Replace runOnUiThread by main handler

app/src/main/java/eu/faircode/email/FragmentCompose.java

@@ -1298,9 +1298,7 @@ public class FragmentCompose extends FragmentBase {
         }
 
         private void check() {
-            Activity activity = getActivity();
-            if (activity != null)
-                activity.runOnUiThread(new Runnable() {
+            getMainHandler().post(new Runnable() {
                 @Override
                 public void run() {
                     if (getLifecycle().getCurrentState().isAtLeast(Lifecycle.State.STARTED))

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -3658,9 +3658,7 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
         }
 
         private void check() {
-            Activity activity = getActivity();
-            if (activity != null)
-                activity.runOnUiThread(new Runnable() {
+            getMainHandler().post(new Runnable() {
                 @Override
                 public void run() {
                     if (getLifecycle().getCurrentState().isAtLeast(Lifecycle.State.STARTED))

app/src/main/java/eu/faircode/email/FragmentOptionsConnection.java

@@ -49,7 +49,6 @@ import android.widget.Toast;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.appcompat.widget.SwitchCompat;
-import androidx.fragment.app.FragmentActivity;
 import androidx.lifecycle.Lifecycle;
 import androidx.preference.PreferenceManager;
 
@@ -295,11 +294,7 @@ public class FragmentOptionsConnection extends FragmentBase implements SharedPre
     };
 
     private void showConnectionType() {
-        FragmentActivity activity = getActivity();
-        if (activity == null)
-            return;
-
-        activity.runOnUiThread(new Runnable() {
+        getMainHandler().post(new Runnable() {
             @Override
             public void run() {
                 if (getLifecycle().getCurrentState().isAtLeast(Lifecycle.State.STARTED)) {