Change Locale not work after migrate to Androidx

UPDATE Aug 21 2020:

AppCompat 1.2.0 was finally released. If you’re not using a ContextWrapper or ContextThemeWrapper at all, there should be nothing else to do and you should be able remove any workarounds you had from 1.1.0!

If you DO use a ContextWrapper or ContextThemeWrapper inside attachBaseContext, locale changes will break, because when you pass your wrapped context to super,

1. the 1.2.0 AppCompatActivity makes internal calls which wrap your ContextWrapper in another ContextThemeWrapper,
2. or if you use a ContextThemeWrapper, overrides its configuration to a blank one, similar to what happened back in 1.1.0.

But the solution is always the same. I’ve tried multiple other solutions for situation 2, but as pointed out by @Kreiri in the comments (thanks for your investigative help!), the AppCompatDelegateImpl always ended up stripping away the locale. The big obstacle is that, unlike in 1.1.0, applyOverrideConfiguration is called on your base context, not your host activity, so you can’t just override that method in your activity and fix the locale as you could in 1.1.0. The only working solution I’m aware of is to reverse the wrapping by overriding getDelegate() to make sure your wrapping and/or locale override comes last. First, you add the class below:

Kotlin sample (please note that the class MUST be inside the androidx.appcompat.app package because the only existing AppCompatDelegate constructor is package private)

package androidx.appcompat.app

import android.content.Context
import android.content.res.Configuration
import android.os.Bundle
import android.util.AttributeSet
import android.view.MenuInflater
import android.view.View
import android.view.ViewGroup
import androidx.appcompat.view.ActionMode
import androidx.appcompat.widget.Toolbar

class BaseContextWrappingDelegate(private val superDelegate: AppCompatDelegate) : AppCompatDelegate() {

    override fun getSupportActionBar() = superDelegate.supportActionBar

    override fun setSupportActionBar(toolbar: Toolbar?) = superDelegate.setSupportActionBar(toolbar)

    override fun getMenuInflater(): MenuInflater? = superDelegate.menuInflater

    override fun onCreate(savedInstanceState: Bundle?) {
        superDelegate.onCreate(savedInstanceState)
        removeActivityDelegate(superDelegate)
        addActiveDelegate(this)
    }

    override fun onPostCreate(savedInstanceState: Bundle?) = superDelegate.onPostCreate(savedInstanceState)

    override fun onConfigurationChanged(newConfig: Configuration?) = superDelegate.onConfigurationChanged(newConfig)

    override fun onStart() = superDelegate.onStart()

    override fun onStop() = superDelegate.onStop()

    override fun onPostResume() = superDelegate.onPostResume()

    override fun setTheme(themeResId: Int) = superDelegate.setTheme(themeResId)

    override fun <T : View?> findViewById(id: Int) = superDelegate.findViewById<T>(id)

    override fun setContentView(v: View?) = superDelegate.setContentView(v)

    override fun setContentView(resId: Int) = superDelegate.setContentView(resId)

    override fun setContentView(v: View?, lp: ViewGroup.LayoutParams?) = superDelegate.setContentView(v, lp)

    override fun addContentView(v: View?, lp: ViewGroup.LayoutParams?) = superDelegate.addContentView(v, lp)

    override fun attachBaseContext2(context: Context) = wrap(superDelegate.attachBaseContext2(super.attachBaseContext2(context)))

    override fun setTitle(title: CharSequence?) = superDelegate.setTitle(title)

    override fun invalidateOptionsMenu() = superDelegate.invalidateOptionsMenu()

    override fun onDestroy() {
        superDelegate.onDestroy()
        removeActivityDelegate(this)
    }

    override fun getDrawerToggleDelegate() = superDelegate.drawerToggleDelegate

    override fun requestWindowFeature(featureId: Int) = superDelegate.requestWindowFeature(featureId)

    override fun hasWindowFeature(featureId: Int) = superDelegate.hasWindowFeature(featureId)

    override fun startSupportActionMode(callback: ActionMode.Callback) = superDelegate.startSupportActionMode(callback)

    override fun installViewFactory() = superDelegate.installViewFactory()

    override fun createView(parent: View?, name: String?, context: Context, attrs: AttributeSet): View? = superDelegate.createView(parent, name, context, attrs)

    override fun setHandleNativeActionModesEnabled(enabled: Boolean) {
        superDelegate.isHandleNativeActionModesEnabled = enabled
    }

    override fun isHandleNativeActionModesEnabled() = superDelegate.isHandleNativeActionModesEnabled

    override fun onSaveInstanceState(outState: Bundle?) = superDelegate.onSaveInstanceState(outState)

    override fun applyDayNight() = superDelegate.applyDayNight()

    override fun setLocalNightMode(mode: Int) {
        superDelegate.localNightMode = mode
    }

    override fun getLocalNightMode() = superDelegate.localNightMode

    private fun wrap(context: Context): Context {
        TODO("your wrapping implementation here")
    }
}

Then inside our base activity class you remove all your 1.1.0 workarounds and simply add this:

private var baseContextWrappingDelegate: AppCompatDelegate? = null

override fun getDelegate() = baseContextWrappingDelegate ?: BaseContextWrappingDelegate(super.getDelegate()).apply {
    baseContextWrappingDelegate = this
}

Depending on the ContextWrapper implementation you’re using, configuration changes might break theming or locale changes. To fix that, additionally add this:

override fun createConfigurationContext(overrideConfiguration: Configuration) : Context {
    val context = super.createConfigurationContext(overrideConfiguration)
    TODO("your wrapping implementation here")
}

And you’re good! You can expect Google to break this again in 1.3.0. I’ll be there to fix it … See you, space cowboy!

OLD ANSWER AND SOLUTION FOR APPCOMPAT 1.1.0:

Basically what’s happening in the background is that while you’ve set the configuration correctly in attachBaseContext, the AppCompatDelegateImpl then goes and overrides the configuration to a completely fresh configuration without a locale:

 final Configuration conf = new Configuration();
 conf.uiMode = newNightMode | (conf.uiMode & ~Configuration.UI_MODE_NIGHT_MASK);

 try {
     ...
     ((android.view.ContextThemeWrapper) mHost).applyOverrideConfiguration(conf);
     handled = true;
 } catch (IllegalStateException e) {
     ...
 }

In an unreleased commit by Chris Banes this was actually fixed: The new configuration is a deep copy of the base context’s configuration.

final Configuration conf = new Configuration(baseConfiguration);
conf.uiMode = newNightMode | (conf.uiMode & ~Configuration.UI_MODE_NIGHT_MASK);
try {
    ...
    ((android.view.ContextThemeWrapper) mHost).applyOverrideConfiguration(conf);
    handled = true;
} catch (IllegalStateException e) {
    ...
}

Until this is released, it’s possible to do the exact same thing manually. To continue using version 1.1.0 add this below your attachBaseContext:

Kotlin solution

override fun applyOverrideConfiguration(overrideConfiguration: Configuration?) {
    if (overrideConfiguration != null) {
        val uiMode = overrideConfiguration.uiMode
        overrideConfiguration.setTo(baseContext.resources.configuration)
        overrideConfiguration.uiMode = uiMode
    }
    super.applyOverrideConfiguration(overrideConfiguration)
}

Java solution

@Override
public void applyOverrideConfiguration(Configuration overrideConfiguration) {
    if (overrideConfiguration != null) {
        int uiMode = overrideConfiguration.uiMode;
        overrideConfiguration.setTo(getBaseContext().getResources().getConfiguration());
        overrideConfiguration.uiMode = uiMode;
    }
    super.applyOverrideConfiguration(overrideConfiguration);
}

This code does exactly the same what Configuration(baseConfiguration) does under the hood, but because we are doing it after the AppCompatDelegate has already set the correct uiMode, we have to make sure to take the overridden uiMode over to after we fix it so we don’t lose the dark/light mode setting.

Please note that this only works by itself if you don’t specify configChanges="uiMode" inside your manifest. If you do, then there’s yet another bug: Inside onConfigurationChanged the newConfig.uiMode won’t be set by AppCompatDelegateImpl‘s onConfigurationChanged. This can be fixed as well if you copy all the code AppCompatDelegateImpl uses to calculate the current night mode to your base activity code and then override it before the super.onConfigurationChanged call. In Kotlin it would look like this:

private var activityHandlesUiMode = false
private var activityHandlesUiModeChecked = false

private val isActivityManifestHandlingUiMode: Boolean
    get() {
        if (!activityHandlesUiModeChecked) {
            val pm = packageManager ?: return false
            activityHandlesUiMode = try {
                val info = pm.getActivityInfo(ComponentName(this, javaClass), 0)
                info.configChanges and ActivityInfo.CONFIG_UI_MODE != 0
            } catch (e: PackageManager.NameNotFoundException) {
                false
            }
        }
        activityHandlesUiModeChecked = true
        return activityHandlesUiMode
    }

override fun onConfigurationChanged(newConfig: Configuration) {
    if (isActivityManifestHandlingUiMode) {
        val nightMode = if (delegate.localNightMode != AppCompatDelegate.MODE_NIGHT_UNSPECIFIED) 
            delegate.localNightMode
        else
            AppCompatDelegate.getDefaultNightMode()
        val configNightMode = when (nightMode) {
            AppCompatDelegate.MODE_NIGHT_YES -> Configuration.UI_MODE_NIGHT_YES
            AppCompatDelegate.MODE_NIGHT_NO -> Configuration.UI_MODE_NIGHT_NO
            else -> applicationContext.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK
        }
        newConfig.uiMode = configNightMode or (newConfig.uiMode and Configuration.UI_MODE_NIGHT_MASK.inv())
    }
    super.onConfigurationChanged(newConfig)
}