view.LayoutInflater.inflate(LayoutInflater.java:397)      at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:317)      at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:429)      at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:389)      at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:548)      at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:533)      at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:966)      at com.android.tools.idea.rendering.RenderTask.createRenderSession(RenderTask.java:533)      at com.android.tools.idea.rendering.RenderTask.lambda$inflate$58(RenderTask.java:659)      at com.android.tools.idea.rendering.RenderService.runRenderAction(RenderService.java:380)      at com.android.tools.idea.rendering.RenderTask.inflate(RenderTask.java:659)      at com.android.tools.idea.uibuilder.model.NlModel.inflate(NlModel.java:327)      at com.android.tools.idea.uibuilder.model.NlModel.updateModel(NlModel.java:373)      at com.android.tools.idea.uibuilder.model.NlModel$1.run(NlModel.java:237)      at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:333)      at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:323)      at com.intellij.util.ui.update.MergingUpdateQueue$3.run(MergingUpdateQueue.java:267)      at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:282)      at com.intellij.util.ui.update.MergingUpdateQueue.run(MergingUpdateQueue.java:234)      at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:238)      at com.intellij.util.Alarm$Request$1.run(Alarm.java:378)      at com.intellij.util.Alarm$Request.run(Alarm.java:389)      at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)      at java.util.concurrent.FutureTask.run(FutureTask.java:266)      at com.intellij.util.concurrency.SchedulingWrapper$MyScheduledFutureTask.run(SchedulingWrapper.java:227)      at com.intellij.util.concurrency.BoundedTaskExecutor$2.run(BoundedTaskExecutor.java:187)      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)      at java.lang.Thread.run(Thread.java:745)    

this happened when I created a CardView for a scrollview inside a Linear Layout. Here is the xml for the activity

  <?xml version="1.0" encoding="utf-8"?>  <LinearLayout 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"      android:id="@+id/activity_list"      android:layout_width="match_parent"      android:layout_height="match_parent"      tools:context="com.example.user.myapplication.ListActivity">        <ScrollView          android:layout_width="match_parent"          android:layout_height="match_parent">        <android.support.v7.widget.CardView android:layout_width="match_parent"          android:layout_height="wrap_content">          <ImageView              android:layout_width="match_parent"              android:layout_height="wrap_content" />      </android.support.v7.widget.CardView>          </ScrollView>        </LinearLayout>    

can somebody explain the cause of this error