#13 add an option to force language X

app/src/main/java/com/geeksville/mesh/BaseActivity.kt

@@ -0,0 +1,40 @@
+package com.geeksville.mesh
+
+import android.content.Context
+import android.os.Build
+import androidx.appcompat.app.AppCompatActivity
+import com.geeksville.android.Logging
+import com.geeksville.mesh.model.UIViewModel
+import java.util.*
+
+open class BaseActivity: AppCompatActivity(), Logging {
+
+    override fun attachBaseContext(newBase: Context) {
+        val res = newBase.resources
+        val config = res.configuration
+
+        // get chosen language from preference
+        val prefs = UIViewModel.getPreferences(newBase)
+        val langCode = prefs.getString("lang","zz")
+        debug("langCode is $langCode")
+
+        if (Build.VERSION.SDK_INT >= 17) {
+            val locale = if (langCode == "zz")
+                Locale.getDefault()
+            else
+                Locale(langCode)
+            config.setLocale(locale)
+
+            if(Build.VERSION.SDK_INT > 24) {
+                //Using createNewConfigurationContext will cause CompanionDeviceManager to crash
+                applyOverrideConfiguration(config)
+                super.attachBaseContext(newBase)
+            }else {
+                super.attachBaseContext(newBase.createConfigurationContext(config))
+            }
+        } else {
+            super.attachBaseContext(newBase)
+        }
+    }
+
+}

app/src/main/java/com/geeksville/mesh/MainActivity.kt

@@ -118,7 +118,7 @@ eventually:
 val utf8 = Charset.forName("UTF-8")
 
 @AndroidEntryPoint
-class MainActivity : AppCompatActivity(), Logging,
+class MainActivity : BaseActivity(), Logging,
     ActivityCompat.OnRequestPermissionsResultCallback {
 
     companion object {
@@ -1079,6 +1079,10 @@ class MainActivity : AppCompatActivity(), Logging,
                 chooseThemeDialog()
                 return true
             }
+            R.id.preferences_language -> {
+                chooseLangDialog()
+                return true
+            }
             else -> super.onOptionsItemSelected(item)
         }
     }
@@ -1167,4 +1171,30 @@ class MainActivity : AppCompatActivity(), Logging,
         }
     }
 
+    private fun chooseLangDialog() {
+
+        /// Prepare dialog and its items
+        val builder = MaterialAlertDialogBuilder(this)
+        builder.setTitle(getString(R.string.preferences_language))
+
+        val languageLabels by lazy { resources.getStringArray(R.array.language_entries) }
+        val languageValues by lazy { resources.getStringArray(R.array.language_values) }
+
+        /// Load preferences and its value
+        val prefs = UIViewModel.getPreferences(this)
+        val editor: SharedPreferences.Editor = prefs.edit()
+        val lang = prefs.getString("lang", "zz")
+        debug("Lang from prefs: $lang")
+
+        builder.setSingleChoiceItems(languageLabels, languageValues.indexOf(lang)) { dialog, which ->
+            var lang = languageValues[which];
+            debug("Set lang pref to $lang")
+            editor.putString("lang", lang)
+            editor.apply()
+            dialog.dismiss()
+        }
+        val dialog = builder.create()
+        dialog.show()
+    }
+
 }