The following classes could not be instantiated - android support v7 widget Toolbar

Question

I am creating an app with the new Material Design used in Android Lollipop  5 0    I am using the following guides    http   android-developers blogspot it 2014 10 appcompat-v21-material-design-for-pre html http   antonioleiva com material-design-everywhere    After I create my toolbar  I receive this error   The following classes could not be instantiated  -  android support v7 widget Toolbar   The app works well in the phone or emulator  but the layout designer of Android Studio doesn t show the layout correctly   Here there are some images   Error in my awesome toolbar xml layout preview   Error in activity my xml layout preview   The xml code of the files   my awesome toolbar xml    lt  xml version  1 0  encoding  utf-8   gt    lt android support v7 widget Toolbar xmlns android  http   schemas android com apk res android  android id    id my awesome toolbar  android layout height  wrap content  android layout width  match parent  android minHeight   attr actionBarSize  android background   attr colorPrimary    gt    activity my xml    lt 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 id    id root              tools context  com myapp test MyActivity              android orientation  horizontal  gt        lt include         android id    id toolbar          layout   layout my awesome toolbar            gt       lt  -- Rest of layout -- gt   lt  RelativeLayout gt    MyActivity java   package com myapp test   import android os Bundle  import android support v7 app ActionBarActivity  import android support v7 widget Toolbar  import android view Menu  import android view MenuItem    public class MyActivity extends ActionBarActivity         Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity my            Toolbar toolbar    Toolbar  findViewById R id toolbar           setSupportActionBar toolbar                Override     public boolean onCreateOptionsMenu Menu menu               Inflate the menu  this adds items to the action bar if it is present          getMenuInflater   inflate R menu my  menu           return true              Override     public boolean onOptionsItemSelected MenuItem item               Handle action bar item clicks here  The action bar will            automatically handle clicks on the Home Up button  so long            as you specify a parent activity in AndroidManifest xml          int id   item getItemId            if  id    R id action settings                return true                    return super onOptionsItemSelected item             xml code of the styles  values styles xml     lt resources gt        lt style name  AppTheme  parent  Theme AppCompat Light NoActionBar  gt           lt item name  colorPrimary  gt  color blue lt  item gt           lt item name  colorPrimaryDark  gt  color dark blue lt  item gt           lt item name  actionOverflowButtonStyle  gt  style AppTheme OverflowButtonStyle lt  item gt       lt  style gt        lt  -- Style Title -- gt       lt style name  Title  gt           lt item name  android textColor  gt  color white lt  item gt           lt item name  android textStyle  gt bold lt  item gt           lt item name  android textSize  gt 16sp lt  item gt       lt  style gt        lt style name  AppTheme OverflowButtonStyle  parent  Widget AppCompat ActionButton Overflow  gt           lt item name  android src  gt  drawable overflow icon lt  item gt       lt  style gt   lt  resources gt    At the moment I use Android Studio Beta 0 8 9

User · Answer

I changed the res values styles xml file from this    lt style name  AppTheme  parent  Theme AppCompat Light DarkActionBar  gt    to this    lt style name  AppTheme  parent  Base Theme AppCompat Light DarkActionBar  gt    and that solved the problem

User · Answer

My Problem has also been solved by changing in styles xml   lt  -- Base application theme  -- gt   lt style name  AppTheme  parent  Base Theme AppCompat Light DarkActionBar  gt

User · Answer

I had the same problem for one of the activities in my app   one of the causes of this problem is that Theme in the theme editor might be different than the theme defined in the  styles xml  change the Theme in the theme editor to your  Apptheme  or your custom defined theme if you have defined   Doing this fixed my issue

User · Answer

Find styles xml in app res values folder   Parent attribute of the style could be missing  Base   It should start as   lt style name  AppTheme  parent  Base Theme AppCompat

User · Answer

From  https   stackoverflow com a 29989542 4123403   Clean project Rebuild project Sync Gradle   This did the trick for me

User · Answer

For Android Studio  or IntelliJ IDEA     If everything looks OK in your project and that you re still receiving the error in all your layouts  try to  Invalidate caches  amp  restart    Wait until Android Studio has finished to create all the caches  amp  indexes

User · Answer

I did what  ang lee said and also i added this line to the app theme style     lt item name  windowActionBar  gt false lt  item gt    i am using version 26 0 1     com android support design 26 0 1 com android support appcompat-v7 26 0 1   building tools   buildToolsVersion  26 0 1

User · Answer

Sorry if I answer myself  but  at the finally  the solution of my problem was update Android Studio to the new version 0 8 14 by Canary Channel  http   tools android com recent   After the update  the problem is gone     I leave this question here for those who have this problem in the future

User · Answer

The solutions above didn t help me  I ve tried 2 first steps from  this link  Worked fine for me   But don t forget to   import com melnykov fab FloatingActionButton     instead of   import android support design widget FloatingActionButton    in your MainActivity java

User · Answer

I did what  gbero said  and I changed the Android version number that Studio uses from 22 to 17 and it works   I am using the backwards compatibility to build for Android ver 22 but to target 17  idk if that s correctly said  I am still trying to figure this app stuff out  so that triggered the backwards compatibility  which afaik is what the android support v7   is  This is probably a bug with their rendering code  Not sure if clearing the cache as suggested above was needed as rendering didn t work just after invalidating the cache  it started working after I changed the version to render  If I change back to version 22  the rendering breaks  if I switch back to 17  it works again

User · Answer

I had the same error   Eventually I got this notice that a plugin was out of date     After I updated  the problem went away

User · Answer

I use android studio 2 3 3  - Open styles xml - Android studio will show a notification on the top right with two options   open editor  and  Hide notification   - Click  open editor  - Under theme parent dropdown  click show all themes - Select any theme starting with AppCompat     I used AppComat DayNight   NB  If your title bar disappears  you need to extend AppCompatActivity instead of Activity   All the best

User · Answer

Another mistake that can have the same effect can be the wrong theme in the preview  For some reason I had selected some other theme here  After choosing my AppTheme it worked fine again

User · Answer

none of above worked for me   i updated the appCompat - v7  version in my app gradle file from 23 to 25 3 1  helped to make it work for me

User · Answer

Clean project Rebuild project Sync Gradle   it work for me

User · Answer

I had the same error on my Android Studio screen when i wanted to prevew my project  I fix the problem by this ways   1- I chang the version from 22 to 21  But if I change back to version 22  the rendering breaks  if I switch back to 21  it works again  Thank you  Overloaded Operator  I updated my Android Studio but not working  Thank you  Salvuccio96

[java] The following classes could not be instantiated: - android.support.v7.widget.Toolbar

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