IssueTracker

check your v21 style, you might never extended the right parent which causes this issue.

@1 According to the docs and the error, I need to extend from the styles of the support library ("You need to use a Theme.AppCompat theme") , which is what I do. It worked before, so it should work fine now too.

My app uses a theme which extends Theme.AppCompat. It works with Proguard disabled but crashes when enabled. It's not just a problem with dinamically setting the theme.

@3 I see. I have no idea then what causes it, as when I try it on a new project it actually works fine.

My demo project depend on com.google.android.gms:play-services-analytics, with version 7.8.0, it works fine, with 8.1.0, this same problem occurs. I also have my app theme extend from Theme.AppCompat. The problem only occurs in release build. The behavior of the problem is the same with android support library version 23.0.1.

If it works with a clean project then it's not an Support Library issue. Over to Tor to see if it's a shrinkResources issue.

@6 I don't know who or what Tor is, but there is definitely a lot of compilation problems over the past new updates of all that's related to Google and Android.

@6 Here. I got to a sample that shows this issue.
Attached sample project. run on Android 2.3 emulator. it will crash with the same theme-exception.

password for the key file is "keykey".

I have the same problem :

java.lang.RuntimeException: Unable to start activity ComponentInfo{*}: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2107)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2132)
        at android.app.ActivityThread.access$700(ActivityThread.java:140)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1238)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4918)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
        at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
        at android.support.v7.app.t.a(AppCompatDelegateImplBase.java:124)
        at android.support.v7.app.AppCompatDelegateImplV7.a(AppCompatDelegateImplV7.java:146)
        at android.support.v7.app.q.onCreate(AppCompatActivity.java:59)

I might be wrong, but I think one of those fix it:

-dontwarn java.nio.file.Files
-dontwarn java.nio.file.Path
-dontwarn java.nio.file.OpenOption
-dontwarn org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement
 -keep class com.google.android.gms.** { *; }
 -dontwarn com.google.android.gms.**
 -keep class android.support.v7.** { *; }
 -keep interface android.support.v7.** { *; }
 -keep public class com.google.android.gms.**
 -dontwarn com.google.android.gms.**
 -keep class android.support.design.widget.** { *; }
 -keep interface android.support.design.widget.** { *; }
 -dontwarn android.support.design.**

This workaround works :

 -keep class com.google.android.gms.** { *; }
 -keep public class com.google.android.gms.**
 -dontwarn com.google.android.gms.**
 -keep class android.support.v7.** { *; }
 -keep interface android.support.v7.** { *; }

@11 I hope Google will put the needed proguard rules inside its own libraries, instead of us trying to find what can fix it.
It should also warn about not adding them, and have the error saying that it might be the cause for it.

@julien: It doesn't work for me. Do you put this in your proguard-rules.pro or in the default proguard-android.txt file? I have tried both, but it doesn't work :-(

@13 Try what I did on @11 . I think it works fine. You are supposed to put it in proguard-rules.pro 

@14: Done this already but the same error. Tried it in proguard-rules.pro and proguard-android.txt! Always the same error :-(