How to fix: “You need to use a Theme.AppCompat theme (or descendant) with this activity”

Question

I am having trouble running my Android app in a fullscreen mode per instructions of a video. When it tries to run, the app crashes with the error.

\"You need t

Answer 1

If you add the android:theme="@style/Theme.AppCompat.Light" to <application> in AndroidManifest.xml file, problem is solving.

Answer 2

Used to face the same problem. The reason was in incorrect context passing to AlertDialog.Builder(here). use like AlertDialog.Builder(Homeactivity.this)

Answer 3

u should add a theme to ur all activities (u should add theme for all application in ur <application> in ur manifest) but if u have set different theme to ur activity u can use :

 android:theme="@style/Theme.AppCompat"

or each kind of AppCompat theme!

Answer 4

Your application has an AppCompat theme

<application
    android:theme="@style/AppTheme">

But, you overwrote the Activity (which extends AppCompatActivity) with a theme that isn't descendant of an AppCompat theme

<activity android:name=".MainActivity"
    android:theme="@android:style/Theme.NoTitleBar.Fullscreen" >

You could define your own fullscreen theme like so (notice AppCompat in the parent=)

<style name="AppFullScreenTheme" parent="Theme.AppCompat.Light.NoActionBar">
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowActionBar">false</item>
    <item name="android:windowFullscreen">true</item>
    <item name="android:windowContentOverlay">@null</item>
</style>

Then set that on the Activity.

<activity android:name=".MainActivity"
    android:theme="@style/AppFullScreenTheme" >

Note: There might be an AppCompat theme that's already full screen, but don't know immediately